Question
Thanks so much for you speedy reply!
I always thought sour milk encourages moss to grow.
If not, I'll try it!
Thanks, again!
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Followup To
Question -
Hi there,

Any suggestions on killing Moss in my Interlocking stones and ckickweed in my  lawn.

Any comments would be greatly appreciated!!
Thanks Irene
Answer -
Hi, Irene.  There are several safe and simple things you can do to get rid of the moss.  

First, my favorite weed killer in my bluestone driveway: Sour Milk.  Milk sours fast in my old refrigerator.  I always make sure to pour it out in the driveway.  Same thing works with expired yogurt and old ice cream.  I think it is worth trying for Moss, no?  The fat in the dairy smothers anything growing under there.  But my neighbors think I'm nuts.

Gardens Alive (www.gardensalive.com) sells something called "Moss Aside".  I have not had to get rid of moss -- I'm actually testing ways to grow it -- but I have dealt with Gardens Alive many times and I think they have some excellent things on the shelf that won't make anyone sick.  "Moss Aside", they say, "uses a blend of naturally-occurring fatty acids to kill unwanted moss, algae, lichens and liverworts within hours."  Fast enough for you?  

I belong to an organization called the Northwest Coalition for Alternatives to Pesticides (www.pesticide.org/pubs/alts/moss/mossinlawns.html) which describes the unique problem of getting rid of moss: a plant with no roots, no vascular system for getting nutrients around, and does not make seeds.  (Alas, These are the things that might render that Sour-Milk Cure ineffective.  I'm not sure.)  

NCAP zeros in on the cause of Moss in the garden, boiling it down to a few simple things.  "The most common conditions that lead to moss problems are a lack of soil fertility, acid soil, dense shade, compacted soil, wet soil, and injured turf." This is slightly different from your Interlocking Stones problem, but the lack of drainage, acid base, shade and moisture create a very comfortable environment for moss to grow.  If you don't change the conditions between your stones, Irene, the Moss is going to come back.

Now for the chickweed.

Treating your lawn with lime and a good Nitrogen fertilizer is the best prevention for weeds including chickweed.  Healthy lawns with a good pH and lots of Nitrogen (the first number on a bag of fertilizer) don't make happy homes for chickweed.  Milorganite is one of my favorite fertilizers.  It's very high in Nitrogen and releases nutrients for some time after application.  This is the perfect time of year to fertilizer your lawn.  The Gardens Alive website I mentioned earlier offers something called "WOW! Plus", a combination organic weed killer/grass fertilizer that you should apply as soon as possible.  There are some other organic weed killers that you might like even more, just read over the product descriptions.  I don't recommend there Q&A department, which does not seem to get things straight, but I have been impressed with their product line so far.  I order Beneficial Insects from them, which can be expensive but are really wonderful ways to get rid of aphids and Japanese Beetles on roses and scale on evergreens and deciduous trees.

A Florida retailer called Crabgrass Alert Company (www.crabgrassalert.com/contact.html) offers an organic weed killer.  I am not familiar with them but it beats turning your house into an EPA Superfund Site.  

Let me know how these things work!


Answer
Sometimes I'm wrong, Irene.  So I have looked further into this matter.  As I mentioned earlier, I am attempting to cultivate moss, not get rid of it.  My favorite recipe so far comes from one of Martha Stewart's Guest during one of her programs which included a lesson on growing moss.  The guy is a Moss Expert and works from the New York Botanical Gardens.  (You can read the show transcript at www.marthastewart.com.  No dairy product in sight.)

Now, I am not a big fan of Martha Stewart or anyone else who doubletalks the FBI for fun and profit.  Martha does not know the first thing about Organic Gardening.  Yet she wrote several books on the subject.  The Expert on Moss from the NYBG -- now, there's someone I am inclined to believe hook line and sinker.  NB: Not a dairy product in sight in the Moss Expert's recipe.  

"Moss Acres", a Pennsylvania Moss Farm that sells Moss to consumers on the Internet, details the technique for growing Moss (www.mossacres.com/info.asp): "Since they obtain all their nutrients from the air (moss has no true roots), moss plants require nothing more than shade, acidic soil, and adequate moisture to flourish."

He continues, but let me point out something here that I learned in a Thai restaurant many years ago.  I had just eaten some nuclear-power spicy food, and was reaching for the Water when the Waiter stopped me and put down a glass of milk.  "Spicy food is very Acid," he explained, "You need to neutralize it and you can't do that with Water, which is neutral.  Milk is a Base; fat in the Milk will neutralize it; if you eat too much spicy food, and drink milk, it won't be spicy any more."  This trick worked like a charm.

Moss fluorishes in "spicy" acid soil (low pH), and languishes in the pH that you would find in a fresh glass of whole milk, which the USDA says is around 6.6-6.8.  But in soil with a Base pH (a high pH -- which let's remember is the favorite pH for grass and many flowering perennials), Moss is miserable.

As the Farmers at Moss Acres point out: "Before utilizing Moss as part of your shade gardening plans, ensure that the pH is between 5.0 and 6.0.  If necessary, the soil for the moss can easily be amended with our liquid sulfur or aluminum sulfate to lower the pH to the desired range."

Still, Irene, you are right to point out that we can find NUMEROUS directions on "How to Grow Perfect Moss" that DO include Buttermilk, Yogurt, even Mayonnaise.  And here is where it gets complicated: Fresh cow's milk has a pH of 6.6-6.8.  But as bacteria grows and milk sours, the pH dives as low as 4.7; buttermilk, 4.4; with Acidophilus, 4.1 -- Moss Heaven!  

What's more, since Moss does not have roots or a vascular system, fat would not result in suffocation.  At least, that's how it seems to me.  What works for crabgrass, chickweed, purslane might have the opposite effect for Moss.

As for your chickweed population, the University of Washington Botanic Garden library (depts.washington.edu/hortlib) spells it out in plain English: "Potassium salts of fatty acids...kills the tops of all plants, but not the roots. It works best on annual weeds like chick-weed and bitter cress, but would have to be repeated a few times to kill perennial weeds with root reserves, such as dandelion."  Potassium in milk helps balance the salt content of the milk with the blood.  

Regarding Corn Gluten, they note, "Corn Gluten Meal prevents seeds from rooting once sprouted. The downside is that it doesn't work during rainy weather."  They reference the popular spray-on Safer Superfast Weed & Grass Killer, Concern's Weed Prevention Plus, and Whitney Farm's Weed Wompin Mulch as examples.  

And if you are considering boiling Vinegar to wipe out your chick or other weeds, note the U of W's views and its warning: "Vinegar from the kitchen doesn't kill weeds, only disfigures them. Commercial products work if used in hot weather, but are quite caustic and great caution must be used not to inhale the fumes or spray the skin. Natural, yes, but toxic."  

This finding is backed up by USDA scientists, who tested Vinegar as an herbicide and concluded it only worked on very young weeds.  They wiped out young common lamb's-quarters, giant foxtail, velvetleaf, smooth pigweed and Canada thistle with ordinary household Vinegar, which is diluted when you buy it to 5-10%.  Older weeds, such as your established chickweed, needed an 85-100% vinegar solution, much stronger than the 5-10% Vinegar we buy in the supermarket, and probably the overly caustic commercial sprays U of W discourages.   

So thank you Irene for your followup question.  I think we can now write a book about this subject.  And probably get a movie deal too.  Best regards,