They are not reliably cold hardy in Britain, so are best grown outside in containers from late spring/early summer to the beginning of autumn, and then brought inside for the winter – preferably a heated greenhouse or conservatory. Most lime varietiess are less cold tolerant than lemons and oranges and need more warmth in winter than both of these.
Lime trees produce lovely, white, fragrant flowers that appear in spring and summer, as well as citrus-fragrant foliage. They are self-fertile, so you will only need to grow one tree to get fruit.
They don’t make great houseplants, as they need plenty of light and most rooms – apart from a conservatory – aren’t really light enough or suitable. They dislike central heating, as this makes rooms too hot and stuffy with a lack of essential humidity.
Lime trees need a warm, sunny, sheltered position outdoors in summer (mainly from early to mid-June until the end of August in most parts of Britain) and a well-lit position indoors for autumn, winter and spring – preferably a cool greenhouse or conservatory.
They ideally need a minimum temperature of 10-13C (50-55F); temperatures below 10C (50F) can cause damage to the plants.
Keep some horticultural fleece to hand to protect plants if sudden cold nights below the minimum temperatures occur.
They are best grown in large, heavy containers using John Innes No3 Compost or a proprietary citrus compost.
Some suppliers simply sell un-named “lime trees”, but you can buy specific varieties from specialist citrus nurseries, such as The Citrus Centre.
Lime trees are best bought in spring or early summer, giving them time to acclimatise to your conditions before the onset of autumn.
Water plants freely in summer, but never allow the pot to stand in water. Water more moderately from autumn to spring, allowing the compost surface to partially dry out between watering. Overwatering in winter is one of the commonest problems. Citrus don’t like very alkaline conditions, so use rainwater or de-ionised water if your tap water is very limey (hard). And, as they don’t like cold conditions and cold shocks to the roots, always use tepid water.
Mist the leaves in early morning in summer. Indoors, stand pots on trays of moist hydroleca or Hortag to help increase humidity or mist plants regularly.
All citrus are hungry plants and need good feeding. Use a high-nitrogen liquid feed plus trace elements from March-July. Then change to a balanced feed with trace elements until October. Specialist citrus feeds are a good choice and are available from garden centres selling citrus plants.
Lime trees don’t need much pruning, but can be reshaped if necessary in late winter by thinning out overcrowded branches. At the same time tall stems can be cut back to encourage more bushy growth lower down. Tall, leggy plants can be pruned back by up to two-thirds into strong, leafy growth.
Throughout summer, pinch back the tips of vigorous growth with thumb and forefinger to encourage bushy growth and more flowers.
When pruning, be careful to avoid their vicious thorns.
Small trees up to 90cm (3ft) high may need fruit thinning to reduce the number of fruit to no more than 20.
If plants need repotting into a larger container, this is best done in spring. But only repot when they outgrow their current container.
In years when repotting is not necessary, remove the top 2.5-5cm (1-2in) of compost and replace it with fresh.
The fruit develops a rich skin colour when fully grown and ready to pick, but it can also be left on the tree for longer if necessary.
Citrus can succumb to the following problems.
Leaf yellowing Excessively wet or dry roots; low temperatures; draughts; lack of nutrients.
Leaf fall Low temperatures; draughts, high temperatures in winter; overwatering.
Flower failure Poor/low light levels, lack of nutrients; erratic watering; low temperatures.
Poor fruit set Drying out; low humidity.