Our Siberian dogwood is spreading sideways but has no height. Is this normal? How do we get it to grow up, as it’s taking over the small space it’s in.
The Siberian or Tatarian dogwood (Cornus alba ‘Sibirica’) is a lovely shrub, valued for its creamy white flowers in late spring and its coral-red stems in winter. It is an adaptable plant that is happy growing in a range of conditions from full sun to part shade.
It has an upright habit and a rounded form. It can grow 8 to 10 feet high (the variegated forms don’t grow quite as tall) with almost an equal spread – so your plant is not unusual in its spreading. And it grows slowly, taking from 5 to 10 years to reach its full height.
Cornus alba is a hardy, resilient plant . If you want to curb its spreading you can prune it back, removing a third of its canes every year. This will also encourage new growth and a renewed plant. If you’ve already tried this type of routine pruning and your plant is still taking up too much space, it will do no harm to prune the whole plant right back, to within 9 to 12 inches of the ground. This is the time to do it, before it starts to bud. The hard pruning means you won’t get any flowers this spring, but the stems will grow back quickly, and because new stems are brighter than old ones, you’ll have much better winter colour. Then, next year or the following year, you can just remove a third of the canes, and do the same for a few years until you need to cut it back entirely again.
Here’s a detailed description of your shrub:
Steve Bradley, The Pruner’s Bible (Quarto, 2005), pp. 76-77.
Michael A. Dirr, Dirr’s Encyclopedia of Trees and Shrubs (Timber Press, 2011), pp. 205-206.