How to grow: Tomato
Tomatoes must be one of the most popular home-grown vegies of all – once you tasted a tomato you’ve grown yourself, there’s no turning back! They’re highly productive plants too and incredibly versatile in the kitchen.
By Phil Dudman
At a glance
Ease of culture: Moderate
Where: All zones
Best climate: Warm conditions
When: Spring (temperate to cool areas), autumn (tropical to subtropical zones)
Harvest: 14 weeks
pH: 5.8 – 6.8
• Tomatoes thrive in warm sunny conditions. They hate cold frosty weather and windy conditions.
• Ideal daytime temperatures for growing are between 21-29°C. Any higher or lower reduces fruit set.
• Spring is the best time to plant in temperate regions.
• In cool areas, plant spring and summer (from October onwards). You can get a head start for spring planting by raising seedlings indoors in pots on a warm sunny windowsill.
• Fruit fly and wet humid weather (which causes disease) makes growing tomatoes more difficult in tropical and subtropical areas. Grow them from autumn to spring in the frost-free subtropics and the dry autumn/winter season in the tropics – and choose hardier cherry varieties for less favourable seasons.
• A spot that gets a minimum of 6 hours direct sunlight is best.
• Tomatoes are tolerant of many soil types, but need high levels of organic matter to help resist pest problems, such as root-knot nematode.
• Add lots of compost and well-rotted animal manure before planting, as well as a balanced organic fertiliser, to provide nutrients required for healthy growing and fruiting.
Sowing and planting
• Seedlings are readily available in nurseries, but the selection is limited.
• Sowing your own seeds allows you to grow a greater variety of tomatoes – there are thousands of different types available – and it’s a far more economical way to go.
• Tomato seed remains viable for at least 2-3 years. One packet of seeds will last a few seasons, and it’s easy to save seed from your own crops.
• Seed germinates easily in temperatures around 25°C. In cool areas, seeds can be germinated in a warm sunny spot indoors when outside temperatures are too cold.
• Sprinkle seeds into punnets of seed raising mix, and keep moist in a warm position until they germinate (about one week).
• Prick out seedlings and plant into small individual pots (50-100mm wide) filled with potting mix mixed with homemade compost. Keep them in a bright warm spot until their roots have filled the pot. Don’t overwater them – they’re very prone to deadly diseases that rot the roots and stems of young seedlings.
• Don’t over-fertilise tomatoes when they’re young. Too much nitrogen will encourage lots of leaf growth, but very few flowers. Just give each seedling a tiny pinch of sulphate potash to help strengthen the plant cells, making the plants more resistant to disease and water stress. Tomato seedlings will fill their pots quite quickly. Allow them to become slightly pot-bound and almost starved of moisture and nutrients. Treating them in this way will help bring on early flowering and fruiting.
• This is the time to transfer young plants to your prepared soil – providing the soil is warm and the risk of frost has passed.
Box: Planting tip
Plant young tomatoes a little deeper than you would other plants – deep enough to bury the first set of leaves on the stem. More roots will form at this point, giving the plants greater access to moisture and nutrients.
Box: Staking or not staking
• Tomato plants have a naturally trailing habit and will cover a large area of ground. This is okay where space allows. Slip some dry straw under the plants from time to time to keep fruit off the ground and avoid rotting. The stems near the ground will often form additional roots, which will further benefit the crop.
• Staking will keep plants more contained and manageable, and avoid risk of fruit rotting from coming into contact with wet ground (a particular problem in areas of high rainfall). Plunge at least 2-3 hardwood timber stakes 4-6 foot long into the soil around plants at planting time. More vigorous varieties may require 3-4 stakes to provide an adequate framework for support.
Watering, fertilising and maintenance
• Steadily increase regularity and depth of watering as plants mature.
• Add a small handful of well-balanced organic fertiliser around each plant at planting, and two handfuls after six weeks, along with a tight fistful of sulphate of potash.
• Give plants a weekly application of liquid seaweed at half strength, to strengthen plant cells and help reduce disease
• Tomatoes ripen on the vine and develop the best flavours in temperatures around 25°C
• In warmer temperatures, pick fruit just as they start to turn pink and ripen in cooler conditions indoors
• Use sharp secateurs to snip fruit cleanly from plants to avoid damage to the fruit and plants.
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