Native Plants for Erosion Control on Steep Banks
Question from Alin:
I’m looking for native plants species for erosion ; many of the plants you mentioned are from Australian/S. Africa.
Answer from Pat:
You are correct. I have indeed recommended many plants as bank covers that are native to Australia, South America, the Mediterranean Basin, and South Africa. Many are colorful and easy to grow in California and easy to grow on banks. Some will survive with no irrigation once established, but many California native plants can survive in summer without irrigation. Thank you for suggesting that I provide some ideas for Cailfornia native plants that can be used to control erosion on steep banks. Here are some ideas:
Many varieties of California lilac (Ceonothus) make fine native ground-covers to grow on steep banks in coastal zones. Among the best selections and varieties for this purpose are Ceonothus gloriosus ‘Anchor Bay’; Carmel Creeper (C.g. exaltatus); and C.h.g. ‘Yankee Point’. Other native ground covers good for banks include Matilija poppy (Romneya coulteri), Manzanita (Archtostaphylos), and Monkey flower (Mimulus).
Taller than the above lilac varieties is C. ‘Julia Phelps’, which is particularly stunning planted on a steep bank next to flannel bush (Fremontedendron ‘California Glory.)—Make sure not to water flannel bush in summer. Plant it in fall and just spritz the foliage with a little spray of water in the evening of hot dry days in summer to make the plant feel as if it has been moistened by a light shower or heavy dew. This is enough to get it through the summer. Summer irrigation can kill it.
Other native shrubs that are useful for controlling erosion on steep banks include lemonade berry (Rhus integrifolia), dwarf coyote bush (Baccharis pilularis), Bush anemone (Carpenteria californica), Western redbud (Cercis occidentalis), island bush poppy (Dendromecon harfordii), toyon (Heteromleles arbutifolia), and coffee berry (Rhamnus californica).
I have a steep slope and looking for some native plants for erosion control. I live in the san Francisco Bay area and could you you let me know where I could buy these plants as well as some trailing Gazania?
Thanks,
Ranmali
One of the best ways to control erosion with native plants on a steep slope is to plant it solidly with California lilac (Ceanothus.) Virtually all species and selections of ceanothus are recommended for erosion control. Though this is what I would do, there are many other native plants one could also consider, including a vast number of shrubs and subshrubs, several trees, many perennials, at least seven grasses, and two vines. You can find an excellent list of native plants for erosion control on pages 220 and 221 of the recent book, “California Native Plants for the Garden” by Carol Bornstein, David Fross, and Bart O’Brien. This book is widely available at bookstores and on the Internet. I recommend you invest in a copy or at least consult it at your local library, since you can then look up the listed plants and learn their various characteristics. On pages 242 to 247 of the above book you will find a list of Sources of Native Plants. By looking at this list you can find the nursery or nurseries closest to your home that can supply your chosen plants.
If you decide to go along with my suggestion on Ceanothus, I also suggest you consult a book called simply “Ceanothus” by David Fross and Dieter Wilken. Before planting Ceanothus it would be a good idea to study the many species and cultivars available so you can choose what you want and like best. Both books are illustrated with informative photos. If I were you I would not mix native plants with trailing gazanias if that is what you were planning. Gazanias are available for sale at virtually all nurseries except specialty nurseries. You will not be able to purchase gazanias at native plant nurseries since gazanias are not California or western native plants. They are native to South Africa. If your local nursery does not have the cultivars you need in stock you can order your desired variety or varieties in flats. (Any good nursery will order plants for you.) If I were you I would insist on one of the newer varieties such as ‘Sunburst’ (orange with black eye), ‘Sunglow’ (yellow), and ‘Sunrise Yellow’ (black centers, with large yellow flower.) All trailers have gray foliage and all the newer ones have larger flowers.
Dear Pat, I am living in L. A. I have a steep hillside which just get cleaned up. In order to put something in quickly before the rain comes. My friend suggested use Japanese honeysuckle as the hillside cover. Would you please let me know if this is a good idea.
