Newly Registered
Posts: 1
Joined: Mon Mar 05, 2007 12:39 pm
Location: Hastings, MN

Landscaping with boulders

Does anyone have tips for building an island (using trees, shrubs & perennials) that would be approximately 3 feet off the ground incorporating 18in diam boulders? I just went to a home & garden show & got inspired. However I've never worked with boulders and am unsure what material is used to create the lift. Is it all compost except for the boulders? Also are there any tricks for keeping the tree stable? I've only planted trees directly into the ground & I would think that fresh compost wouldn't be as compact for supporting a new tree.

Super Green Thumb
Posts: 4659
Joined: Thu Oct 21, 2004 5:58 pm
Location: Victoria, BC

I'm having trouble visualizing the effect that you are trying to correct.

Erratics (boulders) can be used to create some beautiful garden scenary. Just simply plant plants to exentuate existing large rocks that you have. Generally speaking you plant the trees and shrubs into the soil that surround the boulders.

By the sounds of it, you want to have some large rocks in the ground slighly covered by soil with some trees planted around them, am I correct?

Greener Thumb
Posts: 1868
Joined: Tue May 25, 2004 10:44 pm
Location: Maryland zone 7

Hi Sfischbach,

Welcome to The Helpful Gardener. Sounds like you want to build a berm. It can be alot of work but it can be done. If you want a 3' high berm you could use SCREENED topsoil and add 4" of compost on top and mix it in. Making it all compost would probably be too expensive.

About 80% of a tree's roots are in the top 12" to 18" of soil.

When boulders are added to a landscape about 1/3 to1/2 of the boulder is buried to make it look as it's always been there. Try a google search with the terms:
build a berm
landscape with boulders


Newly Registered
Posts: 4
Joined: Tue Aug 21, 2007 1:10 am
Location: Davie


:D hello

have you seen curbwall landscape walls and islands its new for 2007
matching stucco color and texture 8" to 48" tall and come with decorative cap--- diy pieces also available in 4 shapes all with cap feature
here are a few sample pics [url=https://img172.imageshack.us/my.php?image=0000606du6.jpg][img]https://img172.imageshack.us/img172/1282/0000606du6.th.jpg[/img][/url]

Greener Thumb
Posts: 1152
Joined: Sun Feb 24, 2008 10:26 am
Location: North Carolina


I did design/build in Colorado and used moss boulders, biggies, evergreens, aspen, and cotonester as a groundcover with perennials interspersed. If you are landscaping in any other area around start building the berm with dug up sod, including the island you want to make, just don't dump soil without digging up the grass. Have soil brought in once the island is formed and you've dumped on the dug up sod. Now for the planting part because you don't want to stake trees, I never did. Get 1/4" rebar and drive it through the ball of the tree until you hit solid soil. Four feet should be sufficent. Make certain that you tamp the soil down that you are adding to the island and water thoroughly after planting. A sprinkler system would be the best option, because people always take shortcuts that way you know it will be watered for x amount of minutes and not as long as a cigarette lasts.


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