A SLICE OF SUNSHINE

Yes a good lemon tree can be pricey – but it’s an investment that will really bear fruit, says Monty Don

Last year I bought myself a present of two very large lemon trees. It was entirely unplanned but I was at the Malvern Spring Festival, saw the trees, had just finished working on my Paradise Garden and it seemed like the right thing to do. I do not have a smidgeon of regret. They are fantastic and covered in lemons, although the supply is steadily being used up as the gin and tonic season progresses. The point is that citrus trees, especially large ones, do not come cheap and they also need a suitable pot, which can often cost more than the plant. But they are an investment in happiness and so far the dividends have been very good indeed.

Lemons are the hardiest of all citrus plants, but until now I have always taken my citrus plants into a cool greenhouse in the middle of October and brought them out again at the end of April – with horticultural fleece to hand to protect them against any late frosts in May.

This works, although the danger is as much from winter warmth and dryness as early or late frosts. If you take a citrus tree into a centrally heated house over winter you will nearly always see the leaves turn yellow and curl up, with the plant looking very unhappy indeed by early spring. This is because the air is too dry. Ideally, they should be kept frost-free but cool – between 7°C and 12°C – with a fairly damp atmosphere in winter, and then they can have as much sunshine as is available all summer.

But these two new lemon trees were too big and heavy to take into the greenhouse, so I stored them in what we call ‘the bus shelter’, which is the loggia at the end of the Paradise

Garden. This protected them from the rain and the worst of the wind but not from the cold at all. Luckily, it was a very mild winter and we rigged up a screen of hessian and swaddled the trees in fleece when it was frosty.

The secret of potting compost for any citrus plant is drainage. Yellowing leaves are nearly always a sign of too much water, so add plenty of horticultural grit to your mix. Then there’s no need to water more than once a month in winter and once a week in summer. I scrape off the top couple of inches of compost in spring and replace it with sieved garden compost. Once the plant is outside I feed it weekly with liquid seaweed. It will need repotting with fresh compost every three or four years.

Lemons will take any amount of hard pruning, and produce fruit on the previous year’s growth, so don’t be frightened of cutting back hard – but do not expect any fruit from the new shoots until next year. They can, and will, produce flowers and fruit all year round, although it is a good idea to let them rest for a few months in winter by keeping them cool and shaded.

The smaller the tree, the more important it is to remove ripe fruit, even though it is very decorative, as it takes up a lot of the plant’s energy. Removing ripe fruit also stimulates flower production which, of course, will result in more fruit. Knowing when they are ripe enough is not an exact science, but if the lemon has a good, even yellow colour and shiny texture and looks ripe, then it probably is.

nRHS Gardens are open, using a pre-booking system, rhs.org.uk

Monty harvesting his lemons