Pat Welsh Southwest Garden Advice, plus garden ideas for everyone » Shrubs

Native Plants for Erosion Control on Steep Banks

Pat — Thu, 08 Sep 2011 02:32:11 +0000

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).

Pruning Victorian box

Pat — Mon, 28 Feb 2011 08:01:02 +0000

Question from Ruth:
I have a garden question. Father Clark, who is a dear friend of mine, has very old–maybe 20-year-old pittosporum. It hasn’t been pruned much. When would be a good time to cut it back hard. He has green growth on top of a lot of old wood. Thanks so much. It is going to look pretty bad for a bit until re-growth starts.

Answer from Pat:
Cutting a Victorian box tree or shrub (Pittosporum undulatum) back hard can be done at various times of year with various results. If you cut an old pittosporum back in mid summer, regrowth will be very slow. If you cut it back in fall or spring, regrowth will be more rapid and successful. Pittosporum grows a little differently from many other shrubs since each joint or node will put out numerous shoots, often as many as four or five. If you cut off the top growth down to the next joint the entire thing (with leaves removed) looks like the ribs of an umbrella that has been turned inside out by a strong wind. Between the nodes where these radiating branches occur will be a long straight branch in the middle that leads to another node and so forth. So the query is where to cut it? If you cut the central branch back to the lower node the surrounding branches will take off and grow longer, creating a shrubbier tree. Unlike most trees buds exist under the bark all up and down the tree, so even if you cut in the middle of a branch, it will sprout and produce new growth. This means theoretically that you can cut back an old pittosporum pretty hard and it will bounce back and become a shrub again. Or you can prune it more selectively and maintain it as an elegant spreading tree.

Coreopsis maritima – Sea dahlia

Pat — Tue, 28 Sep 2010 08:01:59 +0000

Question from Melanie:
I have several plants of coreopsis maritima which bloomed brilliantly last spring. Now, in summer, they are dormant and dead looking. Should I prune them back or leave them as is? Thanks for your help.

Answer from Pat:
Sea Dahlia (Coreopsis maritima) is a flowering shrub native to the San Diego County seacoast and into the northern Baha California. Its large flowers —5-inch-across—blooming in late winter and early spring, are bright, vibrant yellow and resemble dahlias held on long stems above the foliage. The foliage itself is coarser than its close-relative, giant coreopsis (C. gigantea) which has feathery foliage, and is native to a larger swathe of the California coast—from Los Angeles through San Luis Obisbo Counties and Guadalupe and the Channel Islands and grows to a stunning height of five or six feet.

Both of these plants detest summer irrigation but watering giant coreopsis in summer is more likely to be fatal than summer watering of sea dahlia. Both plants have fleshy roots, but those of giant coreopsis are more prone to rot. Sea dahlia (Coreopsis maritima) can bloom all summer long if deadheaded, grown in fast-draining soil, and watered sparingly. The fact that Coreopsis maritima can be deadheaded without killing the plant tells us that it can be pruned but not too much. It sounds as if you are growing sea dahlia as it would grow in nature—totally dry in summer except for an occasional spritz of rain. This is far safer. I know since I once killed a sea dahlia by watering it in summer even though it was growing in sandy soil.

Left to nature, Coreopsis maritima’s foliage and flowers will fade in late spring and the appearance of the shrub may be messy in a home garden. The correct amount of pruning to do is more like a strong wind might do in nature. Once the flowers have faded, cut these off at the base of their long stems. Once the foliage has shriveled until its crisp and dry, you can simply pull it off the stems with your gloved hand and clip off those that still hang tight. If after doing this you see some dead wood, this may be clipped off too. Beyond this treatment, I would leave the bare woody structure of the plant untouched during summer. Don’t cut it back or you risk killing the plant. You will probably find that without its messy hair of dead flower stems and beard of dried foliage, the plant in bare dormancy is sufficiently statuesque to please yourself and anyone else who sees it or at least it will blend in and be unnoticed in a landscape of succulents or wherever you might be growing it.

