Rhamnus

( RAM - nuss )

At-A-Glance Information

This genus of deciduous and evergreen trees and shrubs, commonly called Buckthorn, have varying exposure and water needs. The berries and flowers produced will attract birds and butterflies to your garden. They are wonderful background plantings and are useful as screens and hedges. They can become a bit invasive via volunteer seedlings, but this quality can be controlled via cutting off ripe berries from the plant and removing volunteers as they pop up.

rhamnus Species and Varietals

The genus Rhamnus includes around 140 species of shrubs and small trees, and is a member of the plant family Rhamnaceae. In 1768, the genus was separated into Rhamnus and Frangula genera by botanist Philip Miller based on flower structure. Rhamnus growing zones vary depending on the species; for more information, see the descriptions below. To find your zone, click here: Zone Map.

Rhamnus alaternus (Italian Buckthorn)
This species takes the form of an evergreen shrub or small tree, and is best in zones 4-24. It is native to the Mediterranean and grows quickly to 10-20 feet tall and wide. Leaves are shiny and bright green and berries are small and black. Can be trained into a single or multitrunked tree, and takes well to shaping and shearing. Can tolerate heat and does well with little to no water, but can also accept regular water. Needs full sun to partial shade. Varieties include 'John Edwards' (15-18 feet tall and 6-10 feet wide), 'Variegata' (also called 'Argenteovariegata'; 6-8 feet tall and wide with foliage edged with cream).

Rhamnus crocea (Redberry)
This evergreen shrub grows well in zones 7 and 14-24, and is native to the Coast Ranges of Northern California down to Baja California. It reaches 2-3 feet tall and 3-6 feet wide with stiff branches and green glossy leaves (that are golden underneath). Fruit is small and bright red. Can take full sun to partial shade and needs little water.

Rhamnus ilicifolia (Rhamnus crocea ilicifolia) (Hollyleaf Redberry)
This species is an evergreen shrub that grows in zones 7-10 and 14-23. They are native to the Coast Ranges and Sierra Nevada foothills and the mountains of Southern California, Arizona, and Baja California. It grows to 15 feet tall and nearly as wide. Leaves are round and spiny; this plant makes a good informal screen. Full sun or partial shade and no irrigation is needed.

Caring for and pruning Rhamnus shrubs

Plant in full sun to partial shade. Ensure that it receives at least 6 hours per day for healthy growth, flowering and fruiting. They thrive in well-draining soil and can adapt to a variety of soil types and textures, but do best in loamy or sandy soil with a slightly acidic to neutral pH level (between 5.0 and 8.5 is good for most species). Water regularly while these plants are getting established in the garden. They are drought-tolerant once mature, but do benefit from consistent, deep watering during the drier periods of the year. Apply a layer of mulch around the base of the plant to conserve moisture and suppress weeds, but be careful that the mulch does not get too close to the stems. Pruning is minimal for these plants, simply remove dead or diseased growth and make cuts to maintain shape and size. Fertilize only when soil is particularly poor with a balanced, slow-release fertilizer in springtime. 

Propagation

Rhamnus 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 shrubs, follow the instructions below:

Propagating Rhamnus 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. 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 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. 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 Rhamnus 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. 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 7-14 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.
  3. 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.
Rhamnus seeds are contained inside of the fruits produced by the shrub.
Rhamnus seed.

Problems and Pests

Rhamnus shrubs are affected by some common garden issues, including:
  • Aphids
  • Spider Mites
  • Scale Insects
For more information, see the following links:
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Gallery

Buckthorn shrubs are great as background shrubs, or to cover eyesores like fences or air conditioning units.
These shrubs have naturalized themselves in the United States.
Birds are drawn to these shrubs.

Videos

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Resources

Rhamnus Growing Guide
California Native Plant Council - Rhamnus alaternus
Wikipedia: Rhamnus (plant)
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 554, Rhamnus
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