Jing
You wrote me three days ago asking if you should plant Japanese honeysuckle (Lonicera japonica ‘Halliana’) on a bank. I replied that it is too invasive and you will never get rid of it, but it went through my mind that I should also have suggested another honeysuckle that might be less invasive, though possibly more deciduous, dropping leaves if there is a hard frost. There is no getting around the fact that honeysuckle is a fast spreading and effective ground cover for steep banks. This morning I woke up with the thought that perhaps I should have recommended woodbine (Lonicera periclymenum.) There are a number of varieties including one called ‘Graham Thomas’ that has white flowers that turn coppery yellow as they age. It spreads as quickly as Japanese honeysuckle. This one may also have seeds spread by birds but it doesn’t seem to cause as many problems as Japanese honeysuckle. Other varieties include ‘Berries Jubilee” with bright red berries bringing birds (but these for sure would be spread around), and ‘Belgica’ which is more shrubby and thus less spreading and rampant. Dropmore Scarlet honeysuckle (Lonicera x brownii ‘Dropmore’) can also be used as a ground cover and it is a hybrid with brilliant summer bloom that brings hummingbirds but has few if any seeds to be spread by birds. The only problem is that aphids love this plant and in some locations it’s prone to mildew. Control aphids by spreading ladybugs in early spring as soon as you see the aphids. Release the ladybugs onto the bottom of the bank at dusk after watering and after chilling the ladybugs in the refrigerator for a couple of hours. I find lady bugs work very quickly to clear up aphids, within a week they can be gone. Other honeysuckles said not to be invasive are L. sempervirens ”Magnifica’, ‘Leo’, and ‘Superba’. Several named varieties of honeysuckle can be purchased from Monrovia wholesale nurseries by your local retail nursery.
I am so glad you wrote me since it is not a good idea to cover a slope with Japanese honeysuckle. It is invasive and spreads by seeds that are distributed by birds. You would never be able to get rid of it. One thing you could do quickly is to plant the slope solidly with gazanias for erosion control, and then later think of deeper rooted plants to put in with the gazanias. You would not need to pull out the gazanias but plant into them with other taller plants such as Pride of Madiera (Echium candicans), for example, if you live near the coast. But I think a far better solution would be to plant California native plants all over the hillside such as Ceanothus griseus horizontalis ‘Yankee Point’, Archtostaphylos ‘Emerald Carpet’ , or Baccharus pilularis ‘Pigeon Point’. This would be a permanent solution and once fully established would need no irrigation. Fall is the correct time of year to plant native plants, though November is the best month and it is cooler then. But in your situation, I would get these plants into the ground as soon as possible. Another idea I have for planting right now for a quick and colorful cover that would last forever is lantana. Plant it immediately from flats and install a low-impact sprinkler system or drip irrigation and you will be amazed to see how quickly it covers the bank in growth and bloom. Lantana montevidensis is a lovely trailer to two feet tall with rosy lavender flowers for much of the year and it is an old-standby, drought-resistant, bank cover that’s tough as nails and good looking. In 10 or 15 years you can cut it to the ground in spring if you wish and let it renew itself from the ground. Other low-growing kinds include ‘Confetti’, ‘Cream Carpet’, ‘Dwarf Pink’, ‘Dwarf White’, Dwarf Yellow, and ‘Gold Rush’. There are many others besides. You can mix colors up if you like for a patchwork look. Finally, not to confuse you, but for an intensely colorful look you could plant the bank with Plumbago ‘Royal Cape’ or P. ‘Imperial Blue’, bougainvillea ‘La Jolla’, and Lantana ‘Radiation’, with yellow trailing gazanias filling in the blank spots between. I’ve recommended this mix of plants many times. The whole thing can be watered with drip irrigation, it’s drought-resistant once established, blooms its head off almost year round, and it’s not to late now in September to plant it. Just make a decision on which of these schemes to use, go out and buy the plants and get them into the ground post haste. Time is of the essence. Lay a tall ladder flat on the ground when you plant the bank so you can get up and down it. I planted a whole steep bank myself once in late summer when I was young and then I kept it watered daily by sprinkling with the hose. The roots took off and it held up fine through the rains. Many times landscapers suggest covering a bank with jute and planting through it. Jute does help the bank hold up, but the problem is that it absorbs water and this often prevents the plant roots from getting enough irrigation, since the jute absorbs it and even pulls the moisture out of the soil and then it simply evaporates into the air. I’ve seen banks languish for years with that ugly jute showing and the plants struggling to survive many years after they were planted. That’s why I didn’t recommend jute. Just decide quickly and get going! I hope whoever cleaned off your bank left the roots of the plants in the ground. If so, this will help hold the soil. When people take ice plant off a hillside for example, they should never pull it up, but simply clip it off. The roots can stay in the ground and will gradually rot thus improving the soil. The ice plant will not regrow from the roots once the top of the plant is removed.
