How liquid corn gluten product can help your lawn this spring

Meet Mike in Fredericksburg!

I will appear Saturday, March 17 at noon and 3 p.m., and Sunday, March 18 at noon and 2 p.m. at the Fredericksburg Home & Flower Show at the Expo Center in Fredericksburg, Virginia.

Special note: This is my only scheduled springtime appearance on the Virginia side of the greater D.C. region. You snooze, you lose!

Can liquefied corn prevent weed woes?

Bill in Winchester writes: “The spring lawn care season is fast approaching. I have used corn gluten meal in the past, but I’m now 70 years of age, and it’s getting hard to lift those 40-pound bags. Can you recommend an effective liquid corn gluten product I can attach to my hose?”

The basic answer is yes, Bill. Although most people are more familiar with the granular form of the natural pre-emergent corn gluten meal, the “inventor” of the product, Iowa State University turf grass professor Dr. Nick Christians, has always felt that the liquid form is even more effective at preventing dormant weed seeds from sprouting.

The straight skinny on liquefied corn

The natural pre-emergent herbicide corn gluten meal was originally meant to be marketed in liquid form rather than granular, but production issues got the bagged product to market decades before the liquid form became available. But it finally arrived a few years back.

A quick internet search found liquid corn gluten meal to be available this season under a variety of brand names, in sizes ranging from a quart to a gallon. The half-gallon size is said to be equivalent to one of those traditional 40-pound bags of granular product and is meant to cover 2,000 square feet of turf.

One warning: Most — if not all — of the quart and half-gallon bottles are designed as “hose-end sprayers,” that is, you hook the bottle up to your garden hose to dispense the product (as Bill wishes to do).

But a large percentage of online reviewers complain that the design does not work well and clogs frequently. So, if you decide to go the liquid route, be prepared for possible troubleshooting and filtering — or, use your own pressurized sprayer.

Weed-beating timing

Bill in Winchester has great timing, as the window for successful application of the natural pre-emergent herbicide corn gluten meal is fast approaching.

The visual cue to apply corn gluten meal to your turf — in either liquid or granular form — is when the first blooms appear on local forsythia and redbuds. More scientifically, the time to apply is when the soil temperature reaches 55 degrees Fahrenheit, as measured 4 inches deep.

Here’s a link to a local soil probe that provides that info updated daily. Scroll over to the right until you get to the “4 inches deep” column.

Helpful hint: the water temperature in the Chesapeake Bay is generally an accurate indicator of the soil temperature four inches down. Here’s a link to current conditions in that wonderful body of water.

Remember: As with any pre-emergent, corn gluten will only prevent weed seeds from sprouting. No pre-emergent will have any effect on existing weeds. Same if you wait too long to apply and your weed seeds have already sprouted; no pre-emergent will hurt those plants once they’re up and growing.

Corn gluten 101

Applied when the (4-inch deep) soil temperature reaches 55 degrees (or just as local forsythia begin to bloom), corn gluten meal has the potential to prevent weed seeds from sprouting.

It’s also a close-to-perfect source of natural slow-release nitrogen, the food that lawn grasses thrive on — so don’t feed your turf with anything else if you do go corny.

Just be aware that no treatment will ever replace proper lawn care at preventing or eliminating weeds. To keep weeds at bay, your mower blade must be super-sharp, so have your old blade sharpened or buy a new one before cutting season begins.

And the height of your lawn must be around 3 inches after cutting. If you scalp it down lower, weeds will always have their way with you.

Spring training for seed starting

In my house, March means Madness, high winds and seed starting, because timing is everything if you want to grow your own tomatoes, peppers, eggplant and such from seed.

The goal is to have 6-week-old plants ready to put out at a traditionally safe planting time, which I will call no earlier than May 15. (Forget “frost”; you don’t want to plant hot weather crops such as tomatoes until nighttime temperatures are reliably in the 50s.)

It takes about a week for seeds to germinate (depending on your skill and supplies), but I allow longer for this part to make it an even two months from start to finish — and that means starting your seeds around March 15.

We’ll delve into the devilish details next week, but first, a warning: Don’t even think about trying this if you’re a first-time gardener. Seed starting requires a different (and more difficult) skill set than outdoor gardening, and rookies should always buy their first plants from pros.

Mike McGrath was Editor-in-Chief of ORGANIC GARDENING magazine from 1990 through 1997. He has been the host of the nationally syndicated Public Radio show “You Bet Your Garden” since 1998 and Garden Editor for WTOP since 1999. Send him your garden or pest control questions at

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