Lily of the Valley After Flowering: Berries, Foliage and Building Next Year's Pips

The flowers are over in three weeks and the important part starts

The display itself is short. Each arching stem carries its row of white bells for two to three weeks in mid spring, and then they go brown and hang there looking scruffy. That is the visible part of the year finished, and most people mentally close the book on the plant at that point. It is precisely the wrong moment to stop paying attention, because everything that determines next spring's flowering happens in the following two months.

Through late spring and early summer the leaves are working at full capacity and feeding the rhizome, and the plant is doing two things with what they make: extending runners outward into new ground, and thickening the pips that are already formed. A pip that accumulates enough reserve by the time the plant goes dormant produces a flower spike next spring. A pip that does not produces two leaves and nothing else. That is the whole mechanism, and everything you do after flowering is either helping it or getting in its way.

Which means the leaves stay, entirely, until they die back naturally in late summer or early autumn. Cutting the foliage down after flowering to tidy up the bed is the most damaging thing you can do to this plant, and it costs you the following spring's display outright.

Deadhead or not, and the berry question

Deadheading is optional for the plant's sake and is not the way it builds next year's flowers, since the reserves come from the leaves rather than from redirected seed energy. The reason to do it is different: any flower that has been pollinated ripens through summer into a coral-red berry, and every part of that berry is poisonous. If children or animals use the garden, taking the faded stems off is a genuine safety job rather than a tidiness one.

Cut or snap the flower stems off at the base as soon as the bells have gone brown, wearing gloves, and take them off the bed. Do it before the berries form and color, not after; a green berry in early summer is easy to remove and a bright red one in late summer is the thing you were trying to avoid. Do not compost the stems in a heap that gets emptied where a dog roams.

If the garden is adults only and you like the berries, leave them. They are genuinely handsome in late summer, sitting low among the yellowing leaves, and birds take them and spread the plant to new corners of the garden, which is either a bonus or a nuisance depending on how you feel about the mat expanding by post. Seed-grown plants take three or four years to reach flowering size, so this is a slow form of spread compared with the rhizomes.

Whatever you decide, do it deliberately rather than by default. The berry is the single most likely poisoning route this plant offers, so the choice deserves five seconds of thought each year rather than being left to whether you happened to have pruners.

The eight weeks that build next spring

Three things help in this window, and they are all small.

1. Feed once, straight after flowering A handful of balanced general fertilizer per square yard, scattered over the mat and watered in, lands exactly when the leaves are provisioning next year's pips. This is more valuable than the early spring feed on a patch growing in the dry root zone of a shrub, where competition is fierce and reserves are thin.
2. Keep the soil damp through late spring This is the one time of year an established patch benefits from watering. A weekly soak of one gallon (4.5 liters) per square yard in any rainless week from the end of flowering until midsummer keeps the leaves working for several weeks longer than they otherwise would, and those extra weeks turn directly into flower spikes.
3. Leave every leaf alone No cutting, no tidying, no folding over, no mowing round the edges close enough to clip them. The leaves are the entire manufacturing capacity of the plant. Even the ones that go scruffy at the margins in a hot spell are still working.
4. Deal with weeds now, while you can see them Perennial weeds coming up through the mat, particularly bindweed and brambles, are easy to trace and pull in early summer when the foliage is still upright and open. Once the leaves flop in late summer, finding them means groping about in a mat of poisonous foliage.
5. Note where you want more, and where you want less The patch outline is at its clearest now. Mark with canes any area you intend to lift and thin in the dormant season, and any front edge you want to pull back. In late autumn, when the leaves have gone, you will have no idea where the boundaries were.

Dieback: early and ugly is normal

In dry shade the leaves often start to yellow and brown at the tips by midsummer and are fully collapsed by early autumn. This looks like failure and is not. Lily of the valley is a woodland floor plant that evolved to work through a wet spring and shut down as the canopy closes and the ground dries, and an early dieback in a dry summer costs you nothing, provided flowering and the weeks straight afterwards went well.

The exception is a patch that browns off badly in early summer, within weeks of flowering. That is genuine drought stress at the worst possible moment, and it will cost you flower spikes next spring. It usually means either full sun, a container that dried out, or a first-year planting whose roots have not spread. Water it, and if the cause is sun, plan to move it in the dormant season.

Once the leaves have collapsed properly, rake them off the bed. They are poisonous, so gloves on, and they are also where slugs and gray mold overwinter, so clearing the crown is the one autumn job worth doing. Do not dig around the patch while you are at it; you will only chop rhizomes into fragments, and every fragment grows.

The two lines to write down

Record the date the last bell went brown and the date the leaves finally collapsed. The gap between them is the length of the window in which the plant built next spring's flowers, and it varies enormously with how dry your summer was and how much shade the patch gets. A short window one year explains a thin display the next, which otherwise looks like an unaccountable failure.

Also record the week the berries reddened, if you leave them. It shifts by a fortnight between seasons, and if you have children or a dog it is the week you need to be out there with gloves and a bucket. Two years of that note and you stop being caught out by it.

If you cut the stems for the house, tip the vase water down an outside drain when you are done. Cut stems leach the same cardiac compounds into the water, so the jug is as much of a hazard as the plant, and it is the part everybody forgets.