Gardening Magazine

Plant of the Week: Trillium Grandiflorum ‘Flore Pleno’

By Davis Landscape Architecture @DavisLandArch

Position: Flourishes in full sun to full shade.

Soil: Moist but well drained, will tolerate a wide pH.

Flowering period: Late spring.

Eventual Height: 40cm

Eventual Spread: 30cm

Hardiness: USDA Zone 3a-9b

Family: Melanthiaceae

Trillium grandiflorum ‘Flore Pleno’ is a perennial with a clump forming habit. It has almost stalkless ovate to rounded, dark green leaves(althought all of the above ground foliage being modified bracts with te true leaves being found as a protective papery layer over the rhizomes) that are up to 30cm long. It bears pure white double flowers which are produced above a whorl of three leaves being cupped at first then opening widely with broadly ovate, slightly wavy petals.

Native to eastern North America Trillium grandiflorum is also known as the Wake Robin. It is unusual in that ants that will carry them back to their nesting sites dispersing its seed. It is also used to measure grazing levels of deer, as they will eat the largest plants available so that the size of the plants is an excellent measure of how many deer are grazing in an area.

Trillium is derived from the Latin triplum meaning ‘triple’ alluding to the three-parted flowers common to the genus, with grandiflorum also being from the Latin, grandis meaning ‘large’ and flora being the goddess of flowers. ‘Flore Pleno’ alluding to the double flowers as pleno means ‘full’ in Spanish.

Trillium grandiflorum 'Flore Pleno' (22/04/2011, Kew Gardens, London)

Trillium grandiflorum 'Flore Pleno' (22/04/2011, Kew Gardens, London)

This plant is highly usefull to the landscape architect as ground cover particularly in exceptionally shady spots requiring no direct sunlight. The plant will however require space, as it will not flower until it reaches an adequate size, for both leaf area and root volume. It is also useful for soil stabilisation on slopes, as its roots will aid in erosion control.

The plant will tolerate a wide pH range so long as the soil is free draining. It requires consistently moist soil and should not be allowed to dry out during droughts.

Ecologically this plant will attract pollinating insects such as bees which feed on its nectar, although it is rarely frequented by them (this led to it once being thought of as self pollinating). It attracts ants as the elaiosome of the seed will evoke their corpse-carrying behaviour, their seeds are also spread by wasps (Vespula vulgaris) and harvestmen (members of the Arachnid family with a near global range). T grandiflorum is also a preferred browsing plant for deer.

The Royal Horticultural Society have given it their prestigious Award of Garden Merit.

Maintenance: requires little to no care, if the clumps become too large, they should be divided after flowering.

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