Over the years I have accumulated orange and lemon trees without ever consciously looking for them and certainly not with the intention of making any kind of collection. At the time of writing, I have nine – mostly lemons but with three oranges.
The most recent are a couple of whoppers I bought on the spur of the moment when visiting Malvern Spring Show two years ago (which, now I think of it, was the last time it was on).
The first citrus I owned was a gift over 30 years ago from the National Trust garden at Peckover House, in Wisbech in Cambridgeshire. It was – still is – a cutting taken from the 300-year-old orange in the conservatory, which is reputedly the oldest surviving orange tree in the UK.
UK-based gardening expert Monty Don, shared his advice for thriving citrus trees. Pictured: Monty with some of his oranges
Until then I had never given them much thought but, given the provenance of this generous gift, I quickly found out how I ought to be looking after it.
No citrus is truly hardy and although lemons will survive quite a few degrees of frost, for most of us, our orange and lemon trees will need winter protection. They are ideally stored at a cool (but not cold) temperature, around 10°C, and with quite high humidity.
A rule of thumb is that if the air is dry enough for soft furnishings then it is too dry for citrus plants, which rules out most modern conservatories and certainly any centrally heated room. A cool greenhouse is fine, as is a frost-free shed, although they do need some light.
However, a darkish shed is preferable to a bright but too hot and dry living room. One of the first signs of any citrus being too hot and dry will be the shedding of its leaves, and plants can (and will) completely defoliate towards the end of winter if kept in conditions that are perfectly acceptable to humans.
The air needs to be humid but their roots can be kept very dry over winter. I water mine once a month or so between October and February.
They do not need feeding in winter as they benefit from a rest with no foliar growth, although flowers will appear, especially if there is some light.
Ideally I like to bring my plants outside sometime in mid-April or as soon as there are new shoots appearing. But this year April was frozen night after night so they stayed in the greenhouse until almost the middle of May.
When they do come outside, they should go in a sunny, sheltered spot and have a good soak. This is also the right time to prune.
Be brave, as citrus trees respond to hard pruning with vigorous regrowth. For best fruit production, encourage an open centre to the plant so light and air can get in and through the tree.
The flowers, and thus fruit, are produced on shoots made the previous year, so any new growth this year will not have any fruit until next spring and summer.
It is also a good idea to pick all and any ripe fruit in spring, although it looks very decorative, as it inhibits the formation of flowers and the ripening of young fruits.
Plants should be repotted about every three years, and the best time to do that is right now, in June. Lift the rootball from its pot and carefully remove about a third of the existing compost.
Trim any extra-long roots and repot with a peat-free compost with added grit to ensure the good drainage that is essential for them. If you have any sieved garden compost, add some of that too.
Finally, I feed my citrus trees with liquid seaweed weekly throughout summer, combining it with their weekly watering.
MONTY’S PLANT OF THE WEEK: RUSSELL LUPIN
Monty chose Russell Lupin (pictured) as this week’s plant, revealing it does best in well-drained but not too dry soil
The herbaceous lupin, Lupinus polyphyllus, comes from America, where it grows along streams and has loosely set flower spikes of faded pastels. In the 1920s and 1930s, George Russell bred them and his intense colours caused a sensation.
Lupins do best in well-drained but not too dry soil and do not like chalk. Deadhead as flowers fade, but don’t cut back too hard.
They are short-lived and resent being moved. Although easy to grow from seed, propagation of a particular colour combination is best done by basal cuttings in spring.
THIS WEEK’S JOB: PINCH OUT TOMATO SIDESHOOTS
Cordon tomatoes – the vast majority of all varieties – are grown as a single leading stem that carries trusses of fruit. But as they grow, they develop sideshoots which should be removed. Pinch them off in the morning, while the plant is still turgid.