Plant to Prevent Erosion on a Steep Hillside
Gardening Question from Kathy:
I love your book and use it as my garden bible.
I have a new problem and do not know what to do. I live on top of a steep hillside and have been here for 34 yrs. I have never had a mudslide. However, the hillside is in three levels and the bottom one had a some mudslide last winter. It was covered with the old heavy ice plant and the woman who lives across the street from my hill started pulling it out and planted red apple and some nasturtiums as she didn’t like the weeds in between the ice plant. Now I need to know how to fix this problem.
What is the best and toughest ground cover ?
I live in Rancho Palos Verdes. The slide is about 3 feet deep by about 4′ wide at the top and a narrow 9′ down to the street . It has thick red apple on one side and scattered old ice plant on the other side. Thank you so much
Answer from Pat:
Thanks for kind comment. Below are a lot of ways to fix a steep bank. I think I was considering a larger space than you actually have, but I have given you so much to chose from you can make it fit your needs. Also this advice may help others who read this site.
As you undoubtedly know landslides on the Palos Verdes Peninsula can be a serious matter since they might signal a problem with an entire strata of wet adobe soil slipping down over a harder layer of soil below. This kind of slide can happen when the “tow” of a hillside has been unwisely bulldozed or cut into. It might be wise for you to contact your UC Extension Home Horticultural Advisor, Department of Agriculture, or your local city officials before trying to do anything to correct the slide so you can first make sure there is no serious slippage problem in this case. In many cases in the past mudslides have endangered houses or even lives, though yours sounds smaller in scope than were those.
Once you have determined that this is not a widespread or potentially dangerous situation, then you can undertake some steps to try to correct the problem. First, ice plant is seldom a good solution for a very steep bank, since it can actually pull a bank down by its own weight. Nonetheless if it is growing there already and holding a bank it’s unwise to pull it out as your neighbor did since this can make the whole bank slide as happened in this case. A wiser way to make a change is to cut the ice plant short and leave the roots in place, then plant right through it. The roots will continue to hold the bank while the new plants take over. It’s too bad your neighbor didn’t know of this old-timers trick, a common practice in California gardens fifty or sixty years ago when people with new homes covered banks with ice plant quickly to hold them through winter rain then soon upgraded to something better.
Also, red apple ice plant is not a very good solution for steep banks since it needs a lot of water and calcium nitrate fertilizer to stay green. It’s far better to plant something more environmentally responsible. When trying to plant a bank for the purpose of stabilizing slipping soil, the very best way is to plant a mix of deeper- rooted larger plants along with shorter-rooted ground covers to cover the ground between them to hold the ground as the larger plants are getting going. Examples of shorter rooted ground covers are gazania or arctotis. Then you could dot such plants as shrubby bougainvilleas all over the bank, along with something like ceonothus ‘Concha’. I recommend bougainvilleas as one of the better plants for such an area. They will grow on a drip system and grab deeply into the soil. Once fully established they become very drought-resistant and you get a lot of bang for the buck. Another fairly deep-rooted bank cover plant is Acacia redolens ‘Desert Carpet’ or ‘Low Boy’. This too is very drought-resistant once established. Lantana montevidensis is hugely colorful with lavender flowers almost year round and also very drought-resistant, easy to grow and good on banks. Finally consider blue plumbago. For a gang busters combination on a bank and drought-resistant year-round color, plan yellow trailing gazanias to cover the ground, then use an equal number of the the following plants to send down deep roots and hold the soil: Bougainvillea ‘La Jolla’, Plumbago ‘Royal Robe’, and Lantana ‘Radiation’.
Another way to go and perhaps more exciting, but best planted in November: You could do the whole thing with native plants. You might try toyon or Calfornia holly (Heteromeles arbutifolia ) at the bottom of the slope. (Get the one from Catalina that has bigger berries.) For a native shrub requiring no water whatsoever in summer, plant flannel bush (Fremontedendron ‘California Glory’.) Or, for a compact one, try F. ‘Dara’s Gold’. Plant this next to ceonothus for a great color combination blooming at the same time in spring. I think natives are probably the way to go with this slope but you could get a ground cover going first to hold everything until fall. Matilija poppy (Romneya coulteri) is a great way to grab a bank but not a good time to plant now. I planted three of these last November and they are all growing and blooming. All natives are best planted in November but it would be all right to cover the bank now with some native ground covers though perhaps not California perfume (Ribes viburnifolium)—great on banks but might not survive planting now. But bear berry (Arctostaphylos urva-ursi) or coyote bush (Bacharis pilularis) I think might mostly survive along the coast even if planted now since we’re having cooler than usual weather, and then plant the bigger things in fall.
