Frangula

( frang - OO - luh )

At-A-Glance Information

Frangula is a genus filled with evergreen and deciduous shrub and tree species commonly known as Buckthorn or Coffeeberry. Their berry fruits will attract birds to the garden and they can provide lovely mass and texture to landscapes in mixed beds and borders. Use Frangula shrubs in woodland areas, as part of shrubberies, or as specimen plants in mixed beds. They can also serve as dense privacy hedges, screening, or erosion control. Take care when planting these shrubs in the landscape, as ingestion of plant parts can cause toxic reactions in humans and pets.

Frangula Species and Varietals

The genus Frangula includes around 50 distinct species of flowering shrubs and small trees, and is a member of the plant family Rhamnaceae. They are closely related to Rhamnus. These plants were at the height of their economic usefulness during the 15 through 19th centuries when their wood was used to make charcoal for gunpowder manufacture. Frangula growing zones vary by species; for more information, see the descriptions below. To find your zone, click here: Zone Map.

Frangula californica (Rhamnus californica) (Coffeeberry, California Coffeeberry, California Buckthorn, California False Buckthorn)
Grows best in USDA hardiness zones 7-10 or Sunset growing zones 3a-10, 14-24, H1 and H2. This species is native to California, southwest Oregon, and Arizona. Individual plants reach 3-15 feet tall and 8 feet wide at maturity. Leaves are dark green to yellowish-green, and are pale underneath. Berries ripen from green to red to black. This shrub will attract bees, and is tolerant of pruning and shaping. Full sun or partial shade is preferred, but it is not picky about soil.

Frangula purshiana (Rhamnus purshiana) (Cascara, Chittam Bark, Cascara Buckthorn, Cascara Sagrada)
This deciduous shrub grows best in USDA hardiness zones 3b-9 or Sunset growing zones 1-9 and 14-17. Native from Northern California to British Columbia and Montana. Reaches up to 20-40 feet tall and 10-30 feet wide at maturity, which typically takes between 5 and 10 years' time. Bark is smooth gray or brown, and has medicinal value. Dark green leaves turn to yellow foliage in fall, and black berries appear in fall. Can take full sun to dense shade, and moderate to regular water. 

Caring for frangula

Take care when planting these shrubs in the landscape, as ingestion of plant parts can cause toxic reactions in humans and pets. Plant Frangula shrubs in well-draining soil in full sun to partial shade. Frangula shrubs are highly adaptable, through they prefer to avoid intense late afternoon sun. Ideally, they should be getting between 2 and 8 hours of sun each day. Frangula shrubs prefer soil that is acidic to alkaline (with a pH of between 5.0 and 8.0). They grow well in both clay and rocky soils. 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. Water new plantings regularly as they establish a strong root system in their new home. At maturity, these shrubs are considered to be drought-tolerant, able to get by for much of the year on rainwater alone, with supplemental irrigations during extended periods of drought. As a general rule of thumb, water deeply when the top 2-3 inches of soil feels dry to the touch.
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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. These plants are not heavy feeders, and this should be sufficient to provide the necessary nutrients for the active growing season. Prune only to remove dead, damaged or diseased branches and foliage; otherwise, these shrubs are best left to their own devices. They naturally form a handsome, rounded shape. Frangula shrubs have a moderate growth rate and can reach mature size in just 3-5 years (5-10 years for Frangula purshiana). They can live for centuries in their native habitats, and have a life span of around 20-35 years in cultivated landscapes.

Propagation

Frangula is most easily propagated from seed. To propagate your shrub, follow the instructions below:

Propagating Frangula 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 strainer, a paper towel, a container for storing your seeds, 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.
  2. Harvest your seeds. The seeds on Frangula shrubs and trees are contained inside the fruits produced in fall. They should be ready to harvest in early to mid-winter. Remove the berries from the shrub at this time, and take the seeds out. Use a strainer to wash the remaining fruit flesh off of the seeds, and set them out on a paper towel to dry. Once they are dried, place them in a container in a cool, dry, dark place for storage until you are ready to sow.
  3. In fall, 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 around 45 days 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.

Problems and Pests

Frangula shrubs have no serious pest or disease issues, but under poor conditions can suffer from the following issues:
  • Cercospora
  • Phylosticta
​For more information on these issues, see the following links:
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Gallery

Pair Frangula shrubs with other shrubs of differing foliage colors; they will add great texture and color with their berries.
Frangula shrubs have beautiful, shiny green foliage and berries that will attract birds to the garden.
Pictured here is a Rhamnus shrub, a close relative of the Frangula genus.

Videos

An informational video on California Coffeeberry.

Resources

Frangula - Landscape Plants
Wikipedia: Frangula
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 326, Frangula