Citrus plants make ideal houseplants for brave gardeners.

The attractive evergreens are perfect for a greenhouse or conservatory, and offer a distinctly different harvest to our normal expectations in cool, dreich Scotland. They can be grown at an altitude of 1200m, but only in frost-free areas.

Where citrus trees were first grown isn't known for sure, but the general consensus is north-west India. They may have reached southern Italy nearly 2000 years ago, but were certainly being grown in Sicily 1000 years later. It's notable that they were taken to the New World by Columbus, not the other way round.

Citrus trees are subtropical woodland plants, so they need careful attention and should only be tackled by more experienced gardeners. Orange, lime and grapefruit are fairly tender, but some lemons tolerate slightly tougher conditions. Overnight lows of 10C are generally best for lemons, though some varieties cope with 5C.

During the summer, higher temperatures are the name of the game. Gardeners in the south happily cart their trees out to their sun-bleached patios, but those in Scotland have to keep them snug in the conservatory in all but the hottest summers.

Light is every bit as important as temperature. Tropical and subtropical plants grown indoors react differently to light than native species. Every plant needs to achieve a balance between the sugars it creates during photosynthesis and the resulting energy it uses for growing. This varies from plant to plant. Cacti need as much sun as possible for photosynthesis, but woodland ones want much less.

The common advice to give citrus plants as much sun as possible might seem strange for woodland species, but light levels in subtropical shade are much stronger than full winter sun in Scotland. So, with lemons as with some other tropical and subtropical house plants, you should lay on whatever winter sun you can. Citrus plants react badly to sudden changes in light levels and must be very gradually acclimatised to any changes you make. Plants become stressed by getting too much or too little sunlight. It's worth looking out for signs of this now, when the sun is weak. If the leaves of a plant start yellowing, becoming twisted or dropping off, it needs more light. And, in the growing season, etiolation is another sure sign of trouble. Leaves can easily shade each other from the sun. Often this doesn't matter, but when a plant is stressed, it often becomes spindly, preventing its leaves from cutting out light from its neighbours. And more of the stem is also exposed to the sun.

Citrus trees are dormant at this time of year so they don't require feeding and need only be kept moist. Water a tree when the surface of the compost dries out, but don't soak the soil as this will damage the tree. It needs generous feeding and watering while growing in the summer, but not now.

There's no doubt that with lemons, like all fruit and veg, home-grown tastes best. Every Hogmanay, my son's girlfriend Tanya arrives with lemons from her parents' garden in Greece, as well as a wee bottle of Greek brandy, Metaxa. Both taste great. If you'd like to have your own lemon tree in the conservatory, Garey's Eureka seems a good choice. This popular variety flowers and fruits most of the year.

Another possibility is Citrus x limon "Meyer". Hailing from China, Meyer's lemon is a cross between lemon and either mandarin or common orange. It's a compact, spiny evergreen with dark glossy leaves. The white flowers with a purple base are quite fragrant and the fruits deeper yellow and rounder than most lemons.