Photo by Upupa4me 
Hi Pat,
Oh wow I am so grateful to you for your wonderful reply. I have been going round and round in circles not knowing what to do with this problem. I really don’t think I have a huge problem because the side is more of a wash due to the neighbor fooling around with that part of the bottom slope as I have lived here for 34 yrs. I have my helper cleaning out the easement which is filled with dirt and he is dumping it in the hole right now as I write this.
I love the color combinations you picked and especially the plumbago as I have two of those planted on my first short level going down and they are now enormous. I may try digging up some of the babies to transplant down below as I really don’t want the plumbago to get much bigger. I thought that the bougenvilla is a more difficult plant to plant as I heard it was touchy. Will the gazanias hold the sold from erosion as well as arcotosis? Can you suggest a nursery where I can find some of the botanical plants you mentioned. I simply love these ideas and am anxious to try them.
Another side question I have is relative to the bearded iris. I have some lovely gold ones and I just reread what to do after they bloom in your book. Do they require much water and also do you ever fertilize them? I usually put down the organic fertilizer three times a year and just wondered if that is enough or too much for them. I have one bunch of gold ones that only bloomed twice and not this year so I guess I will dig them up at the end of June and try doing what you said in your book.
Anyway, you were wonderful to reply to me and my problem and I will later on let you know how I make out.
Regards, Kathy
First regarding the plumbago. Plumbago auriculata is a plant that comes from South Africa and is well-adapted to growing as a bank cover in our frost-free coastal climates., but please don’t transplant roots or take cuttings from the old one you have since, as you have already noticed, the old type is highly invasive and will just take over. Also the flowers are very light blue. Be sure to plant Plumbago auriculata ‘Royal Cape’ which is much better. This superior selection is more compact and has flowers with deeper color. They are a true royal blue and the plant is less invasive but nonetheless still makes a good bank cover.
All the plants I recommended are readily available at nurseries or can be ordered for you by your local nursery. Shop around for a good price. Monrovia Nursery is one wholesale house that carries all of them and has superior plants, but your nursery will need to order from Monrovia. If you order these plants in 5-gallon size, there should be no problem in planting any of them. Just be sure to have a hole dug in advance before you slide a bougainvillea out of the can. When removing bougainvilleas from the can, I sometimes slit the side of the can with a can cutter or I cut the bottom off the can and push the plant out from the bottom, to make it easier to slip the plant out more easily without breaking the roots. Hold the roots together with your hands and make sure that the stems are supported as you lift the roots into the hole, so they don’t break off at ground level. (It helps to have two people.) A well-grown specimen usually won’t have this problem, but many bougainvilleas are broken at planting time simply by careless handling. Their roots and stems are brittle when they are young but soon toughen up once they are in the ground.
This month or next is the perfect time to plant bougainvilleas, plumbago, and lantana, since all are tropicals or subtropicals and will take off in warm weather. Trailing yellow gazanias can be planted now, also. Order these by the flat and be sure to specify a variety. Gazania ‘Sunrise Yellow’ is a good one. Newer types bloom longer and with larger flowers and have resistance to disease. If you don’t name a variety you could get something cheap and inferior that won’t grow as well and will likely get sick with fungus disease causing dieback. I think gazania is a better choice for your needs than Arctotis. Fall is generally considered a better time to plant ground covers, but in this case and your climate zone it doesn’t matter. You can plant all these plants now.
You asked if the gazania would hold the bank. It won’t hold the bank at first, not until it spreads all over, but if you order a good vigorous variety as I suggested above (see Sunset Western Garden Book for others. See page 364 of the latest edition) and if you water often by sprinkling by hand during the summer, the whole bank will be well-stabilized by fall. The deeper-rooted plants will have struck roots into the ground and should be holding the soil deeper down while the gazania should be covering the top. If you are worried the steep slope won’t hold, cover it with jute mesh, stapling it to the ground and making holes through the mesh for planting. Be sure to water well, when using jute mesh. Sometimes banks don’t do well because people don’t realize the mesh is absorbing the water like a sponge and evaporating it into the air, while plant roots down below are dry as a bone. (Water the 5-gallon plants more deeply.) You can put the whole thing on a drip system if you want. Use a circle of laser-cut drip line to go all the way around the 5-gallon plants and low-impact sprinklers for the ground cover. Check by digging with a trowel to make sure water is sinking in and not just soaking the jute. Additionally, fertilize the entire slope with an all-purpose organic fertilizer prior to planting and mulch the top of the ground after planting.
