Growing tomatoes organically
greenhouse tomatoes
greenhouse tomatoes

It’s tomato time again for most Australian gardeners, except for very frosty areas where it is still a few weeks early. In some tropical areas lucky growers can plant tomatoes all year round. Plants established in September and October should produce their first fruit by Christmas.

Tomatoes are the most commonly grown vegetable in the home garden - that probably means one of the most-grown plants in Australia. One reason for its popularity is that it is one of the easiest vegetables to grow. It is also a sensible plant to grow, because it has so many uses - in sandwiches, salads, soups, casseroles, sauces, stews and many other dishes - almost every meal can incorporate a tommie.

Undoubtedly the ultimate reason to grow a tomato in the back yard is taste. Only a rare shop bought tomato can challenge the full flavour of a home grown tom. And how could it be better, when you can lavish all that organic care and nurturing on it. With many varieties to choose from, you can grow a common all rounder tomato, or experiment with sauce varieties, salad tomatoes, cocktail varieties or a yellow coloured low acid fruit.

While a pretty good tommie is easy to grow, the art can be taken to extremes. Many jealous gardeners carefully guard the secrets of the biggest, earliest or tastiest tomato from their prying neighbours. But the secret is out - good organic soil preparation, even watering, and cautious use of simple, safe pest control practices will produce the best fruit on the block. Match the simple hints below with your favourite variety for real tomato taste.

Varietal selection

When I establish a new garden, I grow a wide variety of tomatoes in the first two years. This gives me some idea which varieties will perform well. From then on, I grow a few varieties each year, for salad and sauces, early and late season. I still try new varieties occasionally.

There are excellent new varieties, but the old stayers are still worth considering too. ‘Grosse Lisse’ is still the most popular tall staking variety, ‘Mighty Red’ and ‘Rouge de Marmande’ are also strong performers. Good shrub varieties are ‘Burnley Gem’ and ‘KY1’, and ‘Roma’ or ‘Amish Paste’ for saucing. Off course there is always room for a ‘Tiny Tim’ or another high yielding cocktail tomato.

The staking or ‘indeterminate’ varieties, are generally pruned to a few leaders, depending on plant vigour, and then laterals are removed from the major leaf axis.

Determinate varieties grow into a shrub, and don’t require pruning. Allow them to scramble over a piece of wire mesh, inclined to one side. This helps to keep fruit off the ground, where it is clean and easily seen for harvesting.

There are so many varieties of tomatoes. Unless you live in a very disease prone area, you don’t need to pay the high price for F1 hybrid seed. Ask local gardeners which varieties they grow with success.

Purchasing organic tomato seed and open-pollinated varieties

If you are not lucky enough to have access to an outlet for organic seedlings, try these seed sources:

Eden Seeds; MS 316, Gympie, Queensland, 4570

Phoenix Seeds; PO Box 9, Stanley, Tasmania, 7331

The Seed Savers Network; PO Box 975, Byron Bay, NSW, 2481

Diggers Seed Club; ‘Heronswood’, 105 Latrobe Parade, Dromana, Victoria 3936

Growing seedlings

Some of the best tomatoes I have grown came from the compost (tomato seeds survive a hot composting process) and I often transplant a strong looking plant straight from the compost to the tomato bed.

Tomato seeds are easily started in potting soil. Use a glasshouse or cloche if you live in a cool area, or grow them inside, on a sunny window ledge. Tomato seeds germinate in a temperature range between 12 and 30 degrees.

Don’t start them too early, as tomato roots need to be in warm soil. If you start too early, growth will be slow until the soil warms.

Many stores sell tomato seedling far too small to be safely transplanted. I let them grow four sets of leaves before moving them. If you can only buy the small punnets, grow the seedlings on in a pot.

If you save your own tomato seed, you may find they germinate erratically. Resolve this problem by washing the seed three times with clean rinse water, allowing it to soak a little each time. This will wash out some of the germination inhibiting chemicals contained in the seed coat.

