Caryopteris is not a Spiraea

It is unfortunate that Caryopteris has the common name of Blue Spirea for it is not a Spiraea and it’s just plain confusing. How this came about I do not know as they are not even in the same family; Spiraea is in the Roseaceae family while Caryopteris is in the Verbenaceae family.

The genus Caryopteris is comprised of roughly 15 species, most being native to Asia. Only are few of these species are grown in North America as ornamentals. The majority of the ornamental selections sold here are hybrids; Caryopteris x cladonensis (pronounced Cary-op-ter-is clan-don-en-sis) which is a hybrid between Caryopteris incana and Caryopteris mongholica. Unless otherwise noted, the following information here after refers to this hybrid.

Caryopteris is a fall flowering shrub with rich blue to purple-blue flowers. While it is hardy to USDA zone 5, it is typically a die-back shrub in the North, behaving much like a Buddleia. While the plant makes woody stems, they are tender and die back during the winter. As the plant grows back quickly in the spring and its flower buds (and flowers) are formed on new wood so the plant does not miss a beat.

Culturally there are three things necessary to grow a nice plant. First off, it loves full sun. It will grow in partial shade but it will not look happy or flower nearly half as well as a plant in full sun. In addition, the yellow leafed cultivars have much better color in full sun. In partial shade the leaves will appear a dull, washed out green. The next thing to know is that Caryopteris needs well drained soil. It will not tolerate heavy, wet clay soils, or at least not for long. People often blame the plant for not being winter hardy because their plant did not make it through the winter, but the real culprit is wet soil. Well drained soil is a must. Once established Caryopteris is very drought tolerant and requires even less water. My final bit of cultural advice deals with pruning – as the plant typically dies back in the winter, you should only have to prune the plant once and that is in the spring after the plant starts to grow. Simply cut the plant back to wood with active sprouts. If you wish you can give the plant a slight shearing in early summer to bulk of the body of the plant. Fall pruning is not recommended, as it stimulates the plant to grow when it should be going dormant - the result can be a dead plant the following spring.

Caryoteris is a wonderful garden plant because it offers a mass of colorful blue flowers in late summer when few other plants are blooming. It’s a great source of pollen for bees and butterflies. Its aromatic foliage is turn off to deer so it rarely bothered by Bambi and her four legged friends.

There has been a flurry of Caryopteris breeding over the past 15 years and we have never had such wonderful plants for the garden. Here are a few of the newest cultivars to hit the market.

Petit Bleu (‘Minbleu’) is one of my favorites as it is a semi-dwarf plant with very tight branching and a nice mounded habit. The flower color is a very dark blue and the foliage is very dark and glossy which makes a great background for the flowers.

Sunshine Blue (‘Jason’) is a yellow leafed form of Caryopteris incana. It is a larger plant than most (3-4’) with masses of clear blue flowers that appear a bit earlier than other varieties. This English selection has very good hardiness and is more adaptable to heavier soils. It was a vast improvement over ‘Worcester Gold’ which can look a bit ratty by mid summer.
Lil' Miss Sunshine ('Janice') is new variety that I hybridized using Petit Bleu and Sunshine Blue. This plant has be best attributes of both parents as it is hardy, compact with glossy bright yellow foliage. The abundant flowers are a rich clear blue. It should be available in summer of 2010.

‘Sterling Silver’ is a new selection from the renowned English plantsman Peter Catt. It is a silver leafed selection that will most certainly replace 'Longwood Blue' once it is more widely available.

There has been a rash of variegated forms released in the last few years. Two of the better looking plants are ‘Summer Sorbet’ which has green and yellow leaves, and ‘White Surprise’ has silvery-green leaves adorned with a thin cream margin of variegation. As with most variegated plants, these will throw the occasional non-variegated shoot. Simply prune and remove these shoots as they appear

Dr. Shim - The Mike Dirr of Korea

Some of you may have read one of my older posts on plant hunting in Korea. It was one of my greatest adventures and it explains how I met Dr. Shim. Well Dr. Shim just spent three days with me at Spring Meadow Nursery. He came to see some of his new Hibiscus syriacus selections that we are evaluating for potential introduction. Dr. Shim developed Lil’ Kim Hibiscus – the first dwarf rose of Sharon. This is a great little shrub that unfortunately is still hard to find. If you can find it give it a try!

I like to call Dr. Shim the Mike Dirr or Korea. For roughly 30 years he was the Professor of Ornamental Horticulture at Sungkyunkwan University, in Suwan just outside of Seoul. Just like Dr. Dirr, Dr. Shim has roots at the University of Illinois. This is where he got his Ph.D., and where spent a year as a visiting professor. He is now retired and spends his time golfing and breeding Hibiscus, Forsythia and Korean Tiger Lilies.

Dr. Shim got into horticulture as a young boy. His family owned a pear orchard. He told me that one of his first jobs was bagging pears. In Korea, pear growers bag the fruit while still on the tree to protect them from insects and disease. Ten women would make bags out of old news papers and each tree would require up to 500 bags. You can image it took a good deal of time to bag every pear in the orchard yet this did not dissuade Dr. Shim from continuing on in horticulture. He went on to study post harvest physiology, just as I had. After working for three and a half years on his Ph.D. in Champaign we retuned home to teach pomology in Korea. In time, his position was changed to ornamental horticulture. The rest is history.

While traveling, looking for new plant is great fun; it’s also a pleasure when breeders come to visit me. We spent two days touring the nursery, looking over new plants, scouting the seed beds for treasures and most importantly evaluating his 20 or so cultivars we have under evaluation. I’m happy to report there are many fine plants and I suspect a few will make it to market in the coming years. The hard part will be narrowing the plants down to the best three or four cultivars. His dwarf Hibiscus selections look great and have the potential to widen the Lil’ Kim line with a broader color range.

As I’ve said before I have a great job. I get to see really cool plants long before anyone can buy them. But the best part of my job is meeting the special people that develop these plants. Dr. Shim is more than just a special plant breeder. He' is a special friend.