Rhamnus

( RAM - nuss )

At-A-Glance Information

This genus of deciduous and evergreen trees and shrubs, commonly called Buckthorn, includes species with varying exposure and water needs. The berries and flowers will attract birds and butterflies to the garden. These are wonderful background plantings and are useful as screens and hedges. They can become a bit invasive in the garden through volunteer seedlings, but this tendency can be managed. Use Rhamnus shrubs as privacy screens, formal or informal hedges, or to frame entrances. They can also be used as focal points throughout the garden, in shrubberies or containers, or simply as wildlife plantings for their structure, flowers, and berries. Take care when planting these shrubs in the landscape, as there is some evidence that plant parts are toxic to humans and pets if ingested.

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. The plants in this species are closely related to those in Frangula (Alder Buckthorn), Ziziphus (Chinese Date), and Ceanothus (California Lilac). 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, Mediterranean Buckthorn)
This species takes the form of an evergreen shrub or small tree, and is best in USDA hardiness zones 7-10 or Sunset growing 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), and 'Variegata' (also called 'Argenteovariegata'; 6-8 feet tall/wide with cream margins). This species is considered invasive in California, Australia, and New Zealand.

Rhamnus crocea (Redberry, Spiny Redberry)
This evergreen shrub grows well in USDA hardiness zones 7b-10b or Sunset growing 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 USDA hardiness zones 7a-10 or Sunset growing 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 Rhamnus

Take care when planting these shrubs in the landscape, as there is some evidence that plant parts are toxic to humans and pets if ingested. Plant Rhamnus in a space in the landscape that receives full sun to partial shade; ideally, they appreciate between 6 and 8 hours of sun each day for best performance, but can take afternoon shade, especially in warmer climates. Ensure that soil is well-draining, rich in nutrients, and has a pH of between 5.0 and 8.5 (slightly acidic to alkaline). 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 plants perform well in consistently moist soils, but can also adapt to become drought-tolerant. They can get by on rainwater alone for much of the year, but should be deep watered during extended periods of dry weather.

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. Pruning is simple; remove any damaged, diseased, or dead foliage at any time during the growing season, and remove spent flower spikes to neaten up the appearance of plants and encourage reblooms. Pull up volunteer seedlings; they can be replanted elsewhere in the garden or composted. Rhamnus shrubs can survive in the landscape for decades to centuries before needing to be replaced. Through volunteer seedling, these plants have the potential to provide new shrubs for the landscape indefinitely.

Caring for Rhamnus in Containers
Rhamnus shrubs are wonderful in the ground, but can also be grown in containers. Choose a container that is at least a few inches wider and deeper than the nursery pot or root ball. 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. Rhamnus 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.

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

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.
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.
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 Rhamnus 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.
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.
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 shrubs produce round berry-like drupes containing 2 to 4 seeds.

Rhamnus seeds are oblong and brown to tan.

Problems and Pests

Certain Rhamnus species are considered invasive in some regions; see the species descriptions above for more information. Check with local authorities before planting. Rhamnus shrubs are affected by some common garden issues, including: