Fruit And Nut Trees From Seed


Introduction
Selection Strategy
Obtaining Seed
Germination
Containers
Growing Medium
Indoor Environment
Pests and Pathogens
Planting Out
Outdoor Microclimates


Introduction

This page provides a few tips for growing a variety of edible perennial plants, fruit and nut trees and bushes from seed, especially tropical, subtropical and arid climate species started indoors for maximum growth rate for later planting out.  There is a lot of genetic variability in seeds so general statements are only as guidelines.

Characteristics, including fruit taste, often vary widely across individuals of a species.  Some species exhibit more consistently desirable characteristics among individual plants so that little selection is needed for improvement.  Some varieties have been selected so that seed propagation consistently yields desirable characteristics.  Other varieties have been selected for desirable characteristics but do not replicate these in seed propagation so depend on clonal propagation for their replication.  Commercial growers often graft an optimum fruiting variety onto an optimum rootstock variety.  If you grow a seedling and are not satisfied with its fruit, you may be able to graft something else onto it.

Advantages of seed propagation include the availability of seed, a simpler propagation procedure, and genetic variability for developing new cultivars.  Advantage of clonal propagation include exact replication of selected characteristics that may (or may not) suit your requirements, easier culture given documentation, and in many cases a shorter juvenile period. 


Selection Strategy

If you want to end up with one healthy seedling, try germinating a dozen seed.  Expect only a few to germinate and some to be defective.  Of course there is great variety in germination rate among species and seed sources.  Select the most vigorous one, or even better, grow three healthy seedlings to end up with one healthy adult tree.  But it's very likely that more trees are desirable for selection of a superior producer, and also for pollination.

Isolated individuals of some species, or select cultivars, can self-pollinate and produce abundantly.  But all species exhibit various types and degrees of self-incompatibility and most require the genetic variance of two or more non-cloned trees for good fruit set.  Many species have perfect flowers but produce better with cross-pollination.  Seedlings of these species may be planted in pairs to help ensure good fruit set.  Some species produce male and female flowers on separate trees without a hint of a tree's sex until it flowers.  Other species, like avocado, produce two types with different reproductive timing.  Seedlings of these species may be planted in threes to ensure good fruit set. Other species produce male, female, and some bisexual trees that can pollinate themselves and other females.  Seedlings of these species may also be planted in threes but in the case of papaya, five may be planted to provide a great chance of having one bisexual tree (they flower after several months), so the others may be removed.  

If space is limited, multiple seedlings may be planted in one hole, or in some cases pollinator scions may be grafted onto receptor trees.  Some species have wide variance in fruit quality such that planting extra seedlings offers a better chance of one seedling producing high quality fruit.  This is especially important if you want to market your excess production.  For species not well-adapted to the climate, a large number of seedlings may have to be planted to net just a few productive individuals.  Plant the seedlings in a group and remove your least favorites as they grow large and compete for resources.


Obtaining Seed

Seed viability periods vary with species.  Generally, fresh seed germinates readily, and older seed much more slowly and unreliably.  Expect poor or inconsistent germination rates in bought seed unless you can be sure that the seed is fresh.  I found all shelled nuts sold for food non-viable, probably due to heat-sterilization.  Fresh fruit/nuts in supermarkets tend to readily germinate. Ethnic grocers extend the variety of available fresh produce.  Farmers' markets, country produce stands, u-pick orchards, horticulture clubs, neighbors willing to share, or on the ground under their trees, and the wilds are all places to find fresh fruit/nuts with viable seed.  A mix of seed from different parent trees from different locations for genetic diversity is good.  The parent trees should be healthy, and if from wild stands should be from the perimeters where the climate resembles where the seedling will be planted.  Seed-borne pathogens might be killed by soaking shell seeds in 10% bleach solution for two minutes, then rinsing.  Keep some non-treated seed for backup. 


