Sunday, 07 January, 2001

Don't Use 'Weed and Feed' Fertilizers

If you're fertilizing your lawn this Spring, do not use "weed and feed" products.  These "weed" parts of these products are broad leaf herbicides that do a very good job of killing everything that's not grass, including flowering plants, shrubs, bushes, and trees.  The instructions will tell you not to use the product under the drip line of trees, for this very reason.  What the instructions don't tell you is that many types of trees send shallow feeder roots hundreds of feet beyond the drip line, and those roots will pick up the herbicide.  You'll have a nice green lawn (at least for a few seasons), but your trees will die.

The "feed" parts of these products are NPK (Nitrogen, Phosphorous, Potassium) fertilizers.  They're usually labeled with the NPK percentages somewhere in a form like 12-3-2.  Typically these fertilizers are high in nitrogen, and lower in phosphorous and potassium.  Applying high amounts of nitrogen stimulates growth and greens up the grass nicely, but at a cost:  it stresses the grass, making it much less drought tolerant and disease resistant. 

Compost is a much more effective (if not as dramatic) fertilizer, and horticultural corn meal is a better broad leaf and pre-emergent herbicide.  If you want a "quick greenup" for your lawn, spread dry molasses on your lawn at the rate of 10 to 20 pounds per 1,000 square feet.  It's non-toxic, has almost as much nitrogen as the chemical fertilizer products, and also contains plenty of carbon and other trace minerals that soil microbes need order to combat the pests that prey on plants.  Be careful not to overdo the molasses, though.  Once a year (in the Spring) is plenty.  And if you eliminate the chemical fertilizers and try a more organic approach you'll find that even the molasses treatment is unnecessary.