Spiraea, usually misspelled as spirea, are great for areas of your garden that could do with a multitude of color and structure, and you don’t want to wait very long.
Spirea plants are renowned for their extended flowering season, whether you choose spring or summer flowering types, they will provide you with seas of color for a solid month at a time, or slightly longer.
Interested? Here’s everything you need to know about growing spirea (see also Spirea Uses).
At a Glance: What You Should Know About Spirea
Spirea plants have a multitude of uses in the garden, which has helped stoke their popularity, as well as the many flower forms and colors available.
Some people prefer to plant them as shrubs, some like them best as a carpet of flowers to fill rocky areas or to suppress weeds, and others prefer their more compact habit in pots.
They are part of the rose plant family, and the Spiraea genus is made up of just under a hundred species of flowering shrubs. You’ll also find them labeled under the names meadowsweets and steeple bushes.
These gorgeous plants are perennials, which means that they will come up year after year, provided that you give them the right position in the garden.
How to Make the Most Out of Spirea
Spirea are very hardy plants, both for fierce summers and harsh winters, suitable for locations that get a lot of both.
Hot summers do not shorten the flowering time of these beautiful plants, so you’ll be able to enjoy them for as long as possible. As a bonus, they don’t require any winter protection.
In the autumn months, spirea foliage does fall, but not before it makes the leaves a sight to see. Depending on the variety you go for, the leaves may turn a golden yellow, orange, or crimson, sometimes a combination of these.
Once the leaves give way, they allow the structure of the plant to shine through, as well as making way for autumn plants to really show off, making spirea a very versatile choice.
If you want to maximize the amount of flowers spirea can give you, why not plant a few of these gorgeous shrubs? For the best display possible, plant them together in odd numbers such as threes or fives, creating a natural look.
You can also use a mixture of spring and summer-flowering cultivars, which will give you the most amount of color possible.
In terms of flower color, they can be white, red, or pink, in a lot of different shades, so they’ll fit right in with your current planting scheme.
Most spirea varieties that flower in spring feature bright white flowers, and the majority of summer varieties produce pink or red flowers.
You can expect the early flowering varieties to bloom from April until May, and summer flowering spireas will put on their best shows from June until August.
If you’re looking for a flowering shrub to thrive in your garden, spirea is a good choice, but it’s worth knowing that larger types don’t grow well in pots.
This is because some varieties get far too tall and wide, up to nearly 8 feet tall and wide. These taller varieties do work as a hedge or seasonal screen full of color, so there’s nearly endless possibilities when it comes to growing spirea in your own garden.
How to Make Sure Spirea Thrives
As flowering plants go, spirea is one of the easiest types to look after. They are very robust plants, able to withstand both freezing temperatures and sweltering weather without a fuss.
This makes them perfect for those who don’t have a lot of time to dedicate to their garden, or someone who travels a lot, while having a plethora of color in the garden to enjoy.
Having said that, there are a few things that you can do to make sure you get the very best out of these colorful plants for years to come.
Sunlight and Position
Spirea shrubs love to bask in the sun, and as much of it as possible. To produce as many flowers as the plant is capable of, they need at least six hours each day.
Spireas will survive in partial shade if that’s what you have. The growth will be noticeably thinner, and a little leggier than if it was grown in full sunlight, and you won’t see as many flowers.
Dappled shade can be beneficial in the afternoon if you live somewhere warm, to protect the plant from the fierce afternoon sun, but this isn’t a requirement.
Spirea plants need well-draining soil in order to survive. These plants don’t like water pooling at the roots for long, as they are susceptible to root rot, which is one of the biggest killers of spirea.
They do like soil with a lot of nutrients, so if the soil in your garden isn’t fertile, you can improve the area by adding mulch to the soil before you plant spirea.
If the earth in your garden is slightly acidic, this is the best planting situation possible for your spirea, as the plant will produce better flowers.
When to Water Spirea
The most you’ll need to water spirea is when you first introduce them into your garden. This is to help the roots establish themselves into the soil, but it’s especially important if you plant them while the growth is active in spring or summer.
For best results, plant spirea in the autumn or winter, when they aren’t putting out as much growth.
They’ll largely take care of themselves after they are established, but they will benefit from a good drink during dry spells. Just be careful you don’t overwater them.