Germination

Perennials generally take longer to germinate than annuals so don't use the germination time for wheat sprouts as your standard.  The optimum germination conditions vary widely between species, but all need a certain level of warmth, moisture and time.  Most seed germinate much faster when planted immediately after extraction from ripe fruit.  The riper the better usually.  Seeds that float in water are usually not viable.   If they don't germinate rapidly, allow them to completely dry out, then try again.  Some species' encoded survival strategy involves a randomness in germination time spanning months.  Some species habituated to cold climate require a minimum period of cold and damp which may be created by containing the seed in a damp medium, e.g. sand, in a plastic bag in the refrigerator.  Species vary but generally a 70 to 80 degree F germinating medium is necessary.  Bottom heat may be necessary.

For the medium itself I've used sand but it has to be re-wetted frequently. Covering the container with plastic to maintain moisture invites fungi.  Laying wetted tissue paper over the surface can slow the rate of evaporation.  The medium should be sterilized by boiling in a pot with water for 3/4 hour.  Some seed should be buried to a depth 2 or 3 times their size to hold the seed coat secure while the stalk pulls itself out.  I've had real problems with guavas, cherimoyas and others failing to shed the seed coat.  The other reason to bury is moisture regulation.  I haven't had a lot of success sprouting seeds in water but avocado did fine, and a few pistachios did.  Many species seem to respond better when the medium is allowed to dry significantly between waterings.  

Seed orientation is fairly important to avoid crooks and twists.  Generally the tip where the root and stalk emerge should be placed horizontally so that each can grow in its preferred direction with equal ease.  Seed tips are generally identifiable as the pointed end of the shell or embryo.  Split shells like walnut should be planted so the shell hinges open sideways.  Same for split embryos.  For many seeds, including tamarind, cherimoya and black sapote, the stalk emerges while the bud is still in the buried seed coat, and it forms a 180 degree bend for leverage to pull the bud out.  Carob doesn't do the 180 degree bend and may be planted tip down because its seed coat readily splits away from the emerged bud.  The mango embryo should be planted with the two ends horizontally opposed, edge vertical, with the "garbled" long edge down.  Avocado is planted with the eye or flat end down.  Date palms sprout straight regardless of seed orientation.

Germination is generally faster in species with woody shells when the embryo is removed.  I removed the mango shell with wire snippers, very carefully cutting around half way and pulling the remainder apart.  Canistel shells crack apart quite easily.  Capulin cherry shells are easily split with a pair of pliers.  It appears unnecessary to remove the walnut shell as the shell easily opens like a clam when moist and germination seems to be better in-shell.  Seeds from commercial jujube are usually missing the embryo from a lack of genetic variance in the pollen.  I tried numerous different seed sources and found very few embryos and even fewer that would sprout.  I finally had success with a couple of bags of particularly delicious dried fruit - two pounds of fruit yielded four sprouting embryos.  But three of the four had major problems pulling out of their seed coats and raising their cotyledons above the soil.

During germination, light is less important for most species but air circulation is important to prevent fungus on the growing medium surface.  After the sprout breaks, full light and good air circulation become more important.  Without full light the plant develops long stalk spacing between nodes (where leaves and buds emerge).  This will result in a weaker adult trunk, more vulnerable to wind damage.  A few species may require less light, like tamarind.  It's good to experiment with a groups of seedlings to discover optimum levels of various parameters.  During germination air may be circulated with a fan but should be refreshed from outside often.   I had great variance on the size of the roots and stalks on walnut sprouts.   Terminal buds on walnut, avocado and pomegranate sprouts failed for no apparent reason.  I suspect either asphalt contamination in my sand, a pathogen in either the seed or soil, or environmental contaminants. 

Sprouts are extremely delicate and easily damaged.  I've heard that sprouts should be handled by their leaves.  Sprout roots seem to be much less vulnerable to damage.  At least with a guava I lost the taproot and it didn't seem to slow it down at all.  Nevertheless, take care on transplant because larger plants generally require their roots to be mostly undisturbed.  I've had a lot of dead terminal buds which result in a delayed sprouting of two or more lateral buds. If you lose a terminal bud, snip the stalk right above the topmost lateral bud with a sharp sterile instrument.  The topmost bud will develop at minimum angle into the new central leader and the wound will close up later. 

