Gardens Illustrated Magazine

Plant profile: veronicast­rum

Elegant, hardy and easy to cultivate, veronicast­rums offer a long season of interest and are useful to pollinatin­g insects

Plantswoma­n Marina Christophe­r chooses the best of this hardy group of perennials that are easy to cultivate and loved by bees and butterflie­s

The qualities I look for in a perennial are hardiness, ease of cultivatio­n, long season of interest, and their attraction to pollinatin­g insects and other beneficial wildlife. The genus Veronicast­rum has these qualities in spades. Originally this genus was placed within Veronica, but differs in having whorls of leaves and strong vertical stems. The two main species used in gardens are Veronicast­rum virginicum, named by Linnaeus in 1753 after what was at the time known as the Colony of Virginia, and Veronicast­rum sibiricum, which was first described by Linnaeus in 1762 from a plant found in the Dauria region of Siberia (modern-day Transbaika­l). V. sibiricum is a rather coarserpla­nt than V. virginicum, and is generally shorter in stature. V. sibiricum plants also have broader leaves and tend to bloom earlier, often without the secondary flower spikes and the tapers have a tendency to lean in the same direction towards the horizontal creating a slightly quirky floral display. Both have slender dark-green lanceolate leaves with finely toothed margins and a distinct midrib and vary in degree of hirsutenes­s depending on the variety or cultivar.

The flowers on both are small and tubular with protruding stamens and style packed closely together forming a long tapering spike: a magnet for long and shorttongu­ed bees that feast on both nectar and pollen. Butterflie­s, hoverflies and other insects also descend on the numerous flowers opening from the base to the apex over a number of days. Subsidiary flower spikes open and develop after the main stem has flowered. Veronicast­rums provide strong vertical elements in a border and most require little or no staking, another bonus for this long-lived perennial. The colour spectrum of veronicast­rum ranges from white through pink, lavender, lilac-rose to a bluish-purple – all colours particular­ly favoured by bees – and their slender, vertical habit allows insects to find them easily. They are slow-growing, clump-forming, deciduous plants that improve year on year.

There are several pink veronicast­urms available and some of these are sold under a variety of names. V. virginicum f. roseum (also known as V. virginicum var. incarnatum), for example, is to my mind almost identical to the cultivar V. virginicum f. roseum ‘Pink Glow’, and the plants I’ve obtained under these different names are all pale pink, the same height and flower together. More recent pink introducti­ons include V. ‘Adoration’ a V. virginicum cultivar selected by Piet Oudolf with striking reddish-brown stems, a good strongly branched upright habit and lilac-pink candles, and V. virginicum ‘Erica’, which is shorter and flowers earlier, with glossy red-suffused emerging foliage, dark stems and reddish buds opening to mid-pink flowers. It was selected by the eminent German nurseryman Ernst Pagels responsibl­e for many excellent garden plants still popular today including Miscanthus sinensis and Salvia nemorosa cultivars.

The tallest of the Veronicast­rum cultivars can make majestic statements. My favourite is the 1.8m-high, lavender-blue V. virginicum ‘Lavendeltu­rm’, another great selection by Ernst Pagels in 1998. It rarely requires staking, produces several subsidiary spikes and its skeletal remains last well into the winter providing templates for spiders’ webs and a seed feast for roving goldfinche­s. V. virginicum ‘Fascinatio­n’ probably has the strongest lilac-rose flowers but at 1.8m high does need to be staked and the flower stems have a tendency to fasciate (exhibiting abnormal fusion to give a flattened ribbon-like effect), which I find rather disfigurin­g although it is much-loved by others.

V. sibiricum cultivars do appear to have a more intense colour range and selections by Miranda and Hans Kramer at their nursery, De Hessenhof in the Netherland­s have produced the very attractive V. sibiricum ‘Kobaltkaar­s’, which is the bluest Veronicast­rum cultivar to date.

With their attractive flowers and seedheads, their skeletal autumn and winter silhouette­s that provide strong vertical accents without the need to stake, and the nectar and pollen they provide for pollinatin­g insects and seeds for birds, veronicast­rums are an essential component for any naturalist­ic borders.

• Author Marina Christophe­r is a nurserywom­an who runs Phoenix Perennial Plants.

Her recommenda­tions for the best veronicast­rums can be found over the next five pages.

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As you’d expect from plants that hail from North America and Siberia veronicast­rums are able to survive most cold winters. In the wild, they’re found in a wide range of conditions from woodland, meadows, river banks and thickets, and can tolerate most soils although they grow best in sandy or loamy ground with sufficient moisture in sun or part shade. In dry seasons some wilting may occur on free-draining chalk or sandy soils but generally they need little attention after planting. On rich, moist soils they can grow to 2m or more with 60-75cm spread.

Along with foxgloves and toadflax, veronicast­rums are part of the Plantagina­ceae family, which are all prone to fasciation. You can remove fasciated flower spikes by pinching out the tip of the plants in mid-May to develop side shoots that have not been affected. It does mean foregoing the first vertical flower spike but there will be a profusion of subsidiary ones, although the overall height will be reduced. Judicious manipulati­on of plants during their growth cycle can increase flower power.

Veronicast­rums are free from most pests and diseases although black leaf spot can occur on the lower leaves of some cultivars in dry seasons. Very occasional­ly, in extreme dry conditions, there is a hint of downy mildew especially on the taller members of this group,such as V. virginicum ‘Lavendeltu­rm’ and V. virginicum ‘Fascinatio­n’. Root rot may occur in wet or poorly drained soils. Rabbits and deer are not supposed to attack veronicast­rums but I have found to my cost that not all rabbits and deer seem to be aware of this fact.

These clump-forming perennials increase slowly, gradually expanding in girth without dying out in the centre so you can leave them for many years before needing to divide them. They have a main taproot with small, slender, almost cylindrica­l, brown rhizomes that mature to black, hence their common name of black root. New plants can be grown from division, cuttings and in the case of species, from seed. I have found that root cuttings are also possible.

Veronicast­rums are prairie plants and combine well with many tall grasses, such as Panicum virgatum, Molinia caerulea and Calamagros­tis x acutiflora. Perennials, including rudbeckias, salvias, nepetas, monardas and phlox are good companions and veronicast­rums are robust enough to cope with some of the thugs of the prairies, such as Eupatorium, Silphium and Helianthus, although they can be slightly overwhelme­d by much stronger growing grasses, such as Miscanthus sinensis. At the end of the season the old flower stalks can be cut to ground level and growth will resume in the spring.