safe moss prevention near vegetable field

Asked February 16, 2013, 3:09 PM EST

We have a large garage that has a sloped roof upon which big trees shed needles. On this shady roof, moss grew for ten years. I've swept off the needles, scrubbed off the moss and now wish to treat the roof to prevent the moss from returning. My daughter will cultivate the field onto which the gutters drain, so she insists that I find a product which will not hinder her plants' growth or make her vegetables toxic. The landlord has provided a can of zinc sulfate monohydrate (one version of Moss Out) but the label warns not to let runoff contact plants. Another version of Moss Out contains ammoniate soap and fatty acids and there are other products that contain potassium soap and fatty acids. Some claim to be non-toxic to plants, but warn that they should not be used around edible plants. I've also been told to use straight vinegar. Lime has been mentioned, as has a biological fungicide called Actin Iron but I can't find any info on it -- I might have misspelled it. I've been warned not to nail zinc or copper strips. Maybe it's best to use nothing at all? BTW, my daughter-farmer is not striving for "organic" certification but, again, wants to avoid anything that will hurt either her plants or the marketability/edibility/flavor of her vegetables. We eagerly await your reply. a

Clark County Washington

4 Responses

Moss management in western Washington
Here in western Washington moss is a major concern in the winter months as we have a wet climate that encourages the growth of the moss. Shade on the roof is a contributing factor. Over time a heavy build-up of moss can shorten the life of a composition roof. A metal roof, while more expensive, would be advisable if one built a home in the forest.
In this situation the downspout from the roof should be directed to a rain garden that has been stocked with wetland plants. Possibilities would include: red-osier dogwood, rush, snowberry, Pacific ninebark, alder, flowering currant, etc. There are wide array of plants to choose from. Oregon State University has an excellent guide to the construction of rain gardens. Turn to: WSU Clark County Extension also has a rain garden fact sheet. Turn to: Charles Brun, Ph.D.
Horticulture Advisor
WSU Extension Clark County
360 397-6060, Ext. 5701

Your response is interesting, full of good information, and does not answer my question. Please review the question. I wish to know if there is an environmentally safe product which will prevent or slow the return of moss to this roof. When I say safe, I mean a product which will not affect the plants in the adjacent vegetable field, either by interfering with growth or by making them toxic for human consumption.

This question appeared in my box Wednesday. I see that the response you got 3 months ago did not specifically answer your question of if the was an "environmentally safe" material l that would stop or suppress moss growth on the roof and have no effect on the growth of other plants. I am not aware of any material that would specifically poison mosses and have no effect on other plants. Whatever you use would end up in the runoff from the roof. The suggestion that you use a rain garden to filter the water to remove contaminants is probably the best solution.
Sorry you had to wait so long for a final answer.

Thank you for the clear answer -- at last.