Small seedlings with minimal root systems are more successfully transplanted as bare-root than larger plants with extensive root systems, because the larger plants are much more dependent on and much less able to quickly regenerate their extensive sets of micro-roots.  So the larger the plant, the more important to maintain the root ball on transplant.  It is also much better for these older plants to transplant during a slow or no growth period. In any case, water the plant an hour before transplanting to ensure it is not water stresses.  Immediately water it well afterward to settle the soil around the roots.  Apply frequent light waterings to compensate any root damage, until a day or two of substantial growth, then taper off.  Gradual tapering is key on any change of environment (water, humidity, light and temperature) to avoid shock.  The general idea is to taper the daily dose over a few days when changing rates. 

Leaving sprouts in the germination tray for an extended period can be a problem, despite their receiving plenty of light and water.  Black chilean guavas start out very tiny and I let them grow to about an inch high before transplanting them.   In individual pots they started growing much larger stem and leaves above the spindly little base.  It's tempting to conclude that despite the extremely low root density and abundant light and water, they were constrained by the 1" depth of the germinating tray or by root competition.  I'm suspecting that others such as pomegranate are reacting poorly to the bounds of their pots, despite extremely low root density.  The low fertility of the germinating medium, sand, is another possibility.


Containers

Containers need to be well-drained. Waterlogged soil tends to anaerobic fermentation which presents problems for most plants.  In the presence of oxygen, aerobic decomposition proceeds and is much preferable for the plants.  Oxygen deficiency is lethal to the roots of most species.  Fungi can attack roots in these conditions in any case and is a leading cause of plant failure in containers. Container culture risks moisture extremes compared to the earth which has a great averaging effect.  The strategy is to simulate the earth as much as possible.   I cut four vertical notches in the bottom edges of containers so water can drain through either the bottom or the side.  Any old container will do but it should be strong enough so that when you handle it the roots are not damaged.  It should not secrete any toxins.  And it should be easy to deal with come transplant time.  Styrofoam cups are really handy for small plants because they are so easy to cut apart on transplant.  I cut the bottom off first, set it in the new container then cut the side from top to bottom, fill dirt all around, then carefully pull the styrofoam out.

The container should be washed with soap and water, and 10% bleach if it's being re-used to avoid pathogen transfer.  I also use 1/2 gallon wax-cardboard milk cartons.  I put a strip of packing tape around under the milk cartons so they'll last a few months.  For long taproot plants I roll up newspaper around a four inch jar, tape the seam with a strip of packing tape that goes under the bottom and back up the other side.  Then I make a newspaper bottom that fits inside, and do another layer of sides and bottom inside without tape.  This makes a 12.5"x 3.5" container that may be planted in the soil after the packing tape is removed.  Nine of them fit in a milk crate.  Shallow germinating containers don't need drainage because seeds actually enjoy an occasional flood and the roots won't be sitting there a long time to rot. Consistent regulation of moisture, air, light and temperature are basic necessities to successful plant culture.

The container depth should allow the vertical growth of taproots, found on the large, long-lived tree species and arid climate species.  Some species grow taproots much faster than the stalk but relative growth rates are very species-dependent.  Large embryos tend to grow long taproots fast but so do some small ones, e.g. avocado can grow a three foot taproot before the stalk reaches eight inches, and carob can grow a five inch taproot before emerging.  When the taproot reaches the bottom of a container it makes a 90 degree bend and loops around in the container bottom.  This usually inhibits the taproots growth and function after planting out.  Depending on taproot diameter and brittleness which is species-dependent, looping taproots may be straightened on transplant but many species are shocked when the growing medium is removed from the roots.  If a taproot is damaged during germination or broken during transplant there's a temporary vulnerability to pathogens until the break heals. Generally, a broken taproot won't regenerate, so the long term wind and drought resistance is penalized, but some species are probably able to regenerate taproots.  It has been stated that a taproot that stops at a container drain hole will commence growing when planted out.   An inverted cone shaped container with an open sceened bottom might be good.