Should You Fertilize Spirea?
Spirea plants aren’t demanding when it comes to applying regular fertilizer. In fact, the only time the plant will really thank you for feeding it is once a year when you prune it.
It’s best to mulch it at the same time to give it a boost.
How to Prune Spirea
Depending on the type of spirea you go for, this will dictate when you should prune it back. Let’s take a look at when you should give your spirea a haircut.
Cutting Back Spring-Flowering Spirea
Once the flowers have finished on your spirea that blooms during the spring, it’s time to prune it.
The following year’s flowers will grow on the shoots that the plant grows during the summer, so once it has finished flowering in late spring, this haircut won’t affect next year’s growth.
Prune the growth that has produced flowers, back to the recently-produced shoots, taking it back to two buds.
This will help improve the airflow around the plant, while also stopping the plant from putting its energy into producing seed.
When to Prune Summer-Flowering Spirea
The varieties of spirea that bloom into color during the later stages of summer need to be cut back in early spring. This is because these particular varieties produce flowers on growth which appear earlier in the year.
In the first few weeks of spring, take your secateurs to the plant, taking all the shoots back to about 30cm above ground level.
This will not only improve the flowers and the growth produced, but it will also make sure that the foliage is much more vibrant, as newer growth produces better color.
How to Revive an Overgrown Spirea
If your spirea is looking tired, only producing new growth on the outside of the plant, while the center of it looks like a twiggy, overcrowded mess, don’t worry. You can soon fix it.
You’ll need to do this every couple of years, to help the plant rejuvenate.
Make sure to do this during winter, when the growth of the plant has all but stopped, and this ensures that you won’t interrupt the flowering cycle, or shock the plant too much.
You want to take off some of the oldest stems, cutting them back to the ground. Take about a quarter of these from the plant.
It will promote new growth to help brighten up your spirea, while allowing more sunlight to reach the plant, as well as improving the air circulation, preventing disease.
How to Propagate Spirea
During the height of summer, you can take cuttings to make new spirea plants, and fill your garden with even more color.
You’ll need to take cuttings of semi-ripe growth. This is growth that has been taken near the end of the growing season, still less than a year old, where it is harder than a softwood cutting.
Place each one into damp compost around the edges of a pot, using rooting hormone beforehand if you like.
Keep it somewhere warm and humid, and once you see new growth appear within a month or so, it’s time to transfer the cuttings into their own pots.
Some types of spirea have a clumping growth habit that spreads over time. These spirea plants produce suckers, which form as new plants, growing their own root system.
Once these get big enough to fend for themselves, you can dig them up and plant them elsewhere in your garden.
Problems to Watch Out For
Spirea isn’t affected by a lot of pests and diseases, and provided that you plant it in the right location where it can get plenty of sunshine and the soil drains well, it should be trouble-free.
It is still a good idea to keep an eye on your plants, however, as it’s never guaranteed. Catching and treating any issues early will go a long way into ensuring that your spirea flowers for years to come.
Most likely, if your spirea is going to fall victim to anything, it will be powdery mildew.
This is a disease caused by fungus, primarily attacking the leaves and branches of the plant, but it can also impact the flowers, too.
Luckily, it’s a very noticeable disease. You’ll see a white powdery substance coating the leaves and branches of your spirea, which will spread to other parts of the plant, and neighboring plants, if left untreated.
The best cure is prevention, as the saying goes. The most important thing you can do to prevent powdery mildew is to plant your spirea somewhere that gets full sunlight for as long as possible.
Make sure to give your spirea a good drink during dry spells. It also helps if you can mulch around the plant annually, which stops too much water from evaporating from the soil.
Pruning your plant to keep a good amount of air circulating will also go a long way in preventing fungal infections like powdery mildew.
Ensure you place your spirea in a spot that’s not crowded by neighboring plants, giving it plenty of room to grow.
Aphids can be a problem in any garden, and keeping on top of their population levels is the best defense.
Normally, nature takes care of this, using predators such as ladybugs, soldier beetles, minute pirate bugs, parasitic wasps, and others, but sometimes there is an imbalance which can cause your plants to suffer.
