Trilliums are by nature woodlanders most species come from North America, with a few species in Asia. They can easily be split into two distinct groups. The solely American group with upright petals directly attached to the leaf base called the sessile group with some 23 species. The pedunculate group contains 24 species and can be found in North America and Asia. These have flower stems and often reflexed petals.Trillium are generally placed in their own family Trilliaceae with other closely related genera such as Paris.
They are Spring flowering rhizomatous perennials, emerging in March or April, flowering, setting seed and dying down from July to October. The longer a Trillium can be maintained in leaf the quicker it will multiply and improve the flowering the following year. It is important to realise that reserves are made one year for use by the plant the next. In nature they grow with other plants such as Hepatica and Sanguinaria and can be grown as such in the garden.
How to Buy Trilliums:
Trilliums are not bulbs and don’t like drying out. They lose all living roots and will become limp and have little chance of surviving beyond the first season if bare rooted for any time. The best way to purchase a plant is to obtain a living established potted specimen from a reputable supplier.
Easily Grown Species:
The easiest species to grow and those which should start any collection are the following:
Trillium erectum – Dark red flowered species from eastern USA and Canada, with reflexed wide spreading petals, to 30 cm tall.
Trillium flexipes A taller growing species rather akin to T erectum but larger white flowers. To 50cm tall eventually.
Trillium grandiflorum– White flowered pedunculate species. The most spectacular easily grown species. To 40 cm tall.Trillium chloropetalum – The big spectacular dark red sessile group species, easy species to grow. To 45 cm tall.
Trillium cuneatum – Shorter in stature and flower size than the last but an easy sessile species with upright purple to green petals to
Trillium luteum A sessile group species with upright bright yellow petals and heavily mottled leaves. One of the easiest, best and last to flower. To 40cm tall eventually.
Where to Grow Trilliums:Trilliums grow best under deciduous shade in a soil that is humus rich and doesn’t dry out completely until midsummer. A prepared shady border against a wall or fence also is a good location. As few of us have ideal locations a general aim would be to have good fertile soil in shade (not coniferous), apple trees make ideal shade providers .The commoner Trilliums on the whole don’t worry too much about pH, but some such as T. undulatum do need an acid soil. It is probably impossible to give them too much water while they are growing away in spring. But beware of dank soggy soils which don’t drain. They dislike heavy clay, we are on such a soil and can successfully grow Trilliums and other woodland perennials by making humus rich raised beds around our trees. You can use rocks, logs or even peat blocks to support the beds. Irrigate the beds in dry weather in summer if possible particularly while new plantings are establishing.
Trilliums are very hardy and will take intense cold, they are unlikely to suffer from frost damage over most of Europe including all of the UK.
Trilliums are a bit like peonies in that they are best planted and left to establish into a clump over a number of years. Trilliums only produce one set of stems a year and will need full winter cold to break dormancy so if a plant is purchased in Autumn, plant it out, or if the conditions are unsuitable put the potted trillium in a cold frame exposed to winter temperatures but not excess moisture.
Plant the trillium out in spring as growth commences.
Trilliums are best divided in growth, about three weeks after they finish flowering, they will then root out and establish before autumn.
Seed has complete double dormancy and will need two warm spells and two winters to come up. It is best scattered on the ground around your plants and left to come up naturally. Any collected seed should not be allowed to dry out as if it does it will die.
Pest and Diseases
Trilliums on the whole are trouble free in a garden situation. They can suffer mild aphid attacks but natural pest predators should be able to deal with any outbreak. Some of the Sessile group in wet winters and springs can be susceptible to Botrytis most commonly Botrytis elliptica which will usually start as brown spots on the leaves and will gradually spread. A treatment with a broad spectrum fungicide will usually stop any disease in its tracks if it’s spotted early enough.
Green streaking or mottling on the flowers usually indicates an attack by a mycoplasma and will require the destruction by burning of the infected plant to stop it spreading to
Trillium erectum other plants. Thankfully this is rare but please don’t retain any plants for their novelty as they will weaken and damage others.
Trilliums associate well with a number of different plants which will extend the season of interest . Starting with snowdrops and hellebores and Cyclamen coum right through the growing season to Saxifraga fortunei cvs, Tricyrtis and Cyclamen hederifolium forms. One can grow a large range of shade loving plants with trilliums.