Grow Your Own

by Angus Stewart

‘Protected environment’ houses, as greenhouses, glasshouses and poly-tunnels are often called these days, have some advantages in climate and pest control. They are great for propagating plants, because the success rate for growing cuttings and delicate seedlings is improved by the increased heat and humidity, as well as your ability to exclude snails and other pests.

  However, there are a number of problems of which you should be aware. The first is that daytime temperatures can rise too high and ‘cook’ your plants. It is essential that these houses are ventilated at both the top and bottom of the structure to promote airflow. If necessary, open the vents during the day to cool the structure, and close them at night to conserve heat. This also helps to reduce humidity when it is too high. If humidity rises too much, plants can’t transpire water and hence can’t photosynthesise. If you have water dripping down the inside walls of the structure, it is too humid and you will have to allow in some fresh air.

  Another problem is the build-up of salts in the soil or growing medium. Because there is no natural rainfall leaching the salts away, and you only provide enough water for your crop’s needs, salts and other nutrients can accumulate – sometimes to harmful levels. Make sure drainage is suitable, and give the plants a heavy watering to remove excess salts and nutrients every month, especially during the warmer months.

  A small-scale ‘greenhouse’ constructed from protective wire mesh is known as a cloche.

  Plastic mesh supports for plants are an ideal option for urban farms, as they are cheap, lightweight and re-usable.

  PHYSICAL SUPPORTS

  Whether it is grown in the ground or in a raised bed, a plant needs to be held upright by something, and the job is usually done by the soil or growing medium. If the plant cannot support itself, it will fall over – and rotting of produce will become a problem. In the urban environment, we often want plants to grow upwards rather than outwards due to space and light issues. We can provide plants with all kinds of ingenious methods of physical support, such as stakes, trellises and wires.

  ‘Protected environment’ houses … have some advantages in climate and pest control.

  PROPAGATING AND CULTIVATING PLANTS

  FROM REPRODUCING PLANTS TO HARVESTING CROPS

  The garden beds in your urban farm are ready, but what sort of crops will you plant in them? You can purchase all kinds of plants from local nurseries and garden centres, but propagating your own plants from seed or cuttings, for example, is a fairly simple and very satisfying process. Later, when your plants are flourishing, it’s time to think about important maintenance issues, such as pollination and pruning, as well as harvesting the delicious products of your labour. In this chapter, we will reveal a wealth of handy suggestions and techniques that will help you on your cultivation journey.

  THE ART OF PROPAGATION

  Learning how to propagate plants is one of the most basic and vital skills we can teach you. The good news is that you can accomplish most of the propagating you need to do with very simple facilities, and often right where the plant will grow to maturity.

  The first principle you need to master is when to use sexual (seed) or asexual (vegetative) propagation techniques. Seed is produced by a sexual process that requires both a male and a female parent; this leads to genetic variability in the progeny (see the seed-saving section here for more information about this subject). Most agricultural crops propagated from seed are annuals that complete their cropping cycle within a year. Farming has largely been built on sowing the seeds of our major food plants – cereal crops, such as wheat and barley; vegetables, such as pumpkins, melons, beans and peas; and leafy crops, such as lettuce – directly into the soil in the position in which they will grow.

  Asexual (vegetative) propagation allows us to make exact copies (clones) of a single parent plant by taking cuttings or by using techniques such as division, layering, budding and grafting. An obvious advantage of asexual propagation is that we can reproduce precisely an outstanding individual plant. The vast majority of crops that are propagated in this way are long-lived perennial plants, such as fruit or nut trees, but there are also many soft-wooded perennial food plants that we propagate vegetatively, such as potatoes, garlic and sweet potatoes.

  Many fruiting crops, such as this pumpkin, produce numerous viable seeds that, when planted, become the next generation.

  Tips for success

  The source of your propagation material (propagule) is extremely important, as it determines the genetic potential of your crop. That potential is then realised when you provide an ideal growing environment for the crop (see The Environment for Urban Farming for more information). Heirloom varieties of various fruits and vegetables are rising in popularity for urban farms, as they have important genetic characteristics that have disappeared from varieties bred for industrial-scale agriculture and horticulture.

  When propagating your own plants, it is essential that you start with seed or vegetative material that is free of pest and disease issues, as many problems can arise from using infected propagation material. A good example of this is utilising potatoes purchased for food as a source of propagation material. Even though the newly sprouted tubers seem to produce healthy-looking shoots, the chances are high that they will be infected with one or more viral diseases that will significantly reduce the yield. The answer is to source virus-free seed potatoes from a reputable source, rather than use potatoes bought from a supermarket. Research the various issues that can affect a crop you want to propagate, so you can adopt strategies to ensure you minimise the risk of propagating a pest or disease along with the plant.

  Let’s look at how to propagate plants using the various methods that can be easily applied on the urban farm.

  Peas are best sown in situ, as they put down roots very quickly from their large seeds.

