Sorbaria

sorbaria

( sor - BAR - ee - uh )

At-A-Glance Information

This genus, commonly called False Spirea, includes species which need full sun to light shade and regular water to perform well in the landscape. Leaves are green and ferny, and flowers bloom from in summertime. Blossoms are white to cream and are held in clusters at branch tips. They will spread via suckering, and can cover large swaths if left unchecked. These plants are great for shrub borders or near woodland edges or water, for mass planting, a low hedge, erosion control, and in large open areas where its suckering habit can naturally fill space and not become problematic. Take care when planting these shrubs in the garden, as they can be toxic to humans and pets if ingested in large quantities.

sorbaria Species and Varietals

The genus Sorbaria includes 4 species, and is a member of the plant family Rosaceae. The plants in this genus are closely related to those in Chamaebataria (Fernbush), Spiraea (True Spirea), and Sorbus (Mountain Ash). False Spirea growing zones vary depending on the species. For more information, consult the descriptions below. To find your zone, click here: Zone Map.

Sorbaria sorbifolia (False Goat's Beard, Sorb-Leaved Schizonotus, Ural False Spirea, Pearl Plum, Zhen Zhu Mei, 珍珠梅, Spike-Blooming Rowan, Spike-Blooming Mountain Ash, Hozaki-Nanakamado, ほざきななかかど, 穂咲き七竈, Shittang-Namu, 쉬땅나무)
This species is suited for growing in USDA hardiness zones 2-8 or Sunset growing zones A1-A3, 1-10 and 14-21; native to eastern Asia (temperate China, Korea, and Japan). Reaches 3-8 feet tall and 10 feet wide, and has long flower plumes and large leaves. The genus' specific epithet refers to the leaves, which are similar to those on Sorbus (Mountain Ash). Cultivars include 'Sem' (dwarf to 3-4 feet with vivid spring color), 'Mr. Mustard' (with intense spring foliage) and 'Bococot' (also known as 'Cherry on Top', to 4-6 feet tall with gold-chartreuse new foliage tinted red and pink). This species is considered invasive in the Great Lakes, Pacific Northwest and Midwestern United States and Finland.

Sorbaria tomentosa (Sorbaria aitchisonii) (Himalayan Sorbaria, Kashmir False Spirea, Kathi, Bakre Jar, Bakre Jhaar, Berre)
This species grows well in USDA hardiness zones 5-8 or Sunset growing zones 3-10 and 14-21, and is native to Afghanistan and Pakistan. It reaches 10 feet tall and just as wide, with 16-inch long flower plumes. This species has naturalized in Great Britain, Italy, and New Zealand, but is not considered invasive.

Caring for sorbaria

Plant your Sorbaria shrub in full sun to partial shade in moist but well-draining soil. These shrubs can tolerate periods of drought, but will perform better with regular water. The ideal soil pH for Sorbaria shrubs is slightly acidic to neutral (between 5.5 and 7.0). Water new plants regularly to help them establish a strong root system, and provide extra water during periods of heat or drought to established plants. After planting, apply a 2-3 inch layer of mulch around the base of the plant (taking care to keep the mulch a few inches away from the stems) to increase soil moisture retention and control weed growth. These plants do well without much fertilization unless the plant is truly struggling. In this case, an application of a balanced, slow-release fertilizer in springtime should get the plant to bounce back.

These shrubs respond well to pruning, though they also have a beautiful natural habit if left to their own devices. In early spring, simply remove dead, diseased, or damaged foliage and branches and lightly shape. If the shrub is getting unruly and needs a rejuvenation pruning, cut back a few of the main stems to just a few inches tall; this will encourage vigorous new growth to appear. Sorbaria shrubs can be expected to live for a few decades in the landscape before fading, but will continuously spread through suckering underground roots, allowing colonies to survive indefinitely.

Propagation

Sorbaria shrubs 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 Sorbaria by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, 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.
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 portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Softwood cuttings are best taken in late spring to early summertime, and hardwood cuttings are taken in late fall or winter. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. 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 Sorbaria 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 in late summer or fall. The seed heads on Sorbaria plants are pretty easy to spot. They form as dried, upright clusters of follicles, and each seed head holds about a dozen seeds or more. Cut flower heads off of the plant using sharp, clean shears and place them into a container or bag. Once all seed heads have been gathered, bring them to a calm workspace, and shake seed heads upside down over a tray to release them. Seeds are best stored in envelopes inside an airtight container in the fridge (around 41 degrees Fahrenheit). The seeds will stay viable for between 1 and 3 years if properly stored, but are best used fresh.
Sorbaria seeds will need scarification as well as a period of cold stratification in order to germinate. First, place seeds in a bowl of cool water for 24 hours. This will soften the seed coat; any seeds or other debris that float can be discarded. Next, place the seeds in a container or plastic bag filled with moistened peat moss or sand. They can also be placed in between moist paper towels in a sealed plastic bag. Place the seeds in the fridge for between 6 and 8 weeks' time. Check them often; if they begin to sprout in the fridge, remove and sow 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 1 to 3 months from sowing; Sorbaria seeds have a germination rate of around 40% under proper conditions. The ideal soil temperature for germination is between 65 and 72 degrees Fahrenheit.
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 the new plant in an area with bright light and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until it is large enough to be planted outdoors, hardening off the seedling before installing in the garden.
Alternatively, Sorbaria seeds can be direct-sown in the garden in fall to naturally cold-stratify. This option is open to gardeners in climates which experience at least 6 to 8 weeks of temperatures around 40 degrees or cooler. To sow seeds in fall, rake the planting area so that it has an even surface and water. Broadcast seeds over the area, add some compost on top, and then water again. Mark the planting area so that seeds and seedlings are not disturbed while they germinate and grow.

Sorbaria seeds are contained inside dried upright clusters of follicles (seed pods) that persist into fall and winter. There are a few seeds contained in each.

Sorbaria seeds are very tiny (1.96 million seeds per pound), elongated, and typically tan to brown in color.

Problems and Pests

Certain Sorbaria species are considered invasive in some regions; see the species descriptions above for more information. Check with local authorities before planting. These shrubs are generally resistant to pests and diseases, but can suffer from the following common garden issues: