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Spirea bushes grow in upright mounds from which overhanging branches grace any garden with an array of small clusters of flowers, commonly white but sometimes other colours depending on the variety come spring, and blue-green leaves the rest of the summer. These shrubs are a showpiece in and of themselves for nothing but the floral displays, which are made even more appealing thanks to the large size. In fact, mature plants can reach just shy of 2 metres tall.
These shrubs do best when they are properly trimmed each year. Their flowers are produced on new wood, and some versions produce twice, the second after light pruning. Pruning not only helps produce better flowers, but goes a long way toward rejuvenating overgrown plants and keeping their size in check.
Pruning spirea once a year
Early flowering varietries
If you want to prune your spirea once a year to keep it within a certain size then we recommend pruning straight after flowering which is usually around June in the Uk for most varieties which are all the early flowering varieties which flower in spring. Cut back the flowering stems hard by as much as 60cm. This growth will them be replaced over summer and will produce the growth that will produce the flowers the following year. These include Spiraea ‘Arguta’, Spiraea Snowmound, Spirea Goldflame, Spirea Little Princes, Spiraea japonica ‘Shirobana’.
Late flowering varieties
If you have late-flowering varieties which include Spiraea x douglasii, Spirea billardii and Spirea canescens they flower later in the year and should be pruned hard in early spring as the flower on the current year growth.
Pruning spirea for the dedicated gardner
The question of timing has four parts, one for each season. There are pruning measures to be done in each season, each with a purpose.
Firstly, spring time is when you want to prune the tips of your plant after the initial flush of flowers. Think of this as a cross between deadheading and pruning.
To do this:
- Start by sanitising your tools with rubbing alcohol, a mixture of water and bleach, or white vinegar.
- Sharpen your tools to ensure a quick, clean cut.
- Trim the stem tips back from their highest leaf bud.
Try to maintain the natural shape as you do this. It will go a long way toward removing the dead flowers and maybe even encouraging new ones.
Secondly, summer time is when you want to get rid of diseased branches, dead branches, or any overgrown shoots. The summer is the best time to make cuts that keep the appropriate shape. The cuts should be within 1-2 cm of a bud or leaf if possible. You can hide the cut edge by cutting overgrown stems just slightly shorter than the rest, so they blend in seamlessly.
Thirdly, the Autumn is when you trim back the overgrown foliage. The lower stems can be cut back a bit more severely this time of the year, after the foliage has fallen off, so keep the shape more compact. The stems can be cut back within 20-30cm off the ground.
Finally, the end of the year brings with it another opportunity to get rid of dead and damaged wood. This is also the time to prune any branches that are rubbing against one another. If left unchecked, this will result in damage to the overall plant.
It is very important to follow these seasonal recommendations. Spireas need regular trimming in accordance with the four seasons. If you wait until winter to do a big overheal, it will leave the plant growing in an unbalanced fashion, some areas thicker and others more sparse. At a minimum, be sure to trim twice per year.