Moss moss and more moss. It is in lawns everywhere this year, spreading vigourously and choking out those poor lawn grasses. In spite of all the lime and moss control applied, it seems to get worse.
The problem with moss is our lack of understanding about why it grows in our lawns. We knock it back each year but we never really seem to get rid of it.
Let's start by looking at why moss grows. First, it thrives in areas of high rainfall and it loves shady locations. Wet, poorly drained soil is a wonderful place for moss to become established because the soil is usually acidic. In addition to these conditions, moss does very well in soil that has low fertility. Shaded, heavy, wet, acidic soil with low fertility - those are the ideal conditions for moss to grow and spread rapidly.
To minimize moss, we must rectify these conditions, so let's start with the heavy soil. Light, sandy soils are usually less prone to moss than heavy soils, where water drains away slowly. One of the first things we must do is improve the porosity and drainage of our soils. Short of plowing our lawns under, aeration is the most sensible way to go.
You can do this by using a three- or five-prong hand aerator and pulling out cores of soil throughout your lawn.
For larger areas, a commercial aerator would be ideal but be careful of the roto-tiller types, which basically chew up the turf and loosen your teeth at the same time.
How you get those cores of heavy soil out of your lawn is up to you but once that is done, broadcast a 3/8 inch layer of coarse sand over the aerated areas to fill up those holes. This sharp sand will eat its way down and, in time, help to greatly improve the drainage. You can aerate now and repeat the process often until you see an improvement in the drainage. This is one of the secrets of so many golf courses.
Once you have worked on the drainage, it is important to raise the pH levels of the soil - in other words, make your soil less acidic. Lime will do that but, at this time of year, not just any lime will do the job. Easy-to-apply granulated or prilled limes are the way to go. The new Dolopril or Doloplus lime are two of the best limes available today; they are granular for easy application, fast acting, weigh less by about a half, have twice the coverage and last a long time. Dolopril and Doroplus lime should be applied at 10 kg per 200 sq. m or 2,000 sq. ft.
(Incidentally, the only way to be sure you need lime is to have your soil tested to determine its pH level. There are pH testing kits available at garden centres but after our wet winter and with the copious quantities of moss in our lawns, I am sure you will be safe applying it.)
Once you have increased the pH level, it is time to burn off the moss. Ferrous ammonium sulphate is the best way of doing that. It usually comes in a 20 kg bag, which will cover approximately 2,000 square feet of lawn area. Moisten the moss first, apply the moss control dry and arrange to have two dry days afterwards when the temperature remains above 10 C (good luck). Quite sincerely, though, that is what is required for successful moss control. There are also liquid controls available that can be applied using a garden hose. Combinations of moss control and fertilizer are also available to burn the moss and then give the lawn grasses a boost.
Once you have been able to eliminate the moss, you must rake out all the old dead stuff and apply a fertilizer to encourage the remaining grass to get growing and fill in those bare spots before weeds do. A slow-release, high-nitrogen fertilizer will do the job nicely and will be soil friendly. For those who wish to stay organic, there is a great selection of organic fertilizers available. Now is also a good time to overseed your lawn with some great perennial rye grasses to get new life and vigour into your lawn.
Your lawn will be in good shape as long as you can eradicate the moss everywhere - from your trees, roof and under your rhododendrons. Don't forget: Moss spreads by spores, so a thorough clean-up is important.
All this sounds like a lot of work but it is not really, especially if you lessen the problem each year by improving the drainage and maintaining more consistent levels of nitrogen in your lawn area.
Brian Minter is a well-known Fraser Valley gardening expert.
