Berkheya

These long-flowering thistle-like daisies are well worth a go for consistent interest in the border, writes Miranda Kimberley.

B. purpurea ‘Zulu Warrior’ - image: Flickr/Far Out Flora
B. purpurea ‘Zulu Warrior’ - image: Flickr/Far Out Flora

The daisy family is one of the largest and within its ranks is Berkheya, not as popular as its cousins the Aster or Helianthus but an interesting addition to the flower border nonetheless. For the plant connoisseur it is always worth trying a new name with which to show off.

There are around 75 species of Berkheya but only a handful really in cultivation. More than 70 species are native to South Africa, where they grow mainly on mountain slopes. They are either shrubs or perennials, often with spiny leaves and stems.

Although not perhaps the most beautiful of the daisies, they have a distinctive thistle-like appearance. However, they are long-flowering plants, providing consistent interest in the border. The flowers are generally yellow but sometimes white, purple or brown.

The most commonly grown in the UK is B. purpurea. As its name suggests, it has a purply flower head, though sometimes the ray florets are a little paler than the purple centre, varying from white to pale-mauve and purple. A rosette of spiny leaves gives the plants a strong presence in the flower border.

There are a few good cultivars - 'Silver Spike', which has pastel blue flowers with purple centres, and the brilliantly named 'Zulu Warrior', which has a silvery-blue flower with a purple centre.

Berkheya are not said to be reliably hardy because they can suffer when temperatures fall below -5 degsC, so they are best grown in mild, southern parts of the UK, against a warm wall and protected from winter wet.

However, certain species are said to be surprisingly hardy. These include B. macrocephala, which produces flat, buttery yellow daisies; B. cirsiifolia, which is very spiky, with large, white, daisy-like flowers that have a golden centre ringed with burgundy; and B. radula, which has softer leaves than normal and lemon-yellow flowers.

To grow plants from seed, collect the seed from existing plants in the autumn and sow fresh, or keep it and sow in the spring. Autumn-sown plants will be ready to plant out in the following spring. They like a position in full sun and in well-drained soil.

Berkheya suit rock garden planting, where they receive shelter and free-draining conditions and can become specimen plants. They also look good in groups and look natural planted among low grasses because this is the kind of grouping in which they would be found in their native habitat. One benefit of planting Berkheya in a garden is to deter pets and other unwelcome visitors from coming onto the flower border. They also make excellent cut flowers, either fresh or dried.

B. cirsiifolia - image: Flickr/Wendy Cutler

What the specialists say

- Kathy Moss, manager, The Seed Company, Kent

"Berkheya is not a well-known genus, but because gardeners are always looking for the next big thing Berkheya seeds are becoming more popular. Certainly we get asked for B. purpurea because it's got a very attractive dusky purple flower. I've heard it called 'the thistle that thinks it's a sunflower', and that's a pretty good description. The leaves and stem are spiky, just like a thistle's, and its flowers are open, with the classic ray and floret petals of a daisy.

"The other species are not as sought after. B. purpurea is the odd one out really, with its lilacy flower. The others like B. macrocephala and B. radula have yellow flowers and perhaps lean more to the wild thistle than to a neat border plant. They suit the rock garden though, where their distinct look makes them a feature plant and they will be valued."

B. purpurea - image: Flickr/Lollie Pop

In practice

- John Winterson, deputy plant buyer, RHS plant centres

"We sell B. purpurea as both seeds and plants. The seeds we sell are actually collected from RHS gardens by our very own seed team, packeted up and sold from each of our four plant centres. Sales of seed are very strong for this unusual South African herbaceous plant. The combination of bold daisy flowers against the spiky and woolly foliage makes it very unusual.

"We also sell plants in two-litre pots between April and September - a steady trickle of sales from amongst our A-Z beds of herbaceous perennials - and when they are in flower the plants attract customers to them. We have been selling it steadily since 2007 and it has been known for us to do the occasional display bench in flower.

"On the shop floor they are easy to care for and they can tolerate a little drought between waterings. They make a great addition to your herbaceous border."

B. radula - image: Flickr/Markus

Species and varieties

- B. cirsiifolia is a viciously spiny thistle-like plant from the Drakensbergs that has proved itself reliably hardy. It has large, white, daisy-like flowers with a burgundy ring around the gold eye, from July to September. Height: 60cm.

- B. macrocephala is a hardy plant despite coming from South Africa, with large, flat, yellow thistle-like flowers in a ruff of bright-green bracts appearing between June and July. Height: 55cm.

- B. multijuga is a medium-sized perennial with spiky foliage and golden yellow flowers in July and August. Height: 60cm.

- B. purpurea is a perennial with rosettes of spiny leaves that have a downy-white underside. Open daisy flowers with either white, pale-mauve or purple ray florets, surrounding a darker purple centre, are borne in summer. They are held on short side branches off the flower stem and open in succession from the top down. Height: 60cm.

- B. purpurea 'Silver Spike' has attractive spiky foliage and large pastel-blue flowers with deep-purple centres. Height: 60cm.

- B. purpurea 'Zulu Warrior' forms a smart basal rosette of long, dark-green, thistle-like leaves, cottony beneath, from which arise thick, thistly stems. It also produces silvery-blue flowers with dark-purple centres in late summer. Height: 90cm.

- B. radula is said to be surprisingly hardy. It is less spiny than other Berkheya, forming basal rosettes of large, round lobed and toothed leaves. Winged stems carry soft lemon-yellow flowers in midsummer with a large central cone and narrow, gappy ray petals. Height: 70cm.


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