Moss has a place – but it’s not on your lawn. Unfortunately, there are many reasons it might show up anyway. In this article, we’ll help you find out why you’re growing moss instead of the grassy lawn of your dreams … and how to fix the situation.
Moss only grows where grass is struggling. The most common reasons for moss growth are too much shade and overly moist conditions. Acidic, compacted, and clay-heavy soils may also contribute to the problem; improper mowing or fertilization can too. Correcting the issue will let grass retake the field.
Why Does Moss Grow In Grass
Moss looks nice on rocks and old tree stumps, but it’s not necessarily the look you want for your lawn. Still, there’s no need to panic.
Despite possible appearances, moss doesn’t really attack or invade your lawn … it just seizes an opportunity to grow where your grass is already weak or thin. Moss and grass thrive in very different conditions, so the growth of moss highlights areas where your lawn is struggling.
Moss grows best in wet, acidic, or poorly draining soil. Though it prefers brighter light, moss can tolerate deep shade. Grass doesn’t grow well in these conditions, which opens the door for moss growth.
Grass will out-compete moss in the turf war if its conditions are met, so the problem isn’t really the moss. Remember: moss doesn’t kill grass, but the conditions that let it take over certainly can.
What Is Moss?
Mosses are odd little plants without flowers or roots. They tend to produce dense but very thin leaves, often only a single cell thick. Moss clumps are fuzzy and carpet-like because they’re made of masses of tiny plants. Since they reproduce by spores carried by the wind, moss can seem to appear out of nowhere.
There are about 12,000 moss species, and it may or may not gladden your heart to know they are found in virtually every climate on earth. A number of varieties will colonize your lawn if conditions favor them.
Moss grows pretty quickly and takes up residence in nooks or crannies where no other plants have survived. Expect moss any time your lawn develops bare patches or thin spots.
Reasons Moss Might Grow In Your Lawn
Ridding your lawn of moss is simple: evaluate your growing conditions and correct whatever is attracting moss. The good news is that your grass will triumph if you give it what it needs.
Here are reasons you may be growing moss instead of grass:
Sodden ground is one of the major scenarios that promote moss. Waterlogged soil both harms your grass and helps the moss.
The obvious solution is to water less, especially if the weather is cool or the lawn has had a lot of precipitation. The normal recommendation is to give your grass an inch of water a week, but you’ll need to adjust this according to the season and the makeup of your lawn.
- Cool-season grass typically likes more moisture than do warm-season varieties.
- Newly planted grass consumes extra water until it establishes itself.
- Cut watering to 15 minutes every two or three weeks when the grass is dormant.
If your lawn remains soggy well after a watering session or period of rain, there are two things to check for:
Any spots that don’t drain well can face a moss takeover. Grass roots will rot in sodden ground while rootless moss remains unaffected.
Drainage issues can take significant work to resolve. Raising the soil level or digging out poor-quality earth and replacing it with better soil are possible solutions.
Whether you are topping off poor soil or replacing it, you can speed your lawn’s recovery by reseeding or sodding over bare patches that remain.
Dead grass, called thatch, can build up between the green blades of your lawn and the soil below. A thin layer of thatch provides natural mulch that conserves water and insulates the grass, but a mat that thickens to an inch or more becomes a problem.
Excess thatch can hold water like a sponge and restrict the amount of air and water that reaches the roots, setting up conditions for moss to take over. The parts of your lawn with a heavy thatch mat will feel like you’re walking on a sponge, too.
Vigorous use of a hard rake can pull out the dead grass; a special dethatching rake is even more effective. If the thatch is old and heavy or the affected area is large, a better option may be a scarifying machine with metal blades that rip into turf to remove the buildup. (It’s good for removing moss clumps, too.)
After a good dethatching, the soil will be more open to air, water, and nutrients. It’s a great time to sow new seed or plant sprigs if torn turf has left bare ground showing.
Too Much Shade
Inadequate light is another very common reason for seeing moss instead of grass on your lawn. Moss will tolerate dim light that won’t support a sun-loving grass variety.
Any spot on your lawn that receives less than four hours of sunlight a day is in deep shade. If you have shady areas where grass is losing out to moss, there are two basic solutions:
Trim Obstructions – Clear the brush or tree limbs casting shade on your grass-growing project. To speed the process, consider physically removing established moss and reseeding with your desired grass.
Introduce a Shade-tolerant Species – If you like your lawn’s shady spaces as they are, consider planting a shade-tolerant variety like St. Augustine, Ryegrass, or a suitable Fescue. It’s a good idea to use a grass seed mix and let nature choose the variety that grows best in the area.
Soil is the foundation of any lawn. If it’s inadequate for good grass growth, moss is happy to step in! Three specific issues can give moss the advantage:
Another reason why moss is “invading” your lawn could be that your soil is too acidic. This isn’t the full story, though: moss may prefer a lower pH, but it grows in more alkaline soil too. It just can’t compete against grass in that situation.
