Lobelia × speciosa 'Vedrariensis' - Purple Lobelia, Pond Marginal Plan

Lobelia × speciosa 'Vedrariensis' (often sold as Lobelia vedrariensis), known as purple lobelia, is a bushy perennial with narrow, dark green, red-tinged leaves. From mid or late summer into early autumn it carries long spikes of deep violet-purple flowers, each about 5 cm across.

'Vedrariensis' at a glance

Botanical name	Lobelia × speciosa 'Vedrariensis' (syn. Lobelia vedrariensis)
Common name	Purple lobelia
Plant type	Bushy, clump-forming perennial; dies back in winter
Height and spread	Up to about 90 cm tall, about 30 cm wide
Flowers	Deep violet-purple, about 5 cm across, in long spikes, mid or late summer into early autumn
Position	Full sun or part shade, sheltered
Soil	Moist or poorly drained soil; any type and pH
Pond depth	Up to 5 cm of water over the crown; crown just above the water in winter
Hardiness	RHS H5 – hardy in a cold winter (-15 to -10°C)
Native to	Garden hybrid (not UK native)

Can it grow in water?

Only very shallow water. The RHS lists moist or poorly drained soil, and the RHS Plants shop and specialist aquatic suppliers give up to 5 cm of water over the crown. Crown rot can be a problem, so keep it to the shallowest part of the shelf, with the crown just above the water in winter.

Is it poisonous?

Yes. It is harmful if eaten by people or pets and can irritate skin, so wear gloves when handling it.

How to care for it

Grow it in a sheltered spot in sun or part shade. Watch for slugs.

Which size should I buy?

Bare-root plants (7 cm, 9 cm, 1 litre and 3 litre) arrive without a pot or compost and are the most economical way to plant a group. Potted plants (9 cm, 1 litre and 3 litre) arrive growing in our peat-free compost and give a faster display. Packs of 3 come in 7 cm, 9 cm, 1 litre and 3 litre bare-root sizes and cost less per plant. The 2x Pot & Compost option is two plants supplied with pots and compost.