hillside gardening - plants / terracing?

gam00(z10 ca)May 13, 2005

We just moved into our home with a hillside at the back of the property. The inspector said it was about a 2:1 slope. It has some oleanders and bottlebrush on it but is pretty boring otherwise.

I'ld like to add some plants that will help with soil erosion and help to make it look better. There are no sprinklers up the hill and I'ld rather not have to put any. I'ld like something that will be drought tolerant.

I've attached pictures below that are the view from the pool. Not very pretty. Any suggestions for plants or ideas for adding some terracing would be appreciated?

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1. Plan construction/planting activities during summer and fall, so that erosion control measures can be in place when the rain comes.

2. Preserve existing vegetation as much as possible.

3. Limit grading and plant removal to the areas under current construction.

4. Preserve the natural contours of the land and disturb the earth as little as possible. This latter part is very important.

5. Limit the time in which graded areas are exposed.

6. Minimize the length and steepness of slopes by benching, terracing, or constructing diversion structures.

7. Landscape areas that you do bench to stabilize the slope and improve its appearance.

8. As soon as possible after grading a site, plant vegetation on all areas that are not to be paved or otherwise covered.

Select from the following plants, choosing one or more from each category (mix them up):

Small trees with tenacious root systems --

Callistemon citrinus LEMON BOTTLEBRUSH
Callistemon viminalis WEEPING BOTTLEBRUSH
Heteromeles arbutifolia TOYON
Juglans californica californica CALIFORNIA BLACK WALNUT
Leptospermum laevigatum AUSTRALIAN TEA TREE
Lophostemon (Tristania) confertus BRISBANE BOX

Non-spreading shrubs with deep, bank-holding roots --

Atriplex lentiformis Breweri BREWERÂS SALTBUSH
Baccharis x ÂCentennial DESERT BROOM
Cistus purpureus PURPLE ROCKROSE
Cistus x skanbergii PINK ROCKROSE
Echium candicans PRIDE-OF-MADEIRA
Eriogonum giganteum ST. CATHERINEÂS LACE
Eriogonum parvifolium COAST BUCKWHEAT
Melaleuca hypericifolia RED PAPERBARK
Melaleuca nesophila PINK MELALEUCA
Myrica californica PACIFIC WAX MYRTLE
Rhamnus crocea ilicifolia HOLLYLEAF REDBERRY
Rosmarinus officinalis ROSEMARY
Salvia apiana WHITE SAGE
Salvia clevelandii BLUE SAGE
Trichostema lanatum WOOLY BLUE CURLS

Expansive, low spreading shrubbery --

Arctostaphylos ÂCarmel Creeper C.C. MANZANITA
Arctostaphylos edmundsii LITTLE SUR MANZANITA
Arctostaphylos uva-ursi
ÂEmerald Carpet E.C. MANZANITA
Arctostaphylos uva-ursi ÂPoint Reyes P.R. MANZANITA
Baccharis pilularis ÂPigeon PointÂ, ÂTwin Peaks TRAILING COYOTE BRUSH
Ceanothus griseus horizontalis ÂYankee Point Y.P. CEANOTHUS
Cotoneaster (low-growing types) COTONEASTERS
Juniperus (low-growing types) JUNIPERS
Salvia leucophylla ÂPoint Sal POINT SAL PURPLE SAGE
Salvia mellifera ÂTerra Seca TERRA SECA BLACK SAGE

Stem-rooting perennial groundcovers --

Fragaria chiloensis BEACH STRAWBERRY
Gazania rigens leucolaena TRAILING GAZANIA
Lampranthus ICEPLANT
Rosmarinus officinalis ÂProstratus TRAILING ROSEMARY
Thymus serpyllum CREEPING THYME

All of the above, despite being the most drought-tolerant plants for slopes, require water to get them established. For most of these you can put in a temporary drip system. For the spreading stem-rooting perennial groundcovers, you will have to spray irrigate. An easy sytem to install is a main line along the base of the slope (not the top) and tall rigid risers with roatary heads tilted slightly backwards so that they spray up and onto the slope.


