Tropical herbs need warm temperatures to keep growing year round, making them perfect plants for a greenhouse that’s heated during winter. I grow ginger, galangal, and lemon grass in my winter-heated greenhouse and use them to make delicious Thai food. Here’s how to cultivate each of them.
Ginger (Zingiber officinale)
There are several different types of ginger that you can grow in your greenhouse. Ornamental gingers provide colorful flowers, but for the home cook, fresh ginger has a taste all of its own and is not difficult to grow. If you want to start your own ginger for use in cooking, soak a supermarket ginger root in warm water overnight to remove the inhibitor that prevents sprouting. Then set it in a warm place (no light needed) until little sprout-like knobs appear, after which it can be planted near the potting soil surface in a wide, shallow pot. Keep it warm (over 60oF – 20oC)) and moist and wait for the plant to grow. Ginger prefers a moderately sunny location. In the wild it is an understory plant. At first, it will send up a single shoot, but eventually several other shoots will follow. Fertilize every week with full strength flower fertilizer such as Miracle-Gro’s Bloom. It can take up to six months for ginger to mature in your greenhouse. At that point, you can harvest it by simply pulling up the plant and using the new ginger roots, which are actually rhizomes, or underground stems.
There are two types of galangal, known as lesser and greater, each used in Thai and Asian cooking. I bought both these plants online, potting them up into larger pots as soon as they arrived and eventually transferring them into a bed in my winter-heated greenhouse. For months, nothing seemed to happen. But eventually, as the greenhouse heated up with spring’s arrival, the plants sent up leaves. The plant can be fertilized and grown using the same techniques as for ginger. Now I have two large clumps of leaves and assume there will be rhizomes to harvest by the end of summer.
Lemon grass is fairly easy to grow from seed. Just plant the seeds in regular potting soil, water them, and keep the tray warm (75o-80oF or 24o-27oC). As soon as germination occurs, place each sprout in a separate pot. Then, when the plants are about as tall as the length of your hand, transplant them into a larger pot or greenhouse bed. They’ll grow to a height of about 30 inches (75cm). They can now be harvested by pulling up the plant, but be careful of the razor-edged leaves, which can cut your fingers! If you leave the plant in its pot for one or two seasons, it will self-divide and eventually become a large clump of shoots. To propagate, simply plant a single shoot in a separate pot.