While waiting for the optimum time to plant out, re-potting may be necessary to accommodate root growth.  Although accommodating a long taproot is important for tall trees and arid-climate plants, in general the container size is selected to balance root density.  An oversized container with sparse root density can be a problem for the plant if the container is not well-drained and anaerobic fermentation of organic matter in the soil develops, lowering the pH to excess acidity.  An undersized container with dense roots, i.e. "root bound", will stunt plant growth and demand frequent watering to avoid dry root stress.  A root bound plant sends roots out the drainage holes and above the soil surface.  If you need to limit their growth, many plants can survive in this state as long as you prevent dry root stress but generally for optimum growth the container size should be increased at this point.  Less water encourages more roots while more water encourages more leaves.  Keep a plant in the same position after re-potting to avoid sudden change to its microclimate.


Growing Medium

Roots need oxygen as well as water.  In soil, earthworms and other critters aerate the soil, but in containers without critters a lighter soil type is needed for aeration.  A popular potting mix is equal parts vermiculite, sand and peat moss.  Vermiculite is a volcanic rock that's been expanded by heating with air cavities like popcorn.  It absorbs and releases water and is structurally stable for a good while, I don't know, one year to ten is a guess. Peat moss has similar properties as vermiculite except of course it's organic and contributes to loam as it ages.  Loam is a mixture of sand/silt/clay and organic matter.  Silt is a very fine sand, and clay is even finer.  One problem with finer media like clay is that it can hold too much water and easily suffocate roots.  Another problem is that when the water dries out, layers of clay form barriers to air circulation.  Some species are more vulnerable than others.  Juvenile plants are more vulnerable than adults. 

If you're going to buy potting mix, buy sterilized, otherwise sterilize your material by boiling for half an hour or baking at 200 degrees for an hour.  Peat moss and alternatives, and vermiculite and perlite, make for a lighter container.  They also allow the roots to more easily bind the soil mass together so the pot can be pulled off for root inspection.  The soil binding is also useful in transplanting.  A small root system in a heavy mass of soil, sand, silt or clay is vulnerable to root breakage in transplanting.  I had plenty of burlap on hand so I shredded it into short length fibers and used that.  It actually breaks down much faster than peat moss.  I interleave bunches of it with spoonfuls of sand when filling a pot but it's a slow process.  I also add small amounts of organic material like leaves.  I top off the pot with an organic mulch.  This is needed because sand dries so quickly and the mulch also supplies some nutrients.  Again, all materials should be sterilized. 

Seedlings usually don't need fertilizing the first few months because most soils contain enough nutrients.  The breakdown of peat and mulch provides a small amount but eventually some manure or compost may be added in small amount at regular intervals.  These should be well-decomposed as this process usually causes plants problems.  Under the mulch but above the roots is probably ideal.

I use purified water for small plants.  Distilled water may be better.  Tap water may be ok but there are mineral and chemical contaminants.  If you use high-mineral tap water the minerals may accumulate over a span of months and cause problems, so flush the soil with a lot of water every 2 to 4 weeks.  Softened tap water is full of sodium which may be worst that the original minerals.  Let the tap water sit out 24 hours for the chemicals to evaporate.  This also lets the temperature equalize with room/soil temp, preventing temperature shock.  It's also important to shake up a container of water to get some oxygen dissolved in it.  Sterilizing the water during the sprouting period may reduce seedling defects.  Water should be kept off the plant except for an occasional mist to wash off dust. 

