Gadenin日本語Get the appRooting a bought stalk in water
This works because a lemongrass stalk is not a cut stem but a whole shoot with its basal plate attached, and that plate still carries dormant root initials. What matters is not freshness in the abstract but whether the hard, slightly domed base has been trimmed off. A stalk cut flat across the very bottom will never root, no matter how you treat it.
Pick stalks that are firm, plump, pale at the base and, ideally, still show a few stubby brown root remnants. Take three or four rather than one: some fail, and they cost nothing. Success rates on good material are around half to three quarters.
- Trim the top, keep the base Cut the leaf blades back to about six inches (15 cm) above the base so the stalk is not supporting foliage it cannot yet feed. Peel off any slimy or damaged outer layers, but leave the bottom plate completely untouched.
- Stand it in shallow water Put the stalks in a glass with one to two inches (2.5 to 5 cm) of water, base down. Do not submerge the whole stalk: the part above water needs air, and a fully submerged stalk rots.
- Warm, bright, out of direct sun A bright windowsill at 70 to 80F (21 to 27C) is ideal. Below 60F (15C) very little happens. Change the water every day or two, or it goes cloudy and the bases turn brown.
- Wait for white roots White root tips push out of the base in ten to twenty days, and a new green shoot usually appears from the center at the same time. Wait until the roots are two inches (5 cm) long before potting.
If a base turns brown and soft in the first week, discard it and do not try to rescue it. Rot in the basal plate does not stop, and one rotting stalk fouls the water for the others.
Potting a rooted stalk without checking it
Water roots are brittle and thicker than soil roots, and they break easily. Pot with the same care you would give a seedling, and expect a pause of a week or two while the plant makes soil roots to replace them. A rooted stalk moved into a huge pot straight away often stalls, because the surrounding compost stays wet with nothing drawing on it.
- Start small Use a four to six inch (10 to 15 cm) pot of free-draining potting mix with about a third grit or perlite. Pot up into a ten inch (25 cm) pot once roots show at the drainage holes, usually six to eight weeks later.
- Set it shallow Bury the base only about an inch (2.5 cm) deep, keeping the point where new shoots emerge at or just above the surface. Planted too deep, the crown sits wet and rots.
- Keep it damp for two weeks Water in well and keep the compost evenly moist, not saturated, while soil roots form. After the first new leaf grows visibly, switch to the normal water-deeply-then-let-the-top-dry rhythm.
Dividing an established clump
Division is faster and more reliable than water rooting, and it is what you will use once you have one plant. A clump that has grown through a full warm season can be split into anything from three to a dozen pieces, and each piece with roots and at least two or three stalks will be a full-sized plant by the end of the following season.
Do it in spring, as growth restarts and before the plant puts on bulk, so the divisions have the whole warm season to establish. Autumn division going into cold weather is the common mistake and it produces losses.
- Lift or knock out the whole clump Wear gloves and long sleeves. Dig around the clump and lift it whole, or slide it out of its pot. Wash or shake enough soil off the base that you can see where the individual shoots join.
- Pull the clump apart Work it apart with your hands where it separates naturally. A tough old crown may need a knife or a spade driven straight down through it, which does no lasting harm as long as each piece keeps roots.
- Aim for two or three stalks per piece Single-stalk divisions do survive but they take a season to build up. Two or three stalks with a good root plate makes a piece that grows away immediately.
- Trim the tops and plant at once Cut the foliage back to eight to twelve inches (20 to 30 cm) so the reduced roots are not supporting a full head of leaf, plant immediately, and water in. Do not let the roots dry out in the sun while you work.
How fast one plant becomes many
This is the number that surprises people. A single rooted stalk planted at the start of a warm season commonly ends it with twelve to twenty stalks, and in a hot climate with plenty of water and feed, more than that. The clump widens outward from the base, so what you have in autumn is a ring of shoots several inches across where you began with one.
The practical consequence is that you almost never need to buy or root lemongrass twice. One plant, divided each spring, supplies as many plants as you have space for, and it means you can afford to lose one over winter without losing the line.
| Starting point | Time to a usable harvest | Plants you can take from it after one season |
|---|---|---|
| Rooted supermarket stalk | Three to four months of warm weather | Three to six divisions |
| Division with two or three stalks | Ten to twelve weeks | Six to twelve divisions |
| Bought potted plant | Six to eight weeks | Six to twelve divisions |
| Seed | A full season or more | Not worth counting on |
Seed, and what to record
Lemongrass rarely flowers in cultivation outside the tropics, so seed is seldom available and germination is slow and erratic even when it is. Sown on the surface of warm compost at 68 to 77F (20 to 25C) it takes two to four weeks to germinate, and the resulting seedlings need most of a season before they resemble a plant. Given how easily a stalk roots, seed is a curiosity rather than a method.
Keep a short propagation record: the date you set stalks in water, how many of them rooted, and the date each was potted. Do the same for divisions, noting how many pieces you took from a clump and how many were still alive a month later. Two seasons of that tells you your own success rate and how many stalks to start in order to end up with the number of plants you actually want.