Check regularly on the undersides of leaves, as this is where they will hide. A small infestation can be treated by spraying the leaves – both on the surface and the undersides – and kicking them off the plant.
You’ll also notice aphids by the damage they leave, making the foliage turn yellow, falling from the plant outside of winter.
One method of controlling aphids is to plant alliums, herbs, and flowers like marigolds and sunflowers. These help repel aphids, and attract their natural enemies.
You can also buy their natural predators by mail order. No, really. Just make sure that you get predators which occur naturally in your area, and be careful of upsetting the delicate balance of your garden’s ecosystem. After all, aphids still have a role to play.
Spider mites are another pest you should keep a watchful eye out for. While spider mites and other pests won’t harm your spirea too much to begin with, it’s best to deal with them early, as rife infestations can be difficult to eradicate entirely.
You won’t be able to spot spider mites without a magnifying glass, as they are minute. You will be able to see the carnage they leave behind, however.
Signs of a spider mite infestation include small yellowing spots on the foliage, as well as fine webbing around the leaves and branches.
This webbing can cause other fungal diseases, so make sure you remove it with a cotton swab dipped in rubbing alcohol and water.
To get rid of the mites themselves, you can use a dilution of neem oil and water to spray the plant with, which will help kill off the mites.
Just make sure that you use goggles and gloves, and you don’t do this on a windy day or until the late afternoon, when there will be the least amount of pollinators around.
To help make sure that these spider mites don’t make a reappearance, you should make sure that you water the plant thoroughly. Often, they can affect plants which have gotten too dry for too long.
While all of these potential issues make the spirea sound quite vulnerable, it really is robust when compared to other flowering plants you can grow in your garden.
Spirea Types to Grow in Your Own Garden
If you’re planning on sourcing your spirea from online or mail order, the best time to buy them is between fall and the first few weeks of spring, when spirea is in dormancy.
It’s less stressful for the plant, which means it will arrive in a much better condition to begin with, and it’ll need less time to recover from its journey.
Spiraea japonica ‘Magic Carpet’
Spiraea japonica ‘Magic Carpet’ is an award-winning variety, which is perfect for beginners. It’s easy to grow, and you can grow it in pots, or borders.
Depending on how you prune it, you can cultivate ‘Magic Carpet’ as a ground cover, a shrub, or a hedge. It will provide your garden with color throughout the summer months, when it will burst into glorious shades of pink with tiny flowers.
It’s also great for smaller gardens where space is at a premium, as it will reach 60cm high and wide if you let it grow.
It also helps that it’s a drought tolerant cultivar, so you won’t have to keep a very watchful eye on it very often.
Spiraea japonica ‘Flaming Mound’
A compact variety, Spiraea japonica ‘Flaming Mound’ can reach a maximum of 2 feet tall, spreading about the same. Both the foliage and the flowers are a sight to see.
‘Flaming Mound’ really lives up to its name with its leaves, which have more than one season of interest. When the leaves first appear, they adopt a brilliant red color, which matures to a golden yellow during summer, and then turns a rich crimson in autumn.
The blooming period is also pretty special. During the last few weeks of spring and into summer, ‘Flaming Mound’ produces bright purple flowers at the ends of each branch.
It has a fast but tidy growth habit, making it perfect as a ground cover plant, or in any other way you choose to grow it. It’s also fairly long-lived, able to thrive for at least twenty years under the right conditions.
Spiraea x vanhouttei ‘Renaissance’
If you’re looking for a spirea which will grow well as a large shrub and hold its own as a focal point, Spiraea x vanhouttei ‘Renaissance’ may be the variety for you.
It can reach a maximum height of 5 feet in the right conditions, spreading to about 7 feet, so you’ll need plenty of space, or be willing to prune it regularly.
This is a hybrid variety, which is a more robust version of the Vanhoutte spirea, featuring a tidier growth habit than the original, as well as being more resilient against disease such as powdery mildew.
This is a spring flowering type of spirea, when it really shows off. It produces sprays of cascading, tiny white flowers on top of the green leaves, from the middle of spring, capable of keeping them into the early days of summer.
It’s also known as the bridalwreath spirea. It is worth knowing that the foliage of this particular spirea doesn’t change color before it falls in autumn, so you’ll need to go for a different variety if you want warm tones in autumn.