Sorry I also forgot to ask you is there a specific name for the shrubby bougainvillas for when I order them?
Bougainvillea ‘La Jolla’ is the one you want.
Oh this is wonderful information and specifying the plants name is extremely helpful to me as I am not at all familiar with the plants you mentioned other than the gazania but didn’t know it was called trailing nor the specific color so I am truly grateful to you on this and the other info you offered. I am thrilled to know about the royal cape plumbago as I love blue in the garden so I will get a few of these along with the bougainvilleas.
Can I simply dig a hole in the dry soil and drop all these plants in or do I need to add something in the holes with the plants? I will follow your instructions re the fertilizer on the slope first. What kind of mulch do you suggest? There are so many varieties.
Now also should I just cut out the tops off the old ice plants wherever they are? If I do will they grow back?
We just put some burlap down today on the bare spots as that is all I could find at Home Depot. Is this terribly wrong? We better take it up anyway as we will have to put the fertilizer down first –darn. We thought we would just cut holes in it for the big plants.
Thanks so much I am so grateful to you and you are giving me confidence.
You can if you wish amend the soil before planting the gazanias, with a composted organic amendment recommended for mixing into soil. Mulch with any good grade of organic wood-based mulch you can order by the bag or trucked or get from tree trimmers, often for free. Don not use redwood pellets. This is not a good type of mulch and does not look good either. You can simply plant the other plants in the ground as it is unless planting in pure sand which I am sure your soil is. But don’t “drop” the plants in. Lift them into the holes and make watering basins around them and install drip irrigation. But water by hand at first until they are established. Yes just cut off the ice plant and leave the roots in the ground. No it will not regrow. No it is not wrong to put the burlap down. Just be sure to follow the advice on that which I already gave you.
Thanks so much for your wonderful advice but we do not have sand here but grey or blackish clay soil which gets heavy when wet. I am not sure I could really water by hand or do the soil ammendment as it is too steep a slope. I might take a photo for you to see my problem here.
I will get some good shredded bark. I will have to get a big quantity so will have to see where best to get it. Again thanks for these tips.
I am very familiar with the type of adobe soil found on the Palos Verdes peninsula. I mentioned sand and what to do in the case of sandy soil because many people read the questions and answers on this website and thus I want my answers to work for a larger audience than just one person’s specific problem. Sandy soil needs to be amended with organics because there is basically nothing in it but sand, it dries out quickly and water runs off when it is dry.
About sixty years ago my parents owned a piece of property at the top of Rolling Hills on Palos Verdes. I also visited the garden of Charles Laughton and Elsa Lancaster further down the hill in Portuguese Bend, below Rolling Hills and saw their problems and successes. Their garden had become a jungle. My husband and I also bought a piece of property in Portuguese Bend in the 1950’s but later sold it. Things grew well in the water-retentive soil, but it baked hard in summer and was in danger of slipping after rain, so even without a photo I can imagine the problem. Acacias were easy to grow there. You just stuck them in and they grew.
Amending the planting holes in your case is probably not necessary though you can add compost in the planting holes if you want. In general it’s better if plants get used to the native soil they are going to grow in since the roots need to get out into it anyway and clay is nutritious soil. Also, digging up a whole bank prior to planting will only do more damage than has already been done. The plants I recommended will all take off and grow in the native soil, but a good layer of organic mulch on top will help hold the bank, keep down weeds, and retain moisture in the soil in wet weather. It will gradually break down and thus amend the soil. Replace it from time to time if you can figure out how to do so. Fertilizing the ground will help plants grow faster. Consider using Grow-Power, not fully organic but pretty good anyway.
