The first thing to consider is whether the trees are evergreen or deciduous. Evergreens shed their leaves throughout the year, a few at a time, but few things can get established underneath then due to the low light levels. They tend to be surface-rooted and almost always dry out the soil close by.
The technique of planting beneath trees
If you have evergreens, create an understorey between your evergreens using perennial plants that will live for a number of years.
However if you have deciduous trees and shrubs it may be possible to plant right up to the trunks or main stems, although you may have to remove the lower branches of the shrubs. Look for friable soil among the roots so that you can fill the gaps between the roots, using a small border fork. Hopefully there will be areas to accommodate some plants and bulbs.
If the situation is hopeless you may have to start by sprinkling seeds to break up the soil. I recommend aquilegia and biennial honesty (confusingly called Lunaria annua) as a starting point. Try to get fresh seeds collected in July or August and sprinkle plenty. These should germinate in the following spring and develop tap roots that break into the soil. Wait a year or two and then try to plant some perennials in the ground they’ve penetrated, although you may have to dig your aquilegias and honesty up first.
Choosing perennial plants to plant under trees
Start with small plants, not whoppers, because these suffer less stress when planted. Water them in their first growing season to encourage their roots. Add some shade-tolerant spring bulbs in September and these could include snowdrops, scillas and miniature narcissi. Avoid crocus, or cyclamen, unless they are planted on a south-facing edge, as both need warmth and sun. Try to use some variegated evergreen foliage and sone white flowers, to lighten the gloom.
Twenty permanent plants for dry shade
This British native is a round, small evergreen shrub with dark, glossy rosettes of foliage topped with lime-green flowers in late spring. Berries may follow.
Hedera helix (carpet-forming English ivies)
Not all English ivies climb. Some sprawl very prettily with small leaves that come in ruched glossy green, like ‘Ivalace’. This will cover a metre (39 in) given time, but will never produce adult foliage and flower. Even more diminutive in scale are ‘Anita’ (a small green-leaved arrowhead) and the tiny-leaved, deep-green ‘Duckfoot’. The lime-green arrowhead ‘Goldstern’ will stay bright - for some strange reason, most golden ivies keep their colour in shade, but go green in bright light. Fibrex Nurseries have a wide range - www.fibrex.co.uk.
A fast-growing evergreen that often comes in spotted gold, as in the common variety ‘Crotonifolia’. However ‘Rozannie’ is a self-fertile aucuba that produces large red berries above rich green leaves that are waved and crimped at the edges. Aucubas can be cut back regularly every spring and will grow in dark places, although not all varieties berry on their own.
Periwinkle spreads by runners, but V. minor (the shorter form) produces a mesh of runners, rather than long wands that can root anywhere they land. It is very useful in deep shade and the white form, Vinca minor f.alba 'Gertrude Jekyll', has very neat white single flowers above shiny green leaves. V. minor 'Azurea Flore Pleno' is a slightly double bright-blue and there are also purple and red-flowered forms as well. All flower through spring and summer and there are also variegated forms.
Go for wintergreen ferns: they tend to be much more drought-tolerant than deciduous ferns that die away in autumn. The two best for deep shade and drier soil are Dryopteris and the Asplenium.
Dryopteris filix-mas (the Male Fern)
This strong and upright fern has crozier-shaped new fronds (like fiddle necks) that appear as the bluebells open in May. The fronds become scruffy by the end of the year, but cut back in December they reveal russet-brown knuckles that look very handsome in winter light. Capable of growing in very deep shade.
Dryopteris affinis 'Cristata' The King Fern
A handsome form with crested tip to the fronds. This fern is best grown on the lighter edges, rather than deep shade.
The Hart’s tongue fern is best grown in neutral or alkaline soil and it must have shade, otherwise the tongue-shaped leaves frazzle and scorch. Give it a sheltered position to keep the linear leaves looking pristine. There are many forms with ruffled edges, or crested tops, or lacerated leaves.
Asplenium trichomanes (our native Maidenhair fern)
This lacy fern loves a niche by a step, or a crevice, but would be best on the edge of shade. When happy it will spread.
Our native wood anemone comes in many forms, including white, blue and pink. However the blue and white forms are much better doers than the pinks. 'Robinsoniana’ is a very fine blue and slightly later than most. ‘Bowles’ Purple’ has purple-backed blue petals.
Pulmonarias can do well in shade, but the dark blue forms with plain-green leaves (like ‘Blue Ensign’) are more thirsty. ‘Opal’ has ice-blue flowers and spotted foliage, so it shows up well in shade, and ‘Leopard’ has brick-red flowers and foliage with silver dice-shaped markings.
A refined white campion that grows in deep-shade, even where it is dry. Spreads by rhizomes, but not aggressively so, and looks dainty and fresh in late-April and May, due to the pinked-edges on the petals.
Arum italicum 'Marmoratum'
A woodlander sometimes known as Lords and Ladies or Cuckoo Pint. The arrowhead-shaped green leaves are marbled in white, looking especially glorious in winter. However in summer the plant retreats underground, leaving a gap.
Euphorbia amygdaloides ‘Purpurea’
A refined form of our native wood spurge, with beetroot evergreen rosettes topped by lime-green, long-lasting flowers in spring.
The refined form, ‘Munstead White’ is beguiling in shade, with wide, single white flowers tipped in green. A. chrysantha ‘Yellow Queen’, is also stunning in shade and it will flower on into summer.
A shade-loving hardy geranium, often with sombre flowers that don’t show up too well. Seek out the fine white from ‘Alba’ or ‘Samobor’ which is dark, but with zoned foliage. It will self seed into choicer plants and is difficult to deadhead as the upper flowers open as seed is formed further down. Be prepared to prize the large seedlings out.
Another British native woodlander, with finely divided foliage and maroon-rimmed lime-green bells. Upright and handsome, with flowers that have a meaty scent - hence the epithet 'stinking hellebore'.
Where to buy
Plants for Shade www.plantsforshade.co.uk