Simple layering
This method is most suitable when plants, such as strawberries or raspberries, have branches or shoots that are close to the ground. A long stem is bent down to ground level; its neck is buried, and its tip is left sticking up out of the soil. The stem can be tied to a small stake with an old piece of stocking or similar flexible material to ensure that it stays under the soil. Once it is sufficiently well rooted, the stem can then be removed from the mother plant and potted up, or even planted straight back into the garden.
Another layering option is to follow the same procedure, but bury the stem in a pot filled with coarse potting mix (a 50/50 blend of general-purpose potting mix and either coarse river sand or perlite). This second option is very handy, as it eliminates the possibility of root damage when the layer is eventually removed from the mother plant.
To encourage root formation, make a cut in the part of the stem that is to be buried; this also makes it easier to bend the tip of the stem up. It is also a good idea to mix a generous amount of coconut coir into the soil that is used to backfill around the cut stem. Ensure that the soil does not ever dry out excessively during the root-formation process.
Left to Right: To layer a plant, pick a suitable stem and remove the leaves. Dig a shallow hole, and then bury a few centimetres of the stem in the soil – you can hold the stem in place with bent wire.
Left to Right: Aerial layering involves cutting a section of bark from the stem, packing the wound with a growing medium, such as sphagnum moss, and covering the medium with aluminium foil and/or an airtight material, such as heavy plastic.
For most plants, it is best to start the layers off in late autumn or winter, before the plant starts its surge of growth and new root production in spring.
Aerial layering
This method is suitable for fruit trees, such as apples and quinces. Choose a stem on the plant that is up to 50 centimetres in length and up to a finger size in thickness. Select a straight section of the stem, where you would like the new root system to form, and remove any leaves and shoots for about 10 centimetres along the stem. Then use a sharp knife to make a nick in the stem a few millimetres under the bark and about 2–3 centimetres long. This creates a flap of bark and stimulates the stem tissues where new roots will form.
Coat the cut area with a rooting-hormone preparation, which is available from most garden centres. Take some moist sphagnum moss or coconut coir and pack it into the cut to hold the flap open, as this will encourage root formation. Double over a generous length of aluminium foil, place a couple of large handfuls of the moist growing medium onto it, and then mould the foil around the cut area. It is also a good idea to enclose the foil ‘bubble’ in a layer of heavy plastic that is tied off at both ends, as this prevents the growing medium from drying out in warm weather. The moisture contained within should be sufficient to allow you not to have to unwrap your aerial layer during the rooting process.
After-care for layered plants One of the key indicators that a layer is ready to remove from the mother plant is shoot growth on the new plant. Success should come in a matter of weeks for easy-to-root species, but for more difficult plants it may take a number of months for a viable new root system to form. Carefully inspect the growing medium for new roots before cutting the ‘umbilical cord’ to the mother plant. To ensure success, it is a good idea to pot your layer, place it in a sheltered position and wait until roots emerge from the drainage holes before planting the layer into the garden in its final position.
Not only does the process of division rejuvenate the original plant … it also gives you a swag of new plants.
PROPAGATION BY DIVISION
One of the easiest of all propagation methods is the division of perennial plants. This is particularly suitable for plants that have a clumping habit, such as lemongrass, and those that form an underground stem (rhizome), such as banana, ginger and turmeric. Not only does the process of division rejuvenate the original plant and make it flower better, it also gives you a swag of new plants. It is a very simple process that is usually best undertaken in autumn; however, it can be done at most other times of the year.
Gently dig up the plant with a spade or garden fork. Split the clump up by simply pulling it apart with your bare hands; you can also use garden forks or an old serrated-edged bread knife for harder-to-break-apart types. Try to split sections off in such a way that you do not damage any healthy new shoots, although this is sometimes unavoidable and will not do any permanent harm. Err on the generous side when splitting up the clump – the larger the piece, the better the chance it has of survival. Leave at least three full-sized shoots and as many fresh white roots as possible on each piece to maximise your chances of success.
Remove any obviously dead sections as well as any withered leaves and roots and old flower stems before replanting. Finally, use a sharp pair of secateurs to cut the top third of the remaining healthy leaves to reduce the demand for water as the new plant re-establishes a root system. Many species can be planted straight back into the garden with good results; however, to be on the safe side, it is better to first plant your newly divided clumps into pots in a freely draining potting mix, and then place them in a shady spot until new growth starts.
SPECIALISED PROPAGATION METHODS
There are many specialised techniques for propagation that are beyond the scope of the average urban farmer due to the expertise and/or facilities required to perform them. These methods include:
grafting, where two different plants are joined together
budding, which is used for many fruit and nut trees
plant-tissue culture, which is used to produce clonal, disease-free plants.
It is certainly possible to use any or all of these techniques if you are working on a commercial scale, and there is abundant information on them in Angus’ book Let’s Propagate! as well as on his website; also try the Australian and foreign websites of the various branches of the International Plant Propagators’ Society (IPPS).
