Propagation of organic fruit trees
The propagation of fruit trees, bushes, and vines is a technical field containing considerable traps and difficulty for the inexperienced gardener. For a variety of reasons most commercial growers no longer propagate their own stock. Among these, time constraints, and barriers restricting convenient access to biological materials are believed to deter many growers away from the task. At the same time, the commercial success of large scale nurseries specialising in propagation have enabled these professional breeders to provide large quantities of plants at highly competitive prices.
Despite these inducements to abandon their interest in the field, there is a small percentage of fruit growers who remain devoted to the task of propagating their own varieties. Within this group, the proportion of growers devoted to organic principles is known to be considerably higher than those pursuing conventional agricultural practices. The organic philosophy is traditionally associated with a level of sustainability which encourages the integration of all garden activities throughout the season. The ability to propagate new plants is correctly viewed as a key element for maintaining control over subsequent generations of organic fruit production. In many instances, organic fruit growers will be interested in relatively uncommon, or old fashioned varieties which are difficult or impossible to obtain from professional nurseries. Most of these preferred varieties possess some unique characteristics which make them more suitable for organic fruit production. The most important of these is the correct adaptation to local soil and weather conditions.
Naturally raised plants tend to grow strong, resilient and produce healthy fruit within a surprisingly narrow range of conditions. Over many generations, these plants develop an inbuilt resistance to the commonest types of disease and pest organisms prevalent in their established growing range. This contrasts with newer strains which are developed for their ability to adapt across a wide range of growing conditions. Without the generational links to any particular environment, new strains have a limited capacity to resist the increased quantities of disease and pest organisms which they will potentially encounter. As a consequence of this, many of the newly developed varieties are highly dependent on the sustained chemical treatment and related practices, which are routinely prescribed for conventional fruit growers.
In many cases the plants offered to fruit growers will be heavily sprayed, and are likely to be bred from similarly treated stock. Occasionally, these plants will be separated from chemical treatments for a generation or two, and may even be described as organic varieties in order to command a premium selling price. Despite promotional efforts, these varieties do not possess a genuine pedigree and on account of their impoverished resilience, are unlikely to survive the rigours of an organic fruit orchard. For these reasons alone, fruit producers who remain committed to the organic movement must exercise considerable caution in their choice of stock. For long term success, they depend upon the availability of healthy varieties which have been developed over extended periods within their local growing conditions.
With the exception of melons, pears, and strawberries, there are few species of fruit which can be routinely cultivated from seed. Most of the fruit we consume is propagated asexually, meaning that it derives from a parent plant in the form of a grafted cutting, rootstock, or runner. In comparison to their wild ancestors, most domestically cultivated fruit species are hybridised and do not reproduce effectively or true to type from collected seed. For the sake of convenience, many fruit species are also cultivated on independent rootstock. Once again, this practice contributes to unpredictable outcomes whenever attempts are made to grow fruit plants from seed.
When propagating plants asexually, there is a tremendous emphasis which must be placed upon the health and vitality of the parent stock. For obvious reasons these plants need to be developmentally mature and entirely free of disease. To maintain their disease free status, temperate climate fruit such as apricots and cherries are best propagated in extremely arid regions subject to heavy frost. While these conditions may be considerably harsher than those recommended for commercial fruit production, they possess the benefit of eradicating many strains of disease. Successful propagation of fruit varieties usually requires such tailored conditions, and many are known to be notoriously difficult to manage. For this reason, inexperienced growers are well advised to source their juvenile fruit plants from a reputable organic breeder.
Popular hardwood fruit species such as apples, cherries, blackcurrant, and blueberries can be propagated from carefully selected cuttings. Most sources recommend obtaining these about two weeks after autumn leaf fall, well before the first buds have opened. Damaged or blemished sections of growth are inappropriate for hardwood propagation, as are any sections obtained from diseased or suspect trees. For best results, healthy stems must be selected from the previous season’s new growth and should be around two hundred millimetres in length with a diameter approximating that of a standard drawing pencil. Using a sharp knife, selected stems should be cleanly dissected from their parent plants with the cuts angled to promote water runoff and discourage stagnant dampness and associated problems.
Once removed, the cuttings can be temporarily placed in a jar of water and stored in a cool location. To plant the cuttings, narrow propagation trenches are dug to a shallow depth, enabling approximately fifty millimetres of the shoot to be exposed above ground, ensuring that the carefully angled cut is uppermost. The trench is loosely filled with coarse sand or a fine grit to assist root development and discourage rotting. These cuttings should then be allowed to take root for an entire growing season before lifting and permanently planting at the commencement of a new budding season.
Softwood fruit species like domesticated cranberry and grapes can be propagated from the green and sappy stems which develop from healthy parent plants in late spring and early summer. Measure approximately one hundred millimetres of stem and then dissect below the nearest leaf node. Remove the lower leaves so that roots will develop from the bare nodes and insert stems into a tray of organic potting mixture. Selectively prune upper foliage until there is no contact between individual leaves. Check on the condition regularly and immediately discard dead stems and any which appear sick or diseased. Once the stems recommence growth, they should be individually potted and maintained until the following spring when they are ready for outdoor planting.
Creeping vines and cane fruit can be propagated by the separation of suckers and runners where available or by selective root cuttings. Quality strawberry vines and domesticated raspberry bushes should be inspected for new runners and suckers at the end of their fruiting season in autumn. Clumps of strawberry runners should be divided to ensure a bud and root for each new plant. These can be planted to earth directly or potted and replanted the following spring. Raspberry suckers are treated in similar fashion, separating the rooted suckers in autumn. Blackberry canes can be propagated from root cuttings which are separated from parent stock in winter. With a very sharp knife remove fifty millimetre long root sections of approximately ten millimetre diameter, ensuring these possess at least one bud for renewed growth. The cut closest to the parent plant should be straight and the distant end trimmed at an angle. New cuttings should be wrapped in hessian and stored in a cool, dry, location for several weeks before potting with an organic growing medium. Encourage new growth by keeping the plants moist and providing them with plenty of warm sunlight. They can be safely planted into open ground the following spring.
Grafting and budding are propagation techniques frequently used by professional plant breeders. Both involve transplanting a carefully cut portion of a breeding plant onto the woody stem or branch of a supporting stock. There are many situations where both techniques will benefit organic fruit production. For example, it is common practice to graft apple and pear cuttings onto dwarf rootstock, thereby limiting the size and nutrient demands of each tree without substantially altering the desired qualities of the original breeding variety. A special rootstock may also be selected for beneficial qualities such as an ability to resist fungal or parasitic disease in susceptible soils. Because grafting and budding are both challenging techniques to master, amateur growers are well advised to seek professional assistance from a reputable source, such as an organic propagation nursery.