The amount of soil moisture is crucial.  Too much and the roots are deprived of oxygen.  Too little and the roots will dry out.  Both will kill roots and/or stress the plant, stunt it, and make it more vulnerable to pathogens.  But an occasional stress is good to build strength.  Try monitoring each plant's growth rate to gauge the optimum soil moisture level and use a single soil mix for all plants so it's easier to estimate moisture levels inside the soil by the moisture level on top.  Dig in with your finger to get an idea of the usual moisture gradient with depth.  Larger plants with more leaves and roots draw water faster.  Higher temperature, lower humidity and higher wind draw water faster.   You should develop a feel for the amount to water based on the plant and container size, and adjust as these and the other factors change.  An occasional good deep watering will draw air into the soil and flush stuff out.  Alternate deep and shallow waterings may benefit the plant by equalizing deep and shallow moisture levels.  Most plants have probably evolved a dependency on occasional soil flushes.  Given proper drainage holes in the container, you can put a tray underneath to catch the excess water.  But if the water in the tray is also standing in the bottom of the container, any roots there will be vulnerable to rot.  You can empty the tray an hour after soaking, elevate the container on a layer of rocks or paper, or put a layer of rocks in the bottom of the container. 


Indoor Environment

Plants need maximum sunlight for maximum growth.  If you're growing indoors with artificial light you can extend the daily lighting period but the general limit is 18 hours for 6 hours of darkness.   My rule of thumb is to use a 5000K 23W compact fluorescent bulb per one and a half square feet of plant bed area for small plants and keep the plants about 5 inches from the bulb.  The distance seems to matter a lot.  Farther and the stalk nodes spread excessively, closer and the stalk nodes compress excessively.  I compared plants under this lighting arrangement with plants on a balcony with only indirect sunlight.  The balcony plants have longer node spacing, and wider leaves.  They also seem to be softer despite the wind.  They get some blue sky on the balcony and they look as good or better than the inside plants so I taped blue plastic to the wall for the inside plants.   Reflectors can increase the light available to the plants.  I use heavy aluminum foil bent around a football and fixed in the pot with wire to focus the light on the plant.  The reflectors should not be so large as to restrict airflow.  The plant pots should be turned/moved occasionally to get even exposure unless you're planting them out flush against a wall.  The avocados developed a rust-like problem on the leaves from being two to three inches from the light 16 hours/day.  Tamarind seedlings seemed to do much better in very low light but they also had higher heat in that environment.

A key to growing plants is to duplicate their native environments.  Growing indoors however provides the opportunity to accelerate their growth by extending the daylight length, and the growing season to full year.  This can compress the juvenile period for seedling trees that take several years to bloom.  I had a 5 month old mission fig cutting (from a root sucker) with a 4 inch stem sprout fruit. 

Deciduous species will go dormant during their first winter, assuming they can detect it.  An approximate 33° latitude marine environment (60°F night, 74°F day winter temps using some generated heat), with close grow lights on 14 hrs/day, but with some highly filtered window light was the environment I provided.  Pistachios leaves turned colors in the fall and dropped, not rebudding until the next mid summer, walnut leaves got dead splotches in fall, but kept leaves until next end summer, then rebudded.  Maybe providing them a colder winter temperature would have shortened their dormancy and given faster bud break.  Maybe providing them a hotter winter temperature would have enabled them to skip dormancy.  It seems that these dormancies were not stress-induced.  I don't know if a lack of chilling hours or the extended dormancy stressed these plants but they did seem healthy after bud break, with the walnuts sprouting more growth than their first season.

Regularly refreshed air from outside and good airflow around plants is essential for indoor growing.  So in cooler seasons when airflow from outside is decreased, circulation with a fan becomes more important.  Wind helps plants to develop physical strength.  Various pathogens are less effective in a high airflow environment.  Plants have probably evolved a dependence on wind to aid various processes. 

