After looking after and expanding the Winter Walk at RHS Garden Harlow Carr for several years, many of us have come to love Salix as a species, and try to get any that are appropriate for winter interest whenever we can.
One of our most recent acquisitions is the ghostly Salix irrorata and it is one of our favourites to date! S. irrorata is a deciduous shrub that can reach 6m (20ft) tall, with narrow, dark green leaves and vivid, white-bloomed, purple stems. It also has slender, silvery catkins with yellow anthers. It is very similar to another much-loved favourite, Salix acutifolia ‘Blue Streak’, which has many of the same features but on a bigger scale (it can reach 10m/33ft) with more lax branches. So, S. irrorata is probably better suited to smaller gardens.
The very dark stems are so striking because they are covered in a white waxy bloom (right), which makes the branches appear to be silvery blue colour, looking particularly striking on a cold and sunny winter day. In spring the branches are covered in tiny silver-white catkins which is an added bonus, especially as it seems to be quite difficult to find a Salix which has good stem colour and catkins. One usually has to make a decision on one or the other.
We have five S. irrorata planted together in the newly extended section of the Winter Walk, underplanted with evergreen Leucothoe and Bergenia ‘Bressingham White’ to set off the striking stems. As they mature we will pollard them on a two or three year rotation - this will mean we get the best of the stem colour and the catkins, whilst keeping them at a reasonable size.