We have found 29 plants that meet your criteria.

Aquilegia vulgaris var.stellata 'Black Barlow' (Barlow Series) granny's bonnet Striking dark purple, double flowers £5.99 Buy
Aquilegia vulgaris 'William Guinness' granny's bonnet Unusual purple-black flowers £5.99 Buy
Iris 'Superstition' bearded iris Purple-black flowers £7.99 Buy
Price Pruned
Paeonia delavayi tree peony / tree paeony... Tree peony with deep, maroon flowers NOW £19.99 Buy
Sesleria autumnalis moor grass Perfect for informal edging £6.99 Buy
Agapanthus 'Black Pantha' (PBR) African lily Deep blue, almost black flowers £8.99 Buy
Clematis 'Black Prince' clematis (group 3) Beautiful deep purple flowers £8.99 Buy
Clematis 'Warszawska Nike' clematis (group 3) Sumptuous deep purple flowers, £8.99 Buy
Geranium phaeum var. phaeum 'Samobor' dusky cranesbill Small, purple-black flowers. Good for damp... £5.99 Buy
Crocus Special Offers
Helleborus × hybridus Harvington double purple hellebore Stunning double flowers NOW £10.99 Buy
Crocus Special Offers
Helleborus × hybridus 'Harvington Shades of the Night' hellebore Early spring flowers in... NOW £9.99 coming soon
Crocus Special Offers
Helleborus × hybridus Harvington Smokey Blues hellebore Unusual, dark purple flowers with a deep... NOW £10.99 coming soon
Hemerocallis 'American Revolution' daylily Large, deep blood-red flowers in summer £7.99 Buy
Sambucus nigra f. porphyrophylla 'Gerda' (PBR) black elder (syn. Black Beauty)... Dramatic purple foliage £9.99 Buy
Uncinia rubra red hook sedge Wonderful deep bronzy-red foliage £6.99 Buy
Geranium phaeum dusky cranesbill Small, deep maroon flowers. Good for groundcover £5.99 coming soon
Iris chrysographes black-flowered Siberian iris Stunning, almost black flowers. For a damp spot £6.99 coming soon
Penstemon 'Raven' beard tongue Dramatic, deep purple, foxglove-like flowers £6.49 coming soon
Rudbeckia occidentalis 'Green Wizard' black-eyed Susan Bright green sepals with black centres £6.49 coming soon
Scabiosa atropurpurea 'Chile Black' pincushion flower Deep claret, almost black flowers £6.49 coming soon