The ice plant you had prior was planted by someone who climbed up the steep slope to do it. When a bank is very steep you can lay a long ladder onto it and use this to climb up it for planting. This is what I did on an earth berm of clay soil that had been put there by a bulldozer on my own property fifty years ago prior to the building of our home. (This is where I still live today.) In that case, the bank was made from red clay soil that had been removed from the building site and was pushed out to create a patio and earth berm about thirty feet tall on the outside and about one hundred feet wide. It surrounded our still-existing patio on a higher level up the hill. After this berm was created I realized immediately that it would wash away in the winter rains. So without delay I began planting it. We had little money in those days so I did all the work myself. (My husband was a lawyer and not given to this sort of thing.) I had a little baby but fixed up a clever way to have her sleeping right next to me on the bank. (I was afraid if I left her in the house I couldn’t hear if she woke up and cried.)
After finishing all the planting, which took a few days, I moved the baby out of the way (of course!) and stood on a flat spot down below and watered with the hose daily using what was called a long range “fire-nozzle” that cast a fine spray all over. I moved the spray continually so as not to create runoff and I tested the soil often to see how far the water sank in. After a week of this I lengthened the times between waterings. Later I hardly ever watered, but I live in Zone 24. Years later I met a man who had made a bank such as I described to you and he had put the whole thing on a drip system and it worked beautifully. He made water basins around the larger plants and ran the drip system longer at first so the water went deeply into the ground.
Oh what a great idea re the ladder against the hill. That would work real well I think. Also the other great tips as well. I didn’t know Charles Laugton lived here. I believe I know the area that he lived in from the way you described it.
Yes I think I will add a bit of planting compost in the bottom of each planting hole even with the yellow trailing gazanias to give them a helpful start. I have 3 rotating sprinklers across the top which reach a wide distance. When I finish planting I will try them to see if they are sufficient or not and if not I will have someone put in the drip system. I will turn them on several times a day for short periods maybe 20 min at a time for a week to keep things moist which should help and I am hopeful with the burlap holding down the loose soil it should help keep the soil moist.
I simply cannot get down there to water it by hand as I am now 74 yrs. old but am in super shape but I would have to climb up the bottom bank which is straight up to get to the next bank where I plan to plant some of the bushes and gazanias. The bottom where I have the washout I think will be lost to the red apple as it is so thick on the left side of the wash and will take over anyway with no matter what I plant there. I will plant a bush or two but I think there is so much of the red apple that it doesn’t make sense to me to remove it all. I was down there this past week cutting back the red apple in the easement area but my hands gave out as I have so much arthritis from gardening and they hurt after a while and I have to stop working.
Anyway, thanks again so much. I am looking forward to a gorgeous hill looking down from my yard.
From your emails I had imagined you as a strong young woman just starting out in gardening. You are lucky to be in super shape, but please don’t hurt yourself. The ladder works extremely well but I couldn’t do that myself today. if you’re planning on using the compost in the holes be sure to mix it in and while you’re about it, put a handful or two of gypsum in the bottom of the planting holes too. It wouldn’t hurt to dig a cup or more of it in the bottom of the planting holes for the larger plants. It should help the soil to drain.
Oh that’s a great idea I will do that. I will have the man helping me (who knows nothing about plants) do this. He is a good worker though. His name is Tony and he is 55 yrs old and strong. I am helping him by keeping him working as he cannot find a job as things are tough. Anyway I am excited to be planting some new things. Looks like we are doing primary colors with the blue yellow and red. I will mix in some of the lantana radiation as you suggested as well.
I need to go down to San Diego area next week to visit my daughter and I will stop in at Las Pilitas nursery there and perhaps call them ahead to see if they have any of these plants. If so I can buy some and get started. They have all native plants. I found them on the computor.
Thanks again Pat. You are a most wonderful person to help me out here as I have been worried what to do and you have given me a big boost in confidence.
Blue, yellow, red, and orange. I call this the “Sun Colors”. All the colors of sunshine plus blue for the sky. Would be nice to have white too for clouds but on a hillside this looks fine, a bright happy color scheme for full sun. Las Pilitas will not have a single one of these plants.n Las Pilitas is a native plant nursery. These are not native plants. If these were native plants I would have suggested going to Tree of Life Nursery in San Juan Capistrano. These are all easy exotics. Just go to any good quality nursery and get plants from a fine wholesaler such as Monrovia as I already suggested.
