Growing your own lemon grass
PUBLISHED: 16:53 25 June 2014 | UPDATED: 16:53 25 June 2014
Lemon grass is both easy and inexpensive to grow and brings a welcome taste of the fragrant and exotic to the kitchen
Think of Thai cooking, and one of the first ingredients that come to mind is lemon grass. Think of English vegetable gardening, and the opposite is true – lemon grass is seldom on anyone’s to-grow list. Fortunately, the two extremes are reconcilable, and English gardeners who have a taste for the exotic can have the best of both worlds.
With its trade mark citrus flavour, lemon grass is more herb than vegetable. It is grown for its stems, which stretch upright from the bottom of the plants to a height of more than 60cm. The plants are free from pests and diseases, and as long as they have enough warmth, each one can produce dozens of stems in a growing season.
For something so exotic, lemon grass is both easy and inexpensive to grow. Granted, the plants need more heat than normal, but they are also boldly attractive and bring a welcome taste of citrus to the kitchen.
Genuine lemon grass used by the Thais seldom, if ever, flowers. Because of their recalcitrant nature, plants don’t form seed, and new ones can only be started vegetatively from existing stems. Fortunately, stems normally used for cooking make ideal propagating material, and they are readily found in Thai or Chinese shops, high street greengrocers and supermarkets. Because their tops have been trimmed off, they are only about 20cm long, and these are what you should be looking for.
To raise plants successfully, the stems must be fresh, so avoid any that look dry and wrinkled. Begin propagating sometime in May or the beginning of June (earlier dates are better) by first rooting the stems. Do this is by cutting off their tops and leaving 10cm bottoms, which are then put in a glass filled with water about 3 to 4cm deep. You could keep the glass on a sunny window sill, but to speed root development, place it in a heated propagator set at a high temperature: around 25º C will do. Roots will shortly sprout from the hard base, while new leaves will sprout from the upper end of the stem – both are signs that all is well.
Once the root system is well-developed (this is a judgement call since the timing is not exact), the stems are ready for transplanting. Fill a large pot - 7.5 litres or more - with a multipurpose compost. Make a hole in the compost about 3 to 4cm deep and wide enough to accommodate the roots. Carefully remove the stems from the glass so that the delicate roots don’t break, then nestle the roots of one or two stems in the hole. Refill the hole, pat around the base of the stems to firm the compost, and then moisten with a fine stream of water.
Lemon grass needs lots of heat so the potted plants should be grown in a greenhouse, conservatory or polytunnel. Don’t let the compost dry out, and give weekly feeds of a liquid fertiliser about a month after transplanting. Though any fertiliser will do, those with a high proportion of nitrogen are best.
As lemon grass grows, new stems are produced around the perimeter of the plants. Stiff, narrow leaves grow upwards in profusion, creating a distinctive architectural feel to the plant. Once there are a dozen or so stems, begin harvesting by cutting them just below the level of the compost. Don’t take too many at a time always leave some behind to produce new growth.
The leafy tops can be used to make a delicately-flavoured tea, while the bottom part of the stem, once cleaned, can be added to Thai curries and soups.
As autumn approaches, growth will inevitably slow down with the colder weather. Frost will kill the plants, so bring them inside if you want to overwinter them. But to be honest, lemon grass plants are so easy to start each year, overwintering may not be worth the effort.