Great white trillium

Sun

Partial shade or dappled shade beneath deciduous trees; avoid hot afternoon sun.

Water

Keep evenly moist during spring growth, with good drainage. Do not let the soil become completely dry during summer dormancy.

Soil

Humus-rich, well-drained woodland soil, preferably slightly acidic to neutral; tolerates mildly alkaline soil.

Height

1-1.5 ft (0.3-0.45 m)

Spread

1-1.5 ft (0.3-0.45 m), slowly forming wider colonies

Flowers

Mid- to late spring; large white flowers often turn pink as they age.

Foliage

Three broad, pointed green leaves held in a whorl beneath each flower; foliage yellows and dies back in summer.

Growth

Slow; young plants can take several years to flower.

Care needed

Low

• Pollinators
• Cold hardy
• Wildlife
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Moderate

Toughness

Needs looking after

Pick your zone, country, light and whether you have pets.

1. Planting day

   1 ft (0.3 m)

2. After 1 year

   1 ft (0.32 m)

3. After 2 years

   1.1 ft (0.33 m)

4. After 3 years

   1.1 ft (0.35 m)

5. After 5 years

   1.2 ft (0.38 m)

   full size

About 5 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Mildly toxic: may upset a stomach

Native to

the US and Canada

Growth rate

Slow

• Water during dry spring weather so the root zone stays moist but not waterlogged.
• Apply a thin layer of leaf mould or well-rotted compost each autumn; avoid heavy feeding.
• Leave foliage intact until it has completely yellowed so the rhizome can replenish its reserves.
• Keep cultivation and digging away from the shallow rhizomes, and mark dormant clumps.
• Leave established clumps undisturbed; divide only when necessary.

Pruning. No routine pruning is needed. Remove dead foliage after it has fully yellowed, but do not cut or pick green stems.

Early spring

Watch for emerging shoots and protect them from slugs and browsing deer.

Spring

Water during dry spells and enjoy the flowers without picking their leafy stems.

Early summer

Allow foliage to yellow naturally; mark clumps before they disappear.

Summer

Check dormant planting areas during drought and water if the soil becomes very dry.

Autumn

Plant nursery-propagated rhizomes or carefully divide established clumps if necessary.

Late autumn

Top-dress with leaf mould and retain a loose covering of fallen leaves.

• Plant in small groups beneath deciduous trees for a white spring display before the canopy closes.
• Combine with ferns and hostas, whose later foliage fills the space left by dormant trilliums.
• Use beside shaded woodland paths where the flowers can be seen closely without stepping into the planting.
• Include in a shaded white garden with foamflower and Solomon's seal.

Garden styles it suits: Woodland, Wildflower, White garden, Secret garden, Traditional and Romantic rose garden.

Plant it with: Foamflower, Solomon's seal, Wild ginger, Christmas fern, Hostas and Virginia bluebells.

Wildlife: Flowers attract some native bees and other insects. Ants carry away the seeds for their nutritious attached structures, helping disperse them. Deer readily browse the shoots.

• Slugs and snails chew emerging shoots: inspect during damp evenings, remove by hand, and use wildlife-conscious slug control where needed.
• Deer browse leaves and flowers: protect plants with fencing or a suitable repellent; repeated browsing can weaken clumps.
• Rhizome rot in waterlogged soil: improve drainage or move plants to a raised, humus-rich woodland bed.
• Poor flowering after planting or disturbance: allow several years to establish, retain all green foliage, and check for drought or excessive shade.

Roots and rhizomes contain saponins and may cause nausea, vomiting or diarrhoea if eaten by people. Toxicity information for cats, dogs and horses is limited and inconsistent, so treat the plant as potentially harmful rather than safe to eat; keep pets and livestock from chewing it.

• Nodding trillium (Trillium cernuum)

  Its smaller white flower hangs beneath the leaves; great white trillium holds its larger flower upright above them.

• White trillium (Trillium ovatum)

  This western North American species looks very similar and also ages pink. It generally has shorter anthers and proportionally longer filaments; origin and close inspection are often needed.

• Painted trillium (Trillium undulatum)

  Its white petals have wavy edges and a conspicuous red-purple marking near the base, unlike the usually plain white petals of great white trillium.

Trillium refers to the plant's flower and leaf parts occurring in threes, while grandiflorum means large-flowered.

Propagation. Sow fresh seed promptly in a sheltered outdoor seed bed or pots; germination is slow and may take two seasonal cycles, with flowering often taking five to seven years or longer. Established, multi-crowned clumps can be divided carefully in autumn, but recover slowly.

Accepted botanical name

Trillium grandiflorum

In the US and Canada

Native in Canada and the lower 48 states.

Native range

Alabama, Connecticut, Delaware, Georgia, Illinois, Indiana, Iowa, Kentucky, Maine, Maryland, Masachusettes and Michigan.

Measured

Average height 23 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.