Colder temperatures slows seedling growth but also lower the humidity because colder air doesn't hold as much moisture.  Some tropical plant seedlings may struggle with lower humidity.  In the colder seasons indoor plants do better when the ventilation is kept to something reasonable like one or two air changes per day, and the room temperature is kept around 70 F.  Humidity for the plants is enhanced by keeping them close together, and keeping trays of small pebbles or sand partly submerged in water under or near the plants, or layers of wetted newspaper.

Knowledge of vegitative growth cycles and the lifecycles of leaves is useful in determining the health of plants.  In a moderate indoor envronment, walnut plants produced a flourish of large leaves over a period of two weeks in late summer, then then after another two weeks the leaves started to slowly degrade over the course of a year, finally falling off at the next budding.  Papaya leaves have one to two month lifecycles with new leaves constantly emerging in even spaced intervals.  Wolfberry and pomegrante leaves have two to three month lifecycles, growing on new canes that emerge continuously.  Almond and guava leaves can last six months to a year on new stalk growth throughout the summer.  Avocado, citrus, carob and black sapote leaves can last longer than a year, with growth emerging in the summer.  Avocado and citrus have a long growing season, carob and black sapote is short.  Pistachio leaves bud out once in a quick flourish that lasts about six months, slowly turning shades of red over the last three, then drop and leave the stalk bare for another six.  Pistacho, carob and black sapote are relatively slow growing.  Fig, cherimoya, capulin cherry and tamarind are nearly continuous growers with leaves lasting six months to a year.  Climate and cultural variables can alter growth cycles of course.  To some extent, plants scavenge nutrients from old leaves before dropping them.


Pests and Pathogens

Fungus gnats can feed on roots and cause problems.  Heavier waterings at longer intervals controls them by moving the moisture depth lower, with a risk of stress to the plant.  Maybe experiment with small containers of water. The gnats land on the water and seem to get stuck there.

I had severe spider mite infestation on my almond seedlings.  It first showed up as a yellow patina on young leaves and bronze patina on older leaves.  Finally, I noticed the tiny spider webs around the terminal buds and the tiny white mites crawling along them.  Later I found an infestation causing dark rust on pistachio leaves.  They can easily kill the the seedlings by destroying all of their leaves.  They tend to congregate and do the most damage on the sides of the leaf's main stem, on the stalk end, on the underside of the leaf.  The mites had to be rinsed or brushed off into a wash basin and flushed away, something like twice a week, ongoing.  Later, I found them infesting almost every species, really causing problems on citrus.  Broad mites attack the terminal buds resulting in severely distorted leaves.  They may cause aborted leaves, as I had plenty of aborted almond and citrus leaves, but I can't rule out light and temperature.

I had a problem with prunus seedlings developing bud gall where the terminal bud grows in a knot.  It seems to be solved only by snipping the stalk well below the knotty node.  Use a sterilized sharp razor to minimize damage.  Some wolfberries were spindly, had very yellowish leaves and dying leaves at the bottom.  I don't know if they developed some kind of disease or if their soil was somehow contaminated.  I got the sand from the city which may have mixed in a little asphalt.

My walnut seedlings developed what I believe to be leaf blotch from anthracnose fungus.  It seems to have developed after I closed the outside ventilation although I kept a fan circulating the inside air part-time.  The fungus is said to spread by wind-borne spores ejected from dead leaf material during cool rainy periods.  Removal of dead leaves helps limit infection of new leaves.  The original spores were probably on the nut shells.  It's probably a good idea to clean them before sprouting or remove the embryo and wash them carefully.  One application of dissolved baking soda failed to stop the fungus spread.  My guess is that that ventilation time and intensity matters. I left the fan running non-stop with a faint flutter of the leaves and it seemed to halt the spread of the fungus.  The fungus stopped growing and the leaves remained about halfway covered throught heir life cycle.

