Question
Greetings. I've consistently maintained an organic zoysia lawn since sodding our new lot approximately 4 years ago. This year, we have a serious problem: Dichondra has taken over and there's a decent amount of nutsedge and wild onion taking hold as well. The front yard has two patches of dichondra that's spreading but the grass is looking robust there and starting to choke it out. I imagine the hot Texas sun will put the hurt on those dichondra patches, too. The back yard is a NIGHTMARE. There's more dichondra than grass, really. The back has been slow to come around after top dressing (weed seed free, supposedly) in early spring. There's also a slight tree canopy in the back but nothing too severe and it hasn't been a problem in the past. This is the first year I've considered going over to herbicides and ruining my organic track record but the aforementioned weeds are out of control! Granted, the zoysia has been slow to come around in the back and the days are not really that bright and hot just yet. Also, a couple of bare spots in the back under the trees show some new growth but I'm worried there might be grubs under there (or something going on). Regardless, how can I get my yard back to the way it looked only a year or so ago - mainly control these weeds?! There are plenty of nutrients and microbes available to my knowledge. We are at our wits-end and are watching our formerly lush and beautiful zoysia got to pot. Is the only true answer "Better Living Through Chemicals"?

Answer
My friend, that old DuPont slogan was Better Living Through Chemistry.

I feel your pain.

Dichondra (aka 'Kidney Weed') likes moisture and humus-rich soil.  Leaf undersides of D. repens and D. carolinensis are green; D. micrantha is the greyish version, and all are used from time to time as a groundcover, especially on the West Coast.  Compare your specimens to 'Dollar Weed' (aka 'Pennywort') on Emily's Garden website (http://www.emilycompost.com/dollar_weed.htm) to make ABSOLUTELY SURE you get this genus i.d. right.  You don't want to use the wrong defense.

What slows Dichondra down?

Some authorities claim it dislikes traffic, drought and deep shade.  To get rid of it, Texas-based Dirt Doctor Howard Garrett says, 'If you don抰 like it, let the soil dry out more between waterings.'

He may have a point there.  Especially since once of Zoysia's most celebrated strengths is DROUGHT TOLERANCE.

Find a patch to experiment with, and cover with several large sheets of black plastic (think Garbage Can Liners).  Secure with heavy stones or other reliable plastic pin.  You want everything underneath, including your Zoysia, to completely dry out and lie in the dark.

See how long it takes for the Dollarweed to kick the bucket under there.  Make sure it is totally wiped out.  You want to calculate the minimum number of days of darkness to make sure you keep your Zoysia strong and healthy.

Moving on to the Zoysia under your Tree, not to drag this out, but Trees are just not made to go with Grass.

The slight canopy above, even if it is bright underneath, is not the only roadblock for your lawn; it has to deal with Tree Roots, too.

Get a groundcover or mulch underneath, at least right around the base of the Tree.  I'm not clear on what else was going on back there -- were you seeding Zoysia?  Use plugs.  You don't have an ideal situation for seed right now; it will lose every battle you put it up against, while plugs will just start spreading.

Grubs are the Gardener's scapegoat for every problem.  Yellow grass? Grubs.

It's like the Tech Support people with one solution: 'Have you tried re-booting?'  I don't bother asking anymore, I reboot, then get Tech Support on the line to save time and money.

If you have not been using chemicals for at least a year or longer, I see no reason you should have Grubs -- not at least as a problem.

Possibly another pest, depending on where you are growing this lawn.

Birds love Grubs; a few are normal and nothing to worry about.  The bare spots are probably Zoysia that can't deal with the tree above and below.

If you do have Grubs, go out and get some Milky Spore Disease at Home Depot.  But I would honestly be very surprised.  Does the tan turf come up in large sheets, under which scores of Grubs are attached?  Let me know if it does and we'll work that out next.  If it doesn't, it's not Grubs.  My money's on NOT.

Now, let's suppose none of the above works.  And you decide that you have no choice but to use WMDs to control this Dichondra = Wild Onions problem.  At least make sure you choose a weapon you know will work.

What will NOT work on Dichondra: Clopyralid ('Lontrel', restricted in Oregon and Washington, and sold for use on golf courses only), Tribenuron, Dhlorsulfuron, Haloxyfop, Oryzalin, Oxadiazon, Paraquat/Diquat, Glufosinate, Glyphosate, Linuron and Methabenzthiazuron.

The active ingredients in 'Preen Stepsaver Weed Control': 2,4-D; single isomer form Mecoprop-p; Dicamba (which persists in soil longer than other herbicides); Dithiopyr ('Dimension'); and anything else that is not on the label.  The only reason I can post this and sleep tonight is because there is actually an organic preemergent weed control prodcut in the Preen line, and for that I applaud them -- they have a Cornmeal Gluten based herbicide that is produced under license by Iowa State University, where it was originally formulated.  It is safe on Zoysia, lucky you.

Clemson University Cooperative Extension (http://hgic.clemson.edu/factsheets/HGIC2311.htm) 'Wild Garlic and Wild Onion' page reports that simply mowing your lawn will not eliminate wild garlic or wild onions.  But, they say, 'Regular mowing can weaken plants and prevent them from setting seed.'

Clemson adds: '[Wild Onions/Garlic'] must be treated with a postemergence herbicide, and persistence is the key.  Plants will need to be sprayed more than once and for more than one season.'  Hand pulling is effective -- IF you get ALL the bulblets. Those you miss can persist for years in the lawn.

'Image', active ingredient: Ammonium salt of imazaquin, comes complete with Skull and Bones on the label.  Handle with care.  It destroyes Wild Onions and it may work on Dichondra.  Literature on Image notes: 'Image may be applied prior to or soon after emergence of the weeds listed below WITH THE EXCEPTION OF WILD ONION AND WILD GARLIC which must be emerged at application time for control.'  Emphasis added.

If you do decide to bite this apple, cut your losses.  Prepare in advance generous amounts of Compost Tea to replace, quickly, after any residual toxins have long since washed away and into the local drinking water supply, the microbes that you murdered and all other organic collateral damage.

The Hoerr Nursery in Chicago posts a good page of herbicide notes for reference, and kicks it off with the note: 'No one likes to use herbicides but sometimes there is no other way to protect your green investments from regressing to the wild.  When that time comes make certain you use the right product at the right time for the right job.'  Can't say it better than that.

A bigger concern is that every season, weeds will return to your neighborhood and take advantage of the sleeping Zoysia to establish a foothold in your lawn.  What are you going to do if that happens?

Read labels; choose your poison.

And keep me posted on your progress.  Thanks for writing; any more questions, I'm here.