Question
Hi Kenneth
I am having a lot of trouble controling the moss in my garden. The grass is always cut short (the wife is fanatical)the lawn is about 4yrs old last year we had patches of moss which we treated with moss treatment.Which helped at the time, but it has now covered about 80% of the lawn.The lawn itself gets sunlight but not a lot.(especially in winter)
Q1, Can it be brought back?
Q2, Would it be be better to have it relayed.
Q3, If so could you lay new lawn on old and would this give better drainage with it been a little higher.

Many thanks

Kev

Answer
To understand how to control moss, I would like to tell you how moss grows.

Moss is a relatively weak plant which is easily crowded out by grass which is a stronger plant. However, when the circumstances favor moss and disfavor grass it can be almost impossible to get rid of moss in a lawn. Only changing the cultural circumstances will help.

Moss require consistent moisture. If the top surface of the soil dries out, the moss will die. However, it does not need good soil to grow in. It can even grow on concrete or stone if moisture is consistent. Moss therefore does not like direct sun, but prefers shade which keeps things more moist.

Grass, on the other hand grows best in direct full sun. Even so-called shade cultivars do better with more than less sun. Grass prefers a deep cultivated soil and do poorly in low light, on a hard compact soil surface.

Therefore to encourage grass and discourage moss you would need to provide as many cultural advantages as possible in favor of grass:

- soil should ideally not be hard and compact, but have room for roots to grow. Hard, compact soil such as heavy clay or surfaces with lots of tree roots are not friendly to grass, but adequate for moss.

- the best way for grass to grow (providing soil is loose as above) is to water deeply to throughly wet the soil to a dept of 10-12" and then do not water again until the soil is dry in the top few inches of the soil. This will discourage moss and result in grass growing longer roots in search of water. This will subsequently make the grass even more resistant to occational draught.

In winter (when you would not water) it is almost impossible
to keep the lawn dry and therefore allowing as much sun in as possible is really your only option. If you find that moss grows in the winter, the best you can do is to improve conditions for grass in summer (and discourage moss) but you will never get as good result as a lawn which gets more sun in the winter.

- moss require very little nutrients to sustain itself. Grass, on the other hand, regular regular fertilizer to be healthy especially it is already strained by lack of sunlight, moisture, compaction etc.

- The more grass blade you leave on the grass plants the more leaf tissue there will be to catch the sun. Especially in shade, it is important not to mow the lawn too low. If you do, you weaken the grass. Grass can compete with moss, but not if weakened.

Therefore, to win the battle with moss you should:
- water infrequently but deeply such as once per week for 2 hours instead of frequent shallow applications. The goal is to wet the root zone deeply and then do not water until the top surface of the soil is dry.

- fertilize in spring and fall (in northern areas) and in summer in southern areas of the country

- mow the lawn high and mow frequently. It is better to mow the lawn at 2.5-3.5" (height after mowing) instead of 0.5-1.0". this result in healthier grass and makes it better at competing with moss.

- if possible, prune as many low hanging branches as possible to allow as much light in as possible.

- overseed with a mixture of fine fescues (in northern areas) to allow this type of grass to dominate. Fine fescues are the best grass types for shade.


E.g provided you are located in northern areas of USA, you can overseed with fine fescues in spring and fall, fertilizer in spring and fall, but not during summer. Also water infrequently but deeply when you water to discourage moss and favor deep root growth. Finally, mow the grass 2.5-3.5" tall (meassured after mowing) for maximum leaf surface.

If you have 80% moss at this time, I recommend raking it off and roto tilling the soil to a dept of 1 foot (using a roto tiller which can be rented). Then rake smooth and sow a good quality (shady mix) grass seeds. Do this in spring or fall.

Note: the recommended watering pattern for an established lawn is to water infrequently but deeply such as once per week for 2 hours i/o many frequent shallow applications.

However, when establishing seeds, you need to temporarily reverse the pattern and water frequently and shallowly (such as twice daily for 15 minutes each time). This is because grass seeds require consistent moisture to germinate (sprout). Once the new grass is 2" tall, gradually transition to the infrequent but deep watering pattern over a number of weeks. This is the only exception to the watering rule.