The Only Guide You'll Need for Growing Caryopteris

The Caryopteris genus is made up of seven species of low-maintenance, late-flowering shrubs to liven up your autumn landscape. These aromatic plants are covered with blooms in shades of true blue from late summer up until the first frost, with a few cultivars flowering in white and purple. The small dome-shaped shrubs are valued for finely textured foliage including green, silvery gray, golden, reddish-purple, or variegated color depending on the type.

Cultivars of the species Caryopteris x clandonensis are increasingly popular with American gardeners. These subshrubs share characteristics with butterfly bush including reseeding, however, unlike some buddleia cultivars, caryopteris is not considered invasive.

Caryopteris Care

Caryopteris is a major pollinator plant that provides late-season food for bees and butterflies. It also delivers plenty of color and interest for your effort as a plant easy to grow in pots, perennial beds, borders, and in massed groupings. An added advantage is deer resistance.

Growth habit is similar to butterfly bush with mostly softwood and flowering on new shoots. Caryopteris is also root hardy to zone 5 but top growth often dies back in zones 5 and 6 during winter.

How to Plant Caryopteris

Caryopteris is usually planted in spring but can be planted in autumn in warmer regions. Spring planting should take place after all danger of frost has passed. For autumn planting, set caryopteris out about four weeks before the first frost.

Dig a hole approximately twice as wide as the rootball and deep enough so the crown rests at the same level as in its original pot. Then place the shrub in the planting hole feathering out the roots. Backfill the soil, lightly tamp down, and water well. If you are planting more than one caryopteris, space shrubs about two feet apart.

For growing in pots, choose a container at least twice as wide as the rootball with good drainage holes. Fill it with a combination of high-quality potting mix, compost, and sand. Plant the caryopteris following the directions above. Potted plants need more frequent watering and benefit from regular feeding with a balanced liquid fertilizer.

Light

Caryopteris needs full sun at least six hours daily. Planting in the shade leads to thin foliage and a dearth of flowers.

Soil

This shrub does not tolerate soggy soil which causes root rot. Neutral, well-draining loam is the preferred soil type ranging from slightly acidic to slightly alkaline with pH levels of six to eight.

Water

Water young plants regularly when the top 2 inches of soil are dry to support root development. These plants mature fairly quickly often reaching full height of 2 to 3 feet in one season and are fairly drought tolerant once established.

Termperature and Humidity

Caryopteris is heat- and drought-tolerant once established, but extended periods of temperatures above 90 degrees Fahrenheit create a need for more frequent watering. The ideal temperature is from 65 to 85 degrees Fahrenheit. Roots are cold hardy to zone 5 with top growth dying back during cold weather. Top growth is hardy to zone 7, however many gardeners choose to go ahead and cut the shrubs back at the end of the bloom period. Protect roots with a 3-inch layer of mulch in areas where temperatures dip to 20 degrees Fahrenheit.

Fertilizer

Fertilizing caryopteris is optional and plants respond better to organic soil amendments than to inorganic products. To give young shrubs a boost, apply a balanced fertilizer such as an NPK 10-10-10 in early spring. For a more suitable alternative work aged compost, garden, or potting soil into the planting hole.

Types of Caryopteris

New cultivars from crossbreeding within Caryopteris species appear regularly and cultivars of C. clandonensis have proven especially successful and popular in US gardens.

Caryopteris divaricata 'Snow Fairy': A cultivar from Japan, snow fairy features variegated green foliage with irregular white margins and an off-putting scent. Flowers are blue. Winter protection is advised.
Caryopteris x clandonensis 'Dark Knight': This cultivar blooms in a deep bluish purple with green foliage and a silvery cast on the leaf underside.
Caryopteris x clandonensis 'Summer Sorbet': Notable for its variegated green foliage with golden edges, this plant also features light blue blooms.
Caryopteris x clandonensis 'Hint of Gold': Formally named 'Lisaura' , this cultivar has dark blue flowers and outstanding variegated golden foliage with mint green leaf edges.
Caryopteris x clandonensis 'Lissilv' Sterling Silver: Season-long showy silver foliage elevates this cultivar with violet-blue blooms.

Pruning

Caryopteris blooms on new wood so pruning is done after the bloom period has ended in autumn or in early spring before new growth begins. Cold tolerance of the top growth depends on variety and growing zone but many gardeners choose to prune caryopteris back to ground level in autumn to allow for new growth in spring.