  PROPAGATION FROM SEED

  For the vast majority of plants that you may wish to grow from seed in your garden, all that is required to get them established is an area of prepared soil. Clear away any existing plants, and then use a mattock or hoe to break up the topsoil. Finish the tilling process with a garden fork and/or a stiff rake to create a very smooth seedbed. Soil conditioners, amendments and solid fertilisers (see Fertilisers) can be added at this point.

  Once you have prepared your seedbed, dig a furrow; the depth should be about double the diameter of the seed you will be planting. Sow enough of the seeds so that you will have extra plants if some of the seedlings are lost to pests and diseases. If too many seedlings survive, they can always be thinned out later. Fine seeds can be mixed with a spreader, such as fine sand, to ensure a more even distribution.

  It’s important to remember that the larger the seed, the more successful direct sowing will be. The large seeds of plants such as beans and peas are easier to handle than the fine seeds of plants such as parsley and broccoli, and there is a greater risk of the delicate seedlings of fine-seeded plants being eaten or otherwise damaged before they can grow large enough to be self-sufficient. If you have trouble establishing fine-seeded species, they will generally have a much better chance of survival if they are grown in containers in a protected environment before being planted into the ground.

  Left to Right: It is vital to prepare the seedbed well for good soil-to-seed contact. Sow the seeds at a depth that is twice their diameter, and cover the seeds with soil.

  Growing seeds in containers

  Propagating seeds in pots or punnets allows you to control the growing conditions as well as to protect small, vulnerable plants from predation and weed competition. This can greatly increase your success rate, particularly with very fine seeds, although larger seeds will also benefit from being grown in containers. For the urban farmer, commercially available seed-raising mix is a good investment, because it is specially formulated to accommodate the more difficult-to-raise seed types, and it is free of weeds, pests and diseases (although I have found over the years that a wide range of plant species will grow just as happily in ge
neral-purpose potting mix). Follow the same seed-sowing procedure as in the previous section on direct sowing.

  Seeds are very forgiving and will generally germinate perfectly well if the containers in which they are growing are left in a sheltered spot in the garden and are kept moist but not wet; this is achieved by watering them every few days in the absence of rain. A foolproof way of watering fine-seeded species is to stand the containers in a tray of water; the liquid moves up to the roots by capillary (wicking) action. This avoids the need for overhead watering, which can damage delicate new growth.

  Once the seedlings are big enough to handle, they can be transplanted either straight into their final growing position in the urban farm or into larger, individual containers such as plastic propagation tubes or (preferably) biodegradable pots. Seed germination times vary enormously from species to species, and it is worth doing a little research on what to expect. Most common food crops, for instance, have been bred for centuries, and their seeds have been selected for rapid and uniform germination. On the other hand, species that have not been widely cultivated – such as Australian bush-food plants – still have dormancy mechanisms that prevent all the seeds from germinating at once, a characteristic that ensures survival of a species by keeping some seeds in reserve in the soil.

  Fine seeds are best sown in a seed-raising mix, and then transplanted when the seedling is strong enough.

  Big seeds, such as those from zucchini, can also be successfully sown in pots. The resultant seedlings can then be planted in their final place in the garden.

  Left to Right: Leaf cuttings work well for edible succulents, but you can try them for any large-leafed crop. Cut off the midrib from the leaf, slice the leaf halves into smaller pieces if they’re too big, and insert each leaf section – long cut side down – into a propagating medium.

  Self-sown seeds

  Many of the species we grow for food are annuals that are propagated from seed. These plants grow rapidly and, depending on the weather conditions, will sometimes progress quickly to the flowering stage (known as ‘bolting’) and subsequently a seeding stage. A classic example of this is the herb coriander – it often runs to seed within weeks of being established, and it will readily produce viable seeds. We can easily save these seeds for future plantings, but often they are dispersed by birds or the wind before we have the chance or the inclination to collect them. If a seed falls onto a bare bit of earth in the garden, it will often germinate and grow in situ. There are three options for dealing with the resultant seedling:

  Leave the plant in place, and let it grow.

  Transplant it to another position in the garden, where it may be better suited.

  Consider it a weed, and pull it out (as the definition of a weed is ‘any plant that is growing out of place’).

  Seed collection For plants that shed their seeds as soon as they are ripe (such as beans and peas), tie an old stocking over the seed pods, and then remove it once the seed pods have opened. For fruits such as pumpkins and melons, simply scoop out the seeds and wash them under running water to remove any remaining flesh, then dry them in a cool, moisture-free place.

  Seed storage Regardless of the type of seeds you have, ensure that they are thoroughly dry by laying them on paper towelling (to absorb any excess moisture), then expose them to sunlight and moving air. To guarantee the longest possible life for your seeds, place them in an airtight container and store them in the coolest part of your fridge (not in the freezer).

  PROPAGATION FROM CUTTINGS

  This process refers to taking a part of a plant and using it to generate a whole new plant. While leaf or root cuttings can be used to propagate some plant species (see Angus’ website, www.gardeningwithangus.com.au, for more information on these uncommon forms of cuttings), the most important type of cuttings used to breed edible and medicinal plants is stem cuttings.

