Elisabeth C. Miller Library logo Miller Library Home UW Botanic Gardens Home UW Botanic Gardens Home book graphic

3501 NE 41st Street, Seattle, WA 98195 | (206) 543 0415 | Open: | Library Schedule

Gardening Answers Knowledgebase

Search Results for: Mosses | Catalog search for: Mosses

PAL Questions: 4 - Garden Tools: - Recommended Websites: 1

Keywords: Moss gardening, Mosses, Lawn alternatives

PAL Question:

Could you tell me how to replace grass with moss in the shady areas of our lawn?


There are a number of options for replacing the grass in the shady part of your garden. Should you decide to cultivate moss, Oregon State University's page on Encouraging Mosses should be of interest.

There are two books I would recommend, Moss Gardening by George Schenk (Timber Press, 1997), particularly the chapter on "Moss Carpets," and How to Get Your Lawn Off Grass by Carole Rubin (Harbour Publishing, 2002). Rubin gives directions for preparing your site, which involve digging out existing plants or smothering the lawn with mulches of leaves (12 inches), bark (3 inches), or newspaper (10 sheets thick). Schenk offers several different methods for creating a moss garden. Briefly paraphrasing, these are:

  1. Work with nature, allowing self-sown spores of moss to take hold. (Prepare the site by weeding, raking, and perhaps rolling the surface smooth).
  2. Encourage the moss in an existing lawn by weeding out grass. You can plant what the author calls "weed mosses" which will spread, such as Atrichum, Brachythecium, Calliergonella, Mnium, Plagiothecium, Polytrichum, and others.
  3. Instant carpet: you can moss about 75 square feet if you have access to woods from which large amounts of moss can be removed legally.
  4. Plant moss sods at spaced intervals (about one foot apart) and wait for them to grow into a solid carpet.Choose plants that match your soil and site conditions.
  5. Grow a moss carpet from crumbled fragments. This is rarely done, and only a few kinds of moss will grow this way, including Leucobryum, Racomitrium, and Dicranoweisia.

In her book Big Ideas for Northwest Small Gardens, Marty Wingate recommends Mazus reptans. It is semi-evergreen to evergreen with tiny blue flowers from late spring through summer. It takes full sun to part shade and is delicate looking, but takes foot traffic. It requires some fertilizer to stay perky. Another source of ideas is the website www.stepables.com. Click on "plant info," then "plant search."

Another ground cover that can take foot traffic is Leptinella gruveri "Miniature Brass Buttons."

Season All Season
Date 2017-01-12
Link to this record only (permalink)

Keywords: Mosses

PAL Question:

I'd like to hear your thoughts about the safest way to remove moss from the north side of my roof. I do organic gardening, and I don't want to contaminate the soil with runoff.


The City of Portland had a guide to safe moss removal (formerly available online) indicating that that the most common product sold for moss removal, zinc sulfate, is a pollutant and is toxic to aquatic life. They do say that zinc strips on the roof are an alternative, but they also release zinc, and are pretreated with pesticide.

Toxic-Free Future (formerly Washington Toxics Coalition) offers several recommendations, including physical removal of the moss, landscape planning to keep the roof clear, and the aforementioned zinc strips

Oregon State University maintains a website devoted to mosses, and one page addresses the use of zinc strips as a control. Here is an excerpt:
"Zinc strips are usually considered the long-term solution to controlling mosses [...] Zinc strips and galvanized flashing are apparently relatively safe and inexpensive. They effectively kill or retard the growth of mosses and fungi and appear to have effect up to 15 feet below the zinc flashing along the length of the flashing. To use: apply the rolled zinc or galvanized flashing to each side of ridge caps along the roof peaks. Place a nail down each foot of the zinc strip. With each rain zinc is released from the strip and kills the mosses below the strip. For best results remove the existing mosses prior to treatment. The active ingredient is metallic zinc.
Effectiveness: Zinc strips are considered to be effective for up to one year for most brands. The effect of galvanized flashing (example above) can persist for decades. Success rates vary with the degree of moss development and weather. Zinc strips or flashing are most effective before mosses are well developed. Physical removal of existing moss followed by installation of zinc strips or flashing is an effective long-term strategy for suppressing moss growth.
Negative Side Effects: Direct runoff from the zinc strips or flashing to surrounding vegetation, fish ponds, or water supplies should be avoided, because some contamination by zinc is likely to occur. Zinc strips should not be used with strong acids or bases."

