sorbaria

( sor - BAR - ee - uh )

At-A-Glance Information

This genus, commonly called False Spirea, needs full sun to light shade and regular water. Leaves are green and fern-like, and flowers bloom from the middle to end of summertime. Blooms are white to cream and blossom in clusters at branch tips. These plants are great for shrub borders or near woodland edges or water. They will spread via suckering, and can cover large swaths if left undisturbed and unchecked. 

sorbaria Species and Varietals

The genus Sorbaria includes 4 species, and is a member of the plant family Rosaceae. 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)
Zones A1-A3, 1-10 and 14-21; native to eastern Asia. Reaches 3-8 feet tall and 10 feet wide, and has long flower plumes and large leaves. The specific epithet refers to the leaves, which are similar to those on Sorbus (Mountain Ash). Variety 'Sem' is a widely grown dwarf selection.

Sorbaria tomentosa angustifolia (Sorbaria aitchisonii) (Himalayan Sorbaria, Kashmir False Spirea)
Grows well in zones 3-10 and 14-21, native to Afghanistan and Pakistan. It reaches 10 feet tall and just as wide, with 16-inch long flower plumes.

Caring for and pruning sorbaria shrubs

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. 

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
  1. 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. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
  2. 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.
  3. 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. 
  4. 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
  1. 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. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows. 
  2. Harvest your seeds. The seed pods on Sorbaria plants are pretty easy to spot, they're 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.
  3. 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. 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.
  4. 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.
Sorbaria seeds are contained inside the dried flower heads on the plant.
Sorbaria seeds.

Problems and Pests

These shrubs are generally resistant to pests and diseases, but can suffer from the following common garden issues:
  • Aphids
  • Scale
For information on these pests, including how to eradicate them, see the following links:

Gallery

These shrubs add lush foliage to landscapes.
Sorbaria sorbifolia 'Sem' is a great dwarf variety with beautiful foliage color.
Sorbaria shrubs are great as background plantings.

Videos

All about Sorbaria shrubs.
How to prune a Sorbaria.

Resources

Wikipedia: Sorbaria tomentosa
Wikipedia: Sorbaria sorbifolia
Wikipedia: Sorbaria 
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 607, Sorbaria
If you have any questions, comments, concerns, or photos you’d like to add to the gallery, please let me know by sending me a message using the button below!
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