Any other pruning to shape the plant should only be done in fall after rains have begun and the plant has resumed growth, but usually no pruning is necessary. Both sea dalia (Coreopsis maritima) and giant coreopsis (C. gigantea) have fleshy, succulent wood that they need in summer to tide the plant over during summer dormancy. Part of the pleasure of these plants is the windblown form they eventually develop. The branches often curl at the tips as they dry out. Let them be. They will plump up and straighten out when rains return. Cutting into this wood in spring or early summer might cause rot. Also, as soon as rains begin in fall the bare branches will awaken and spring to life, pushing out new green leaves and soon after will arise the flowers.

Colorful Taller Shrubs And Trees For Banks

Pat — Sun, 13 Dec 2009 05:07:41 +0000

In many California housing developments, roads are created on hillsides and pads bulldozed off for houses. Then the problem becomes how to cover steep banks with plants to hold the soil. In some case banks are steep and extensive. Ground covers often are not sufficient to hold the soil through heavy rains. What is needed is a mix of groundcovers cloaking the ground and deeper-rooted shrubs and trees to grip deeply into the subsoil. Here is a list of possible choices that was created by us for a housing scheme where the landscape was 30 years old and needed replanting with better replacements for plants and more drought-resistant plant choices than those planted by the developer.

Taller Shrubs: (8 to 12 feet tall, including one to 20 feet high.)

Bottle Brush (Callistemon citrinus ‘Pink Perth’): 8 to 10 feet tall, 5 to 8 feet wide. Weeping foliage, pink flowers in spring. Use low on banks as big, colorful screen.
Bottle Brush (Callistemon citrinus ‘Splendens’ and C. citrinus ‘Improved’):
Massive shrub, 10 to 15 feet tall and wide. Use low on banks as big, colorful screen. Brings birds.
New Zealand Christmas Shrub (Metrosideros collina ‘Spring Fire’): 8 to 12-feet high, 6 to 10-feet wide. Gray-green foliage with a profusion of showy flowers in late spring to early summer bringing butterflies and birds. Makes attractive hedge, but is sensitive to frost. Use high on banks, thus safe from frost.
Weeping Bottle Brush, (largest shrub form) (Callistemon viminalis ‘McCaskillii’): 20 feet tall, 15 to 20 feet wide. Flowers bring mockingbirds, orioles, and flocks of hummingbirds for their nectar. Improved varieties, such as this one, tend to be thickly bushy with brightly colorful flowers. Drought-resistant once established but adapted to garden water.

Colorful Mid-Height Shrubs And Trees For Banks

Pat — Sat, 12 Dec 2009 05:06:23 +0000

Mid-Height Shrubs: (5 to 10 feet tall)

Bottle Brush ( Callistemon ‘Canes Hybrid’): 10 feet tall, 15 feet wide. A big screen, measure so eventual height hits at the right level to see over. Narrow leaves and arching branches with pink-tinged foliage, soft pink bottle-brush flowers in late spring, early summer. Easily pruned to a tree shape. Can be kept smaller by pruning but why have that problem? Instead plant where it can grow to full size.
Bottle Brush (Callistemon viminalis ‘Captain Cook’): Dense, rounded plant to 6 feet tall and wide. For border, hedge, or screen. (‘Red Cascade’ is similar with large abundant rosy red blooms.)
Geraldton Waxflower (Chamaelaucium unicatum ‘Vista’): Pink flowers for long season from fall to summer on rounded drought-resistant shrub, to 6 feet tall, for full sun. Cut back after bloom.
New Zealand Tea Tree ((Leptospermum scoparium ‘Silver and Rose’): Dense growth habit to 4-to 5-feet tall and wide. Rose-pink, green-centered flowers with bright gray-green foliage. Excellent plant to use as screen high on bank.
New Zealand Tea Tree (Leptospermum scoparium ‘Gaiety Girl’): Slow growing to 5 feet tall and 4 feet wide. Double flowers are pink with a dash of lilac.
New Zealand Tea Tree (Leptospermum scoparium ‘Pink Damask’): Dense growth habit to 6 to 8 feet tall and 4 to 5 feet wide. Double ruby-red flowers red tinged leaves. Particularly good screen plant.
Plumbago (Plumbago auriculata ‘Royal Cape’): Makes a mounding shrub 6 feet tall, 8 to 10 feet wide with large rounded deep blue flowers blooming over a long season. Excellent bank cover when placed away from paths. Give it room to spread. Named varieties are not invasive like the older unnamed type. Good mixed with lantana.
Pride of Madeira (Echium candicans): (5 to 6 feet tall and 8 to 10 feet wide.) Blue spiky blooms on a gray woody shrub. Dot these around on banks. They will spread from seeds.

