False spirea or false spiraea is a species of flowering plant in the sorbaria genus of shrubs. Native to parts of Asia, this plant was later introduced to Europa and North America.
False spirea now commonly grows in gardens as an ornamental, producing clusters of showy white flowers in the Summer.
This deciduous perennial has serrated leaves rather similar to those of ferns, and there are several award-winning cultivars that have been developed.
Known as false spirea due to its similarity of its flowers to those of spirea, false spirea has become considered as an unwelcome, invasive species in many regions.
Sorbaria sorbifolia is the most widely grown and easiest species in the sorbaria genus and grows rapidly. It also suckers freely and forms dense thickets that can out-compete native species.
The cultivar “Sem” developed by a Dutch plantsman combines the tough hardiness of its parents, together with a compact, slower growth rate. “Sem” also provides considerable leaf interest, changing color from Spring to fall.
The colorful foliage is especially noticeable when the false spirea is planted in good light. This deciduous shrub sports clusters of white flowers that resemble those of astilbe.
|Scientific name||Sorbaria sorbifolia|
|Common names||False spirea|
|Height||5 to 8 feet (2.5 m)|
|Width||5 to 8 feet (2.5 m)|
|USDA Plant Hardiness Zone||Zones 2 to 9|
|Native to||Central and Eastern Asia|
|Plant specific features||Leaf color in fall can be showy with some cultivars|
How to Plant and Grow a False Spirea Bush
Once planted, beware! If you don’t keep control of the false spirea, it will grow and colonize. This is how it can become invasive and take over native species.
If you have plenty of space to allow the shrub to spread naturally, then there is no problem. However, where space is limited, if you plant a false spirea in an already well-filled border, it will send up suckers that shoot from the base of the shrub and spread widely.
Fortunately, false spirea is tough and will survive harsh pruning in the early Spring. You can even chop off the new shoots at the root level.
Where to Plant
False spirea will grow in the toughest climatic conditions. It comes from the Ural Mountains in Russia, and grows in Siberia and Kazakhstan, so not surprisingly, it is resistant to extreme cold!
Sorbaria sorbifolia is a shrub that is tolerant of both atmospheric pollution, and also of salt. Therefore, it can be used successfully in coastal gardens and for sites next to a roadside.
False spirea is a shrub that can be useful for erosion control, and for planting where the soil is unstable. This is a great choice for planting on a slope or bank.
This shrub can be used for mass planting and will provide cover for large spaces relatively quickly. It can also look good as a specimen shrub when planted singly, although this will require quite a bit more care and regular trimming in order to maintain an attractively shaped, controlled plant.
Even the more compact cultivars of false spirea can produce unwanted, excess growth. If you wish to contain the shrub’s spread, consider planting it in a pot. The pot will restrict the growth and spread of the root system.
It is easy to control the top growth with a container-grown plant. Keep the pot somewhere that gets some shade, and it will need more watering than an in-ground plant.
Pots, particularly those made from plastic or similar material, dry out quickly.
When to Plant
Ideally, plant the Sorbaria sorbifolia in the Spring. A container-grown plant can also be planted at any time of year, although it’s always best to avoid planting or transplanting during periods of extreme heat or cold.
And if the ground is frozen, you won’t be able to plant a false spirea or anything else, of course!
False Spirea Shrubs Care and Maintenance
For optimum results, plant the false spirea in well-drained soil. It will grow in all types of soil, from clay to sand. However, it will grow less vigorously when planted in heavy clay soils. The soil should ideally be neutral or just alkaline.
You can add some organic matter to the soil when you plant the false spirea; this will help to provide richness to the growing medium and encourage rapid and vigorous growth.
One of the reasons this plant does so well and can become a nuisance is that it is low maintenance! False spirea is resistant to dry spells, so it is unlikely to need supplementary irrigation.
If however, the leaves start to go yellow, then this can be a sign of water shortage particularly in hot dry weather.
A newly planted shrub must be kept moist for its first growing season in order to allow its roots to become established.
Fertilizing the newly planted false spirea will result in more flowers and larger blooms. The best type of fertilizer is a granular, slow-release product that is designed for deciduous, flowering shrubs.
A balanced, universal composition should be used, such as 20-20-20. Mix a little into the soil or other growing medium at the time of planting to get your shrub off to a vigorous start.
Alternatively, you can use an organic product, which will also produce good results.
