Lily of the valley

Light and exposure

Lily of the valley is a shade and part-shade plant, built to live under the cover of trees and large shrubs. It is there, in the dappled light of woodland or at the foot of a wall that stays shaded all day, that it gives its finest carpet of leaves and its most generous flowering.

It copes with a little more sun if the soil stays permanently moist, for instance on the shaded side of a hedge or under a deciduous tree that still lets light through in spring before coming into full leaf. In full sun with dry soil, on the other hand, the foliage scorches quickly and the flowering gets poorer year after year.

Watering

Once established, lily of the valley manages very well on its own in woodland soil that stays naturally moist. Watering is really only needed in the first year after planting, while the rhizomes root in, and during very dry summers, which are becoming more common across temperate climates.

In the full heat of summer it is normal for the foliage to yellow and flop to the ground: this is the plant’s natural summer dormancy, not a sign that it lacks water. Watering at this point changes nothing, the lily of the valley will come back from its rhizomes the following year regardless.

Soil and repotting

Lily of the valley wants a humus rich, cool soil, close to what it finds naturally in woodland: full of decomposed leaves, loose and well drained without ever drying out. Working in some compost or leaf mould at planting recreates these ideal conditions.

It tolerates neutral soils just as well as slightly chalky ones, and it is one of the few woodland perennials that does not insist on acid ground, which opens up most gardens to it. Only dry, sandy soil in full sun really causes problems: the foliage scorches within a couple of summers and the clump weakens.

Temperature and humidity

Lily of the valley is among the hardiest plants in the garden, from USDA zone 2 to zone 7. It withstands, with no protection at all, cold down to minus thirty-five degrees, since the rhizomes sit safely underground. No winter frost, however hard it bites, troubles it.

It actually needs that winter cold to flower well the following year, much like a spring flowering bulb: count on several weeks below five degrees. A winter that stays too mild clearly delays or weakens the flowering, and that is the whole difficulty with lily of the valley in a warm climate. Beyond zone 7 it needs the deepest shade in the garden and constantly moist soil to see the summer through.

Pruning and upkeep

Lily of the valley is not really pruned. Leave the green foliage in place after flowering: it keeps feeding the rhizome through photosynthesis and sets up next year’s flowers, exactly as with a daffodil.

In late summer or autumn, once the foliage has fully yellowed and died back, you can cut it down to ground level to tidy the bed. If young children or pets use the garden, also cut off the faded flower stems before the red berries form, since they are the most toxic part of the plant.

Pests and diseases

Lily of the valley is a tough plant, not prone to serious disease. In hot, humid summers, fungal leaf spots can appear on the oldest leaves, without any real consequence for the clump as a whole.

In spring, the tender young shoots sometimes attract slugs and snails, especially after wet spells as they push through the soil. A mulch of dead leaves, which otherwise suits it very well, can also shelter these pests: keep an eye on the young shoots as they break through the soil.

Propagation

Dividing the rhizomes, known as pips, is by far the simplest and fastest method. Split them in autumn, once the foliage has yellowed and died down, or right at the start of spring before growth resumes, keeping at least one well formed bud on each piece.

Space the pips ten to fifteen centimetres apart, they will fill in the gap within two or three years thanks to their spreading rhizomes. Sowing the seeds found inside the berries is possible but very slow, expect several years before the first flowers: division remains far preferable for anyone who wants quick results.

Toxicity

Lily of the valley is one of the most toxic plants found in gardens. The leaves, flowers, rhizomes and above all the red berries that appear in summer contain cardiac glycosides, notably convallatoxin, which act directly on the heart. Ingestion can cause nausea, vomiting, heart rhythm disturbances and, in severe cases, cardiac arrest, in people as well as in dogs and cats. Even the water in a vase that lily of the valley stems have stood in becomes toxic and should never be drunk or left within reach of a child or a pet. The sweet, tempting red berries cause a number of accidents every year: it is safer to cut the flower stems before the berries form if young children use the garden.

Month-by-month care calendar

Green Hub tips

• An unbeatable shade groundcover under trees and hedges, in spots where almost nothing else will grow and flower reliably every year.
• Contain the spreading rhizomes from the moment you plant with a buried barrier, or lily of the valley will take over an entire perennial bed within a few years.
• Never confuse its leaves with wild garlic when foraging: the two plants grow in the same woodland and look alike, but lily of the valley is highly toxic.
• The whole plant is dangerous, especially the red autumn berries: keep children and pets away, and never drink the water from a vase that lily of the valley stems have stood in.