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Growing Tomatoes in a Greenhouse

by Matt W (Greenhousestores)

Tomatoes come in a baffling array of colours, sizes, textures, and flavours. Heirloom striped Tigerellas, pink Brandywine beefsteaks, old Italian classics like the oblong San Marzano, and wild selections like the mini Currant tomato are just the tip of the iceberg in terms of what is available on the market today.

Choosing Your Tomatoes

There are a number of factors to take into account when choosing which tomato is best for growing in your greenhouse.

Climate: Outdoor or Greenhouse?

The first thing you need to determine in selecting the right tomatoes to grow is the climate in which they will best produce fruit.

Since greenhouse space is valuable, if you are cultivating a tomato cultivar that can withstand the challenges of the season outdoors, it is best to transplant it out after starting it in the greenhouse, in order to maximise the hothouse space available for cultivating less weather-adapted specimens.

Pedigree: Heirloom or Hybrid?

There are costs and benefits to cultivating each kind of plant. As a rule, heirloom plants tend to have more varied flavour, shape, and colour profiles, whereas hybrids tend to be more vigorous, have superior disease-resistance, and a longer shelf life.

Heirlooms are more often than not preserved by home gardeners, whereas hybrids--more suited to mass-production--tend to be what can be found in farmer’s markets or grocery stores.

For gardeners with a little more horticultural aptitude, a novel solution to getting the best of both worlds is in grafting heirlooms to hybrid rootstocks. This way, you can get all the taste and uniqueness of an heirloom, with some of the disease resistance and vigour of a hybrid.

Purpose: Fresh Eating, or Cooking?

It’s important to read about how the tomato you are planning to grow is best consumed. While some tomatoes--like beefsteak and cherry tomatoes--are excellent for fresh eating, others--like plum tomatoes--are perfectly suited for processing, into preserves like tomato paste.

Harvest: Determinate (Bush) or Indeterminate (Vine)?

Determinate tomatoes are generally stocky, bush-shaped plants that will bear a single crop in a particular time of the season. Thus they are great if you are planning canning projects like sauces, salsas, and pickled tomatoes. Generally, they require a tomato cage for support.

Indeterminate tomatoes grow on a tall, vine-like plant, and will bear continually. They require supports to grow, and are great if you want a longer-term harvest plant that delivers fruit for fresh eating. They require trellising infrastructure, and vertical space in the greenhouse.

Planting and Care

Sowing

Tomatoes are easy to grow from seed, usually germinating within 3-10 days of planting.

They should be sown in the greenhouse when the average daily temperature is between 21 to 27 ?C, so keep an eye on the temperature gauge to find the best time for sowing. If your growing season is short and the greenhouse takes a little longer to warm up, consider starting your tomato seeds in a kitchen window in early spring.

Transplanting

Tomato plants should be transplanted as they outgrow their pots or planting cells. If the plants are “leggy” (ie. tall but weak), the stem can be transplanted well below the soil line, where it will grow more roots.

The plants require abundant water, abundant sunshine, and abundant nutrients in order to be productive.

The best way to grow them is under irrigation, or in capillary (“self-watering”) planters, which minimizes the risk of the plants drying out.

If space on the ground or shelves is unavailable, certain indeterminate tomato plants can be grown upside-down, or in a hanging basket.

They should have full-sun exposure, with adequate ventilation on the hottest of summer days.

Fruiting

Tomatoes require pollination in order to produce fruit. As most are self-fertile, they often don’t need more than a breeze to be fertilised; however, the best results are achieved with buzz pollination, which is something honeybees do. When the flowers are open, it’s best to open the vents and allow honeybees in: if there are no honeybees, the same effect can be achieved artificially with a handheld electric toothbrush.

Diseases

A common affliction of tomato fruits is blossom end rot, which causes the ends of the fruits to turn brown and open up to bacterial and fungal pathogens. This disease is caused by insufficient calcium, and can be treated with adding crushed seashells or eggshells to your soil mix, or using a tomato-specific fertiliser.

Other pathogens--like fungal blights, bacterial diseases, soil nematodes, and insect pests--can be controlled with good greenhouse hygiene, clean potting soil, resistant cultivar selection, as well as chemical pest control measures.