During the year, you can apply liquid fertilizer in both the Spring and early Summer, diluted as per the manufacturer’s instructions.
Never continue feeding your shrub after the middle of the Summer, as this will encourage new growth to form when the temperatures are starting to fall.
Plant the false spirea shrub somewhere that receives full sun or at least only a little shade. Especially important for growing the cultivars, because the attractive foliage color is much more showy when the shrub receives plenty of sunshine.
Sorbaria sorbifolia will also grow faster and more vigorously if planted in full sun. So if you wish to control the growth and spread of the shrub, consider planting in partial shade, where it will still thrive, but grow slower.
Pruning and Repotting
Unless you have the space to let it wander, you will need to keep the false spirea in check. Hard annual pruning should be carried out in the early Spring.
You can also take a sharp spade to the base of the plant and chop off the new shoots that will form suckers if left attached to the plant.
If the shrub has become too unruly, you can dig it up and cut off a section of its root formation. A small section can then be replanted, which can be controlled by annual pruning.
S. sorbifolia will not suffer if you cut it back to the ground each winter. It will come back in the Spring and continue its vigorous growth!
Pruning the false spirea will result in larger flower clusters, so it is a worthwhile task, even if you don’t need to reduce the size of the shrub.
As with all shrubs, it is important to maintain a healthy plant. Remove any dead or damaged wood as soon as you notice it, as this will help to prevent pests or diseases.
Remove the spent blooms once they start to fade in order to keep the plant looking more attractive. Deadheading the false spirea promptly will also result in more flowers that continue coming for longer in the summer.
This is a shrub that is easy to propagate, and there are many ways in which to do so. You can sow seeds, harvested at the end of the Summer.
False spirea will self-propagate if allowed to do so, and this is how it can become invasive. This shrub will send up suckers from its base.
These already have roots attached, so an easy way to multiply the false spirea plants is to simply cut these off and replant them. You’ve already had the difficult job done for you!
Similarly, if you dig up part of the false spirea, you can replant through root division and multiply the shrubs in this way. Propagation can also be effectively carried out by layering low-growing branches.
Simply peg these branches down into the ground and leave them alone to root naturally. Once rooted, you can detach them from the parent plant and pot the rooted cuttings up in the normal way.
Finally, it is possible to take stem cuttings of the false spirea in the Spring or early summer. They should root easily, provided they are kept moist. Protect the cuttings until they have rooted and allow them to over winter before planting out the following spring.
Pests and diseases
In common with the low-maintenance, easy-care nature of the false spirea, this is a shrub that isn’t likely to be troubled by pests or disease. Just make sure it is planted in soil that drains freely.
The fast, sometimes aggressive growth of the false spirea can result in unwanted spread and the shrub can take over and risk eliminating neighboring plants. To avoid this, remove the runners that shoot from the roots as soon as they appear above the ground.
Temperature and Humidity
False spirea hails from some parts of the world that are known for extreme, harsh climatic conditions. It will grow in USDA zones 2 to 9 and survive even at temperatures that go as low as -40° C.
Other Uses for False Spirea
False spirea, particularly the smaller compact cultivars, can be used to improve soil stability and erosion control. The shrub’s extensive and quick-growing root network will compact the soil and hold it together, minimizing dust and soil loss.
Similarly, you can use this shrub to make an effective windbreak.
Since parts of the false spirea, notably the flower buds, and leaves, contain hydrogen cyanide, it is not advisable to ingest this plant.
Despite its toxicity, however, there are claims that in very small quantities, and under professional advice, false spirea can treat certain maladies.
S. sorbifolia can tolerate atmospheric pollution, so it is a useful addition for roadside planting.
Types of False Spirea You Can Grow
Sorbaria sorbifolia “Sem” is a dwarf cultivar that will only grow to a maximum of 5 feet
(1.5 m) in both height and spread. The cultivar “Sem” is also known as ash-leaf spirea or Ural false spirea.
This plant has received the Royal Horticultural Society (RHS) Award of Garden Merit. False spirea “Sem” is a shrub that grows with upright stems, and forms a dense foliage. When planted in good light, it is very colorful, providing long-lasting and multi-seasonal interest.
This shrub flowers on new wood. If it has become too large and untidy for its planting position, cut the false spirea hard in the late winter or very early Spring, just before the buds start to develop.
You need to keep a continual eye out for the root suckers and dig them out promptly.
*image by aga77ta/depositphotos