Acidic soil can develop over time as fertilizer residue builds up and organic materials like thatch and tree sap decompose. The problem becomes visible when low pH affects the health of your grass to the point a more adaptable moss jumps in.
The ideal grass-growing pH is about 6.0 to 7.0. It’s a good idea to do an inexpensive pH test to see where your soil scores.
The traditional solution for acidic soil is to add lime to increase the pH. This can be so effective that it’s become the go-to advice for any mossy lawn – but it only works if that’s actually the issue!
Compact or clay-heavy soil drains poorly and blocks oxygen exchange. In this way, hard-packed soil makes life difficult for grass roots – but moss doesn’t have roots to damage.
Soil can gradually become compacted simply from kids playing on it and other normal activities. Digging in deep with the tines of a stiff rake can help loosen the soil if compaction is light, but hard-packed ground will do better with the assistance of a mechanical aerator.
The best kind of aeration machine doesn’t simply poke holes – which actually compacts the soil more – but instead pulls little dowel-shaped segments out of the ground. This leaves empty spaces for the surrounding soil to expand into.
In areas where the soil is highly compacted, give the ground multiple passes with the aeration machine. Let the extracted soil dowels dry out, and then crumble them with the back of a rake to lightly backfill the holes and even up the turf.
Pro Tip: Adding a thin layer of sand or compost before raking will improve and open up the soil even more!
You only need to use an aeration machine once or twice a year, and they are usually available for local rental. The best time to aerate is in spring before the growing season or before seeding.
Wrong Soil Type
This is a big one, because soil is your lawn’s foundation. Shallow, rocky, or clay soil is home for moss, not grass.
The solutions are usually obvious: add extra soil, mix in suitable amendments, pick out the rocks, or replace the earth … the hard part is doing it!
One relatively easy fix is clay soil. The soil’s texture can be improved by mechanically aerating it and back-raking sand or compost into the holes afterwards.
It’s important not to cut your grass too short. Every variety has an ideal range, and cutting the stalks too short weakens the grass and exposes it to damage. This sets the stage for a moss revival.
Follow these tips:
- Find out the best height to keep your type of grass and adjust your mower to cut correctly.
- If your lawn has grown too high, don’t remove more than the top third of the grass in a single mowing session.
- If you have high grass you’re bringing down to the proper height, let it recover between mowings. Your lawn needs time to thicken and increase lateral growth for the best results.
- If you see moss in closely shorn areas of your lawn, let any remaining grass in that area grow a bit higher than normal. This helps block sunlight from the moss until grass can regain the upper hand.
Lack of Nutrients
Infertile ground is a less common reason for moss to grow instead of grass, but it does happen. Turf grass is a heavy-feeder during its growing season and needs more nutrients than moss does. Happily, this isn’t usually a hard issue to fix.
Soil can become depleted in several ways:
- Years of growing without supplemental fertilization have exhausted the soil’s fertility.
- Heavy rains have leeched nutrients from the soil, especially those supplied by water-soluble synthetic fertilizers.
- The soil has compacted and lost its permeability.
Having your soil tested for its nutritional profile is a good idea. You might find some nutrients are especially lacking: in which case, supplying them could bring dramatic results.
Fertilize in the spring after your grass has greened up and low temperatures don’t fall below 55ºF (º13C). Follow this in the summer about six to eight weeks later, and again with a final autumn feeding anywhere from August to November.
Be careful when applying fertilizer. The object of fertilizing is to supply grass with the tiny amount of chemicals it needs to produce its own food through photosynthesis: it’s easy to overfeed.
Too much fertilizer can shock or “burn” the roots, damaging the grass and opening the door to – you guessed it – moss. You can’t make up for a long-term deficiency in one application!
You may want to remove at least some moss for aesthetic purposes, but it’s not necessary. Healthy grass will eventually replace moss after you fix the underlying issue that’s holding it back.
You can remove the moss physically or with chemical treatments but, unless you solve the problem, the moss will grow back.
Treatments to eradicate moss can be more or less aggressive. Some contain salt to dehydrate the moss. Iron sulfate products will turn the moss black and kill it. An easier, non-toxic solution is to sprinkle the moss with baking soda and wait a few days.
The Last Resort
It can take a lot of effort to correct drainage or rework your soil. You may not want to sacrifice a shady tree or import dirt to fill a low spot. Coming to terms with the moss is always an option.
In low doses, moss isn’t the worst thing that can happen in a landscape: it’s fuzzy, but it’s low-growing and green, too. Moss can even provide benefits – it reveals trouble spots where your lawn is struggling and puts some green color into places where grass refuses to grow.