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Sunday - March 30, 2008

From: Twin Falls, Idaho, ID
Region: Rocky Mountain
Topic: Soils, Herbs/Forbs, Shrubs, Trees
Title: Plants for soil with basalt outcroppings in Idaho
Answered by: Barbara Medford


We have basalt (lava) outcropping in part of our back yard and know we'll have to search for pockets of soil in which to plant. Any suggestions about what trees or shrubs would have a chance in these challenging conditions?


We found this a fascinating question, and went hunting for more information on basalt. This Columbia River Flood Basalt Province website has maps detailing the presence on the basalt in Washington, Idaho and Oregon. Since Twin Falls County is in the southwestern portion of Idaho, it would seem that we have found the source of the basalt in your soil. The main thing we would advise about plants that can grow in that environment is that you observe plants that are already growing in it. Obviously, you're not the only ones with lava in your garden. Plants that have survived over the millenia have done so by adapting, pushing roots into cracks in solid rock, pulling nutrients out of clay or sand or whatever was available to them. So, we went to our Recommended Species for Idaho webpage, which gave us 111 plants native to Idaho from which to choose. We then clicked on "Narrow Your Search" and checked Idaho as the state, Habit (herb, shrub, tree), duration-perennial, sun exposure-6 hours or more a day and soil moisture dry. From each of those we selected four examples that should do well in your location. You can follow the same procedure and find others that suit you better. Just click on the link of the plant name and it will take you to a webpage with descriptions of the plant and the conditions in which it does best.

Herbs (flowering plants)

Sphaeralcea munroana (Munro's globemallow) Here is a page of images of this globemallow.

Gaillardia aristata (common gaillardia)

Phlox longifolia (longleaf phlox)

Anaphalis margaritacea (western pearly everlasting)


Amelanchier alnifolia (Saskatoon serviceberry)

Artemisia tridentata (big sagebrush)

Arctostaphylos uva-ursi (kinnikinnick)

Cercocarpus montanus (alderleaf mountain mahogany)


Juniperus scopulorum (Rocky Mountain juniper)

Pinus flexilis (limber pine)

Populus tremuloides (quaking aspen)

Prunus virginiana (chokecherry)

Gaillardia aristata

Phlox longifolia

Anaphalis margaritacea

Amelanchier alnifolia

Artemisia tridentata

Arctostaphylos uva-ursi

Cercocarpus montanus

Juniperus scopulorum

Pinus flexilis

Populus tremuloides

Prunus virginiana




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