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Timing is everything: Crabgrass and cherry trees

Friday - 3/2/2012, 10:54am  ET

What an early spring means for early flowers, blossoms

Mike McGrath, WTOP garden editor

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Mike McGrath, wtop.com

Meet Mike in Fairfax Next Weekend

WTOP Garden Editor Mike McGrath will appear next Saturday and Sunday, March 10 and 11, at the Fairfax Home Show on the Annandale campus of Northern Virginia Community College. He'll speak at 1 p.m. and 4 p.m. on Saturday, and noon and 2 p.m. Sunday.

Time to place your bets on cherry blossom bloom

When will the famous cherry blossoms reach the peak of their bloom? National Park Service Chief Horticulturalist Rob DeFeo went on record recently calling for March 24 to March 31, which, while not setting a record, would be among the earliest bloom times in the trees' 100-year history.

Always one to up the ante, I'm going to suggest that we might see major color as early as the Ides of March this year, with the peak much closer to that 24 number than the 31.

But for tourists and residents alike, more key is the length of time the blooms hang in there. So let's all hope for somewhat chilly temps that don't drop below freezing and little to no rain after the fairly fragile flowers open because hot weather, a hard freeze and/or thunderstorms can knock those blooms right off of our trees and send them on their way.

Don't mess with mother nature

How should gardeners react to the unseasonably warm winter weather? By not fussing with our flowering plants, that's how. I call your attention to Exhibit A: A recent note from Pat, down in Lake of the Woods, Va., that reads: "You were right - they are blooming. Thanks for not letting me cut them off."

Pat emailed a few weeks earlier to say, "My daffodils came up early in the warm weather. They formed buds, but I think they might be frozen since we had temps in the teens a couple nights ago. Should I cut off the buds and hope they will bloom again?"

I urged her to leave these tremendously cold-hardy plants alone, they can take a hard freeze and keep on ticking-on -- and to email me a thank you when they bloomed beautifully. Which she did. Thank you, Pat, from me and those dazzling daffs.

What about timing corn gluten to prevent crabgrass?

Mary in Fairfax writes: "I've been looking forward to my lawn's second springtime application of corn gluten meal. The forsythia have net yet bloomed, but we do see other spring flowers. Have we missed the best timing to apply the corn gluten?"

No, Mary, we're still in a waiting game. The ideal time to apply this great natural pre-emergent weed and feed is generally when the local forsythia blooms, but it is always when the soil temperature reaches 55 degrees, as measured 4 inches down. And the man who discovered corn gluten, Dr. Nick Christians of Iowa State University, estimates that even with our warm winter, that will happen around April 1 in the D.C. area. So between the Ides of March and the first week of April should be the ideal time. And, it's always better to get it down a little early than a little late.

Jeff in Chevy Chase has a similar question that brings up a very good point. He writes: "This will be the third year I've used corn gluten on my lawn, and the results have been great. In the past, you have advised us to spread the product when forsythia and eastern redbuds are in bloom. This year is a little crazy and some of the forsythia in my neighborhood are already blooming. Do you think crabgrass germination will also be early, or should I wait for the redbuds?"

I had a long chat with Iowa State's Dr. Nick Christians about all these different layers of corn gluten concern, Jeff, and he revealed that he's learned something new since he originally formed his 'apply corn gluten when the forsythia blooms' advice: Different named varieties of forsythia can have very different bloom times. In fact, university horticulturists have told him that the earliest blooming varieties can pop close to six weeks before a late bloomer.

So that makes the eastern redbud -- a much less diverse specimen -- a better cue. Even better would be to use a soil thermometer and apply the crabgrass, defeating corn when that thermometer reads 55 degrees at 4 inches below the soil line. Oh, and to follow the new legal guidelines designed to protect the bay from nitrogen pollution, apply no more than 10 pounds of corn gluten per thousand square feet of turf.

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