    Bookmark   May 13, 2005 at 9:26PM
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calistoga_al ca 15 usda 9

I live on a steep site and worried about erosion. I planted for it was very careful for the first few years as the property was rented and I lived 175 miles away. In Dec. 1990 everything froze and a pipe ran for several days. I was ammazed that there was no erosion, the water soaked into already wet soil within a few feet of the break. What I mean is it depends a lot on the soil whether erosion will be a problem. Al

    Bookmark   May 14, 2005 at 3:01PM
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Bob_B(Sunset 14, Ca.)

How long has your slope been there, and have you had any erosion problems? None is evident from the photos. In fact, the slope looks kind of nice to me. If it were mine I would treat it as semi-wild or semi-maintained area. I'd stick in a couple of hundred plugs of Vinca minor, spread out a truck load of redwood bark, and water periodically with a rainbird on a stand just long enough to get the Vinca established.


    Bookmark   May 14, 2005 at 3:47PM
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catkim(San Diego 10/24)

I think it would be a mistake to do a do-it-yourself terracing job on this slope. I would be concerned that disturbing the natural contours would cause more problems than it would solve. I can understand wanting more vegetation, and Bob's low-growing vinca idea has appeal.

I will warn against planting iceplant on a steep slope. This winter many iceplant-covered slopes here were a problem when the iceplant became heavy with water and slid downhill taking surface soil with it.

One more suggestion, if you are in a fire-prone area, consult with you local fire department about appropriate plants for your hillside.

    Bookmark   May 14, 2005 at 4:20PM
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Lantana montevidensis is another good one for erosion control.


    Bookmark   May 14, 2005 at 10:04PM
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hoovb zone 9 sunset 23

My property consists of a lot of steep slopes. This is what I've learned:
if you put in a plant that needs maintenance (such as pruning), you have to have a way to easily get to the plant and a place to stand while you maintain it. Standing on a slope pruning something is pretty awkward. So you either need terraces or no-maintenance plants.

The best no-maintenance plants on my slopes are Myoporum 'Pacifica' and Baccharis pulularis (CA native), both of which can survive and look good on winter rain alone. They both have nice webby root systems that hold the soil tightly. I do get a few weeds, but one weeding session a year does it. About every 7-10 years they need to be pulled out and replanted. But that is pretty low maintenance to me. I tried lantana but it builds up a dead thatch that is a fire hazard and it needs some watering to look pretty.

    Bookmark   May 15, 2005 at 11:48AM
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gam00(z10 ca)

Thanks for all your comments. The hillside is in the Hollywood Hills. On the left side, you can see a ridge line (over the ficus) where they cut into the hill to make flat space for the house. That is basically rock with a little soil cover on it. The right side (second pic) is deeper soil. We are in a fire zone.

I don't want to overplant the hill. I do want it to stay natural looking (maybe with a medditeranean feel) but there is a noticeable gap between were the oleanders & bottle brush are that is bare.

I'ld like just a handful of shrubs or plants to balance things out - maybe some succulents for interest. Ideally, just want to go up the hill every 3-5 years for a mild pruning to keep things in shape other than the once a year fire cleanup. We also want to remove the cypress.

There is no easy way to get up the hill & it's very hard to stand up straight. And I will have to put in at least one terrace on the right side (2nd pic) as you can see there is debris behind the fence and it is starting to push the fence down. That debris has been building up for years as the previous owners didn't maintain it but the fence will need to be addressed. Maybe some simple railroad tie steps to get up the hill for some annual maintenance.

I like the idea of the vinca minor so I don't have to look at all dry dirt. Any disadvantages to that plant? Any other ground covers that are carefree and flower? What plants would look good with the red bottlebrush & pink oleander and maybe provide color at different times of the year than the existing trees?

Sorry for the long post & thanks again.

    Bookmark   May 15, 2005 at 1:10PM
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calistoga_al ca 15 usda 9

Hoovb mentioned having to replant Coyote brush every 7 to 10 years because they get so woody ugly. I have found that when that happens I can just break the whole plant off at ground level. A new plant will grow from the roots and all I do is haul away the old wood. Al

    Bookmark   May 15, 2005 at 5:52PM
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gam00(z10 ca)

Just checked up on vinca minor and it says part sun to shade. My hill faces south and gets sun all day. Needless to say, it gets very hot, so I don't think the vinca would work. Any other ground covers?

