Consider growing spirea when you’re looking for a fast-growing, flowering shrub to fill in those sunny gaps in your garden. These low-maintenance species are easy to care for and attractive to pollinators. However, you might have to factor in regular trimming to prevent your spirea from getting spindly or sprawling.
Read on to learn more about how and when to prune spirea to help them maintain a healthy, tidy form.
When to Prune Spirea
The most common recommendation for when to prune spirea is to do it after they have finished flowering. However, the best time depends on the species you have and why you need to prune the shrub.
Doing any major pruning within two weeks of the last blooms dying off works well for spring- or early summer-flowering spirea. If you wait too long, you risk pruning wood with new flower buds, meaning your shrub might not bloom as impressively the next spring or summer.
For later flowering species, such as Japanese spirea (Spiraea japonica), significant pruning in late winter or early spring, just before new growth emerges, works well. Pruning these shrubs after flowering finishes in late summer or fall stimulates new growth. These tender branches probably won’t have time to harden off sufficiently before the cold weather arrives. This can result in winter injury and fewer flowers the following year.
You can prune away dead, dying, damaged, or diseased branches and trim lightly to tidy the shape most of the year. However, where possible, avoid the period between mid-August and early winter to avoid winter injury on new growth.
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How to Prune Spirea
The spirea pruning tips below will help you make the right chops to improve the shrub’s health, vigor, and appearance.
- Use a sharp, sterile type of hand pruner to cut off any individual dead, dying, twisted or damaged branches. Wiping down the blades with rubbing alcohol is a simple way to keep them clean.
- Thin out old branches from the dense center to improve air circulation and light access. This boosts growth and reduces the chance of disease developing.
- You can leave spirea shrubs to grow naturally with a loose habit or trim to achieve the desired shape and size.
- If you want to see vertical growth, focus on trimming back the lower branches. To promote outward growth and reduce the shrub’s height, focus on trimming the tops off the branches.
- While following the 1/3 rule for pruning shrubs generally works well, overgrown spirea can handle harder pruning. Cutting back this fast-growing shrub by as much as 2/3 can promote a tight, dense habit and the formation of new tight clusters of small flowers.
Tips for Growing Spirea
It’s not just pruning that can help you produce the healthiest, shapeliest spirea shrubs. Keep these growing tips in mind when cultivating spirea species in your yard.
- Grow in full sun: While some spirea species can handle a partial shade position, these flowering shrubs prefer full sun. Otherwise, they can become leggy and won’t produce as many beautiful blooms.
- Select a well-draining site: Spirea are hardy shrubs tolerant of a wide range of soils, but super soggy conditions are a no-no. Pick a site with good drainage and consider adding aerating soil amendments (like compost) to help water pass through more effectively.
- No need for fertilizer: Spirea aren’t heavy feeders, and too much nitrogen can promote leafy growth and fewer flowers.
- Avoid invasive species: Popular Japanese spirea (Spiraea japonica) is considered invasive in some eastern and southern states. Always check species status before planting.
- Mulch for moisture: While spirea aren’t fans of soggy soil, they appreciate even moisture, especially in hot, dry locations. Adding a layer of mulch helps to retain available moisture.
FAQ
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If your spirea shrub looks leggy or hasn’t had a good flowering season, cutting it back to the ground in late winter or early spring before new growth appears can rejuvenate it. While you don’t want to do this too often as it can weaken the shrub, it’s not a problem to do this type of rejuvenation pruning every three to five years.
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As long as you don’t cut your spirea shrub back hard too often and wait until winter to do it, this can be beneficial. These fast-growing shrubs can quickly get overgrown. Cutting back hard encourages a more compact, denser growth habit and abundant blooms when it flowers again.
