Caryopteris

Botanical/Latin
   Caryopteris

Pronunciation
   Kar-i-op-ter-is

Common Name
   Blue Spirea

Hardiness zone range
   6

General Comments
Valuable late summer flowering shrubs that are small in stature but big in ornamental value. They grow into neat, rounded bushes with slightly aromatic, silvery foliage and clusters of finely textured blue flowers that are carried at the tips and leaf axils of slender branches. They are highly prized for a variety of reasons, most importantly the flowers come in shades of blue (true blue) and break into flower in late summer and early autumn at a period when most other plants are in decline. The individual flowers are small but packed in clusters that show up and blend beautifully with the foliage.

Light Preference
Full Sun

Culture & Care
They are resilient, easy to care for plants that thrive in most well drained soils; they cope with less than perfect conditions, tolerating alkaline and sandy soils and, once established, withstand moderate drought and even root competition from other plants. While they are tenacious, they grow and perform best in fertile conditions, so improving the site at planting time and then following up with good culture is well worth the effort. Incorporating extra organic matter (peat, planting, compost, etc.) into the surrounding soil and mulching after planting will help retain valuable moisture and improve the soil structure. A spring dressing with a well-balanced fertilizer, worked into the surrounding soil, will sustain healthy growth and improve vigor later in the season. They are generally free from any serious pests or diseases.

Pruning
They flower on the growth made during the current year, so they should be pruned hard (cut back to 4-6 inches of ground level) in the spring of each year after danger of hard frosts has passed. This stimulates strong, vigorous growth, nicely formed bushes, and improved flowering. In colder areas, this often happens naturally; the branches die back to the crown rendering them more herbaceous than woody. In this case, it is best to wait until the new basal growth begins to sprout in spring, removing the dead wood and trimming back those remaining.

Uses
They are great for small-scale situations and work equally well as individuals, or, if space allows, placed in small groups. They are very effective when used as low flowering hedges and a favorite spot is towards the front of shrub or mixed borders or, on a larger scale, grouped informally on banks and sloping sites. They are quick to establish and are ideal for placing in new gardens among other slower to mature species. They give an almost instant display without becoming invasive or overpowering. Since the foliage is a gray-green color and their habit is rounded and mounding, it is worth thinking of placing them in the midst of dark colored, low ground cover or in perennial borders where the icy blue flowers and silvery leaves make a welcome and cooling contrast to the late summer conditions. The foliage is slightly aromatic, so they would not look out of place in herb gardens. They are sun lovers, making them useful in raised beds and rockeries, or in beds around patios, decks, and swimming pools, or placed at the base of sunny walls and buildings. They last well as cut flowers and a few stems placed in a vase or arrangement will brighten and freshen rooms and dining tables. Butterflies are attracted to the flowers and, while it is true to say they are not butterfly magnets, butterflies still will visit, adding life and movement to the garden on a warm summer's evening.