I gave you two schemes. One was all native plants (the one with ceonothus next to flannel bush). You may not have understood what you were doing but you chose the exotics. Stick with the plan, don’t go changing it now!
Hello Pat thanks for all your plant wisdom…
I have a few questions;
1. What kind of plants do ground squerals hate and will avoid nesting near on this very steep, very high hill side in Oak View Calif.
It is covered with these little darlings and their homes.
I don’t want to trap, kill, or hurt them.
I just want them to leave peacefully.
I’m afraid their ground tunneling will bring the whole hill side down onto the property.
Thank you for any help.
Maria
No plant will make a ground squirrel go away. There is nothing they hate that much. If they like your hillside they are there for good unless you do something about it, and unfortunately there is no magic bullet that can get rid of them humanely. Also I don’t think of these unclean creatures as little darlings, no matter how cute the young ones may be. They belong out in nature but not in our gardens. However, I doubt they will make your hillside fall down. How many hillsides have you noticed or read about falling down as a result of ground squirrels? I am not aware of any myself and I have lived in California for over sixty years and I read the newspaper every day and listen to the PBS NewsHour nightly. If any banks were falling down as a result of ground squirrels I would have heard about it by now.
In order that you can understand what I am going to advise on this subject, I have to share with you that after my family emigrated from England to America during the 1930’s, my mother bought and ran a family farm in Bucks County Pennsylvania which is where I spent my teen years during the war. In order to get a tax deduction as a family farm, my resourceful mother discovered we needed to have 10 various kinds of domestic animals. She put us all to work raising 2,000 chickens, plus bantams, Pekin ducks, Muskovie ducks, geese, turkeys, 2 breeds of pigs, sheep, 2 breeds of cows (which I milked) and rabbits, which were in my total charge. All these animals were gentle and friendly and we loved many of them, though not the chickens. Nonetheless, we had to kill some of them in order to put food on our table and money in our pockets. I had to kill many chickens, but I flatly refused to kill the rabbits I had raised with love so my brother had to do it. My brother also shot pheasants in our woods, pigeons off our enormous barn, and from our fields in autumn, wild hares which we marinated for three days and ate as hasenpfeffer. Having experienced this toughening childhood with its many challenges and its great joys, I find I have little sympathy for destructive and disease-carrying pest animals, even though they are all live beings created by the same power that created me. Gophers, rats, and ground squirrels may have their place in the balance of nature, but not in my garden. I usually talk aloud to them before setting forth on a hunt which will end with their demise. It may sound silly but even as a child I used to lecture the chickens on the evils of pecking each other before I would kill them and the ones that did not peck another chicken got a reprieve from me. I took the time to go catch another of the meaner chickens and cut its head cut off instead. In the same spirit, I tell any gopher that sets up housekeeping in my garden that he had better leave post haste or he will soon come to a sudden end with a wire around his neck. Then if he doesn’t get the hint and leave I trap him. The Black Hole Trap works exceedingly well if one follows the directions. I told this to a close friend who has a bad gopher problem but she was not brought up on a farm like me. This friend of mine has a heart of gold and was shocked to find out that when I said, “I trap any gopher that comes in my garden” that the gopher would end up dead. She thought I was releasing them in the wild.—No way!
But gophers are not on the bottom of my black list. That place is reserved for ground squirrels and rats. In my garden gophers eat more white grubs than plants, but they ruin my rock walls and make mounds in the wrong places, thus they have to go. Rats are far more destructive of plants. They eat roses, bougainvilleas, and Madeira geraniums among other things, but ground squirrels, besides eating tomatoes and other vegetables and fruits and some plants, also carry bubonic plague. My great-grandchildren play in my garden quite often and they are dear to my heart. Thus I want no unclean animals frequenting my premises. Ground squirrels are more disease-ridden than roof rats. I tell ground squirrels they need to leave my garden in a great rush or they will soon meet up with a sudden and untimely death and like other pest animals should choose to reincarnate as a better animals the next time around. This is not totally organic gardening, but in the case of ground squirrels if I ever needed to get rid of one, I would purchase a proper bait box for ground squirrels and the correct bait to go inside it. Always use gloves when handling these baits and keep the box replenished with fresh bait. Follow directions exactly.