    Bookmark   May 15, 2005 at 5:57PM
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Revisit gardenguru's list of plants. There are lots of gems there that would be great for your site (and more original than vinca).


    Bookmark   May 15, 2005 at 6:12PM
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Just as there are MANY kinds of Junipers and Eucalyptus, there are many kinds of iceplants.

The one notorious for taking down whole slopes with its waterlogged weight is Carpobrotus ("hottentot fig" or "pickleweed" or "not-THAT-dang-plant-again"). This large-leafed iceplant was widely planted back in the 50's and 60's, including on steep freeway cuts; fortunately, we've learned since then of its water-gobbling-weight-gaining habit. It's also escaped and become a serious plant pest in many coastal areas. Even a nasty scale insect pest imported some years back hasn't put a dent on this one's population, though. And bad nurserypeople still sell it.

The two iceplants on my list are tiny-leafed species and, as far as I know, have not pulled down any hillsides in Southern California.

By the way, there are some truly beautiful Junipers and some very showy and small Eucalyptus species.


    Bookmark   May 15, 2005 at 11:21PM
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cleatscrea(So Cal-22)

...can't quibble with the gardenguru who has it down. I have an LA hillside, albeit not quite that steep but I have had good luck with ceanothus, cestrum, Laurel Sumac, toyon, the dreaded Pyracantha (they don't call it firethorn for nothing), rockroses, some lavateras, lavendars, quail bushes, heartier salvias (Clevelandii, greggii), Matilija Poppies, mock orange, and the crazy conquerer of all it surveys tecomaria.

    Bookmark   May 16, 2005 at 6:42PM
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arvind(San Jose, CA)

You can keep coyote bush (Baccharis pilularis) looking green and terrific with periodic pruning. I would avoid vinca like the plague. It wants shade and moisture, not quite the conditions on your slope. CalIPC recommends not using it. Try dwarf coyote brush instead, which does not want summer water, still stays green. Try California fuchsia which spreads slowly by rhizomes and is great for slopes.

    Bookmark   June 1, 2005 at 5:24PM
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sumcool(Cen. Coast/s17)

I've been using gardenguru Joe's lists for a while now and highly recommend them. The CD is inexpensive, and lots cheaper than printing out all the wonderful info he's given us in this forum. (I know, because I've printed out hundreds of his pages.....)
Hey, Joe, quit blushing, we all do appreciate you.

    Bookmark   June 2, 2005 at 12:13PM
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>I've been using gardenguru Joe's lists for a while now and highly recommend them. The CD is inexpensive...

Joe has a CD? How do I order one?

    Bookmark   June 2, 2005 at 4:13PM
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sumcool(Cen. Coast/s17)

Just email gardenguru. He can let you know how to order the CD.

    Bookmark   June 2, 2005 at 10:29PM
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scrub_sage(9b So. Calif.)

I've almost completed landscaping a hot, steep western slope. Following are some of my favorites for dry conditions:
Foothill Penstemon (CA native, low with purple flowers)
Wooley Yarrow (low ground cover, yellow flowers)
Desert Globemallow (med shrub w/small orange flowers)
Toyon (shrub/tree)
Lemonadeberry (open form shrub)
Laurel sumac (large shrub)
Catalina Ironwood (lacy leafed tree)
Brandagese Sage (large sage with dark green leaves)
Pony Tail "Palm"
Coast Live Oak

Plantings were done year-round as ice plant was removed. Therefore, sprinklers and a LOT of hand-watering were required to get things established.

Young Toyons were planted in front of each Catalina Ironwood to help keep the trees upright on the steep slope, in addition to stakes.

    Bookmark   September 17, 2005 at 2:04AM
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arvind(San Jose, CA)

Iceplants don't belong on slopes: it is not just their own weight that drags them down the slope. It is the fact that their root systems are so shallow, and have no erosion control potential whatsoever. There are lots of eroded slopes in and around the Bay Area where iceplant was planted. There is a high-end home in the Fremont hills by Hwy 680 where large swaths of the hillside were planted with iceplant, and the hillside just slid down during winter; now it is all covered up with black tarp. Neighboring homes show no such erosion because they left the original landscape in place.