Background
The common name Blue Spirea comes from their resemblance to shrubby Spireas. The Genus name Caryopteris comes from the Greek words Karyon (nut) and pteron (wing), which relates to the small winged fruit that forms after the flowers. There are about 5 or 6 species, all native to Eastern Asia, and are represented in our gardens by cultivars of a chance hybrid (Caryopteris x clandonensis) that first occurred in the garden of Mr. A. Simmonds at West Clandon, Surrey, England around 1930. Arthur Simmonds wanted to propagate Caryopteris mongolica; it is a small bushy species with comparatively large rich blue flowers that had been introduced from Mongolia which experiences frigid winters and hot summers. He gathered seeds and when they grew and flowered, he noticed that some seedlings had characteristics which resembled another species from China and Japan (Caryopteris mastacanthus now C.incana) that he had growing nearby. He deduced that they were hybrids and since Caryopteris mongolica was short lived and not suited to the mild temperate conditions, they might be worth cultivating. Then, quite by chance, he noticed a vigorous, self-sown seedling with similar hybrid characteristics growing near the original Mongolian plant. It proved to be more vigorous and floriferous than either parent and combined the reliability of C. incana with the deeper blue flowers of C. mongolica. This was named Caryopteris x clandonensis and later became known as Caryopteris'Arthur Simmonds.' It grows between 2-4 feet with slightly aromatic, silvery-gray foliage with powdery blue flowers. It was awarded a First Class Certificate and Award of Garden Merit by the Royal Horticultural Society in Great Britain and when evaluated in trials at the Chicago Botanical Garden, it proved to be the hardiest of all the cultivars tested. Other cultivars of note are: Caryopteris 'Blue Mist': A nice selection with attractive, silvery foliage and powder blue flowers. Caryopteris 'Dark Knight': A sturdy grower with dark, blue-purple flowers Caryopteris 'First Choice': An excellent selection with compact habit and noticeably darker, rich blue flowers that start appearing earlier than most other cultivars. It was recently developed and introduced by noted nurseryman Peter Catt at his Liss Forest Nursery in Hampshire, England. Caryopteris 'Longwood Blue': An outstanding cultivar selected at Longwood Gardens, Pennsylvania for its upright silvery growth and abundant production of light, sky-blue flowers. It flowers extremely well, even as young plants. Caryopteris 'Worcester Gold': An eye catching selection discovered by Claude Palmer in Worcester, England that has soft golden colored foliage that blends with the vivid light blue flowers to make a most appealing combination.

Splendor Suggestions
Consider trimming back the spent flower heads (late autumn) to prevent the production of seed and, later on, unwanted seedlings. Caryopteris bushes have a habit of throwing lots of little seedlings that crop up in all sorts of places including paths, cracks in pavement and flower beds. The seedlings are usually inferior with pale insipid coloring and not worth nurturing. On the other hand, if you model yourself on Arthur Simmonds, Peter Catt, or Claude Palmer, we might want to talk to you when you find a new and distinctive selection that is worthy of becoming a Garden Splendor selection. Good Luck!

Companion Plants
The silvery-gray foliage and soft blue flowers are neutral in the color spectrum, rendering them among the easiest of all plants to position with compatible partners without any concern of creating a color clash. Many perennials are well suited to the same soil conditions, so there are masses to choose from. We suggest Aster x frikartii 'Monch' with its blue, daisy-like flowers or the compact dark purple flowered New England Aster, Aster 'Purple Dome'. If your taste leans more to soft pastels, try it with Dendranthema 'Clara Curtis'; the combination of pink and light blue is simply stunning. Nipponicanthemums (Montauk Daisy) with their big white daisies and the taller growing Boltonia 'Snowbank' break into flower when caryopteris are about halfway through their flowering period and, if trimmed back earlier, the almost perpetual flowering Scabiosa 'Pink Mist and 'Butterfly Blue' and the Ornamental Sages (Salvias) make their encore as they repeat their flowering cycle. The compact Salvia 'Blue Hill' is a particular favorite of ours that is perfect if you are considering creating a "garden of blue". Summer flowering shrubs like Hibiscus 'Diana' 'Aphrodite' and 'Helene' will still have a few lingering flowers and the blue forms like 'Ardens' 'Blue Bird' and 'Woodbridge' will compliment them well. Buddleias, particularly the darker colored forms such as Buddleia 'Black Knight', 'Dubonnet', and 'Nanhoensis Purple', provide nice backgrounds, and, if the weather is kind, they will keep going until Callicarpa bodinieri 'Profusion' drops its leaves and will start to display the spectacular berries that look magnificent. Evergreens and ornamental conifers carry the interest through the rest of the season, and grasses with their glistening heads look wonderful when positioned behind, to the side, or in between flowing drifts. Pennisetums, Miscanthus, and Panicums offer lots of opportunity to find good partners, matched only by the rustling, pendulous heads of Chasmanthium. All combine to form a magnificent autumnal display.