Gardening Information Leaflet No.5                                                                                                            




The Only Way to Grow!

Lawn Moss Control

Though green and low growing, lawn moss offends the eye of many yardeners. Arguably it is also a sign of an unhealthy lawn as far as grass growing is concerned. A number of conditions usually characterize where and when moss will be found in lawns and these suggest strategies for its control. Shade, wetness, and acidic soil are characteristics of places where moss usually thrives, but aren’t necessary. Lawn moss is most prevalent in very early spring when high rainfall and cool temperatures prevail, and it fades back in summer. Also, moss can often be found where it isn’t supposed to be and, unfortunately, there is  no silver bullet known for completely controlling it, at least organically and without toxic chemicals. 

Nevertheless, the basic strategy in organic control is do the things that favor grass and discourage moss. What the grass (or turf) likes, the moss hates. Among these are correct liming, proper fertilizing, and mowing at the correct height and frequency. But first we need to get the moss out. The simplest and cheapest way to do this is “chemically” with iron sulfate (a.k.a. ferrous sulfate) followed by mechanical (physical) removal of the dead moss with a rake (a.k.a. hard work).

Ferrous sulfate occurs naturally, but practically is probably only available as an industrial product. Iron and sulfur are both plant nutrients and, at low concentrations, do not pose any health hazard to humans or animals. Likely it is the iron that does the killing of the moss, but the grass apparently loves it, along with the sulfur. In fact, iron sulfate is sold as a lawn feeding amendment because the iron causes grass to develop deep green color.

To get the iron sulfate on, you dissolve it at the rate of two tablespoons in a gallon of warm water and make enough gallons to cover the entire moss-infested area. This solution needs to be applied liberally and evenly over the entire area using a sprinkler can (or possibly a sprayer, but no guarantees that it won’t plug your sprayer). Iron sulfate is inexpensive and available from Black Lake Organic.

Within a day or so the treated moss will be dead and turn black. Now it needs to be raked out and could be used as an ingredient in making compost. By itself however, it will not “compost”. Removing the dead moss has the bonus of creating bare and scratched up spots onto which over-seeded grass seed can land, then sprout, send down roots, and get established. Wherever a grass seedling grows it crowds out future moss growth. The thicker and more lush the grass blades, the less moss will come back. Don’t forget to continue with calcitic lime and a quality organic lawn fertilizer such as BLO’s Organic Lawn Food (BLOOM No. 4). We can assist in determining which lime and fertilizer to use and how much.

The Lawn:  To Mulch or Not

We are told to “mulch” our lawns with the grass clippings rather than catch and dispose of them.  The reasons are just two:  1.) To keep the clippings from going to the landfill and taking up valuable space, and 2) To “fertilize” the lawn by returning the nutrients that are in the clippings back to the growing grass (a.k.a. turf).  But there are other options to consider.

First though, let’s take a look at those words “mulch” and “fertilize”.  Letting a thin layer of clippings lie for a short while on top of the growing turf doesn’t really qualify as mulching where usually you are trying to suppress or smother whatever is beneath with a fairly thick covering of mulch material that lasts a relatively long time.

Fertilizing a plant or crop (or turf) by feeding it back to itself is of limited effectiveness.  It presumes the lawn is in good health to begin with and thus that the clippings contain rather high levels of all the necessary nutrients for supporting continual good health.  It’s a quality issue (as is so much in life). 

Certainly it is better to “mulch” with the clippings and recycle them rather than throw them away.  Grass clippings rightfully should be treated as a valuable resource rather than a disposable waste.  However, there are other good ways to recycle them and make use of grass clippings. Of course, all of this presumes the lawn has not been sprayed with toxic herbicides.

In most cases relying on a grass clippings mulch for your sole fertilization program is insufficient and does not replace the need to apply a good quality organic fertilizer and lime.  If the Second Law of Thermodynamics (which essentially says that all things run down and dissipate) is still being enforced you realize that there is no perpetual motion machine and that the mulching program “leaks”; or put another way, the creek can’t rise any higher than its source.  The turf will do better if it gets at least an occasional fertilizing and liming (semi-annually). 

The important point here is that productive use be made of your grass clippings.  A good way to do that is to collect and use them in fairly thin layers alternating or mixed with brown materials (dead leaves, cardboard strips, chopped straw, pine needles, ground bark) and kitchen scraps to make compost.  For a high quality, nutrient-rich compost, it is a good idea to incorporate a fortifying organic fertilizer mix as well.  A second way to use clippings is around your vegetable plants in not too thick layers (3-4 inches) as a true mulch that suppresses weeds, moderates temperatures, and holds moisture.

There are a couple of precautions to follow. When composting, try to use the clippings while still fresh and green rather than store them in a pile. This way you capture the most nitrogen. Alternate shallow layers of greens with browns (such as fall leaves) or intermix the two. Mowing the lawn after some dry leaves have fallen on the grass automatically gives you a chopped intermixture that is an ideal combination. For complete instructions on composting ask for our two Gardening Information Leaflets (GIL No.2 and No.3)

When mulching, such as around your vegetables or along rows, put down only shallow layers (3 to 4 inches) and allow to dry or yellow before adding more to prevent making a stinky, slimy, slippery mat. Beneath trees and shrubs, follow the method outlined in our Fertile Mulching leaflet (GIL No. 4) for great results.

Bagging isn’t necessarily bad, but uses a different mower blade, ideally. In conclusion, you don’t need to feel guilty about not letting your clippings lie, as long as you make equally productive use of them in composting or real mulching.

Note: To our knowledge there is, as yet, no organic weed and feed, other than corn gluten, which is effective on sprouting weed seeds, but not on established weeds in the lawn. Corn Gluten is effective for up to two months, but also kills grass seed and other seeds.

All rights reserved © Gary Kline

Black Lake Organic Garden Store

4711 Black Lake Blvd. SW
Olympia, WA. 98512

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