For slopes, you can't go wrong with California natives, most of which are deep rooted to survive our dry summers, and hence bind the soil really well. Your only challenge is to narrow down your choices from the approximately 6000+ species and subspecies.

    Bookmark   September 30, 2005 at 12:55PM
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BecR(zone 9 CA 19)

There are some varieties of acacia that are low growing, that I have seen on hillsides. Also, low-growing rosemary is excellent for erosion control (we have it in our common area hillsides, along with common thyme at the base of the hillside---very nice). I am not sure about soil erosion/fire area qualities of the following, but have seen them on sunny dry hillsides: bougainvilla, ceanothus, dwarf arbutus, plumbago, and honeysuckle (although Sunset Western Garden Book states that lonicera 'Halls' is good for erosion control, but can become a fire hazard unless pruned back severely annually).


    Bookmark   September 30, 2005 at 11:21PM
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habitat_gardener(z9 CA/Sunset15)

scrub_sage, I love your plant list. That is going to be one spectacular hillside!

    Bookmark   October 2, 2005 at 11:53PM
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I live in the Oroville foothills, zone 9. My yard is similarly sloped like yours. I experimented and have been very successful with creeping Manzanita, Cape Plumbago, and Matilja poppies, and Pride of Madeira (which I was told would not grow here but are thriving). Not only do these provide erosion control, but adds nice texture, color all year round and survives on watering only three times between May and October.

    Bookmark   April 8, 2006 at 11:34AM
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We had ice plant on a hill behind our house for years but it all died, so we had all the dead stuff removed and planted new plants about two weeks ago. I was told to water them every 3 days at first, for about 10-15 minutes each time. However, I wasn't told how long I need to keep doing this. Do I keep watering every 3 days for a few months (I'm in So. Calif. so we get pretty hot summers and the hillside is in the sun most of the day), or do I cut down the watering soon? The gardeners who did the job never told me what to do to sustain the plants in the future and I don't want to overdo it or underdo it. Thanks much.

    Bookmark   April 4, 2007 at 9:40PM
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A friend of mine witnessed a hillside of rain-swollen iceplant avalanche down the hill - and the hoards of rats and mice come flying out. Unless you're planting a toybox for your mouser, avoid it. =^,,^=

    Bookmark   April 7, 2007 at 11:15AM
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scrub_sage(9b So. Calif.)

Update (2013 follow-up) of successful steep slope plantings on a dry sandy slope in So. Calif.

In my previous post, I listed drought-tolerant Calif. natives used in my initial plantings. But the fire department does NOT like summer-deciduous plants such as sages. And as water was reduced, plants such as Wooly Blue Curls did not survive. It has been a 10-year project and this is how I turned a steep dry sandy slope into a drought-tolerant garden:

1) Basic Calif-native trees & shrubs were planted (a couple of Coast Live Oaks, lots of fire-resistant Toyons, McMinn Manzanitas, Sunset Manzanitas and the wonderful Hollyleaf Cherry are good choices). At the driest upper areas, Palo Verde Trees were planted for their deep tap roots and provide 25% shade cover when leafed out during the summer.

2) The slope is very steep. As I worked the sloped while planting and watering, a curvy informal foot trail started to form. As the trees and shrubs took hold of the soil, these foot trails were gradually deepened. Most native ground covers are sold as tiny little things that can't get a hold on steep slopes or are buried under a shovel of dirt unless planted at the base of an agave for protection. Tip: Buckwheat prostrate is a great steep-slope ground-cover that drapes down and hides the vertical cut edge of pathways.

3) The native flower shrubs (Wooly Blue Curls) died. Calif. Fushia is very dought resistant and is best if tucked under an agave to brighten up the driest desert plantings at the upper level. As the trees, shrubs and trails became established, lots of agaves were added to hold the surface soil. Cabbage-sized boulders were often used to hold new plants into the slope.

4) Erosion: A line of three monster Blue Agaves were planted in a horizontal line whenever a "dam" was needed to divert rainwater from running straight down the slope. The maturing slope contours (trails) were gradually deepened and dirt bermed up so that rainwater would travel across the slope and flow into collection basins behind trees and shrubs along the way. The pathway/contours took a lot of time to evolve but was well worth the effort. Instead of walking "on" the slope, the deepened pathways amongst the plantings now gives the feeling of a nature hike.

5) Gradually, non-native plants (aloes) were added to the semi-shaded areas. For the upper "desert" area, tons of barrel cactus and agaves were used as a ground cover alongside uprights such as pony-tail palms and colorful upright non-native Sticks on Fire & Crown of Thorns.

This large (1/2 acre) hot dry, sandy steep slope was a real challenge and still is not finished. To make things look right on a large steep slope, you will need dozens of each plant to form groupings. You can use dozens of spikey Agave Geminiflora to give the illusion of a "meadow". Dozens of Golden Barrel cactus planted in an informal "swirl" along a switchback gives the impression of a flower garden from a distance. With a little imagination and a lot work, a steep slope can become a beautiful garden. Take courage, though, because it takes YEARS before others are able to "see" what you have planted. And on difficult slopes, it is better to overplant your basics of trees & shrubs because on a contoured steep slope, a sprinkler grid is too complex and you will lose some trees/shrubs when hand-watering is reduced.

    Bookmark   August 29, 2013 at 4:04AM
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hosenemesis(SoCal Sunset 19 USDA 8b)

I'd love to see a photo of all of your hard work, scrubsage.

    Bookmark   August 31, 2013 at 11:17PM
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    Bookmark   September 17, 2013 at 5:01AM
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hosenemesis(SoCal Sunset 19 USDA 8b)

I see how you made the terraces. It looks so lush! Thank you for putting up the photo.

    Bookmark   September 18, 2013 at 12:07AM
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our house is in the dc metro area. We have been here for over 40 years. Three years ago we landscaped a hill, added a fence and all was okay except for weeding and planting. This year with huge amounts of rain 8 inches in last 22 days, our had the swail remove topsoil and messed up all our mulch downhill. We tried adding large stones, re mulching but again it happened after a long rain. Our neighbor recently cleared his yard of lots of trees, Help!

    Bookmark   May 17, 2014 at 1:07AM
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missingtheobvious(Blue Ridge 7a)

You lost me with our had the swail remove topsoil.

I'm assuming you meant "swale" rather than "swail."

Which leaves me wondering: your what had the swale remove topsoil? (And just how does a swale remove topsoil?)

But really, this is the California Gardening forum, and you're in or near DC. You'd be better off posting this on the Landscape Design forum (which is considerably busier than GW's Hillside Gardening forum).

It would help if you could show a photo of the hill in question. And explain what you planted on the hill, and where in relation to your yard is the neighbor who cut down the trees. Google Earth photos are good too.

    Bookmark   May 17, 2014 at 10:09PM
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Our house is built into nothing but slope from back to front and there's a flume on the side to carry water away when it rains. Not being a fan of exposed soil or grass, I planted everything out with ground covers like fragaria, archangel lamium, cerastium, stachys, ground ivy, dymondia, Carmel creeper, and there's Algerian ivy down the slope in front some contractor had the bright idea would look great throughout the neighborhood back in the fifties. They were wrong as it tries to bring the trees down and eats small animals, and maybe children too. But it is what it is. I mixed in architectural plants like palms, tree ferns, Mexican bamboo ( stays in a manageable clump ), New Zealand flax, purple hop seed, thatching reed, California reed, Mr. Happy echium, hardy ferns, and there's a cranesbill volunteer on one slope that probably came on my shoes from restoring a friends garden. Among other plants and annuals I put in for a pop of color here and there. I let them fight it out and grow together to tether everything in as we are prone to landslides in Wildcat Canyon where we live. I am not huge on maintenance either and like the Jurassic Park look as a friend calls the garden. On your slope, that could work as viable solution. The various colors of the foliage might be a nice backdrop to what you already have.

    Bookmark   May 26, 2014 at 1:35PM
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This is the slope in front that goes to the road. Not as steep as yours though ours is covered with ivy and woods beyond has heavy ivy running through. This is what purple hopseed looks like and a bloom on a Mr. Happy echium, which takes a couple years to get. I rotate those in seasonally. Hop seed on a hillside does well, is drought tolerant, and does not get out of hand in height. I have three in front.

    Bookmark   May 26, 2014 at 1:44PM
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