St Augustine

Having looked high and low on this wonderful forum for a reference to St. Augustine and not finding one I am posting this.

A little more than a year ago I moved into a 1940's house with an established lawn near Atlanta. My dear ole' dad who loves lawn care was surprised to see that the backyard was a full, lush St. Augustine expanse as St. Augustine is rarely found this far north. A little research told me that you can indeed find it this far north in sheltered areas, like my backyard. Early in the spring I cut down a giant 40 year old cedar tree in the backyard and plugged the large, bare area with more St. Augustine and by the end of this summer it was completely covered. St. Augustine is amazing as absolutely no weeds seem to be able to penetrate it or take root. Truly it is low-maintenance.

The front yard is the problem:  from the neighbors I understand that at one time it too was fully St. Augustine but today has only a quarter of that left mostly in the area closest to the house. Another quarter is some variety of Centipede (I am fine with that-wonderful grass). The other half is a mixture of annual weeds that have just now turned brown.

I bought a half pallet of St. Augustine in the spring, plugged it, and hoped that it would take off like the large bare spot where the cedar tree was in the back yard. No luck. Weeds that grew faster than cancer quickly hemmed my plugs in and while the plugs did take root they could not spread.

Now that the weeds have gone brown I can clearly see the missing St. Augustine plugs which are still a beautiful blue-green surrounded by a sea of brown.

Any advice as to what I should do next spring?

My guess is that part of the difference was the tremendous amount of organic matter from the roots of the cedar, which would hold and distribute moisture quite well.  It might also have beneficial fungus that is missing in the front yard, or any of a number of other reasons.

There are lawn-specialized master gardeners on this forum, and I'd go with their recommendations over mine any day, but from what you're describing, I'd consider the following plan: digging in wood chips etc. fairly deeply or driving in stakes where the weeds are, transplanting a few plugs of your own sod from the fastest-spreading part of your backyard (I would cut deep: beneficial fungus can extend several times the depth of the roots), and perhaps planting some clover in between the plugs if you're confident that St. Augustine can overtake it in time, both to turn that area perennial and to fix nitrogen that the decomposing wood will absorb.  If you do go with clover, sawdust could make nitrogen scarce enough to give it an edge over the annuals, depending on whether they fix nitrogen or not.

Over the winter, it might be instructive to send samples of your best and worst (for St. Augustine) soils for testing...that might suggest an entirely different course of action, like altering the pH.  If you use cedar waste for the above plan (presumably you have some lying around?  ), that might ultimately bring your front yard's pH more in line with the cedar-influenced part of your back yard.

I think that you have enough wood in your soil already and suggest that you not add more.

Cedar duff has four different kinds of natural herbicide in it.  It's gonna be a while until that is all gone.  In the meantime, the high carbon of the rotting wood roots is gonna suck up extra N from the soil.  Grass LOVES N! 

I suspect that the weeds that were doing well, do well without much N and can cope better than most other plants with the natural herbicide left in the soil by the cedar duff. 

I would rake up as much cedar duff as possible and next spring (warm season grasses would like to receive their fertilizer in the late spring) put down some organic lawn fertilizer - which would give the grass a big leg up over the weeds.

Paul, kayomuchi wrote that the St. Augustine grass had spread very quickly over the area the cedar had occupied, and the weeds were holding it back in an area very far from the cedar (opposite side of the house).

Point taken on the allelopathy of cedar (I had forgotten!), and of course about the N, but it sounds like those issues have not been a problem for the conditions and species we're being asked about.

I'm curious what the weeds are exactly, and what else is different between the two sites.  My guess was that St. Augustine would normally struggle to get enough moisture in those parts, but the influence of the house, and some extremely deep soil, had helped it out in places.  A further guess was that an enormous mass of mycorrhiza had lost its partner when the cedar was felled, and recently found some grass to live with instead, but further reading since my post yesterday suggests that this isn't as likely as I had supposed.

Joel Hollingsworth wrote:
Paul, kayomuchi wrote that the St. Augustine grass had spread very quickly over the area the cedar had occupied, and the weeds were holding it back in an area very far from the cedar (opposite side of the house).

Point taken on the allelopathy of cedar (I had forgotten!), and of course about the N, but it sounds like those issues have not been a problem for the conditions and species we're being asked about.

I'm curious what the weeds are exactly, and what else is different between the two sites.  My guess was that St. Augustine would normally struggle to get enough moisture in those parts, but the influence of the house, and some extremely deep soil, had helped it out in places.  A further guess was that an enormous mass of mycorrhiza had lost its partner when the cedar was felled, and recently found some grass to live with instead, but further reading since my post yesterday suggests that this isn't as likely as I had supposed.

Interesting thoughts on the effects of cedar debris on weeds and on the St. Augustine, of course. As to your questions, the St. Augustine in the backyard is more sheltered than that in the front yard and I think that is the difference, and not the soil. Don't know what those weeds are but they look almost identical to the St. Augustine but grows in clumps and doesn't have the deep, deep green of St. Augustine. After last summer's struggle I can spot a single blade of that nightmare weed 6 feet away!

After I wrote the initial post last fall I simply fertilized with Ringer Lawn Restore and left it alone ... by late winter/ early spring I had a bumper crop of fall/winter weeds. It was truly horrifying. After deciding not to feel guilty I sprayed this mess with a product designed for St. Augustine and Centipede and watched the weeds melt away and discovered that every plug of St. Augustine had survived the winter and the established St. Augustine quickly greened. I bought a pallet of Centipede (it is more hardy than St. Augustine in this area) and filled in the areas that were formerly filled with weeds and used the rest to cover another area in the backyard where I had had another cedar tree cut down. In a matter of days the St. Augustine in the front yard began to send out runners like crazy and in another month my front lawn will be solid.

If the St. Augustine in the backyard is a reliable indicator, once the lawn becomes thick it won't need anymore weed killer ... got my fingers crossed. That being said, my neighbors on both sides both used to have strong, healthy St. Augustine lawns (I am told) but are letting them "go native," one out of laziness and the other out of old age. Is it possible to keep a lawn weed free naturally when almost every other lawn on the street is full of weeds?

If you have annual weeds just use corn gluten as a preemergent herbicide next year, stops germination and breaks down to N in the soil which the grass needs in abundance.

Emerson White wrote:
If you have annual weeds just use corn gluten as a preemergent herbicide next year, stops germination and breaks down to N in the soil which the grass needs in abundance.

Isn't there some controversy regarding corn gluten? Some say it works, others are not so sure?

These forums do not support the use of herbicides.  I'm locking this thread.