Does your flowering shrub bloom in summer or in spring? If it flowers in summer, it may be one of those bushes that blooms on new wood, forming flower buds on the current year’s growth. Why is that important? Well, knowledge of this fact will make pruning a whole lot easier for beginners.
You will appreciate such knowledge if you've ever been guilty of a classic dumb mistake like pruning azaleas in spring before they flowered because you figured they needed some shaping. Maybe they did need some. But as in other areas of life, timing is important in landscaping. And you picked the wrong time to prune. You discovered your error later that spring when the flowers you expected to come never showed up. What happened? It's simple: When you pruned those branches, you accidentally removed the flower buds for that year. Lesson learned: Azaleas bloom on old wood (last year's growth).
Due to such experiences, some beginners have a serious case of fear of pruning, to the point that they just don't dare prune at all. That's not good either. Whether they are deciduous or evergreen, proper pruning is often beneficial to plants. Trimming a flowering shrub that is supposed to be cut back in late winter or early spring can result in better flowering and a more compact shape.
By consulting this list, beginners will learn which shrubs they can prune early in the year, worry-free. If your bush is not on this list, simply assume (until you've researched it further) that the best time to prune it will be right after it finishes blooming (as is the case for the majority of flowering shrubs).
Commonly-Found Shrubs That Bloom on New Wood
Let's begin with some flowering shrubs that are commonly found in people's landscaping in North America. The following bushes all flower on the current year's growth and can be pruned (without qualification) in late winter or early spring:
A few other shrubs popular in the landscape also fall into this category. Most notably, some types of Hydrangea and Spiraea can be pruned in late winter or early spring without fear of removing any flower buds. Take careful note, however, that this advice applies only to the particular kinds of hydrangeas and spireas (because other types flower on the prior year's growth; for example, oakleaf hydrangea).
In the case of hydrangeas, it's the Annabelle and panicle types that bloom on new wood. Here are some examples:
Likewise, not all spireas are created equal in terms of when the best time is to prune them. An example of a spirea that you wait to prune until after it is done flowering in spring is Vanhoutte spirea. But certain others bloom on new wood and can be pruned in late winter or early spring. Examples are:
Less Commonly-Found Shrubs That Bloom on New Wood
We'll conclude the list with three flowering shrubs that you're less likely to encounter in the average landscape in the U.S. but that you will find interesting. The first two are wetland plants native to North America. The fact that they grow in wetlands in the wild is your cue that they're excellent choices for those problematic wet spots in your yard:
- Ruby Spice summersweet
- Summer Glow tamarisk
Buttonbush (Cephalanthus occidentalis) likes full to partial sun and can be grown in growing zones 5 to 9. It commonly grows anywhere from 5 to 12 feet tall, with a narrower spread. Its spherical flower heads are attractive not only while in full bloom with their tiny white flowers (when they resemble pincushions) but also before and after blooming. Use it as a plant to attract butterflies.
Like buttonbush, you will often find summersweet along the banks of ponds and rivers. But the wild version has white flowers. Most homeowners will find the pink cultivar more landscape-worthy. It is called Clethra alnifolia Ruby Spice and is suited to zones 4 to 8. Grow it in full sun to partial shade. It typically attains a height of 4 to 6 feet, with a spread slightly less than that. As a plant that loves acid soils, you can grow it in that acidic spot in your landscaping without having to worry about first changing the soil pH level.
Tamarisk is quite a different bush from either of these. It is native to the Old World, specifically to habitats where conditions are dry. Given this fact, it is not surprising that it craves a loam that drains sharply (mixing organic matter into the ground can improve drainage). While not tolerant of clayey soils, tamarisk is otherwise quite tolerant. It tolerates:
The Summer Glow cultivar (Tamarix ramosissima Summer Glow) has rosy pink flowers and can grow quite large (often 12 feet tall, with a spread of about 9 feet, at maturity). Plant this bush in full sun in zones 3 to 8. Warning: Tamarisk is considered invasive.
Other Shrubs to Prune in Late Winter or Early Spring
In addition to bushes that flower on new growth, it often makes sense to prune certain other shrubs in late winter or early summer. These would be the bushes that are considered mainly foliage plants. Since they are not valued for their blooms, you might as well practice size-control on them (if desired) early in the growing season, before they get out of hand. Examples include: