Native Plants

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Tuesday - October 14, 2014

From: Austin, TX
Region: Southwest
Topic: General Botany
Title: Water Use Versus Soil Moisture
Answered by: Anne Van Nest

QUESTION:

In the Native Plant Database, under Growing Conditions what is the difference between water use and soil moisture? Sometimes they seem contradictory.

ANSWER:

Good question! Thanks for using the Native Plant Database and noticing this. Plants that are listed in the Native Plant Database under Growing Conditions do have designations for Water Use: Low, Medium, High and Soil Moisture: Dry, Moist, Wet.

Most often one logically matches the other. For example for Salvia azurea, water use is listed as low and soil moisture is indicated as dry. But these two growing criteria can be mutually exclusive. The water use designation is how much water that the plant needs to survive, while the soil moisture listing indicates the soil conditions that the plant (roots) will tolerate. There are some unique native plants that don't use much water but their roots can tolerate being quite soggy.

For example, Carex stipata (awlfruit sedge) uses a medium amount of water but can tolerate moist to wet soil moisture.

Another example is Arctostaphylos uva-ursi (kinnikinnick) which has low water use but can tolerate moist, boggy soils (and dry, rocky soils).

And lastly, there's Magnolia grandiflora (Southern magnolia). This plant has a high water use rating but can tolerate a dry soil moisture level (but not totally dry as it does prefer moist soil).

From the Image Gallery

Awlfruit sedge
Carex stipata

Kinnikinnick
Arctostaphylos uva-ursi

Southern magnolia
Magnolia grandiflora