Selecting the tomato bed

Tomatoes don’t like ‘wet feet’ so you have to keep the crown root (base of stem) from puddling. If your ground is not free draining, plant them on a mound.

Tomatoes also like plenty of sunlight. I have had very shady gardens where tomatoes produced fruit, but never the quantities they can produce with full sunlight for part of the day. Best to have a full eight hours of sunlight.

Plant rotation

Some growers insist on new ground for tomatoes every year. Two years is OK if there has been no history disease in the first season or in nearby plots. Soil borne diseases and root nematodes weaken tomatoes grown on ‘old’ ground.

Remember that the rotation has to apply to all members of the solanum family - including capsicum, chilli and eggfruit.

Soil preparation

Soil preparation is the key to best practice tomato culture. While the tomato bush is a gross feeder, it is also a constant feeder. It respond best to slow availability of just enough nutrient - a major feature of a well developed organic soil. Composted or well-rotted animal manures should be dug into the ground at least six weeks prior to planting - three months would be better. If you have not done this for your early tomatoes, its already too late - use only a well made garden compost immediately prior to planting, to avoid burning plant roots.

Soil fertility

Blood and bone is an ideal fertiliser for tomatoes and can be used safely at planting time, but you will need a potassium source too. A good general purpose organic fertiliser will also do the job. Don’t add too much fertiliser at planting time, it will only produce lush, bushy growth and won’t improve the quantity or quality of the fruit. Side dress additional fertiliser during the growing season.

Organic sources of potassium include composted poultry manure. granite dust and liquid seaweed fertiliser.

Don’t hesitate to use side dressings of potassium fertiliser or blood and bone during the growing season rather than trying to put all the goodies in the soil prior to planting.

Boron deficiency causes black areas on the stem tip, stunted tip growth and very low ‘bushy’ vine shape. Terminal shoots nay curl and die, or fruit may darken and die. use a handful of ordinary borax scratched into the soil around the plants. Most other trace element problems are solved best by compost and liquid seaweed fertiliser.


Transplant the seedlings deeper than they were planted in the pot or nursery bed, If there are five rows of leaves, you can plant up to or above the bottom row. Extra feeding roots will grow from the stem, and the deeper root system will aim drought resistance and hardiness.

Use a sieved compost around the roots and water thoroughly.


Pruned ‘indeterminate’ varieties to one or two leaders, depending on plant vigour, and remove laterals from the leaf axis.

Determinate or shrub varieties don’t require pruning. A low, inclined trellis will keep fruit off the ground.

You don’t need to prune foliage, it protects the vital stem and the fruit from burning or overheating and makes food (ie photosynthesis) for the tomatoes.

Broken or damaged pieces may be safely removed with clean (ie disinfected) secateurs.

Water management

Tomatoes are very sensitive to water management. They should be allowed to wilt a little between waterings and the rule is fewer, deeper irrigations. The best way to apply water will vary greatly between soil types, but flood irrigation once per week is a good guide to aim for (they won’t last this long in very hot weather).

Except for the odd wash-down with the hose to remove summer dust and freshen the leaves, or perhaps a fortnightly application of dilute liquid kelp fertiliser, do not wet the leaves of tomatoes (it encourages fungal diseases).

Keep the soil mulched once it has warmed up. Tomato roots will exploit the environment under the mulch, running over the old soil surface. Deeper roots draw moisture from below.

Early fruiting

Keeping the seedlings a little root-bound will promote early flowering, and a potassium rich liquid fertiliser will also help. Too much nitrogen fertiliser will delay flowering.

Overly harsh pruning also weakens the plant, delays fruiting and reduces yield. You only need to shape the staking varieties to one or two leaders and prune laterals. Minimal leaf removal for sunlight penetration is required in outdoor crops.

Pest control

Bugs think tomatoes are good food too. The worst pests are generally caterpillars, surface mites and sap sucking bugs.

Bronze surface mites cause ‘bronzing’ of leaves, especially low on the plant (they shelter in shady areas).

