Sowing and planting organic vegetables

There are a few genuine perennials but most organic vegetables are annuals selected for either warm or cool season propagation. Because they produce their entire crop within a single growing season, consistent outcomes depend upon sowing at the best times within the correct half of the year. A normal temperature range of 7-20 degree Celsius is ideal for cool season varieties. They are sown in autumn and the maturing vegetables will develop their distinctive flavours during the shorter days of winter. Some will tolerate cooler temperatures and frost better than others, so this is worth investigating for gardens of inland or elevated regions. Examples of cool season vegetables include onion, turnip, broccoli, cauliflower, brussels sprouts, and spinach.

Warm season vegetables prefer temperatures ranging between 20 and 30 degree celsius. These are sown in spring and grow most vigorously during the extended warmth of summer. Included in this category are the beans, capsicum sweetcorn, potatoes, sweet potato, and vine crops such as cucumber, zuchini, and aubergine. A group of vegetables including celery, beetroot, carrots, and silver beet prefer intermediate temperatures (15-25) and should therefore be treated as cool season vegetables in warmer climates or as warm season vegetables in cooler regions.

Starting with good quality organic seeds

When raising plants from seed, it is vital to obtain good quality supplies. Avoid using any seeds that may have been mishandled or stored incorrectly. The best option is to purchase from reputable organic suppliers who offer a guarantee of quality. Before planting, seeds must be carefully stored in a cool, dry location, preferably sealed against air and moisture. Each variety of seed will have its optimal storage period, although most will remain viable over several years. A simple test involves placing around twenty seeds onto a moist towel which is stored in a drying cupboard. After a few days a percentage of the seeds should have germinated. A minimum of twelve seeds (60% germination) is indicative of viable stock.

Many vegetable plants have large seeds which are suitable for direct sowing in prepared soil. In addition to convenience, direct sowing avoids the problem of transfer shock that can occur whenever punnet seedlings are suddenly introduced to outdoor garden conditions. Direct sowing avoids double handling but will also assist plants to catch up whenever their seasonal sowing date has been delayed. Corn, peas, beans, and most of the root crops like beetroot and turnip are ideal candidates for direct sowing.

The main disadvantage with direct sowing is that seedlings need to quickly establish themselves in order to compete against other plants for their share of sunlight, water, and soil nutrients. They may also need to withstand temperature fluctuations, soil borne disease and predation from insects, birds, and other animals. Green leafy vegetables, particularly traditional salad varieties, have small seeds and a delayed germination that often produces delicate seedlings. This restricts their ability to cope with conditions in the open garden. Modern varieties of lettuce, celery, spinach, and cabbage are now selected to produce rapid growth as seedlings. This trait assists them to secure territory quickly and offset the relative disadvantage of their small seed size.

Supervision and protection

Even when they have been directly sown, seedlings raised in outdoor gardens require appropriate levels of supervision. They are particularly exposed and vulnerable to unsettled cold periods and seasonal shifts of weather. Some protection can be provided by sheltering them with clear plastic tarpaulin, or the individual cloches that are sold in nurseries and garden supply centres. Covers made at home from plastic cups, sawn off drink bottles, or large diameter tubing can also provide some temporary protection that is both inexpensive and effective. Juvenile plants are susceptible to snails, slugs, and assorted larvae which will feed voraciously on new shoots and leaves. Simple physical removal is the most effective remedy against slugs and snails. The task becomes easier after dark when a flashlight is used to locate the feeding molluscs. When this is done consistently over several weeks, the local population will be significantly decreased, at which point weekly maintenance patrols should be sufficient.

New seedlings also require protection from birds and animals. Birds are initially attracted to the raked surfaces of new seedbeds where they bathe in the dust and capture any worms or larvae that become exposed near the surface. Once the seedlings emerge, many species will attempt to feed on them. Barriers constructed from semi circular hooping with fine mesh coverings will protect plants from birds as well as from other animals and domestic pets. Without this restraint, cats and dogs can cause a lot of damage to immature plants by physically rolling or digging within the garden bed.