Another black rust of some sort has attacked the chilean guavas, carissas, pistachio, cherimoya, citrus and guavas.  On chilean guava and carissa it forms a scale on the stem, attacks the leave underside on each side of the leaf stem but not the leaf stem.  This scale seems to be carried by the mites.  On pistachio it attacks the main stem, terminal bud, underside of leaf, and leaf stem.  On cherimoya it attacks the main stem, terminal bud, underside of leaf stem.  On citrus and guava seedlings it attacks the terminal buds, and on larger guava it develops a scale on the stem and may be the culprit in killing new leaf growth.  It always stunts leaves and kills the terminal buds, though cherimoya terminal buds seems to survive but are severely set back.  I tried a mixture of one part each baking soda, olive oil and mild dish soap to 100 parts water, coating the leaves stems and buds.  It seems to have helped, but may need several applications.  This mixture also works on the mites.

Another sort of rust appeared on the avocado leaf tops wherever there was direct exposure to light.  One of the avocados has had aborted bud growth, which may or may not be the result of this pathogen.  I had an outbreak of mealybugs on figs and wolfberries.  I had an outbreak of scale on one fig and it is trying to expand to others.  I'm testing the baking soda/oil/soap mixture on that.  A white cottony fungus attacked the pomegranates after an outbreak on wet newspaper pots.

So it seems pests and pathogens are a big challenge in a seedling nursery.  Various strategies include consistent air circulation, long dry periods between watering, regular inspections with magnifying glass, manually picking off, brushing, cleaning with water streams, weekly soda/oil/soap applications, qurantine or systematic isolation of seedlings, selecting individuals with higher tolerance, and keeping the plants as strong/healthy as possible.


Planting Out

Planting out has to occur before the seedling is stressed by root containment.  This of course varies with species but nurseries generally keep seedlings in containers for one to three years.  Long taproot species natually outgrow containers first.

The plants have to be slowly acclimated to the outdoor environment over a period of one to several weeks with a couple days in the hole to equalize soil temperatures, checked with thermometers.  On any transplant the soil height on the trunk should be preserved as many species may be killed by burial of the trunk.  Keep mulches off the trunk.  Keep the trunk exposed down to the root flair.  The ground and container soils should be blended at their interface.  The reason is that water likes to disperse but likes to pool more, so a smoothly changing interface promotes dispersion over pooling.  Get some extra soil of the type in the container to mix with the ground soil in the interface area.  Generally plants like a significant radius of this mix to build new roots in.  Cut the bottom of the container off, snip any curled roots on the bottom, place the container in the hole, slit the side of the container while keeping it on, lightly fill in around container with soil mix, then carefully pull the container out.  Tamp lightly and water heavily to settle the soil.   Water well until roots are established.  Protect from sun, heat, cold, wind and pests.

Pruning is performed to develop a strong tree structure to support larger crops later on.  Pruning encourages vegetative growth and suppresses reproductive growth.  A non-pruned tree will flower and produce fruit sooner than a pruned tree.  Node/branch heights remain fixed as the tree grows.  A tree will generally shed lower branches as it grows higher branches unless you keep it as a shrub by pruning the central leader.  Prune lateral branches right above the branch collar for better wound closure than a flush-to-trunk prune.  A 90 degree angle is the strongest branch angle because there is maximum connective wood on the top side of the branch supporting it against gravity and wind.  Weak branches often break under fruit load. 


Outdoor Microclimates

You can choose only species well-adapted to your general climate, find the microclimates in the yard most suitable for a species' individual needs, and add a microclimate enhancement for very alien species.  This is obviously the most work, but may be limited to a seasonal chore, only during the plant's juvenile period.

An example would be to get tropical plants to grow and produce fruit in an arid climate.  The potential problems in this example are too much heat in the summer, too much cold in the winter, and too little humidity.  Wind lowers humidity so the strategy to maintain humidity would include wind breaks, made of native species of trees and shrubs on the perimeter, plus the more arid-tolerant members of the orchard closer in.  Training the plants as low-growing shrubs instead of trees also reduces exposure to wind and provides increased ground heat radiation to the plant (frost protection).  Other benefits of low-growing forms include ease of maintenance and harvest, and reduced trunk exposure to sunburn. 

