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LifestyleColumnistsJessica Damiano

Garden Detective: Ground ivy, hydrangeas and crape myrtles

Ground ivy, or creeping Charlie, is taking over

Ground ivy, or creeping Charlie, is taking over Nancy Stepkowski's Locust Valley lawn. Photo Credit: Nancy Stepkowski

DEAR JESSICA: This weed grew in my lawn and abutting areas for the first time this year and spread like wildfire. It is extremely low, somewhat shiny, and has small white roots. My gardener treated it with a liquid spray. None of the weed-control product labels show this weed. Can you tell me what it is and how to treat it? — Nancy Stepkowski, Locust Valley

DEAR NANCY: Unfortunately, you’re dealing with a ground ivy infestation.

The weed, also known as Creeping Charlie, belongs to the mint family — and that alone explains how invasive it is. What’s more, if left unchecked it will return year after year.

Under the right conditions, it can spread like wildfire, as you’ve noticed, and form a dense mat. Those conditions need to be changed to stand a chance against it.

Ground ivy thrives in shade and when soil pH is outside the 6.3 to 6.8 range. In addition, bare spots in the lawn or a too-low mowing height pretty much roll out the welcome mat for this guy.

“The plant is somewhat unique among turf weeds in that it senses variations in light intensity and adjusts new growth to move toward the most favorable conditions,” according to Andy Senesac, a weed scientist at Cornell University. “Ground ivy will thrive in heavy or partial shade, but, being a successful weed, it can do very well in full sun, too. Another unique quality about ground ivy that we found in some research a few years ago was that unlike most weeds in turf, if you increase the level of fertility to make the grass more lush and competitive, ground ivy will not be put at a disadvantage. It will also take advantage of the increased fertility and continue to send its snakelike stolons running along the soil surface unimpeded.”

Take these steps to discourage the weed:

1. Never cut the grass lower than 3 inches.

2. Have your soil tested (call the Cornell Cooperative Extension at 516-565-5265 in Nassau, 631-727-7850 in Suffolk for details) and apply amendments, if recommended, to bring soil into the required range. This is important because grass can't benefit from nutrients in the soil or in applied fertilizers if the pH is too high or low.

3. If there are tree branches overhead, prune them in March to allow more sunlight to reach the lawn.

After correcting these cultural conditions, seed the entire lawn once a week, beginning in early April, until the grass fills in and chokes out the weed. Senesac recommends “overseeding with hard fescue or other types of fine fescue. Once established, these species become almost impenetrable. The downside is that they are not suitable for all situations and may not play well with Kentucky bluegrass.”

Herbicides with triclopyr typically provide only mediocre control against ground ivy and need to be repeated annually for a few years to see benefit. Even so, if you don’t correct the underlying problems, the weed likely will return. Also, you should know that the chemical will injure stoloniferous grasses like zoysia. 

DEAR JESSICA: I read your recent article about pruning hydrangeas. I have a healthy plant that has grown too big. My previous attempt at pruning caused a complete absence of blooms the following season. I’ve been confused by what constitutes “weaker stems” or “old wood." My stems are either a healthy green or a dry brown, and sometimes a mix. Also timing would seem to be not during autumn or following spring, leaving summer to trim. Please help, I love my plant but remain confused. — Robert Taylor, Seaford

DEAR ROBERT: Some hydrangeas bloom on the current season’s growth, others bloom on both old and new stems, and Hydrangea macrophylla plants, such as yours, bloom on stems that grew the previous year, or “old wood.” Those stems are typically sturdier and darker than newer growth, and they should have telltale faded flowers on them. As long as you don’t remove stems that didn’t bloom this year (or have buds on them), you won’t risk a flowerless plant next year.

“Weaker stems” simply means those that do not appear strong or are broken. Those should be cut off at their base.

DEAR JESSICA: I just finished reading your column on crape myrtles and need to share this little story with you. I too, fell in love with this tree the first time I saw it in 2012 outside a little gift shop just northeast of Claudio’s restaurant in Greenport. There are two there, one on either side of the entrance. At the time, I asked the ladies in the shop what kind of tree it was, but neither knew.

A few months later, I donated to the Arbor Day Foundation and received my 10 free trees; take a guess what they were. Yup — crape myrtle! Only one partially survived at my home in Lake Panamoka in Ridge.

I moved off the Island in 2015 and relocated to South Carolina, where there are crape myrtles everywhere, as you wrote about. Now I have my own beautiful red crape myrtle! — Betty Collins, Rock Hill, South Carolina

DEAR BETTY: I’m sorry to hear nine of your crape myrtles didn’t make it. A stand of 10 would have made some statement! Although the Arbor Day Foundation is knowledgeable and typically sends plants that are well suited to a donor’s growing zone, I wonder if your trees weren’t quite hardy enough. Your former garden might have had its own microclimate, too much shade or perhaps the soil’s nutrient levels were inhospitable. No matter now, I’m glad you found your crape myrtle happy place — and that you continue to read my column from South Carolina!

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