The PAN Pesticides Database has an entry for one type of rolled zinc strip product.

Washington Department of Ecology has a lengthy document analyzing zinc concentrations in industrial runoff, and you can imagine that homes with zinc strips are simply smaller contributors to this problem.

The Environmental Protection Agency lists zinc metal strips (consisting solely of zinc metal and impurities) as minimum risk pesticides.

I think there is no easy solution, and it is a matter of deciding on a lesser of two evils: the physical difficulties of cleaning the moss off the roof, which is most environmentally sound, versus the relatively small amount of pollution from using zinc strips.

Season All Season
Date 2016-11-03
Link to this record only (permalink)

Keywords: Mosses--Control, Soil amendments, Mosses

PAL Question:

I have a small rooftop plant bed that's full of moss. Is that an indication of sour soil, and if so, can it be sweetened with Dolomite lime?


Moss is often simply an indication of a shady site or compacted soil, but can also be an indicator of low soil pH (i.e., acid soil). I wouldn't recommend adding lime without doing a soil test for pH (you can buy an inexpensive kit at most garden centers), and without considering the pH needs of the plants you have in the bed. You would not want to increase the alkalinity of the soil if your plants are acid-loving.

You may find this link about moss growing in garden beds (from Oregon State University) of interest. Here is an excerpt:
"Mosses grow in garden areas for the same reasons they grow in lawns: for example, deep shade, high acidity, poor drainage, and soil compaction. As in the lawn, mosses do not compete with other plants. Rather, they establish in bare areas where conditions are favorable (Cook and Whisler, 1994).
Mosses have not been shown to hinder the growth of garden plants or trees. Reasons for removal are generally aesthetic. But aesthetics are in the eye of the beholder, and mosses are commonly viewed as positive features in landscaping. For example, traditional oriental gardening holds distinctive roles for mosses (Japanese Garden Society of Oregon 1996; see also Encouraging Mosses). Furthermore, in some situations mosses may help reduce moisture loss and crusting on soil surfaces."

Season All Season
Date 2016-12-02
Link to this record only (permalink)

Keywords: liverworts, Mosses, Lichens

PAL Question:

Both my front and back gardens have become covered in moss and/or liverwort. It has intermingled with groundcovers such as sweet woodruff and blue star creeper. I have dug up the liverwort in the past but it comes back. Any suggestions towards eradicating it would be greatly appreciated.


It would be important to distinguish among mosses, lichens, and liverworts. Mosses and lichens are not harmful to garden plants. One species of liverwort is known to be a bit of a pest, mainly in greenhouse-grown plants. A first step would be to bring samples to a Master Gardener Clinic for identification. See the following on moss and lichen in gardens:

There are researchers at Oregon State University who have done work on the species which is prevalent in greenhouses, Marchantia polymorpha, but the following information may not be relevant if that is not what you have growing in your garden. The first thing to do--if this is indeed the liverwort you are seeing--is to make sure you are not providing the ideal conditions for liverwort growth. Note that high nitrogen and phosphorus levels encourage growth: if you use fertilizer, check the levels of these nutrients. Avoid quick-release synthetic fertilizer. Below is information on methods of greenhouse (not garden) control of liverwort, from the OSU website:
"Before talking about how to kill liverworts, let's talk about conditions in which liverworts thrive. Liverworts grow vigorously in conditions with high humidity, high nutrient levels (especially nitrogen and phosphorus), and high soil moisture. In an environment that has any of these 3 conditions, it will be difficult to control liverworts (even when using herbicides). In order to effectively control this weed, you must make growing conditions for the liverworts as difficult as possible. To do this, you should attempt to create an environment where the ambient air is dry, the surface of the container is dry (as dry as possible), and nutrients are not available on the container surface."

The link above discusses postemergence control, but bear in mind that if something like acetic acid is used on liverwort growing on your plants it will affect the plants as well.

The Royal Horticultural Society says that liverwort will not harm plants (except by causing competition for small plants) but its presence indicates compacted, acidic, and/or bare soil.

The only time I have encountered liverwort is when transplanting nursery-purchased plants. With these, I physically remove the liverwort from the pot before planting into the garden. I wonder if your soil drains poorly, gets too much water, and/or too much fertilizer. I hope the information above will give you some ideas. Again, I recommend getting a conclusive identification before proceeding.

Season All Season
Date 2017-01-13
Link to this record only (permalink)

Didn't find an answer to your question? Ask us directly!

Browse keywords or Search Again:

March 22 2017 13:26:25