Nov 082011
 
Low retaining walls can help prevent erosion

Low stone retaining walls keep soil from falling into the driveway

Erosion of  hillsides can range from minor movement that is easy to repair, to major and dangerous situations.

Caveat! Caveat! Caveat!

If you think you have a major problem, please refer to a professional soil engineer or contractor to help you.  In this post, I am only going to address simple  erosion problems.

 

 

 

 

Building low stone retaining walls can be simple and effective for keeping  hillsides from eroding.

These walls were built without mortar in  a method called drystack.  Only soil was used to hold them in place.  Cutting back into the hillside, laying the stone, back filling with soil and then planting keeps the base of the wall stable.

Loose soil will collect in the beds at the bottom of the hill.

Vegetated swale

The swale is covered with a biodegradable erosion blanket and sowed with clover and wildflower seeds

 

When assessing your slope for erosion problems look for these signs:

  • Channels already formed in the hillside from runoff
  • Bare soil that is exposed to  rain or water runoff
  • Downspouts or other water sources

Ways to minimize water damage include:

  • Create swales that are on the contour of your slope
  • Build retaining walls that have drainage in them
  • Sow seed and plant  fast growing shrubs to cover bare soil
  • Mulch, mulch, mulch

 

Wild strawberry and Mahonia with stone wall

At the top of the stone wall you can see the wild strawberry (click to enlarge)

In the photo above I planted a native strawberry that sends out many runners and roots into the hillside.  It will cover the hill very quickly. Other California native plants that provide excellent cover are creeping Ceanothus, trailing Manzanita and  Sonoma Sage and Coastal Sage Brush.

Planting on steep hills

Creeping ceanothus, trailing manzanita and other natives were used on this steep shady slope

Small stone walls

Small walls at the base of trees keep soil and mulch in place

The most important action for you to take in your garden is OBSERVATION.  Go out in the rain and storms and watch how the water flows.  This is the best way to learn about your garden and the only way to really know what is happening.

 

Nov 072011
 

 

Retaining walls

The hill came down, the walls went up

 

Before the rains come crashing down, take a good look around your property.  It’s especially important if you are on a hill or have slopes around you.  When water picks up speed it can really create havoc.  Take a look at this hillside. After a number of rainy days, the whole hillside came down into the driveway.  Fortunately, no person and no cars were there when the soil came down.

In an effort to get more light in the property the owners cut down many trees.  The result, light came down and so did the hillside.  They should have made sure the ground was planted and drainage was put in place.  To do it after the soil erodes is much more expensive. In addition to cutting back the hill and putting in retaining walls, we also put drain pipe behind the walls, at the top of the hill and at the bottom.  Water has to go somewhere!  Take a look.

Erosion control for steep hills may mean building retaining walls

Cement block wall at the bottom and wood retaining walls will hold back this hill

Construction of the retaining wall

Retaining wall in process

There's still too much soil, and erosion can be a problem

Cement block wall is not high enough, and soil needs to be removed

After the walls are built, it is important to plant for soil coverage.  I use seeds for immediate coverage and plants for long term coverage.  At the top of the hill we put in a swale to redirect the water away from the main walls. We covered it with erosion control blankets.  They are both 100% biodegradable, but they are slightly different. One is thicker and made of coconut fiber and the other has straw put between cotton netting. The thick mat is better for stronger erosion control and the straw allows better germination of seeds.

Two types of erosion control blankets - coconut and straw

The blanket on the left has straw and the blanket on the right is coconut fiber.

Swale

A long swale covered with netting and also planted with seed

For quick germination I used rye grass, Dutch white clover, vetch and California wildflower mix, with extra California poppies. We were lucky with early October rains that helped with excellent germination.  If you don’t expect rain, you should water the seeds to take advantage of warmer weather in the early Fall.  Once the winter rains come it gets too cold for most seeds to germinate.

Erosion control seed mix

Rye grass, Dutch white clover, Vetch and Wildflowers

Seeds germinating through straw mulch

Straw mulch holds the soil in place and protects the seed

 

Tomorrow I’ll talk about other simple erosion control  methods.

Curving path on steep hill

Using plants and curving path for hillside erosion control

 

 

 

 

 

Oct 252011
 
Large trees give a lot of leaves

The Might Oak Tree over our House

It used to be that I could never find enough leaves to compost for the garden. I used to drive to the nearest cemetary. I kid you not. Now I have an embarrassment of leaf riches. Leaves are everywhere around my house. If you have this problem, DO NOT DESPAIR! Do NOT rake up those leaves, put them in a plastic bag and give them to the garbage men.  That would make me cry. It would be a crime against nature.

All leaves are not created equal.  The oak tree, or Quercus, has roots that go deep into the earth and bring up many minerals and nutrients.  These then go into the leaves.  The leaves fall to earth and are a gift to the gardener. The oak contains qualities that are oceans above other trees.

Huge pile of oak leaves

This pile of oak leaves will compost over the winter

Do not use leaves from Eucalyptus, Bay laurel or Walnut.  They contain tanins that are not good for your plants.

To make sure your pile stays together and creates enough heat to break down, you might want to consider getting a simple wire cage.

 

Although the leaves falling continuously may get a little annoying, and even a little messy, be grateful for they will make next year’s garden even better. Trust me, you want to keep these guys on the premises.

 

Leaf mold

Composted leaves look clean and smell earthy

 

 

When the leaves break down, they turn into leaf mold, which is not really mold, so don’t hold your nose. It smells clean and fresh.  You can add this to your strawberry beds, raspberries, and blueberries, who all love a little acidic soil.  You can also add it to your topsoil for working into the beds.

Acer palmatum

Japanese Maples are beautiful in all seasons and give great leaves for your compost

Oct 062011
 

The Edible Landscape

Edible landscaping is the type of garden design I’ve been doing for 35 years.   With landscaping ideas based on the principals of organic, sustainable and beautiful, I will pass on my hard earned lessons to those who are ready for the edible journey. Scroll down the page for all the entries, or go to Click on a topic on the right and choose a category to read. I write about landscape design, ornamental and edible plants, tools, gardening books, critter control and more.

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Yours in the joy of gardening,

Avis

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