If you don’t want to manage your ground-squirrel problem this way and if you don’t care to hire a company to do the job for you, then you will need to plant flowering shrubs, such as plumbago, bougainvillea, callistemon, Solanum rantonnettii, leptospermum, melaleuca, rosemary, and lantana on the bank. All these shrubs and many others can be grown where ground squirrels are located with no problem whatsoever. The roots of these shrubs will hold up the bank. Ground squirrels are vegetarian and they will graze on a lawn like rabbits. They will eat the seed pods of ice plant, and chew at various plants but other than making holes and taking the occasional bite out of plants they really don’t eat to an annoying extent except for food plants. You can’t grow a vegetable garden with squirrels around. They will eat all the tops of the young plants and chomp on the vegetables before you get them.
Ground squirrels prefer open areas of bare land where they can climb up on something low and see all around and sun themselves. Unlike regular squirrels, ground squirrels are not forest animals. If you can thoroughly cover your bank with a thick shrubbery so that all parts of the ground are thickly shaded, then the ground squirrels will be unhappy on your bank. They will go away and find a sunnier area to make their burrows. So maybe there is a magic bullet after all. It just took me a while to figure this out. This is why I don’t have a ground squirrel problem myself, despite the fact they are in my neighborhood. From time to time through the years they have come to my garden but they always go away and never settle down to stay. This behavior does not result from the little lecture on their mortality that I give them but comes from the fact that my garden is surrounded by a thick and shady shrubbery. That’s what ground squirrels detest.
Do you know the hillside of nasturtiums – you can smell it before you see it – I think in La Jolla? I was there in 2009 and doubt I will ever be there again. Don’t know how I got away without photographs of it.
Also – how can they be there in such abundance if they are annuals?
Thanks,
Nancy
I have seen the hillside covered with nasturtiums in La Jolla and here is the explanation: Once years ago someone sprinkled nasturtium seeds there and they naturalized. I knew the gardener who did it and she got some other things going too. Nasturtiums (Tropaeolum majus) are native to South America, but easily become naturalized in Sunset Zone 24 (in other words in the “fog bank” close to the ocean.) In mild-winter climates, if you toss the seeds in fall onto north-facing slopes—on the bare, north-facing walls of canyons for example—ahead of the rains, they will sprout with the rains, bloom massively in spring, die down in summer and leave many seeds to grow and bloom the following year. Even during this dry winter they have done extremely well without irrigation. Trailing varieties are best for this purpose but all of them will eventually revert to the trailing type once they have naturalized and set seeds. So if you happen to know a bare, north-facing bank near your house you could produce the same effect just by tossing some nasturtium seeds onto that bank next fall before the rains. Purists will say this is not good because nasturtiums are not native plants and might crowd out the natives. Personally I see no harm in the practice. Native plants seem to be able to live in harmony with nasturtiums. Meanwhile a bank covered in nasturtiums is beautiful and gives joy to many people. Annual flowers that leave many seeds are often hugely abundant when they are in bloom. Think of all the great sheets of wildflowers one sees on mountain tops in mid-summer.
Are nasturtiums at all gopher resistant? I have a north facing slope on the central coast of California (Pismo Beach) and it has been stripped bare by gophers! It is also shaded part of the day by a large oak tree.
I don’t believe that nasturtiums are gopher resistant. However, nasturtiums grow so vigorously in late winter and spring they hide the gophers’ mounds and holes, but once the nasturtiums die back to the ground, you will once again see the gophers and their mounds. I used to trap gophers on my property with the Black Hole Trap. It really works. However I now use the services of a man called “the Gopher Getter Guy”. In most areas of California one can find such a person who will trap gophers, and really that’s the only way to get rid of them in towns and villages. The gentleman who does that job in my town charges $25 for each dead gopher. He only charges when he catches the gopher. If you live in a rural area you can use a propane machine called a Rodenator Pro to blow up the gopher runs and rid your field or bank of gophers.
I just bought a home that backyard drops off into a little greek. I am a little worried that the slope of my backyard will get worse after the snowfall this winter. So I liked tha you pointed out that ice plant can help prevent erosion on a steep hill. I didn’t even realize that there was a special type of plant that is made to prevent snow erosion from happening. I will have to look a little more into ice plants to see if they can grow in my area.
Unfortunately ice plant does not grow in ice and snow. The common name ice plant comes from the inside appearance of the foliage. Controlling erosion of snow on banks is best done by the installation of a snow fence in autumn before the snow begins to fall.