Caterpillar pests can be controlled with Dipel (bacillus thuringiensis) or by hand picking (at night, with a torch).

Whitefly are tiny white flying insects. They are easily controlled with an insecticidal soap or potassium soap in a mixture with citrus oil. If you have serious problems (such as in glasshouse culture) purchase the parasite Encarsia formosa from a mail order supplier or use yellow sticky boar traps (these have become quite common in garden centres over the last few years). Light spraying oils also work well on whitefly.

Trichograma wasps are excellent parasites of many tomato caterpillar pests. They can be purchased by mail order. All soft bodied pests and beetles can also be controlled with plant-based insecticides such as pyrethrum, garlic, chilli and neem oil or azedaractin, but use these poisons as a last resort to give the beneficial insects maximum opportunity to do their work.

Disease control

Organic disease control is limited severely in the choices of preventative chemicals, and for some diseases there are no chemical controls (this is true for all growers). Organic disease control therefore has to rely on the following:

• Varietal selection: It is possible to select varieties for disease resistance and F1 hybrids are often sold on these claims. Once the value of hybrid seed is considered, loosing a few tomato plants to disease is not a big concern for an average home gardener.

• Seed selection: I prefer to use organic seed so I save my own and I use several mail order sources, for variety and experimentation. ‘Mass market’ seeds are bred in a chemical regime, and may not perform well in a low input system, Hybrid resistance may be limited to one or a few diseases. Organic health is far better.

• Good hygiene: Keep the weeds under control. Remove and burn or dispose of infected plants early.

• Good nutrition: Good all round nutrition is a basic tenet of organic growing and it does work. Trace elements such as zinc have a major role in disease resistance, and any plant with adequate nutrition will have thicker, stronger cell walls which limit insect and disease attack.

• Natural preventative’s: Liquid seaweed fertiliser or herbal sprays, such as chamomile tea which is an excellent preventative for ‘damping off’.

Target spot produces brown circular spots on the oldest and lowest leaves. Leaves may also turn yellow and drop off.

Verticillium and fusarium wilt or ‘yellows’ are fungal diseases which may affect fruit, especially in hot weather. They are controlled by crop rotation and varietal selection. destroy any infected plants

Tobacco mosaic virus is a major problem for tomatoes. Smokers should wash their hands before touching tomatoes, and never drop butts in the garden.

Septoria leaf spot can also be a problem, especially if soils stay very well or are worked when too wet. It can be treated with Bordeaux mixture.

Bacterial canker is revealed by wilting of the margin of lower leaves. Leaves curl upwards, turn brown and die. It can be distinguished from Verticillium and Fusarium wilt because the leaf petiole stays attached to the stem

Blossom end rot causes the end of fruit to become soft and mushie. It is caused by a calcium deficiency, which can be induced by repeated cycles of droughting and waterlogging as well as calcium deficiency or mobility problems. Use mulch to help keep soils in good moisture status.

Blossom drop is sometimes mistaken caused by disease but is more likely to be caused by physical conditions such as overly dry soils, sudden cold spells, heavy rain or hail or high soil nitrogen.

Sunscold is another physical problem, especially when leaf pruning is used.


Vine ripe fruit is excellent, but tomatoes can also be ripened successfully by picking fruit when it is just pink in colour. An old wives tale tells us to leave them in the window sill, but they will actually ripen to a better flavour away from direct sunlight.


Don’t store home grown fruit in the refrigerator - it will taste better if ripened and stored at room temperature. You might not notice the difference with a supermarket tomato, but allow the full flavour to develop from your home grown tomato by keeping in a bowl. Use a plain brown paper bag or Peakfresh® bag for long keeping

The secret of the biggest tomato

There are excellent organic sources of beefsteak tomatoes, and other ‘huge-fruited’ varieties. Pruning off most of the fruit shortly after fruit set concentrates the energy of the plant into fewer, larger fruit. Always cull the fruit furthest from the vine in each cluster - the closest fruit to the stem is always the largest.

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