  It is possible to take cuttings from either woody plants (such as shrubs and trees) or soft-wooded (herbaceous) plants. Cuttings from herbaceous plants (such as sweet potato and many herbs) generally root much more easily than those from woody plants. However, the advantage of using cuttings from woody plants is that they are much tougher and will not dry out as easily as soft-wooded cuttings, and they can generally be placed under a shady tree and left to their own devices (however, we still need to water them every few days). A bit of research in books or on the internet will tell you the best type of wood and what time of year to take cuttings for the species in question.

  Plant Breeding on a Local Scale

  For thousands of years, farmers have been selecting and reselecting parent plants and saving seeds from them to create their own varieties (called ‘land races’ by plant breeders). Modern plant breeding for ‘factory farming’ has taken a different direction, because we are rearing plants that are designed for the needs of the grower and retailer, rather than those of the consumer. So, instead of breeding for the best crop nutrition or flavour, they breed plants that look perfect and are easy to transport, allowing them to survive the dreaded modern ‘supply chain’. Tomatoes are the perfect example of how fruits grown originally for taste and nutrition are now selected for their ability to bounce off the wall.

  Selecting and saving your own seeds is a very rewarding pastime that enables you to create varieties that are well adapted to your particular growing environment and that offer nutritious and tasty produce. You can use heritage species or modern plant varieties as the basis for your very own breeding program.

  Step-by-step guide to taking cuttings

  Shoot tips that are not in flower make the best cuttings. The length is generally not critical, but the cutting should have several nodes (the points where the leaves join the stem). If you have enough material, we recommend making your cutting as long as possible – this ensures that there is plenty of stored energy in the cutting. Always make the cut a couple of millimetres under a node, as this is usually the most active site for new root formation. Remove the leaves from the bottom third of the stem by simply running your finger and thumb down that particular part of the stem. Easy-to-root cuttings, such as those taken from sweet potato and tomato plants, can be planted straight into their final growing position, while species that take longer to root (using cuttings from woody material) are usually planted in containers so that the growing environment can be controlled. This will generally result in much better success rates.

  There are plant hormones that can be used to stimulate the growth of strong and healthy roots. These are commercially available as gels or powders – simply dip the bottom of the cutting in the hormone just before planting. The hormones have various brand names, and there are differing strengths; the weakest are usually used for soft-wooded cuttings, while the strongest are reserved for semi-hardwood or hardwood cuttings from woody plants. Scraping a sliver of bark from the bottom couple of centimetres of the cutting before applying the hormone treatment generally improves strike rates, as this exposes and stimulates cell growth in the tissue that will form the new roots.

  Left to Right: Root cuttings work very well for perennial plants, such as horseradish. Wash the soil off the roots, and slice them into sections with a slanted cut at the bottom. Push the slanted end into a propagating medium, so the top of the cutting is level with the surface.

  Left to Right: Soft-wooded cuttings benefit from being treated with plant hormones. Cut off a section of the plant below a node, remove the leaves from the bottom of the stem, and then dip the cut tissue into the hormone treatment before planting the cutting.

  How do I look after my cuttings? Those with lots of soft, moisture-filled leaves need to be kept fairly humid or they will dry out and die. For a small number of cuttings in a pot, you can create a mini greenhouse. Take a rigid plastic bottle, and cut the bottom off. Then simply place the bottle over the cuttings with the lid on, and position your pot in a shady spot in the garden. Other cost-effective options include planting your cuttings in recycled cherry-tomato containers or sma
ll portable trays (with a plastic lid) that are specifically designed for propagation.

  When are my cuttings ready? After a week or two, take the lid off the bottle (if you needed to protect the cuttings); after a few more weeks (or sometimes months), when you see roots emerging from the base of the pot, the bottle itself can be removed. It will take a few days before the plants have become fully ‘hardened off’, so keep them in a shady spot; ensure that the plants are well watered if the weather is warm. Soft-wooded cuttings should take a few weeks to strike roots, while woody cuttings will generally take a few months and will therefore require a little more patience.

  What do I do with my cuttings? Once they have ‘hardened off’ for a few days, they are ready to transplant. They can be either put into individual pots or planted straight into their final growing position.

  PROPAGATION BY LAYERING

  A handy method for vegetatively propagating species that are hard to strike from cuttings is layering. This is like taking a cutting, except that it is left attached to the mother plant, which continues to nourish it until it has developed its own root system. This method has no special requirements for greenhouses or other environmental controls. Another advantage is that much larger plants can be produced than is possible by cuttings – your layered section can have 30–50 centimetres of growth above the area where the roots are induced to form. By the time it is ready to go into the ground, the new plant will be quite substantial in size.

  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. There are a couple of particularly useful layering techniques that are successful for a wide variety of plants: simple layering and aerial layering.