Get ready for fall: Tackle those invasives, learn about fruit trees

From stiltgrass to fruit trees, people had plenty of questions to ask about their gardens. Here are some selected questions and responses.

Corn gluten vs. stiltgrass

Clemencia in Potomac writes: “I was only away for 10 days and returned to a sudden invasion of Japanese stiltgrass in my garden beds. I’m having trouble manually controlling it without removing small bedding plants I want to keep. I heard you recommend using corn gluten meal for controlling it in lawn grass. Would it be OK to use it in the garden beds, or will it kill the other plants?”

Corn gluten meal is a natural pre-emergent herbicide: It only prevents seeds from sprouting, and doesn’t hurt existing plants. (So you would not use it if you were direct seeding anything in that bed.)

And no matter what, you would use it in the spring — not now.

Stiltgrass, like crab grass, is a warm-season annual; it’s dropping seed now that will sprout in the spring. Spreading corn gluten meal next year when the soil temperature approaches 55 degrees, which is when local forsythia and redbud trees begin to bloom, will prevent at least some of those seeds from sprouting.

The perfect time of year to subdue stiltgrass

The good news is that this is the best time of the year to control this persistently pesky invasive. Like crab grass, stiltgrass is a warm-season annual that is now setting seed, so pulling out the mature plants now can prevent a return of the problem next year. And stiltgrass is very shallow-rooted, which means it’s easy to pull out of soaking wet soil, roots and all. Just pull very slowly.

It’s also a weed that thrives in overly moist and shady conditions, so cutting back on water can help keep it at bay in general — and could actually improve the health of your wanted plants, as gardens growing in shade generally need much less water than gardens growing in full sun.

Not the time for zoysia

Bob in Springfield writes: “I know you say that this is the perfect time of the year to plant cool-season grass seed, but is it also a good time to plant zoysia plugs? I’ve got a section of lawn along the street that gets so much traffic that cool-weather grasses never survive.”

I think that zoysia grass is a great choice for a problem area like that; once it gets established, zoysia is the toughest turf in town.

But alas, it is a warm-season grass that you can’t establish in the fall.

Order the plugs now and they’ll be shipped to you in the spring. Zoysia spreads quickly, and will have the area covered by midsummer — especially if you order slightly more plugs than the minimum suggested for the size of your site.

Just be aware that zoysia is a spreading grass that will quickly creep into any adjacent lawn areas. It’s perfect for one of those small green areas between a street and a sidewalk, but if it can touch another lawn, it will invade it.

Many acorns make many little oaks

Dave in Pasadena has an unusual issue. He writes: “Thousands of little oak trees have sprouted in my lawn this summer. I’ve been pulling them out, but need help getting rid of them. Is there a product that will kill them and not kill my grass?”

Repeated mowing alone should kill the little saplings. Deprived of their leaves, the roots will eventually die on their own.

But yes — there is a relatively new type of herbicide that you could use, as well. Sold under a variety of brand names, the active ingredient is iron — which kills plants with big leaves but is relatively gentle on lawn grasses, especially when the weather is cool and the grass is well-watered. Best of all, it doesn’t harm, people, pets, earthworms, birds, bees, butterflies, frogs, toads or anything else.

The mail order supplier Gardens Alive sells it as “Iron-X,” and there are several different brands available at retail. Look for “HEDTA” of “FeHEDTA” as the active ingredient on the label.

And in the future, promptly clean up the acorns that have to be dropping from that big old oak tree that must be nearby!

Short course on fruit trees

Leslie in Gaithersburg writes: “I’m interested in planting some fruit trees in my backyard. Is there a particular type of fruit that does well in this area? (I was thinking of cherry or apple trees, maybe sour cherry). And what time of year is best for such planting?”

Now through October is the ideal time to plant new trees in our region and local nurseries generally offer very good deals on any stock they still have on hand in the fall.

Apple trees require a lot of care: annual pruning, thinning of the developing fruits and protection from insects and (evil) squirrels — same with peaches. The rewards can be big, but you have to make a serious time and care commitment to get good quality fruits from apple or peach trees in our area.

Cherry trees are much easier to care for, but you can only grow “sour” cherries — aka tart or pie cherries — in our region, not the sweet ones. (Although, I find so-called sour cherries to be deliciously sweet.) Anyway, the biggest issues with cherry trees are their size (that’s why they call those big elevated machines ‘”cherry pickers”) and protecting the fruits from birds.

Pears are probably the easiest fruit trees to grow in the D.C. area. They require very little care — just proper planting, lots of sun, good airflow and soil that drains well.

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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