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Botanical names: Spiraea japonica is the most likely grown and best-known of the species that make up the genus spiraea, derived from the Greek word speira, which can also be used to denote a floral wreath.
It was named originally for some southern European species, but these are not in cultivation.
Although there are a few species, such as Spiraea canescens, that are not of Japanese origin, the preponderance of garden varieties has been derived from the more decorative Japanese ones.
The Latin word canescens means whitish in colour.
Family: Although it may not look like a member of the rose family, the Rosaceae, a closer inspection of the small flowers will reveal that spirea has the same structure as single flowered roses.
It is a very large family with many garden flowers, including rose, many apple-like fruits, cotoneaster, cherry and the herb burnet.
Garden value
The summer spirea, Spiraea japonica, can make a bush to chest height.
It will reach this size after 10 years or more and it is by no means a large plant, and it is not a plant that is too big for small, modern-day gardens. The colour is a soft raspberry red, somewhat faded, especially as the flowers age.
There are several smaller kinds that suit the small spaces, or the middle-to-front areas, of a mixed border.
‘Little Princess’ makes a rounded bush to less than waist-height with masses of pink flowers now, lighter in colour than the species.
‘Goldflame’ is remarkable in spring for its blazing orange-yellow colour – its foliage turns greenish yellow and the flowers are pink, not a great combination but still a worthwhile summer colour contribution.
‘Anthony Waterer’ is well known with some leaves having a creamy edge and masses of flat-topped dark-pink flowers.
There are white forms too, notably ‘Snowmound’, which has a spreading growth habit. A remarkable form, not often seen, is ‘Shirobana’.
Almost unique among shrubs or other garden flowers, this has puffy heads of either pure white or rich pink flowers, separately on the same bush.
It is obviously some sort of ‘sport’ that does not produce the red pigment in some twigs but does in others. The result is most unusual, but eye-catching and decorative.
Although it receives little mention as a choice garden shrub, the summer-flowering spiraea is still very popular and widely grown in gardens.
Growing spiraea
This shrub is easy to grow and contributes both foliage and flowers, some more than others.
Spiraea is not a plant that jumps out. In fact, it might take a while to realise that this shrub carries a surprising show of flowers. Not a star plant, it is a good filler, a middle-ground plant; and a garden needs plants in this role.
In winter, the leaves fall and the fine twigs have a pale-brown colour, which though unremarkable, still makes a bit of a decorative contribution.
Any of these shrubs can be pruned to keep them to size, but since most are smallish anyway this is not a major requirement, and they are trouble-free, not being much bothered by pests or diseases; except sometimes mildew, if grown in very dry soil.
Spiraea begins to flower in June and continues into August, given sunshine and good soil.
Fruit, vegetables and herbs
Peas could still be sown but are unlikely to give much unless weather conditions suit them. A late crop of carrots could be sown, also the salad vegetables that mature quickly.
Harvest herbs for winter use as they come ready by drying or freezing. Late-planted potatoes may need spraying if the weather is wet.
Lawns
Continue mowing lawns regularly and feed them if the grass looks pale or yellowish. Many lawns are showing signs of hunger as growth slowed due to cool weather and may need feeding with a high nitrogen fertiliser.
If weeds are a problem, apply a lawn weedkiller during a fine spell when growth is active.
Trees, shrubs and roses
Young trees and shrubs, especially bare-root kinds, often take a while to settle in. Even a few dry days after rain, some plants can begin to suffer if they have not made good root growth.
There is rose blackspot and leaf spot disease about. Take note of which varieties are worst affected with a view to removal.
Flowers
Bedding plants in pots and baskets need regular watering and feeding. The roots have filled the pots and watering has become more critical.
Feeding every two weeks or so is essential to keep the plants going after the first flush of flowers. Remove seed heads of flowers that self-sow, such as foxgloves and alchemilla, if not wanted.
Greenhouse and house plants
Continue to train and side-shoot tomatoes and cucumbers. Continue watering and feeding all greenhouse plants to maintain strong growth, especially plants in pots or grow-bags because these can dry out.
Take cuttings of deciduous shrubs of all kinds — especially roses and clematis. Pot on house plants as necessary.
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