Gadenin日本語Get the appThree ways, and when each is the right one
Lemon balm is one of the easiest perennial herbs to increase. You can split a clump, root a cutting, or raise it from seed, and all three work. The question is only which suits what you are trying to do.
| Method | Best time | How long to a usable plant | Use it when |
|---|---|---|---|
| Division | Early spring as growth starts, or early autumn | Picking the same season | The clump needs renewing anyway, or you want plants fast |
| Cuttings in water | Late spring to midsummer, from soft shoots | Roots in two to three weeks, picking the following year | You only have a shoot, or you are taking it from someone else's plant |
| Seed | Sown in warmth in spring | A light picking by late in the first season | You want many plants, or you have no plant to start from |
| Volunteer seedlings | Lifted in spring while small | Picking by late summer | The parent has already seeded and you want a replacement clump for nothing |
Dividing a clump
This is the method to default to. It gives you plants that are already established, and it fixes the woody bare center that every lemon balm develops after three or four years. Do it in early spring just as the new shoots appear, when the plant is a few inches high and you can see what you are cutting.
Lift the whole clump with a fork. Shake enough soil off to see the crown, then cut it apart with a spade or an old knife into pieces the size of a fist, each with several shoots and a decent share of root. Discard the woody middle entirely. Replant the outer pieces at the same depth they were growing, water them in, and cut the top growth back by half so the roots are not asked to support more leaf than they can supply.
Autumn division works too, provided you do it early enough that the pieces root before the ground gets cold. A division made just before winter in heavy soil is the one most likely to rot.
Cuttings in water
Lemon balm roots very readily in a glass of water, which makes it the easy way to take a plant from a friend's garden. Cut a soft, non-flowering shoot about five inches (12 cm) long, trim it just below a leaf joint, and strip the leaves off the bottom half so nothing sits in the water.
Stand it in an inch or two of water somewhere bright but out of direct sun, and change the water every couple of days. White roots appear from the buried joints in two to three weeks. Pot it up once the roots are an inch (2 to 3 cm) long: leave it much longer and the water roots are brittle and struggle when they hit compost.
Pot into a small pot of ordinary compost, keep it shaded and evenly moist for a week while it adjusts, then treat it as a young plant.
Take cuttings from shoots that have not started to run up to flower. A flowering stem roots reluctantly and makes a poor plant even when it takes.
Cuttings straight into compost
This makes a stronger plant than water rooting because there is no transition, and on a herb that roots this easily the extra difficulty is small. Prepare the cutting the same way, push it into a small pot of moist gritty potting mix, and cover the pot loosely with a clear bag to hold humidity without letting the leaves touch the plastic.
Keep it out of direct sun and open the bag daily so it does not go moldy. In two to three weeks a gentle tug meets resistance, which means it has rooted. Take the bag off then and grow it on.
Using the seedlings you never sowed
Any lemon balm allowed to flower will seed itself, and the seedlings that appear around the parent in spring are free plants. They lift easily while they are two or three inches (5 to 8 cm) high and still have a fine root system, and they establish quickly if you move them straight into a prepared spot and water them.
Two cautions. Seedlings vary: some are markedly less fragrant than the parent, so rub a leaf and smell it before you decide which to keep and which to hoe off. And once a seedling is a season old it makes a deep root that resents moving, so lift them young or not at all.
When it does not work, and what to record
Cuttings that blacken at the base were taken from stems that were too old and hollow, or stood in water that was not changed. Cuttings that wilt and never recover had too much leaf left on. Divisions that fail were usually planted too deep, or made in autumn into ground that then stayed wet.
Because lemon balm roots so readily, take more cuttings than you need and throw the surplus away rather than nursing weak ones. And decide before you start where the extra plants are going, because three rooted cuttings become three vigorous clumps in a single season.
Write down the date you took each batch and the date roots showed. Rooting speed varies a great deal with the time of year, and after one season your own notes will tell you the fortnight in which lemon balm roots fastest in your garden, which is more useful than any general figure.