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Saturday - December 11, 2010

From: Kerrville, TX
Region: Southwest
Topic: Butterfly Gardens, Compost and Mulch, Soils
Title: Soil improvement near Kerrville, TX
Answered by: Brigid & Larry Larson


We live in the Kerrville area; the soil is extremely shallow and deficient. The yard consists of mainly native plants, with a concentration of plants for butterflies and birds. What kind of soil and fertilizer should we add and when? Thanks very much!


Ahhh – good old Hill country rock soil!  Just for the fun of it – I looked up the soil composition in Kerrville on the USDA Soil Survey - It was just as bad as I expected:    “Typically, the surface layer of the Kerrville soils is calcareous, pale brown gravelly clay loam about 8 inches thick. The next layer to a depth of 15 inches is calcareous, very pale brown clay loam that is 10 percent limestone gravel. The next layer to a depth of 24 inches is calcareous, extremely gravelly clay loam that is 75 percent limestone gravel and flagstones. Below that is coarsely fractured indurated limestone.”

   Congratulations on your native plant garden.  While clay has nutrients in it that plants need, it compacts so readily that the tiny little rootlets on plants that are responsible for picking up nutrients and moisture from the soil cannot access them. You could help your plants by adding a good compost and crushed decomposed granite soil [say about ¾ compost and ¼ crushed granite]. The granite adds trace minerals that your plants will love.  You can also fertilize once a month with seaweed or compost tea (no toxins that may kill butterflies & birds) – do that early in the morning or later in the evening during the bloom season.   However, with a good compost layer you might not even have to fertilize!

Hopefully you can scan the list of suppliers that support the Wildflower Center and find one that offers these kinds of soil.  Alltex Nursery and Landscape is close and a WIldflower Center associate.  Garden-ville offers all the materials recommended and has a store in San Antonio. 

 But, while we’re on the subject – how about setting up a nice compost pile for kitchen and yard waste – your own compost will gradually build up the soil in a really nice natural manner.


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