Prune old and damaged wood from the center of both in-ground and potted plants in early spring before new growth appears. Gentle trimming can be done to maintain a pleasing shape throughout the growing season, but heavy pruning significantly reduces the number of flowers later in the season.

Propagating Caryopteris

Softwood stem cuttings are the easiest method for propagating caryopteris. It can be grown from seed collected dry in autumn then surface sown and given a period of cold dormancy. However, since most cultivars are hybrids, increasing your collection with softwood cuttings is more reliable and best accomplished in summer. You'll need a hand pruner or snip, small pots, rooting hormone, and potting mix. Follow these steps.

1. Use the pruner or snip to remove a 6-inch green stem from the terminal end of a branch, cutting just above a leaf node.
2. Remove all but the top set of leaves.
3. Fill the pot/s with moistened, loose, well-draining potting mix.
4. Use your index finger or a pencil to make a narrow, deep hole in the center of the pot.
5. Dip the bottom portion of the cutting in rooting hormone. Caryopteris will form roots between leaf nodes,
6. Insert the cutting into the hole in the center of the pot and firm the soil around it.
7. Water gently but thoroughly and place in a sunny location.
8. Roots should form in seven to 10 days. Give the cutting a gentle tug to check for resistance which indicates roots have developed.

Potting and Repotting

Caryopteris are relatively small shrubs with a natural neat growing habit and adapt easily to growing in large pots. Follow the directions under "Planting" for container and patio gardens.

The shrub reaches its mature size in one season. You may need to pot up initially during the first year into a slightly larger pot to allow room for mature root growth. Starting out with a pot that's too large can result in overly soggy soil and root rot. In subsequent years repotting need only be done to renew the growing medium.

Overwintering

Caryopteris roots are cold hardy to USDA zone 5 but a layer of mulch can help protect them when temperatures drop below 20 degrees Fahrenheit. If you experience especially harsh winters you may want to plant in a protected location. Move pot-grown shrubs into an unheated garage, basement, or porch. When overwintered indoors as a houseplant, the plant goes into dormancy and loses all its foliage.

Common Pests and Plant Diseases

Caryopteris is relatively free of both pests and plant disease. Depending on where you live, your shrubs may attract pests or fungal diseases endemic to your specific environment.

Infestations are rare and the only real issue to guard against is root rot. Avoid overwatering, plant in a sunny location with well-draining soil, and choose containers no more than twice the width of the rootball. Cedar and cypress mulches emit oils that insects don't like so choose these materials to keep roots hydrated and healthy.

How to Get Caryopteris to Bloom

Caryopteris blooms vigorously and, even though the shrub doesn't have a long life span, it compensates by providing unparalleled color and interest to the late-season garden.

How Long Does Caryopteris Bloom?

Bloom time may vary somewhat on where you live but caryopteris is a late-blooming shrub that begins its display in late July, lasting through September and often up until the first frost.

What Do Caryopteris Flowers Look and Smell Like?

True blue flowers from light to darker violet shades are a hallmark of caryopteris. New cultivars sometimes offer blooms in white or shades of purple. Both flowers and foliage are fragrant with leaves giving off a eucalyptus-like aroma when crushed. Not all cultivars are especially pleasing to the nose as is the case with the variety 'Snow Fairy.'

How to Encourage More Blooms

Make sure to plant in plenty of sun as shade results in shaggy plants with fewer flowers. For in-ground shrubs, avoid overly rich soil amendments and fertilizers which increase foliage but decrease flowering. For container-grown plants use a well-draining potting mix and a balanced liquid fertilizer according to the label.

Caring For Caryopteris After It Blooms

While caryopteris can reseed, it is not an aggressive reseeder like some varieties of buddleia. However, you can prune your shrub partially to remove spent flowers or you can prune caryopteris to the ground after the bloom period has ended. It will regrow in the spring and bloom on new wood.

In zones 5 and 6 foliage is likely to die back in winter regardless. In zones 7 to 9 foliage may remain on the plant. No matter your growing zone, you'll want to prune out dead wood and, at minimum, do a little shaping either in late autumn or early spring before new growth begins.

Common Problems With Caryopteris

The most common problem with caryopteris is wilting due to oversaturated roots. Amend heavy clay soils or plant in a location with loose well-draining soil. Avoid overwatering established plants by irrigating when the soil is dry to a depth of 5 inches. Young plants should be watered when the top 2 inches of soil is dry. Check the soil for moisture since wilting can be a sign of both under and overwatering.

From: thespruce