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Top verbascum to grow

Top verbascum to grow

V. ’Tropic Sun’ is hard to track down, but worth the search. Photo: Hoo House Nursery

Mulleins can be annual, biennial or perennial and come in a range of forms and colours, says Sarah Morgan

As mulleins bloom when the RHS Chelsea Flower Show is on, they are usually a hit in many show gardens. Their flowers come in utterly lovely tones of white, yellow, dusky plum or peachy-apricot and look just as Vita Sackville-West once put it – “as though a colony of tiny butterflies” has settled all over them.

Around 300 species originate from Turkey and southern Europe, where they enjoy the hot summers and cold, but not wet, winters. Once planted they will quickly bulk up and flower, so can be used as an early star in a newly planted area. Not being too bulky, the taller ones allow you to see around them, so they can frame a path or add height to borders, with their spires held high above other perennials. Designers can choose between annual, biennial or perennial verbascum – and it’s worth knowing which one you’re buying. The perennials, which don’t produce seed, have more flamboyantly coloured flowers that come out during May and June.

The favourite at the 2008 trial at RHS Wisley was the Great Dixter introduction V. ‘Christo’s Yellow Lighting’ AGM, a pale yellow hybrid described as ‘breathtaking’ in their catalogue. The annual and biennial species, which by contrast are seed producing, are mainly yellow flowered and bloom later in the season, from July to September. They need space, on open ground or gravel, to unfurl their wide leaf rosettes; then will happily pop up around the place in the random fashion of self-seeders.

V. ‘Firedance’ is one of the newly bred, longer lasting cultivars. Photo: Howard Nurseries

Designer’s choice

“I have a V. olympicum that self-seeded in the dry shade at the bottom of my hawthorn hedge,” says garden designer Sarah Morgan MSGD. “It’s a huge, fun plant and copes well with competition from other plants – I use it if I want to be bombastic, as it is 2.5m tall. Generally verbascum need space and air around them, but that also means you can appreciate their fantastic vertical forms better,” explains Sarah. “I do a lot of low planting on sites where there’s a mix of light pedestrian footpaths and driveways. I like to break up the paving with gravel in-between the slabs, and then plant low mounds of traditional alpine plants – the types that cope with paving crevices. Then just on the edge where there’s less competition, I’ll plant something like V. (Cotswold Group) ‘Gainsborough’ AGM.” This is a deservedly favourite old-timer that Sarah finds has the right credentials: it’s robust with a good longevity of flower and well-branched, so you get a lot of flowers per plant.

With the pressing need for new housing, Sarah has found developments can be on increasingly challenging sites. “I work on new builds around the Medway Towns in Kent, with ridiculously steep chalk embankments as back gardens. But instead of putting terraced decking in, I’ve used traditional scree planting, which is also a much cheaper option, seeding species of verbascum in with a few other genus that are similarly competitive. I’d use this technique anywhere with a gradient and thin-to-no topsoil that reduces competition from other plants,” she says. Sarah’s unsung star is the rich-yellow V. nigrum, “It’s my favourite and a self-seeder: unusually, the eye gets drawn into the centre of the flower and its vibrant yellow colour works so well with strong pinks or whites. I also love to use it in medicinal gardens, as it’s a useful antiseptic.”

V. ‘Merlin’ is tough with purple flowers and soft grey foliage. Photo: Howard Nurseries

Specialist’s view

Former National Plant Collection Holder Claire Wilson and the late Vic Johnstone spent years trying to produce longer-lasting Verbascum in exciting new colours. Their work culminated in the enticing rusty-red V. ‘Firedance’, launched last year. “My advice to designers is to choose perennials that are known to be robust, as you should get three to four years out of them, sometimes longer if you give them the right conditions,” says Claire. “Top of my list would be one of the toughest, V. ‘Merlin’, which has pale purple flowers above soft grey foliage; we’ve kept this one going for five to six years. Chris Beardshaw used it profusely in his RHS Chelsea show garden last year. Another good one that Joe Swift MSGD used is V. ‘Petra’, which is a deep rosy-pink, and there’s a nice pale yellow called V. ‘Clementine’.

“For self-seeders, I think the biennial V. phlomoides is the best. It’s very tall with large yellow flowers and comes in a striking white form, too. I’d use it as a focal point in a border. Another jolly nice self-seeder is V. speciosum, but be warned – it’s prolific!” The most reliable perennials that Claire has produced are a range called Tropic Series, such as V. ‘Tropic Sun’ AGM. These come in different colours from dusky bronzy-pink to orange. They’re hard to find, but according to Claire, they are worth the search.

Some Verbascum have handsome foliage that works well at the edge of gravel paths or by steps. The one that wowed at the RHS Trial was V. epixanthinum AGM – also a favourite of Claire’s. “Its handsome leaf rosettes span 90cm across and are a feature in themselves,” she says. “And everyone always loves V. bombyciferum, with its woolly stems and silvery leaves. It is a wonderful foil to blues and greens.”

V. ‘Gainsborough’ is robust and holds the RHS AGM. Photo: Howard Nurseries

Top growing tips

• Verbascum prefer well-drained alkaline soil, but will grow in loamy soil as long as they don’t stand in winter wet.

• All the perennial hybrids are sterile, which means they don’t produce seed – the only way to keep them going is by taking root cuttings in late September onwards or when the plants are dormant.

• Although recommended to be grown in sun, former National Plant Collection Holder Claire Wilson prefers morning sunshine or semi-shade, particularly for the coloured hybrids, as they lose their flowers daily after pollination, which then shrivel up quicker in hot sun.

• The taller ones need staking in spring as their multi-branched inflorescences can catch the wind and topple over.

• If there’s overcrowding and lack of airflow they can also get fungal disease. A recent RHS Trial discovered it was useful to get any fallen leaves out of the basal leaf-rosettes to prevent rot, especially in autumn.

• The mullein moth caterpillar can defoliate plants. During the RHS Trial these were initially removed by hand, but by June had become too numerous, so were sprayed in the evening. Organic gardeners can grow a couple of sacrificial mulleins and transfer the caterpillars. A weevil can also burrow into the flower buds; these should be removed by hand.

• Cut any old flowering stems to the ground to get further flowers throughout the season. Remember to allow the annuals and biennials to set seed.

Thank you to Dawn Edwards, RHS Wisley Trials Office, for additional advice.

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