Colorful Low Shrubs And Trees For Banks

Pat — Fri, 11 Dec 2009 05:05:03 +0000

Low Shrubs: (3 to 5 feet tall)

(Use these on low banks and at the top of tall banks so that they create a screen but do not hide views.)

Bottle Brush (Callistemon citrinus ‘Compacta’): Mounded plant to 4 feet wide and high.
California Lilac (Ceonothus ‘Concha’): Good blue color. This one can take garden irrigation without dying
Matilija Poppy (Romneya coulteri): Superior, drought-resistant yellow-centered white poppy flower for banks. Gray foliage should be cut down in November if possible and will spring again from ground to bloom in spring through summer.
Radiation Lantana (Lantana ‘Radiation’): 3 to 5 feet high and wide and one of the better and most colorful lantana’s for banks. Drought-resistant with long bloom season. Flowers are yellow, orange, and pink. Looks good when mixed with blue plumbago and red bougainvillea.
Yellow Bush Daisy (Euryops pectinatus ‘Viridis’ or ‘Green Gold’): Long-lived woody, drought-resistant, evergreen shrub, native to South Africa, 3-to 6-feet tall and wide bears yellow daisies over a long season, mainly in winter. Shear off faded flowers and a little of the green growth once a year in June. (Provides good yellow color to go near blue Pride of Madeira and pink and white dwarf tea trees.)

Colorful Very Low Shrubs And Trees For Banks

Pat — Wed, 09 Dec 2009 05:04:49 +0000

Very Low Shrubs: (Up to 3 feet tall, not higher than 4 feet.)

Use these as fillers on banks or at the tops of banks.
(Sensitive to frost, but if you place these high on banks they should be in a frost-drained site, thus safe from frost.)

Bottlebrush (Callistemon viminalis ‘Little John’) 3 feet tall and wide. Very colorful waves of flowers fall, winter and spring, on superior dwarf bottlebrush with weeping habit.
Dwarf New Zealand Tea Tree (Leptospermum scoparium ‘Nanum Ruru’): 2 feet tall and wide. Dense growth. Dark-pink single flowers in winter, spring, into summer.
Dwarf New Zealand Tea Tree (Leptospermum scoparium ‘Pink Cascade’): 1 foot tall and 3-to 4-feet wide. Single pink flowers, sprawling, weeping, cascading growth.
Dwarf Pohutukawa (Metrosideros villosa ‘Tahiti’) (to 3-feet tall and wide): No pruning needed. Gray-green leaves and clusters of orange-red flowers in spring, with sporadic rebloom. (Sensitive to frost, but high on banks should be a frost-drained site.)
Groundcover New Zealand Tea Tree (Leptospermum scoparium ‘Horizontalis’): 3 to 4-feet tall, 12 feet wide. Profuse show of white blossoms on drooping branchlets, spreading plant, makes good bank cover.
Groundcover New Zealand Tea Tree (Leptospermum scoparium ‘Snow White’): 2 to 4-feet tall, 4 to 5-feet wide. Double white flowers with green centers on compact, spreading plant
Shrubby New Zealand Christmas Tree (Metrosideros collina ‘Fiji’): is even smaller, just 2 feet tall and wide. Available from Monrovia Nursery. Red powder-puff flowers, winter and spring, bring butterflies.