Jennifer Schultz Nelson
Extension Educator, Horticulture
It seems like this time of year our gardens are just as exhausted in the heat as we are. Some might say their garden just looks "tired out". We've waited in anticipation for spring and summer's colorful displays, and by August sometimes plants are looking a bit stagnant and worn.
One way to reinvigorate the late summer garden is by using later-flowering plants, those that don't start to put on their display until August or even September. Their fresh blooms will liven up the "same old same old" garden and provide a brand new scene to enjoy.
In my quest to find true blue flowers for my Illini garden, I stumbled on the perennial Caryopteris. Caryopteris, sometimes called Bluebeard, Blue Mist, or Blue Spirea, not only has blue flowers, it typically doesn't start to bloom until at least August and continues through early autumn. In all honesty I bought it for the blue flowers, but am realizing now that the late show of blooms may be equally as valuable.
Caryopteris is a member of the verbena family, and is native to Asia. The genus name Caryopteris comes from a Greek word meaning "winged nut" in reference to the winged seeds that the plant produces following flowering. These seeds will remain on the stems and provide some visual interest during the winter months.
In warmer climates than central Illinois, Caryopteris will grow much like a small shrub, becoming woody and growing each year from buds on last year's growth. But in our Zone 5b climate, it is very common for it to die completely, or for the top portion to die back to the ground each year.
The Caryopteris I purchased several years ago, 'First Choice' has managed to survive above ground, but it is in a fairly sheltered area. I have noticed some dieback at the branch tips, which I simply prune away in the spring.
Depending on the cultivar, Caryopteris are anywhere from 24 to 48 inches tall and wide. They grow unassuming in among the earlier blooming plants, attracting little attention. As the dog days of summer approach, so does their bloom time, and they take center stage.
The flowers are borne at the base of each leaf, in what's called the leaf axil, the area where the leaf attaches to the stem. I've watched in eager anticipation for the last month as tiny flower buds have swelled on my Caryopteris, ready to burst into bloom. Clusters of blue to purple flowers cover the upper portions of the stems from late summer through early autumn. There is one pink flowered cultivar, a new introduction called 'Pink Chablis'. The flowers also attract local butterflies and provide them with a sweet drink of nectar in the oppressive summer heat.
Flowering is not the only attractive feature of Caryopteris. The foliage is also one of its great attributes. The leaves are generally scalloped or notched, fuzzy, and are fragrant when rubbed or crushed. For a few cultivars, the fragrance of the leaves is not appealing. The cultivar 'Snow Fairy' comes with a warning that the leaves smell like cat urine when crushed! Caryopteris are also considered to be deer resistant, probably because of their fragrant foliage.
Several cultivars of Caryopteris are available with gorgeous variegated foliage. Despite their noxious scent, the leaves of 'Snow Fairy' are variegated in bright white. The cultivar 'Summer Sorbet' is an award winning introduction with green leaves edged in bright chartreuse. Other cultivars, like 'Sunshine Blue' have leaves that are entirely chartreuse. The contrast between the blue flowers and chartreuse leaves is particularly eye-catching.
I have added the cultivars 'Snow Fairy' and 'Sunshine Blue' to my garden, but it took a few tries. These cultivars, with their uniquely colored leaves are reportedly even less winter hardy than the green-leaved cultivars. I'll admit I did successfully kill 'Sunshine Blue' twice before I found a spot where it could overwinter in my garden. 'Snow Fairy' survived its first winter, hopefully this coming year will be as successful. Even if these plants fail to overwinter, small specimens are fairly inexpensive and grow into nice sized plants in just one season.
Another feature of Caryopteris that makes it a great garden plant for the heat of summer, is its drought tolerance. Once established, Caryopteris require very little water to not only survive, but thrive and bloom. This is great news for those of us wanting low maintenance plants for the garden, aiming to avoid toting sprinklers or watering cans around in our hot and humid landscapes.
As watering restrictions and even bans become more and more common to conserve municipal water supplies during the heat of the summer, my prediction is that drought tolerant plants like Caryopteris will become far more well-known and popular.
About the only way to fail at growing Caryopteris is to plant in poorly drained soil. They will not tolerate boggy or otherwise waterlogged soil. Mulching in winter is recommended, especially for new plantings. If your plant does not die completely back to the ground, a good haircut in late winter or early spring will help keep the new growth neat and compact.