Left to Right: To divide a plant, dig up the root ‘crown’, and wash it to remove as much soil as possible. Carefully separate the clump into ‘plantlets’ that have plenty of healthy roots. These smaller plants can be potted up or planted directly into the ground.
Left to Right: Bulb propagation is very easy. Divide the bulb into separate bulblets, and plant these at the right depth (about as deep as the bulblet is wide). Cover the bulblets with soil or compost.
PROPAGATION FROM BULBS AND TUBERS
Crops such as garlic, onion and their relatives can be propagated from bulblets formed at the base of the parent bulb; in the case of garlic, it can also be propagated from tiny bulblets known as bulbils that form spontaneously on the flower heads at the end of the flowering season. These bulblets are planted in the same way as seeds, and they will take a year or two to grow to maturity.
Plants that grow from tubers, such as potato and Jerusalem artichoke, are handled in the same way you would a bulb – the small tubers are planted directly into their final position in the garden. A handy tip for propagating plants that grow from vegetative structures such as tubers is that the tender new shoots can often be used as a source of soft tip cuttings or simple layers to further multiply your stock, should you need to do this.
PLANTING
We covered seed sowing earlier in this chapter; however, we also have some helpful tips for transplanting established seedlings and cuttings that will improve your success rates. First and foremost, we recommend ‘deep’ planting soft-wooded plants such as tomatoes and potatoes. In other words, place these plants in the ground below the level at which they were planted in their pot. By burying the stem deeper than it was in the pot (particularly if the plants are a bit floppy anyway), you will stabilise them in the soil. Over time, new roots will form along the buried stem, which will stimulate increased water and nutrient uptake, resulting in better overall plant performance.
For long-term woody plants, such as fruit t
rees, we recommend planting at the same depth as the trees were in their pots. These trees are often grafted, and deep planting may cause failure of the graft union.
Whether you use the ‘deep’ planting method or the normal technique, your plant will benefit greatly from appropriate soil preparation before planting. Dig a hole that is at least three times the volume of the root ball, and mix in some compost with the soil you have dug out of the hole (this will be used as backfill around the plant’s roots). After planting and backfilling, it is worth creating a small well around the base of your plant to allow water to collect and then soak in directly around the root system.
POLLINATION
Where we are growing and harvesting fruits, pollination is a vital process that needs to be understood and considered. Our definition of fruit in this case is the seed-bearing part of the plant, so it includes vegetables such as tomatoes and pumpkins. In many situations, pollination happens spontaneously without our intervention; however, if we understand the process, then we can ensure that a pollination process occurs that maximises our desired result, whether that is a harvest of food or the collection of seeds for the next crop.
Many important crops – such as beans and tomatoes – self-pollinate, and they will not need any assistance from pollinators such as bees. Other crops – such as cereals – are wind pollinated (the clue here is that the flowers are inconspicuous, as they don’t need to attract pollinators). However, for most crops grown on urban farms, pollination is an essential process.
What is pollination?
Pollination occurs when pollen from the male parts of a flower (anthers) makes its way onto the female part (stigma). If the pollen is genetically compatible with the stigma, it germinates and grows a tube that transports the genetic material down into the ovary, where fertilisation of the ovule (which grows into a seed) takes place. Once fertilised, the seed develops and the fruit ‘sets’ and begins to grow. As the seed develops to maturity, the fruit reaches full size and usually changes colour to indicate that it is ready for harvest.
Grafted and woody plants are best placed in the ground at the same depth as they were in their pot, so the soil reaches no higher than the junction between the roots and the stem tissue.
Whether you use the ‘deep’ planting method or the normal technique, your plant will benefit greatly from appropriate soil preparation before planting.
Hover flies look like bees, and they feed on nectar and pollen. As they move from flower to flower, they help to pollinate plants.
There are two reasons why pollination is vital for the crops from which we harvest fruits:
The pollination process is often essential for fruit development. Indeed, for many crops, if pollination does not occur, the flowers will drop off without any fruit set at all. There are exceptions, however, as some crops can revert to self-pollination (in other words, they are pollinated by their own flowers) if cross-pollination does not occur. It is worth researching each crop to see whether it needs cross-pollination for the best possible fruit set, as some fruit and nut trees will need other varieties planted nearby for good pollination. In another interesting example, pumpkins and their relatives have separate male and female flowers. It is sometimes necessary to transfer pollen by hand from male to female flowers if insect pollinators are not present in sufficient numbers.
If we want to collect seeds for subsequent crops, then it is particularly important to understand the pollination process. When we collect seeds for propagation, we can be positive about the female parent because that is the plant from which we are gathering the seeds. However, unless we have hand pollinated the flower and ensured there was no chance of pollination from another source, we cannot be sure of the male parent. In turn, this means that we cannot be sure that the progeny from those seeds will be ‘true to type’ with the parent plant. In many cases, the progeny will be perfectly acceptable for your purposes. However, there may be the odd case where the progeny is not as good as the parents, particularly if you have started with F1 hybrid seeds that have been specially bred by commercial seed companies. The answer, if you want to collect your own seeds, is to research your sources and find varieties that have been produced by open pollination (where the seeds will breed true). Open-pollinated varieties can be sourced from entities such as Seed Savers (www.seedsavers.net), a not-for-profit organisation dedicated to maintaining the genetic diversity of food plants.