Raising seedlings indoors

Raising seedlings indoors is the most convenient and popular method for controlling and protecting the early development of many plants including those grown as garden vegetables. Commercial organic and mainstream vegetable producers often rely on indoor sowing techniques to achieve the volumes required for viable results. Numerous seedlings are raised in small containers or punnets until they are mature enough to be transferred to outdoor conditions. One advantage of this method is an ability to sow on a given date, irrespective of external weather conditions. This requires spacious indoor nurseries that are climate controlled plus additional propagation equipment that can be expensive to purchase and operate.

Germination conditions

Whether raised indoors or sown directly into a garden, seeds require a well aerated, moist environment and a minimum temperature (around 10 degree Celsius) to successfully germinate. Seeds contain a fat store to provide energy for the first few days of growth. After this period they will be dependent on sunshine (or artificial lighting), moisture, air, and soil nutrients to facilitate their development. Depending on the variety, vegetable seedlings that emerge in clumps should be thinned after several weeks. Plants crowded too close together will compete for resources and can be prone to fungal disease, as the circulation of air is restricted. Removing the weaker plants at this early stage will reduce competition and enable the strongest plants to mature under ideal conditions.

Once they have reached a height around twelve centimetres, container raised seedlings can be transplanted into open ground. At this stage extra attention is required to ensure they are protected from direct sunlight or exposure to drying heat. Water them carefully the night before transplanting and discard any that appear weak or damaged. Overcast conditions or light rain can be ideal, since this helps prevent the delicate roots from drying out. Dark plastic bags can be used to cover seedlings and maintain a protective humidity. It is best to prepare several shallow soil depressions in advance so that each seedling can be transferred efficiently, with minimum handling. With a punnet positioned alongside the depression, squeeze the sides together, tilt upside down then reverse, allowing its contents to slip neatly into an open hand. Lay the transplant gently within the soil depression and secure with a handful of soil and a firm but gentle pat.

Interplanting, crop rotation and companion cropping have been used for centuries to improve the quality and efficiency of organic vegetable production. The techniques are flexible and relatively simple to initiate when sowing a garden. When space is limited, two crops can be planted together so long as they do not compete or interfere with each others growth.

The classic example of interplanting is to sow shallow rooted vegetables such as lettuces or spinach with deep rooted ones like carrots and beetroot. Crop rotation is used to protect soil quality as well as preventing soil borne disease. An example of effective crop rotation is a garden bed that grows legumes (peas or beans) followed by leafy vegetables such as spinach or kale. During their growth, legumes release bacterial enzymes, fixing nitrogen that will benefit leaf development of the subsequent crop. Companion planting is used as a means to control insect pests and to bring out rich flavours in organic vegetables. Evidence based research is limited however there are good publications available, containing regional surveys and planting recommendations.

Quick tip

A lot of the people we meet are absolutely passionate about their gardening. When the topic of seeds is raised there is always a widely agreed wisdom, which rarely changes. Start with the highest quality seed available. Purchase the stock from local seed merchants who care about their reputation. For a number of reasons, organic gardeners may prefer to obtain original heirloom or open pollinated varieties as opposed to the hybrid stocks which are commonly distributed by leading horticultural companies.

In partnership with her husband, Anne Foss operates a niche business out of Hallandale, Florida. Eden Organic Nursery Services (E.O.N.S) offer gardening enthusiasts a spectacular diversity of seeds, the majority of which are open pollinated. Anne explains that government regulations have now enabled hybrid stock to be organically certified. While these certified seeds may be chemical free, hybrid plants have generally been associated with increased levels of fertiliser and pesticide input. Selectively bred from distant relatives of the same species, hybrids were often developed to obtain increased yields. The downside is that many hybrid species have significantly lower resistance to disease and insect problems. By contrast, open pollinated or traditional plant varieties have been developed over centuries of agricultural endeavour. By breeding true to type, open pollinated plants possess an ability to adapt to local garden conditions. As an added bonus, many experts are convinced that produce obtained from open pollinated plants is superior in flavour or in the case of medicinal plants, contain higher concentrations of their active substances.