Whether you’ve grown your own from seed or bought them at the garden centre, you’ll want to get the best from your tomato plants this summer. Where you’re growing them outdoors, it needs to be a resilient and blight resistant variety to be certain that they’ll survive. And if they’re under cover, then it’s a good idea to provide good ventilation and some shade from the heat of the sun.
And of course, the plant will want enough water to prevent them from wilting. But they’ll also really benefit from periods when the compost or soil dries out to let air in for the roots to respire. This will allow them to more effectively take up water and nutrients. And the result of this will be that they’ll grow better, and the fruit will have an improved flavour.
When to start feeding tomatoes
With that all set in place, the plants will, by late May or early June, start to need some extra nutrients. There is usually enough to last 4-6 weeks in fresh compost, a growing bag, or soil. This baseline nutrition will have been enough to have got the plant going – roots, stems and leaves. But tomatoes benefit from plenty of potash if they are to produce a good quantity of flowers and fruit.
Without this potash, the plants would undoubtedly continue to grow and produce some fruit. But in order to optimise the amount of stocky growth, flowers and fruit, the nitrogen in fertilisers needs to be balanced against potash.
What fertiliser to use on tomatoes
There are lots of branded tomato feeds – usually in red bottles – and all of these contain high levels of potash. Bear in mind, however, that ‘feeding’ plants is very different to feeding ourselves. A ‘little bit extra’ won’t do the plant good. In fact it may actually do harm. Too many chemicals in a limited volume of compost can result in a build-up of salts. These can not only be toxic to plants, but may also cause water to be sucked out of the plant roots by their high concentration.
It pays to follow the instructions on the bottle and not exceed the application rate. In fact it may be worth growing the plants a bit ‘hungry’ to ensure the best flavour from the fruit.
How to make your own comfrey feed
An alternative to branded feed is to make your own from comfrey leaves and/or nettles packed dry into a black bucket and then covered. Place the bucket in a partly sunny place so it gets warm to speed up the breakdown process. Adding water to the foliage will usually cause it to smell.
The dark fluid that drains off as the leaves break down is concentrated and so needs to be diluted 1-part with 10-parts water, and applied a couple of times a week.
Instead, you could dress the surface of the compost with a small gloved handful of sulphate of potash powder. This will be washed down by watering. Such an application only needs to be made at 4 week intervals and is the way Victorian gardeners would promote good flowering and fruiting. Be careful not to overdose.
So here’s to a healthy, tasty crop of tomatoes – one of the best tastes of summer.