Physocarpus

( fiss - oh - KAR - puhs )

At-A-Glance Information

Commonly called Ninebark, this genus of deciduous shrubs includes species that need either sun or shade and moderate to regular water to perform well in the garden. Their common name refers to the peeling quality of their bark, which strips off to reveal many layers underneath. Flowers bloom in clusters of white or pink during spring and early summer months and will draw pollinators into the landscape. These are versatile plants that provide seasonal foliage color and are great in mixed beds, as formal hedges, and as background foliage. They are also great for mass plantings on sloped areas for erosion control and in rain gardens or bioswales.

Physocarpus Species and Varietals

The genus Physocarpus includes 8 to 10 distinct species and is a member of the plant family Rosaceae. Plants in this genus are closely related to Spiraea (Meadowsweet). Ninebark growing zones vary depending on the species; for more information, see the descriptions below. To find your zone, click here: Zone Map.

Physocarpus capitatus (Pacific Ninebark, Tall Ninebark, Western Ninebark)
This species of Ninebark grows well in USDA hardiness zones 4-8 or Sunset growing zones 2b-9 and 14-19 and is native to the mountain ranges of western North America. Individual shrubs reach up to 5-10 feet tall and wide at maturity and produce dense clusters of white flowers that open from attractive buds. Seed heads that follow are attractive and can be left on shrubs through winter.

Physocarpus opulifolius (Common Ninebark, Atlantic Ninebark, Eastern Ninebark, Ninebark)
This species of Ninebark grows well in USDA hardiness zones 2-8 or Sunset growing zones A1-A3, 1-10 and 14-17 and is native to eastern and central North America. These shrubs reach to 9 feet tall and 10 feet wide, with white to pink clusters of flowers. Cultivars are more ornamental and more commonly cultivated than the straight species. They are listed and described below:

'Diabolo'
9-12 feet tall and just as wide, with red-purple foliage. Better color in sun.

'Luteus'
Foliage is yellow in sunlight and yellow-green in shade; reaches 9-12 feet tall.

'Center Glow'
6-8 feet tall and wide, with green-gold new foliage that matures to burgundy.

'Coppertina'
6-8 feet tall and just as wide, with copper-orange foliage.

'Dart's Gold'
This variety reaches 4-6 feet tall and wide with bright yellow-green foliage.

'Summer Wine'
Dark purple leaves on a compact plant 4-6 feet tall and wide.

'Nanus'
Foliage is dark green, leaves are lobed. Compact variety.

'Lady in Red'
Purple-red foliage on a compact plant reaching 4-6 feet tall and wide.

'Nugget'
Leaves begin golden-yellow and mature to lime green, turning gold again in fall.

Caring for Physocarpus

Ninebark shrubs will naturally spread in favorable growing environments, forming thickets or colonies through root sprouts and basal suckers. Before planting Physocarpus shrubs, consider installing a 24-36 inch deep root barrier that extends an inch or two above the soil surface to prevent spread and possible damage to nearby foundations, patios, or pipes. Plant Ninebark shrubs in full sun to partial shade. Ideally, they should be getting between 6 and 8 hours of sun each day for the best overall growth and flowering. Check sun exposure requirements for your specific shrub before planting, as it will vary depending on the species and cultivar. Those with dark foliage will have deeper color the more sun they receive and those with chartreuse or golden foliage appreciate more shade, especially in the afternoon. Ensure that the soil is fertile, loamy, and slightly acidic to neutral (between 5.0 and 8.0). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention.

After planting, water regularly to ensure the shrub establishes a strong root system. Once mature, provide consistent moisture. Although these plants are relatively drought-tolerant, they will look better with regular water. As a rule of thumb, water deeply when the top inch of soil becomes dry. Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. Ninebark shrubs are generally low-maintenance when it comes to pruning; they bloom on old wood, so the best time to prune for shape is just after flowering ends in late spring or early summer. Simply remove dead or damaged branches and lightly shape. Flowers can be deadheaded, but doing so will not encourage more flowers to form, and the seed capsules that follow have ornamental value. For older, established plants in need of a rejuvenation, cut older stems to the ground (about 6-8 inches tall) in early springtime. Ninebark shrubs are considered long-lived perennials, with an average life span of 15 to 20 years in the landscape.

Caring for Physocarpus in Containers
Physocarpus shrubs are wonderful in the ground, but can also be grown in containers, where their pendulous branches can take center stage. Choose a container that is at least a few inches wider and deeper than the nursery pot or root ball. When mature, they will require a pot that is at least 24 inches wide and deep. Ensure that the pot has adequate drainage holes on the bottom to allow for excess water to flow away. Fill with a well-draining potting mix amended with organic material and perlite, and top with a layer of mulch to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water regularly as the plant establishes itself in its new home. Once established, waterings can be lessened. Physocarpus plants grown in containers will need more frequent irrigation than those grown in the ground. As a general rule of thumb, water whenever the top few inches of soil feels dry to the touch. Prune to remove dead, damaged, or diseased foliage at any time during the growing season. Every few years, check the bottom of the pot to ensure that the plant is not outgrowing its root space. If roots are growing through the drainage holes in the bottom of the container, it is a good indication that it needs to be potted up; choose a slightly larger container and repot.

Harvesting Physocarpus
Ninebark shrubs produce flowering stems, foliage and late summer seed capsules that are highly prized in floral design. The best time of the day to harvest is in the morning, after dew has dried but before the heat of the day has set in. The species most commonly grown for its cut flowers is Physocarpus opulifolius (Common Ninebark), which offers cultivars with white or pink blooms. To harvest flowers, wait until about 50% of the tiny, delicate florets in the clusters are open. Using sharp, clean shears, sever the stem from the rest of the plant below a node, remove the leaves below the water line, and drop the stem into a bucket of cool water. They have a vase life of 7 to 14 days. To harvest the decorative seed capsules, follow the same instructions but harvest in late summer or early fall when they have attained their desired color. Ninebark foliage is used as filler in fresh flower arrangements as well, and is typically harvested in summertime. Cultivars with bronze, maroon, or purple foliage can really make a statement in bouquets.

Propagation

Physocarpus can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your shrub, follow the instructions below:

Propagating Physocarpus by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch softwood portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Place your cutting in the hole and fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.

Propagating Physocarpus by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds. The seed pods on Physocarpus plants are pretty easy to spot, they're large and are left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will begin to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 3-4 weeks from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.