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For months on end, sumptuous, tubular blackcurrant blossoms emerge in exquisite spikes above clumps of narrow leaves. Penstemon 'Raven' is an eye-catching cultivar, especially when combined with pale-flowered perennials like anthemis and gypsophila. It, like all penstemons, attracts pollinating insects, giving it a spot in natural habitats. This easy-to-grow semi-evergreen perennial has an RHS AGM for its garden performance. Height: 90cm (36). Spread: 30cm (12).