Mulching reduces water loss to soil evaporation and helps moderate soil temperature in extreme heat.  Wind breaks reduce water loss to transpiration and moderate air temperature, which can be important for some plants in extreme arid climates.  Wind breaks on the north side often protect against cold wind and on the south side against hot wind, but this is only a generality.  Natural convection usually causes colder air to move down slopes and can pool in a valley or where obstacles, including plant growth and buildings, break the drainage to lower ground.  It may be necessary to break up hedges along the lower side of the orchard to improve air drainage in the winter.  But if heat in the summer is a bigger issue, the wind break on the lower side may be beneficial.

A plant's summer sun exposure may be limited by positioning another plant on its east or west side.  For plants vulnerable to both light and heat stress, the west side shade provides protection during the hotter part of the day.  A building may also provide shade.  Tropical plants grown in higher latitudes generally want maximum sun in the winter so the equator-facing exposure should be maximized.  If a light-colored building or wall is present on the opposite side this can increase the light on the plant through reflection.  For plants vulnerable to frost damage, a nearby wall may also provide some thermal averaging, especially massive materials like stone.  Soil around and upwind of plants also provides thermal averaging if the sun is allowed to reach it and the top foot is kept relatively firm and moist.  Darker, denser soil absorbs more heat.  Thermal averaging may even protect temperate climate plants and their flowers that are vulnerable to rapid temperature changes.

More intensive climate management involves rigging straw or plastic screens around plants.  Full enclosure in black plastic screen may reduce sun and wind, increase humidity and also serve to keep birds from stealing fruit while allowing pollen and insects through.  Clear plastic sheet may allow nearly full sun to penetrate while lowering wind and raising humidity, but plenty of ventilation is needed to avoid overheating.  White plastic sheet provides wind/humidity control and reduced light/heat.  All such coverings reduce the chance of frost damage by reducing heat loss to both wind and sky. 

For young tropical plants in higher latitude arid climates, a plastic or straw sunscreen on top and east/west sides, and a high-mass wall on the side opposing the equator reduces light/heat in the summer, breaks wind from most directions, and increases light/heat in the winter.  Add chicken wire on the open side for critter control.  Closely spaced stakes in the ground may also be necessary to thwart burrowers and root chompers.  Any rigging has to withstand wind and rain so it doesn't collapse on the plant. 

Effectiveness of high-mass walls in moderating heat depends on the amount of mass in the wall.  In humid climates, the wall can attenuate the seasonal heating/cooling cycle peaks in proportion to the amount of mass, but in arid climates the greatest benefit may be with an amount of mass that phase-shift-cancels the diurnal heating/cooling cycle (fun experiment with thermometers).  The wall surface treatment affects the level of heat radiation and light reflection during the winter.  For higher frost risk, paint the wall surface a darker color so it will collect more heat, and for lower frost risk lighten the color, which benefits the plant with more reflected light. 

Other means of dealing with frost include wrapping trunks with insulation (may require fungicide treatment), and draping blankets, tarps or plastic over the tree (or better still, a frame around the tree).  Soil warmth provides a good deal of frost protection to plants.  With generally sunny, warm and calm conditions, exposing the soil to the sun may increase soil warmth to help guard against unpredicted, sudden frosts, but in low light, low temperature or high wind conditions, mulching may be used to preserve soil warmth.  Either way, increased soil moisture (for tolerant plants) increases the frost protection benefit.

The intensive climate management strategies that moderate the seasonal climate changes are best applied incrementally over a period of days or weeks but should not start too early in the season because plants need to experience seasonal changes to fully acclimate to them, to maximize their tolerance to weather extremes.  Timing and rates of fertilizer, water and pruning also affect acclimation in various ways.

Climates:
Tropical - 75°F - 95°F with seasonal and diurnal consistency


Malcolm Beck's articles on organic agriculture




Copyright (c) 2005, 2006, 2007 Robert Drury
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