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Weeds Good Indicator of Soil Type

FOR IMMEDIATE RELEASE
October 10, 2013

We tend to see weeds as unwelcome intruders that threaten our efforts to create the perfect outdoor sanctuary. But the new gardening philosophy is to be more accepting of them because they are a food source for insects and habitat for wildlife.

For instance, the wild Queen Anne's lace is a great larval food for swallowtail butterflies, and dandelions are and excellent source of nectar and pollen for honeybees.

Horticulture educator, Kelly Allsup, says your weeds also can tell you a lot about your soil and gardening practices. There is no need to pull out the herbicides; rather, botany can help you prevent large aggressive populations of nuisance weeds by identifying soil issues. Geochemical botanists read the kind of plants growing in an area and are able to determine what minerals are in the soil. If you have the following weeds, your soil may be letting you know about a gardening issue:

-- Chicory and bindweed are indicators the soil is too compacted. Aeration and a soil conditioner like compost or cover crop can help reduce the populations of these offenders.

-- Foxtails, dock and horsetail thrive in wet conditions. Try growing goldenrods, joe-pye weed and other moisture-loving perennials and grasses.

-- Dandelion and stinging nettle is an indication of acidic soil. Most plants prefer a slightly acidic soil so a soil test may be necessary to determine if the soil is too acidic for plant growth.

-- Thistle is an indication your soil needs more acid. This can be achieved with soil amendments like ferrous sulfate or aluminum sulfate. A soil test will indicate how much will be needed to apply.

-- Wild carrot, wild radish and wild parsnip grow in infertile soils. A fertility treatment, cover crop or additions of compost to condition the soil may be needed.

-- Pigweed indicates an abundance of nitrogen.

-- Red clover indicates an excess of potassium.

-- Purslane and mustard are an indication of an abundance of phosphorous.

-- Crab grass is an indication of poor fertility.

In conclusion, a few pre-emptive actions could make weeds disappear faster than any herbicide. Any horticulturist will advocate for soil testing to find out exactly what needs to be added to any crop (vegetables, trees and grasses).

However, this science of reading the weeds could not only reduce the population of the most detested pests but with the proper soil amendments make everything else grow better. On a side note, cover crops are an excellent way to deter weeds, add organic matter and can improve the health of next year's gardens.

Source: Kelly Allsup, Extension Educator, Horticulture, kallsup@uiuc.edu