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The best time to plant tomatoes

Labour weekend is the perfect time to plant tomatoes, but other factors need to be right, too, if you want good crops.

Tipping laterals on a tomato plant. Photo/David White.

Skype is marvellous. While I was overseas on a long work trip recently, the morning video calls somehow made the distance seem ordinary and normal. Being “with” the family at the kitchen table gave me a view of not just the family but also the garden. I could see the first sweet pea flowers opening and the broad bean plants weighed down ready for harvesting.

Well, it was like that for a while, but then the camera revealed a new sight: the bamboo stakes standing strong, but the beans arcing outwards in a circle. “What’s happened to the beans?” I asked. “What do you mean?” replied the family, adding “they are delicious”, and “we did water”. This was the most I could get out of them.

On my return, my suspicions were confirmed, although the Skype camera had shown things to be better than they were. My broad beans hung sagging and limp, still cropping with beans but too sad for a gardener’s eye. No explanation was forthcoming. Unfortunately, Skype doesn’t provide the arms to reach out and re-tie, water and feed plants, so although it’s a good thing, it’s not the real thing.

But the broad beans are yesterday’s news. It’s finally tomato season and now I have the ideal sunny spot ready to fill.

Labour weekend is the perfect tomato planting time, and the pay-off for patient gardeners who didn’t plant early is that they’ve avoided the cold snaps and stormy weather of the past couple of weeks that would have set back the plants.

First, decide whether you want to start with plants or seedlings – although your choice may be dictated by the availability of your chosen variety.

If you want a healthy crop, put the stakes in place early, tie the plant to the stakes and remove the laterals as the plants grow. Photo/David White

Select a plant with strong top growth as well as a good root system, as both are important for crop performance. This is why watering tomatoes must be consistent, especially if they’re being grown in containers. Deeper watering that’s less regular is better for the roots than frequent shallow watering.

I recommend watering pot plants every second or third day and the garden every third or fourth day. Water must go straight to the roots and not be applied to the foliage. Tomatoes don’t like wet leaves, and fungi will thrive in such conditions.

Tomatoes should be given the warmest spot in the garden, so don’t plant other crops that will overshadow them. Corn or beans will happily steal the best of the sun, so keep them to the south of your garden beds. Along a north-facing fence line is an ideal place for tomatoes, as it will retain warmth and provide shelter from strong summer winds. A sheltered position is always best, especially for taller varieties.

Feeding is a must for tomatoes. Start with good soil that contains plenty of fresh organic matter. Then use a liquid food that’s designed for fruiting plants, such as a fish fertiliser, as this will provide the high levels of phosphorus and potassium essential for a good yield. If the fertiliser carries only nitrogen, you may have healthy leaves but not much fruit.

Staking is also essential. Put the stakes in place early so you can support the plant as it grows, tying it gently with soft garden ties or old stockings. Staking a mature plant is likely to result in broken stems or damage to the soft tissue. Ascertain the likely final height of your chosen variety and use stakes that will go the distance; otherwise you’ll have to change them as the plants develop.

The night before planting, water the ground well, as this will give the plants a good start and help the roots head in the right direction.

Mulching will assist the plants’ water retention and root health, so is well worth the effort. If pea straw is a bit expensive, substitute a 1cm-thick layer of compost around the roots as the plants come into fruit. If you want super tomatoes, apply both (compost then pea straw) two or three times during the growing season.

Photo/David White

I recommend you remove the laterals as the plants grow. Tomatoes are essentially a vine and will get wild and tangly if left to their own devices. Laterals grow at a 45° angle to the main stem and should be pinched out when small. As well as making the plant unwieldy, laterals tend to be all leaf and so are a waste of the plant’s energy.

Their removal also improves airflow, which helps plants to stay disease-free. Keeping plants healthy can be a challenge as the crop starts ripening.

Tying plants to stakes. Photo/David White

Companion planting with aromatic herbs such as basil, garlic and chives and edible flowers such as marigolds and nasturtium will assist. To combat psyllids, commercial organic growers use a fine clear mesh to cover the plants, then spray with copper if fungus is a problem. For powdery mildew, a spray of baking soda diluted in water is a fast and effective treatment.

The first steps, though, should be good practice involving regular staking and feeding and a careful watering regime, especially as the summer holidays can divert our attention from the garden, leaving plants to suffer.

Before you disappear on a quick break, ensure there’s a watering plan in place and that the plants are staked and well-mulched. And don’t forget to turn off the computer. Some things are best left in the hands of fate.

Send your questions to: goodtogrow@xwd.co.nz