Aconitum napellus (Monkshood): Dark blue hooded flowers over finely divided foliage. This Aconitum flowers early, in late spring/early summer. Height to 1.5m. Hardy. [Collect Only]

Agastache rugosa 'Liquorice Blue' (Korean mint 'Liquorice Blue'): Spikes of warm blue lipped flowers from late June onwards. Very attractive to bees. Aromatic foliage. To 1.5m. Hardy in light soils. [Collect Only]

Amsonia hubrichtii (Hubricht's bluestar): Clumps of soft feathery green foliage and palest blue star-like flowers in late Spring. Textural plant. Attractive autumn colour. Up to 60cm. Hardy

Baptisia 'Indigo Spires' (Indigo weed 'Indigo Spires'): Spikes of violet-blue pea-like flowers with a yellow edge above a mound of grey-green foliage. Long flowering. Hardy. Up to 1.2m [Collect Only]

Baptisia australis (Indigo weed): Spires of lipped indigo flowers over olive-green foliage. Flowering height 1.2m.

Eryngium bourgatii Graham Stuart Thomas's selection (Sea Holly Graham Stuart Thomas's selection): Spiny, violet blue flowers in summer of even spinier blue-green leaves with white mid-ribs. [Collect Only]

Eryngium planum 'Blue Hobbit' (Sea Holly 'Blue Hobbit'): A more compact form with steely blue flowers on dark stems. Spiny glaucous foliage. Loves sunshine and very well-drained gritty soil. Hardy. Up to 30cm.

Eryngium x zabelii 'Big Blue (Sea Holly 'Big Blue): Large electric-blue thimble-shaped flowers with a spiky collar and silver-green foliage. Long flowering and bee-friendly. Hardy. Up to 75cm [Collect Only]

Eryngium x zabelii 'Jos Eijking' (Sea Holly 'Jos Eijking'): Large steely blue bracts surround a dome of tiny blue flowers in summer. Long-lasting flowers.Thrives in a sunny,dry spot. To 70cm. Hardy. [Collect Only]