How to Control Moss in your Lawn

The legacy of El Ninos past will always linger as we view newscasts of flooding in the east, mud slides in California and wind in the south east. In comparison, our suffering in the Pacific Northwest will be minor. Perhaps no more than the inconvenience of the higher levels of lawn moss seen in recent years (warmer winters or not normally a reason to complain). Encountering this low form of green life is normal for most gardeners as they approach annual spring gardening chores. But this non-vascular plant, that can account for thousands of different species, is perhaps the most responsive to environmental conditions of any plant in the garden. Its needs are simple, and moss is actually a very poor competitor when up against healthy turfgrass. So, considering excessive moss in the lawn is really a discussion of what makes the lawn less competitive.

What makes lawns less competitive are things like poor drainage, low light, low soil pH and higher temperatures – when all of the above are happening. So, back to El Nino. A quick glance at the weather data will show more rainfall, less sunlight, and higher temperatures over the past six months. Lawn moss, unhappily, is quite content with all of the above. The moss has no vascular system to transport water from a root zone, up a stem and into the leaves. It rather relies on absorbing moisture out of the air and other surrounding elements (which also means that it will survive in times of drought better than the grass). When the turfgrass is weakened through poor drainage, poor light and lower soil pH, it provides for exposed soil area for surface growing moss. In short, El Nino is great for moss but murder on grass.

The best response is two-fold. Control or eliminate the moss and encourage healthy grass. Existing moss can be controlled by raking it out – often called power raking. It may be helpful to apply a moss killer first as this will reduce the shear bulk of the stuff that has to be raked up and lugged away. There are many good iron sulphate moss control materials available from your local garden retailer. Apply them to moist moss. This will allow for better adhesion to the moss. Do not water for 48 – 72 hours to provide for the best reaction. You may then want to actually rake out the debris. Be sure not to damage the turfgrass by raking too deep. Also, if you leave exposed soil, overseed to ensure a rapid recovery of the turf. Exposed soil provides opportunity for weed seeds to become established. Now, back to the turfgrass. The best defense against lawn moss, or any turf grass weed or pest, is a healthy lawn. So, consider the basics. To control moss, apply lime, aerate to relieve compaction, and add a properly formulated spring lawn fertilizer. But, don’t forget the big picture.

We may not have much control over El Nino, however, there is a great deal that can be accomplished on the home front. Like keeping the nutrients in balance – don’t be tempted by promises of green lawns through fertilizer application alone. Then there is proper drainage. If you have poorly drained soil, like most of us, aerate at least twice each year. Top-dressing after aeration with a properly prepared organic soil mix – or even medium garden sand – will assist in providing a long term solution. Remember, as well, light plays an important part in all of this. Your lawn may be suffering from lack of light simply because, over time, trees and shrubs grow. So do some selective pruning to allow for greater light penetration. And, last but not least, consider over-seeding – especially if your lawn is over 10 years old. There are now many new turfgrass species that will adapt much better to your particular conditions. Ask your local garden retailer for more information.