We have found 30 plants that meet your criteria.

dusky cranesbill
Geranium phaeum 'Lily Lovell' dusky cranesbill Iridescent saucers of purple flowers. Good for shade £7.99 Buy
Siberian iris
Iris chrysographes black-flowered Siberian iris Stunning, almost black flowers. For a damp spot £8.99 Buy
bearded iris
Iris 'Dusky Challenger' bearded iris Huge ruffled silky rich purple-blue blooms £8.49 Buy
bearded iris
Iris 'Sultan's Palace' bearded iris Sultry, maroon flowers £8.99 Buy
bearded iris
Iris 'Superstition' bearded iris Purple-black flowers £8.99 Buy
lavender
Lavandula angustifolia 'Imperial Gem' lavender An excellent variety for low hedges £7.99 Buy
French lavender (syn. Papillon)
Lavandula pedunculata subsp. pedunculata French lavender (syn. Papillon) Distinctive butterfly-like, mauve flowers £7.99 Buy
French lavender
Lavandula 'Helmsdale' (PBR) French lavender Burgundy-purple flowers topped by purple bracts £7.99 Buy
lavender
Lavandula 'Sawyers' lavender Compact mounds of silvery foliage £7.99 Buy
Jerusalem sage
Phlomis tuberosa 'Amazone' Jerusalem sage Whorls of lilac flowers and architectural seedheads £8.49 Buy
rosemary
Rosmarinus officinalis rosemary A deliciously aromatic favourite £7.99 Buy
lamb's ears
Stachys byzantina 'Big Ears' lamb's ears Purple flowers large Grey-green leaves £7.99 Buy
convolvulus
Convolvulus sabatius convolvulus A prolific display of violet-blue flowers £8.99 Buy
shrubby veronica
Hebe 'Red Edge' shrubby veronica Small hebe with lilac flowers £8.99 Buy
lavender
Lavandula angustifolia 'Hidcote' lavender A compact lavender, with intense, violet flowers £7.99 Buy
French lavender
Lavandula 'Fathead' French lavender A hardy French lavender £7.99 Buy
French lavender
Lavandula 'Regal Splendour' (PBR) French lavender Incredible dark purple-violet flags £7.99 Buy
Crocus Special Offers
lavender promotion - 6 pack
Lavandula angustifolia lavender promotion - 6 pack... 6 Lavenders for less than £2.50 each NOW £14.99 Buy
Crocus Special Offers
rosemary promotion - 6 pack
Rosmarinus officinalis rosemary promotion - 6 pack... 6 rosemaries for less than £2.50 each NOW £14.99 Buy
yarrow
Achillea millefolium 'Lilac Beauty' yarrow An unusual lilac, yarrow £6.99 coming soon