Bees see colours, so planting bright flowers will attract them to your orchards and vegetable plots.
Ensuring pollination occurs
Bees and other insect pollinators are attracted by colourful flowers – the showier the better. Therefore, growing a selection of plants with brightly hued blooms that appear at the same time as those of your crops is a good strategy. Long-term perennial herbs such as rosemary, lavender, bergamot, mint and thyme are the perfect complement to edible crops with less spectacular flowers, and they can be used as border plants around cropping areas.
It is not just exotic bees that are important as pollinators on the urban farm. Many other insects play a significant role, so having a garden that includes a variety of ornamental plants, both native and exotic, is extremely desirable. Australian bees are increasingly being kept in urban areas so they can be used as pollinators, and looking after these insects is a fascinating pastime to boot!
Espalier pruning saves a lot of space and allows light to enter the canopy – it also looks appealing!
BY THE LIGHT OF THE SILVERY MOON
‘Moon planting’ – an odd technique that involves planting according to the moon’s phases – lacks any evidence base. Our experiments have shown that plants are completely insensitive to the moon and its phases. They are, however, sensitive to day length (increasing or decreasing) and temperature, which is why we divide plants roughly into two types: cool season (plant in late summer to winter) and warm season (plant in late winter to summer). If you plant corn seeds in autumn, they won’t germinate – not because of the phase of the moon, but simply because they need soil to be at least 20°C to germinate. Plant cabbage in mid-summer, and it will bolt straight to seed – as its genes are hardwired to equate the long day length with the notion ‘seed fast before the summer heat kills you’. Our advice? Completely ignore any nonsense about moon phases. At best, it is an entertaining waste of time; at worst, it can lead to plant death.
PRUNING
Management of plant growth through pruning is a particularly useful tool whenever you are farming in small urban spaces. We normally think of pruning in association with woody plants such as fruit trees, but a little judicious pruning of herbaceous edible plants can also greatly increase yield and make plants easier to manage. It is important to observe very good hygiene when pruning, because fungal, bacterial and particularly viral plant diseases are readily transmitted from one cut surface to another.
Here are some examples of simple pruning techniques for commonly grown crops (as it is not an exhaustive list, it is useful to research the specific pruning needs of each plant on your urban farm).
Espalier This is a technique whereby fruit trees and vines are trained to grow in a single plane, such as flattened on a trellis or wall, by pruning unnecessary branches and carefully tying others to the vertical structure. It is a useful technique for urban farms, where space may be limited, as an espaliered plant does not take up much ground area. Keeping the trees flattened makes it much easier to maintain them and to reach the fruits for harvesting, while a wall can be used to create a warming microclimate in frosty regions.
Removing tomato laterals When growing tomatoes on a support, such as a stake, it is advisable to thin out the number of shoots that are allowed to grow and fruit. By pinching out the small lateral shoots that develop from the nodes along the stem, we can stop the plant becoming too dense with foliage, something that tends to encourage fungal and bacterial diseases of the foliage and fruits.
Maintenance pruning Regular annual pruning of fruit trees and vines k
eeps edible woody plants, such as citrus trees and grape vines, within a manageable framework in urban environments. Different groups of fruiting plants have their own particular growth patterns, and it is important to research pruning techniques on a case-by-case basis. It is beyond our scope to go into that level of detail here; however, the information is readily available in horticultural literature.
HARVESTING YOUR PRODUCE
Picking fruits and vegetables that you have grown is one of life’s greatest pleasures. With an understanding of the physiology of plant development and fruit ripening, we can harvest our crops in such a way as to maximise both the yield and the flavour of our food. Some crops, such as avocados and tomatoes, can be harvested before they have fully matured, and the ripening process can be finished indoors to protect your precious crop from predation by pests (particularly large animals, such as birds and possums).
Regular and timely harvesting of your crops every few days (or every day for some types of crops) will not only minimise any losses to pests, but also encourage your plants to produce more fruits or foliage. Generally speaking, leaving crops unharvested will cause plants to run to seed and to finish their growing cycle, so we can prolong their life (and total yield) by harvesting as often as possible.
Health and safety issues
Washing your fruits and vegetables properly after they have been harvested is a routine with which most of us are familiar. There are also two other dangers to look out for:
Chemicals – while we recommend avoiding the use of toxic chemicals wherever possible on the urban farm to control both pests and diseases (see our safer solutions described in the Pest and Disease Management section), sometimes they are an absolute last resort if your crop is being devastated. If the use of a toxic biocide becomes unavoidable, be aware that washing your produce will only remove surface residues of applied chemicals. Many chemicals are also absorbed by the plant. The clue to this is if a chemical is labelled as ‘systemic’, in which case it is transported within the sap of the plant – and you will be eating whatever residues are left in the plant. It is ALWAYS critical to observe the withholding periods that are given on the labels of biocides.
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