Plants for steep, full-sun, sandy soil.
Forget standard recommendations or you will need to do a lot of hand-watering or replanting. Standard recommendation is to hold the soil with grass (it dies in tough dry situations). Start by planting desert trees at the upper level such as Palo Verde (long tap root to stabilize soil), provides 25% shade during the summer. Dot the steep slope with native, drought-tolerant shrubs (Toyons, Lemonade-berry, low-water Manzanitas). Add a few decorative trees such as Desert Willow if you are willing to handwater. If your hillside is really steep like mine, you will automatically create curving footpaths across the slope as you plant & water. Plant desert groundcovers such as groups of Agave Angustifolia for holding soil on steep slopes, spikey A. Geminiflora grouped together gives the illusion of a grassy meadow. Clusters of small (young)Ponytail Palms are also very drought resistant and their bulbous “feet” can be planted to hold and divert rainfall across the slope and into little swales created behind trees and shrubs. As the slope trees, shrubs & groundcovers mature into an interlocking root network , deepen the pathways across the slope to give rainfall plenty of time to sink into the soil. Large slopes need a lot of groundcovers and the Fire Department likes to see fire-resistant succulents rather than sages. You can check Craig’s List for homeowner Aloe cuttings & pups. When I first planted my steep slope, I used dozens of standard recommendations of groundcovers such as grasses, desert penstemons and they either died or looked horrible. Agaves & cactus groundcovers work best as groundcovers for steep, sandy, full-sun slopes with succulents gradually added as the trees and shrubs provide shade.
Many thanks for this excellent comment. Your plant suggestions are outstanding. I hope many gardeners will see this helpful solution to dry sandy banks.
Pat,
Thank you for your above recommendations. I have a currently stable slope, but have just installed an in-ground pool and am now researching landscaping options for the slope and the rest of the yard. There is no irrigation currently, however there is the option to install irrigation if needed. My main concern is finding plants that will help control any future erosion of this bank that leads to the pool, while being visually pleasing as well as “pool friendly”. There isn’t mush access, as it is behind the pool, so maintenance is also a concern. Thank you for your help!
When planting close to a swimming pool, choose plants that are clean and won’t drip leaves, flowers or debris into the water. Lantana is one of the best shrubs to plant near swimming pools that will survive longterm and hold a bank. You can mix the flower colors or just have one color. If just one color, lavender-hued Lantana montevidensis would be an excellent choice, since it tends to spread and stay low. Another idea is to cover the bank with gazaneas. Install a drip system or low-level water system. You don’t mention where you live, but need to be aware that no plants can be planted and forgotten. All, including native plants, need irrigation to become established and also natives will look better and do better if given a spritz with the hose at the end of the hottest summer days—not enough to wet the ground but enough to moisten the leaves and the top of the ground as would occur if a light rain had fallen.
For more ideas, why not look online or in a book store for books on landscaping near a pool. A particularly attractive though usually expensive option is to install a rock garden. Some pool companies are expert at building these, even perhaps adding a stream and waterfall to the scheme. But whatever you do, I strongly suggest you build a low retaining wall on that side of the pool to hold back the bank. Your retaining wall should be about 18 inches to 2-feet high and can be as simple as a concrete block wall, covered with stucco and topped with red tile. If desired, tile the side of the wall facing the pool in order to create a feature of the wall. Tiling the front of the wall is a particularly good idea if there will be no path on that side of the swimming pool. In that case a wall is all the more necessary because it will keep all earth and debris from falling into the pool when you need to plant or maintain the bank. You could then landscape the bank in an artistic way with rocks, trees, shrubs and perennials and a winding path or steps for reaching them. If the wall is on the far side of a path, however, it could be a little higher and act as a place to sit. In this case a stucco wall with red tile top is perfect. If there is no pathway around the swimming pool on that side, however, this wall can go straight up from the edge of the pool. Kids are likely to use it for jumping into the pool, and the tile front will make it look as if it’s a part of the swimming pool. For a list of plants good for planting near swimming pools check the lists on pages 64 and 65 in the New Sunset Western Garden Book. (This is the recent and most current edition and has an orange gazania on the cover.)