Idiots on the Airwaves
This past Saturday morning, while running errands for the family (not just my wife, but my daughter…WTF?), I had occasion to listen to a popular talk show host on the AM airwaves. I concede that this person has a few key strengths (indoor horticulture, annuals, perennials) in the broader field of horticulture, but his understanding of the SCIENCE of pesticides, especially herbicides, is woefully inadequate. Every summer, right on cue, this goofball says, “Summer weeds have hardened off so much, you really can’tkill them with herbicides!” What a load of crap! He proclaims this for both nutsedge and the entire collection of broadleaf herbicides. He’s dead wrong!
Before I skewer him on his abject stupidity in this specialty area, I’ll try to give him the benefit of the doubt. I’m a fair guy…even-tempered…open-minded—for an Irishman (50%). Maybe he’s thinking about those huge mats of crabgrass, two feet in diameter, or a hefty clump of goosegrass (aka “silver crabgrass”)(below left). Or maybe it’s an established area of deep-rooted black medic (below right). [By the way, the photo of black medic also has some white dutch clover in the photo–both are legumes–and both are tough weeds, but black medic is tougher!] These tough weeds become quite noticeable in late summer because they love the heat and they get very large. Herbicides have their limits–they kill small seedlings easy but an established monster weed won’t be controlled. There are no “selective” POST herbicides that will kill these tough weeds with only one application, this time of year. A “selective” herbicide means it will kill weeds but not grass (if used properly). But a non-selective herbicide, glyphosate (Roundup), CAN kill all these weeds, along with the turf!. STOP HERE! It’ll take at least two applications of glyphosate to kill established black medic. It will take at least 3 applications of common retail broadleaf weed killers to kill established black medic.
Herbicides used in turfgrass work by preventing weed seeds from developing (PREEMERGENCE or “PRE”) or killing established weeds after they are emerged (POSTEMERGENCE or “POST”). Every single herbicide used in turf can injure turf if over-applied, and most herbicides can even kill turf if horribly over-applied. There are “easy-to-control” weeds and there are “tough-to-control” weeds for every product used in your lawn and landscape. For example, dandelion is an “easy” weed for the multitude of broadleaf weed herbicides, while wild violet is a tough weed (3 applications required). Crabgrass is an easy weed for PREEN to prevent but nightshade is a tough weed for this product. PRE herbicides cannot control weeds beyond the seedling germination stage and POST herbicides work best on weeds less than 4 inches tall/wide. So our talk show host is only partially right about why herbicides might disappoint when applied in late summer. THE WEEDS ARE TOO FREAKIN’ BIG! They aren’t “tougher!”
Halosulfuron, the best herbicide on the face of the earth for control of nutsedge, is sold under “at least 3 different names, such as PROSEDGE, SEDGEHAMMER, and NUTBUSTER. It still works GREAT right now! But the host of this show will tell you otherwise. [SIDEBAR: i did 75% of the development research for this herbicide while employed by Monsanto in the mid- to late-80’s, and it was introduced as MANAGE herbicide. I know WTF I’m talking about!] The broadleaf herbicides (no fewer than half a dozen) will still control weeds 4 inches tall if you apply them now, as long as it’s an easy-to-control weed.
In summation: this guy doesn’t know crap about herbicides and weed control.
The Value of Compost
There are two ddifferent guys on two different stations that over-promote their proprietary compost blends. Not just for turf, but for ALL lawn and landscape woes. Compost is wonderful as a topdressing in turf, or when incorporated into the native soil when you’re establishing new beds. I don’t recommend it as a mulch because it becomes very powdery when it dries out. Heavy rains or heavy irrigation can wash compost downslope quite easily.
My beef with these two hosts is that they OVER PROMOTE the nutrient content of compost, and one says you don’t need to fertilize your lawn all season long! This is just pure crap.
The vast majority of our soils in St. Louis are typically adequate in phosphorous (P) and potassium (K) thus good turf management generally comes down to proper management of nitrogen (N). Fertilizer values for these there macronutrients are provided in the order of N-P-K. Compost typically 1-1-1. Furthermore, the nitrogen in the compost is very slowly released, in YEARS. Not days, not months, but YEARS. It may take 3 years for all the nitrogen in compost to be made available for use by plants. Compost usually has about 1% phosphorous, but it is essentially unavailable for several years. Finally, compost has about 1% potassium and it is readily available.
Let’s get back to the N, because good turf is all about the N! Healthy cool season turf in the transition zone needs between 2.5 and 4 lbs of N per season, per 1,000 sq ft. By simple math there is no way a single application of compost will provide you with a decent looking sward. We always want to limit our nitrogen to only 1 lb of actual N per 1,000 sq ft in a single application. With compost having only 1% nitrogen, that’s 100 lbs of compost per 1,000 sq ft. That’s certainly “doable” but a lot of work.
There’s nothing wrong with adding compost to the lawn, especially if it’s applied as a top-dressing after heavy aeration and seeding. There are billions upon billions of beneficial microbes in compost which serve to break down thatch, improve soil structure, combat pathogenic fungi, and improve aeration.
In summation: these guys should stop over-promoting compost as an adequate source of nitrogen.
Remember folks, the month of September makes or breaks the turf studs from the turf duds. If you aspire for a great lawn, work hard now through mid-October.