We have found 36 plants that meet your criteria.

African Lily ‘Agapanthus Black Pantha’ Deep blue, almost black flowers £8.99 Buy
Hollyhock (Althea) ‘Alcea rosea Nigra’ Deep burgundy flowers £5.49 coming soon
Price Pruned
Granny's Bonnet ‘Aquilegia vulgaris var. stellata Black Barlow’ Striking dark purple, double flowers NOW £4.99 Buy
Granny's Bonnet ‘Aquilegia vulgaris William Guinness’ Unusual purple-black flowers £5.49 Buy
Price Pruned
Clematis (Group 3) ‘Clematis Black Prince’ Beautiful deep purple flowers NOW £7.99 Buy
Price Pruned
Clematis (Group 3) ‘Clematis Warsaw Nike’ Sumptuous deep purple flowers, NOW £7.99 Buy
Dusky Cranesbill ‘Geranium phaeum’ Small, deep maroon flowers. Good for groundcover £5.99 Buy
Price Pruned
Dusky Cranesbill ‘Geranium phaeum var. phaeum Samobor’ Small, purple-black flowers. Good for damp or dry shade NOW £5.49 Buy
Lenten Rose ‘Helleborus x hybridus Harvington Shades of Night’ Early spring flowers in shades of deep purple £9.99 Buy
Harvington Hellebore ‘Helleborus x hybridus Smokey Blue’ Unusual, dark purple flowers with a deep blue sheen £9.99 Buy
Day Lily ‘Hemerocallis American Revolution’ Large, deep blood-red flowers in summer £5.99 Buy
Amaryllis Black Pearl ‘Hippeastrum Black Pearl’ Stunning dark maroon flowers £8.99 Buy
Siberian Iris ‘Iris chrysographes’ Deep purple flowers. Gorgeous beside water £6.99 coming soon
Siberian Iris ‘Iris chrysographes black-flowered’ Stunning, almost black flowers. For a damp spot £6.99 Buy
Intermediate Bearded Iris ‘Iris Langport Flame’ Sumptuous purple and orange fragrant flowers £6.99 Buy
Price Pruned
Bearded Iris ‘Iris Superstition’ Purple-black flowers NOW £5.99 coming soon
Lily ‘Lilium Black Beauty’ Stunning dark red, turkscap flowers £7.99 coming soon
Tree Peony / Tree Paeony... ‘Paeonia delavayi’ Tree peony with deep, maroon flowers £16.99 Buy
Price Pruned
Beard Tongue ‘Penstemon Raven’ Dramatic, deep purple, foxglove-like flowers NOW £5.49 Buy
Black-eyed Susan ‘Rudbeckia occidentalis Green Wizard’ Bright green sepals with black centres £5.99 Buy