Plants growing under tree canopies suffer from lack of moisture and nutrients because of the strong competition from the trees. Another problem is the lack of light.
Where the canopy is high and soil moisture retention is good, it may be possible to grow suitable plants well within the area of the canopy. Spring flowering plants such bluebells, lily-of-the-valley and hardy cyclamen may be clustered around the base of the trunk itself.
Planting under trees with low or spreading canopies is more restricted, and it may only be possible to grow plants at the perimeter of the canopy area. Common ivy is worth trying in even the gloomiest conditions.
Ground under conifers: It is very difficult to establish plants under conifers as the soil is dry and the evergreen canopy shades the site all year round. Often accumulating needles and debris create very acid conditions, making it difficult for anything, including grass, to grow satisfactorily.
Aspect: There is a greater chance of successful planting on the lighter south-west side of trees where rain is more frequently driven under the canopy, than to the north-east where conditions are usually drier and more shaded.
Planting and aftercare: Prepare the site by adding well rotted organic matter such as garden compost, farmyard manure or leafmould plus a dressing of general fertiliser (such as Growmore or fish, blood and bone) to enhance plant establishment. Autumn planting will allow plants time to become established before the leaf canopy develops in spring. Deep mulching and watering in dry spells for at least the first full growing season are important for successful establishment.
Shrubs for deep shade under evergreen or low tree canopies
Large evergreen shrubs
Buxus sempervirens (box) – dense bushy rounded shrub up to 5m (15ft) high that tolerates regular pruning to shape
Ilex aquifolium AGM (holly) – large dense shrub with glossy spiny leaves that tolerates regular pruning
Taxus baccata (yew) – dense large evergreen shrub/tree that tolerates regular pruning
Small evergreen shrubs
Daphne laureola – yellow-green flowers in early spring. Height 1m (3¼ft), spread 1.5m (5ft)
Gaultheria shallon – suckering, small pink flowers in spring are followed by purple fruit. Requires acid soil. Height 1.2m (4ft), spread 1.5m (5ft)
Lonicera pileata – spreading shrub with small creamy flowers in spring followed by purple berries; height 60cm (2ft), spread 2.5m (8ft)
Ruscus aculeatus (butcher’s broom) – clump forming, spiny foliage; female plants produce red berries in late summer. Height 75cm (30in), spread 1m (3¼ft)
Ground cover evergreen shrubs
Cotoneaster salicifolius 'Gnom' – small white flowers in early summer are followed by red fruit. Height 30cm (12in), spread 2m (6½ft)
Hypericum calycinum (rose of Sharon) – spreading shrubs with yellow flowers from mid summer. Height 60cm (2ft), spread indefinite
Rubus tricolor – spreading, arching shoots covered in red bristles, with white flowers followed by raspberry-like edible fruits. Height 60cm (2ft), spread indefinite
Vinca minor (lesser periwinkle) – mat-forming shrub with with trailing shoots and violet-blue flowers from mid-spring to autumn. Height 10-20cm (4-8in), spread indefinite
Plants for under raised or deciduous canopies, or for peripheral planting at the edge of the canopy
Aucuba japonica 'Crotonifolia' (spotted laurel) – large glossy speckled leaves. Height and spread 3m (10ft)
Cotoneaster simonsii – deciduous or semi-evergreen with good autumn leaf colour; small pink flowers in summer followed by bright orange-red fruit. Height 2.5m (8ft), spread 2m (6½ft)
Fatsia japonica – evergreen with large leaves and creamy flowers in autumn. Height and spread 1.5-4m (5-13ft)
Mahonia aquifolium - evergreen with yellow blooms in spring. Height 90cm (3ft); spread indefinate.
Osmanthus x burkwoodii – evergreen, with small fragrant white flowers in spring. Height and spread 3m (10ft)
Sarcococca hookeriana var. humilis (Christmas box) - evergreen with scented flowers in winter. Height 60cm (2ft); spread 1.2m (4ft)
Viburnum tinus – evergreen, with clusters of small white flowers from late winter to spring. Height and spread 3m (10ft)
Bergenia - evergreen leaves may colour in winter; white, pink or red flowers in spring. Height 20-45cm (8-18in), spread 45-63cm (18-25in)
Geranium macrorrhizum – deciduous leaves colour up in autumn; pink flowers in summer. Height 50cm (20in), spread 60cm (2ft)
Lamium maculatum (dead nettle) – red-purple flowers in summer. Height 20cm (8in), spread 1m (3¼ft)
Liriope muscari - evergreen, with violet-mauve flowers in early to late autumn. Height 30cm (12in), spread 45cm (18in)
Tellima grandiflora – semi-evergreen, with greenish white flowers from spring to mid-summer. Self-seeds freely. Height 40cm (16in), spread 25cm (10in)
Bulbous or tuberous plants
Anemone nemorosa – white flowers from spring to early summer. Height 7.5-15cm (3-6in), spread more than 30cm (1ft)
Colchicum autumnale – showy flowers in autumn before the leaves, with foliage produced in spring. Height 5- 15cm (2-6in), spread 5-10cm (2-4in)
Cyclamen hederifolium – attractively marked foliage and pink to maroon flowers in autumn, seeds freely. Height 10-13cm (4-5in), spread 15cm (6in)
Galanthus nivalis (snowdrop) – white flowers in late winter. Height and spread 10cm (4in)
Hyacinthoides non-scripta (English bluebell) – vigorous, with blue flowers in spring. Height 20-40cm (8-16in), spread 7.5cm (3in)
Iris foetidissima (stinking iris) - blue flowers in late spring and orange berries in autumn/winter. Height and spread 40cm (16in)