University of Vermont Extension 
Department of Plant and Soil Science

Summer News Article

LET YOUR WEEDS BE YOUR GUIDE

Leonard Perry, Extension Horticulturist, and
Sid Bosworth, Extension Agronomist
University of Vermont
 

Knowledge of what weeds you have, and what conditions they prefer, can be your guide to what may need correcting with your lawn, garden, flower beds, or landscape.  Change these growing conditions, and you will go a long way to preventing future weeds without the use of excess labor or herbicides.

The first step is to find out what weeds you have.  Many are wildflowers, so can be identified from wildflower books or websites.  A weed is simply a plant out of place by some definitions, so when not in your garden where you don't want them they become wildflowers.    There are useful books and websites which also can help identify weeds in your region.

Once you know what you have for weeds, you need to know what conditions they prefer in order to know what may be wrong.  Keep these facts in mind with your diagnosis.

*Many plants are very adaptable across a wide range of conditions.  Therefore, it is advisable to also use other diagnostic tools such as soil testing.
*Do not use single plants to judge a condition.  Use plant communities--groups of the same plant, as well as the combination of all the plants.  For instance, moss may indicate several conditions.  When found with chickweed or creeping speedwell, this combination may indicate too low mowing.
*Use the healthiest plants as indicators.  Stunted, poor growing plants may be growing in their own marginal conditions.
*Perennials are the most reliable since they must live longer in one place.  Annuals often appear over a wider range of conditions.

Moss has already been mentioned, and is one of the more common "problems" we hear about with lawns.  Actually this may not be a problem, as moss gardening has become quite popular.  Unless you really want or need a lawn, if you have a healthy crop of moss, perhaps you should consider this trend!

If you do have moss, this may indicate too low mowing, low pH, excess soil moisture, or shade.  Chickweeds may also indicate too low mowing, and mouse-ear chickweed may indicate substantial shade.

If you think low mowing may be the problem, simply raise the height of mower blades.  Most lawns generally should be mowed around two inches high, and with no more than one third of the grass blade cut off at any one time.

Annual bluegrass may indicate too low mowing, but may also appear in compacted soils, or those with excess moisture.  Creeping speedwell may indicate too low mowing, excess shade, or drought conditions.  Prostrate spurge may also indicate compaction or drought.

If you think soils are compacted, you can rent or buy an aerator for you lawn.  This is merely a series of forks or spikes which make holes in the soil, helping to break the surface and to allow water and air to enter, hence the name.  You can even buy shoe attachments  with spikes (similar to golf shoes, only with longer spikes) to wear while mowing, aerating the soil as you walk.

Clover species may indicate low nitrogen.  Rabbit's foot clover may indicate drought or low pH (soil acidity).  Hop clover, on the other hand, indicates possible high pH.  We actually like some clover in our lawns, as in drought it will remain green.  It is also a legume-- a type of plant whose roots take nitrogen from the air and turn it into forms plants can use.  Having clovers in your lawn means you wont need to add as much nitrogen fertilizer.

Birdsfoot trefoil and vetch, similar to the clovers, also indicate low nitrogen .  Docks, mullein, hawkweed, sheep sorrel, and wild strawberry may indicate low pH.  Mullein may indicate low fertility in general, as can wild carrot, wild parsnip, wild radish, foxtail grass, or mallow.  In addition to creeping speedwell and spurge, dry soils may be indicated by the presence of crabgrass, pigweed, yarrow, yellow woodsorrel, and curly dock.

So before you rush out to spend money on herbicides or a lawn care service, look at your weeds more closely.  Let them be your guide on what corrective measures to take first.  You merely may need to aerate a compacted soil, add some lime to increase the soil pH, cut a few tree limbs to allow more light, or improve watering practices and organic matter for dry soils.


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