How to Divide and Propagate Lily of the Valley from Pips

Division is the only method worth using

Lily of the valley increases by rhizome, and the rhizomes are so willing that division is essentially free. Any piece of rhizome carrying a bud and some roots grows into a plant, and a mature patch contains hundreds of them. There is no skill in getting it to take. The skill is entirely in choosing which pieces to plant and how deep to set them, because those two decisions are the difference between a new patch that flowers in its first spring and one that produces nothing but leaves for two years running.

Seed exists but is not worth your time. The red berries do contain viable seed, and it germinates after a long cold period, but seedlings take three or four years to reach flowering size and the plants you get are no better than the ones you would have had from a spade's worth of pips. The only reason to bother is curiosity. Every part of the berry is poisonous, so if you do handle seed, wear gloves and keep it away from anywhere food is prepared.

The most useful thing about division is that it is the same operation as the thinning an old patch needs anyway. A congested mat stops flowering, so you have to lift half of it every four or five years regardless. That work generates far more pips than you can use, which is why this plant travels between gardens as a gift more than as a purchase.

Reading the pips: which ones will flower

Wash the soil off a lifted section and look along the rhizomes. You will see two clearly different kinds of bud. Flowering pips are fat, blunt and rounded, noticeably wider than the rhizome behind them, and often with a visible slight swelling near the tip. Non-flowering pips are narrow, sharply pointed, and no wider than the rhizome. The difference is obvious once you have seen it side by side, and it is completely reliable: a fat blunt pip flowers next spring and a thin pointed one produces a pair of leaves.

This is why a division taken carelessly disappoints. If you simply chop a spadeful into blocks and replant them, you get whatever mixture was in that block, and in a congested patch that mixture is overwhelmingly thin pips, because congestion is exactly what stops pips fattening. You will have moved the problem rather than solved it.

So sort them. Take the fat blunt pips for the new patch and for anything you are giving away, and either compost the thin ones or line them out somewhere unimportant to fatten for a couple of years. A dozen good pips make a better new patch than a hundred poor ones, and they make it a year sooner.

Keep the roots on whatever you keep. A pip with its full spray of thin roots establishes in one season; a pip snapped off clean will still grow but spends its first year building roots instead of flowers.

Doing the division

The whole operation belongs in the dormant season, from the point the foliage has collapsed in autumn through to late winter before the buds start extending. The plant moves best when it is asleep and there is nothing above ground to support. Gloves throughout: rhizomes and roots carry the same cardiac glycosides as the rest of the plant.

1. Mark the patch while you can still see it Push canes in at the corners of the area you intend to lift while the leaves are still up in late summer. Once the foliage has gone, a dormant patch is invisible, and people routinely dig the wrong ground or miss half of it.
2. Lift in blocks, not by teasing Drive a spade in vertically around a block the size of a dinner plate and lift the whole thing out with eight inches (20 cm) of soil under it. The rhizomes run shallow and interlock, so trying to pull individual runners out of undisturbed ground just snaps them.
3. Wash the soil off and sort Hose or shake the block clean so you can actually see what you have. Separate the rhizomes into individual pips or short lengths carrying two or three, each with its roots, and put the fat blunt ones in one pile and the thin pointed ones in another.
4. Replant immediately, or wrap them Pips dry out fast once cleaned. Get them back into soil the same day, or wrap them in damp newspaper or moist compost in a plastic bag and keep them cool and dark for up to a fortnight. This is also how you post them to somebody else.
5. Set the depth precisely The bud tip goes half an inch (1 cm) below the surface, no more, with the rhizome laid horizontally and the roots spread out and downward in the hole rather than bunched. Deep planting is the commonest reason a division fails to flower in its first spring.
6. Space, water and mulch Four to six inches (10-15 cm) apart for cover within two seasons. Water in once to settle the soil around the roots, then lay one inch (2.5 cm) of leaf mold over the top, keeping it just clear of the bud tips.
7. Backfill and finish the parent patch Fork leaf mold or compost into the holes you have made in the old mat and firm it. The surrounding rhizomes will run back into that loosened ground within a season, and the thinned patch usually flowers better the following spring than it has in years.

Forcing pips in pots for early flowers

Because the flower is already formed inside a fat pip before winter, lily of the valley forces easily, and a pot brought into gentle warmth flowers weeks ahead of the garden. Choose the fattest, bluntest pips you have, six to eight of them to a five-inch (13 cm) pot, in soil-based compost with the tips just at the surface.

The cold period is not optional. The pips need a proper chilling, six to eight weeks below about 40F (4C), before warmth will do anything, so either lift them late enough that winter has already done the work or stand the potted pips outside in an unheated frame until midwinter. Bring them into a cool room at around 55 to 60F (13-16C), keep the compost just damp, and they will be in flower in three to four weeks. Any hotter and you get long weak stems and short-lived flowers.

Forced pips are exhausted afterwards and rarely flower again the following spring. Plant them out into the garden when the weather allows and treat them as a two-year investment rather than throwing them away; most recover and flower again in their second season outside.

Keep the pot out of reach in the house. It is a poisonous plant standing at table height in a warm room in midwinter, and the scent draws people to it.

Sharing it honestly, and what to record

When you give pips away, say what the plant does. Somebody receiving a handful of pips as a pretty scented woodlander and putting them in the middle of a mixed shade border is being handed a problem, and they will find out in four years. Tell them it runs, tell them it is poisonous in every part including the berries, and suggest dry shade under shrubs or a contained pot. It takes one sentence and it is the difference between a gift and a nuisance.

For your own records, note the date you divided, how many fat pips you planted and where, and how many flower spikes appeared from that new patch the following spring. That ratio is the single most useful number you can hold on this plant: it tells you how good you are at reading pips, and it settles the question of whether your divisions are failing because of depth, because of timing, or because you are planting thin pips and expecting flowers. Add a note on the parent patch as well, because a thinned patch that jumps back into flower the next spring is the evidence that tells you what interval your ground wants.

If you are lining out thin pips to fatten them, put them somewhere you are prepared to lose to the mat. They spread while they fatten, and a nursery row of lily of the valley is a patch of lily of the valley two years later.