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LifestyleColumnistsJessica Damiano

Acorns beget oak trees — and a tick concern

Vinnie Drzewucki, horticultural resource educator at the Cornell

Vinnie Drzewucki, horticultural resource educator at the Cornell Cooperative of Nassau County advises homeowners to "buy the mulch and don't store it -- spread it around as soon as possible and keep it 1-2 inches deep so it can do its job without fear of causing fire." Credit: Dreamstime

As I reported in November, acorns were uncharacteristically aplenty on Long Island last fall. This could be attributed to the cyclical nature of mature oak trees, which shed an increased number of acorns during a “mast year,” which occurs every three to five years. Last year was that year, and while squirrels no doubt were burying their good fortune, we cleaned and raked, fished them out of our ponds and swept our walkways and driveways, then headed into winter blissfully unaware that we hadn’t seen the last of them.

Now that it’s spring, acorns are back, but this time we won’t simply be able to sweep them away. Long Islanders are reporting that acorns that overwintered in lawns and garden beds have now rooted into the soil. Unless you’re in the market for shade and privacy, they need to be removed now.

Removing acorns from turf, followed by repeated mowing of the area will eradicate the aspirations of any seedling to become a mighty oak, as eventually its roots will run out of energy and just give up trying. This could take three or more mowings, but it will be effective.

Acorns rooted in beds and borders pose a bigger challenge, however. If you spot rooted acorns in your perennial bed, you’ll need to dig them out, taking care to lift up their entire taproots. Place them into a bucket as you work instead of piling them up on the soil for later retrieval or you’ll risk leaving a few behind. Dispose of them in the trash, as composting may not kill them. Then, keep an eye on the area throughout the growing season, digging out any sprouts you notice.

Another consequence of all those acorns is that the rodent population is exploding, according to Vinnie Drzewucki, horticultural resource educator at the Cornell Cooperative Extension of Nassau County in East Meadow. And where there are more rodents, he says, there could be more ticks.

“Do what you can to dissuade rodent populations,” Drzewucki advised, including “trapping, stocking bird feeders with only enough seed that can be consumed in a day, and eliminating wood piles and debris, which rodents like to inhabit.” We could be facing a tick-infested summer, and potentially a rise in Lyme disease cases.

Keep mulch cool

Covering bare soil around plants with mulch isn’t merely aesthetically pleasing, it serves several important purposes. Mulch deters weeds — and those that root in it are easily lifted. It retains moisture, cutting down on the need for supplemental irrigation. And it helps keep soil temperatures even, which insulates roots year-round and prevents heaving during winter. But there’s a darker side to mulch that most homeowners aren’t aware of: It can be flammable.

After a co-worker’s son’s house caught fire earlier this month, it was determined the cause was a plastic bag of mulch that had been in a black trash can leaning against an exterior wall. The sun apparently had heated the bag to the point of fire. The house sustained quite a bit of damage, from melted vinyl siding to an entire bathroom needing to be gutted.

The risk is not limited to sun-heated mulch contained in plastic bags, however. According to a 2003 study published in the Journal of Arboriculture, under-the-surface fires can, in fact, happen, but not all mulches pose the same risk. Shredded pine bark, for instance, will only ignite after it has weathered on the ground for a season or more, according to the study, while those composed of coco shells, shredded hardwood or pine bark nuggets are considered fire-resistant. Larger pieces retain more moisture so are less likely to ignite than smaller particles. And piles of mulch left sitting around waiting to be spread are far more likely to spontaneously combust then what is spread around your garden, so there’s no need to swear off mulch altogether.

Acknowledging that mulch can, indeed, self-generate if hot and dry, and that mulch that is dried out can be flammable, Drzewucki, of the Cornell Cooperative Extension of Nassau County, cautioned against throwing out the proverbial baby with the bath water and emphasized there isn’t any need to panic.

He advises that homeowners “buy the mulch and don’t store it — spread it as soon as possible, and keep it to 1 to 2 inches deep so it can do its job without fear of causing a fire.” To minimize the already-small risk, you might keep a 2- to 3-foot mulch-free zone around the foundation of your house, and if you must mulch up against a structure, consider pea gravel. Watering mulch during hot, dry spells is a good idea, too.

The benefits of mulch far exceed any risks, Drzewucki stressed. “Mulch builds up the macro- and microorganisms in the soil, so there are some very good reasons besides weed suppression and moisture retention to use it,” he said. “It actually improves soil health. If you really use the same risk assessment when it comes to driving a car, you’d never get into a car because it’s so much riskier.”

Oak wilt disease watch

There’s a new disease in town, and the New York State Department of Environmental Conservation’s Forest Health Department is taking it very, very seriously.

Oak wilt disease, caused by the Ceratocystis fagacearum fungus, and spread by the nitidulid — or picnic — beetle can be devastating.

The disease can affect all varieties of oak trees, presenting a bit differently in each. It will kill red oaks in as little as a few weeks, spreading quickly to other trees in the meantime, but can take years to kill white oaks, and they’re not as likely to spread the disease, according to the DEC. There is no cure or remedy besides cutting trees down. Sometimes nearby trees also are removed as a precaution.

After multiple identifications of oak wilt disease in Suffolk, the county has been declared a “protective zone,” which is similar to a quarantine, as has Brooklyn. This means it is now illegal to remove oak wood — or firewood of any kind — from the area to avoid spreading the disease to neighboring counties. In addition, suspect trees should be reported to the DEC, which, after confirming a diagnosis, will remove them and sometimes trench the area.

“The disease is spread by insects but also by root grafts,” said Rob Cole, a forester with the DEC. That means that oaks growing in groups will often intertwine their root systems and can transmit diseases to one another underground. “Normally, the infected tree gets cut down, then around that the closest trees are taken down, and then we trench around those buffer trees” to disconnect their roots, Cole added.

Symptoms will become visible in late July or August. Telltale signs include rapidly dropped green or brown leaves during spring or summer, or the appearance of brown edges that spread inward on green leaves during the growing season. Residents who spot these signs should email a description and photo to or call the DEC’s Forest Pest Information Line at 866-640-0652.

In addition, Cole cautioned, it is very important that oaks are not pruned during the growing season. If pruned during spring or summer, he said, sap that bleeds from the wound can attract the beetles in 15 minutes or less, and continue to attract them for 72 hours. If it’s imperative that a limb be removed during the growing season, wound paint should be used to contain sap, he added.

In addition to the oak and firewood transportation ban, Cole cautioned that in general “people shouldn’t be taking trees down in their yard, then driving them to their camp up in the Catskills, because that’s how these diseases spread throughout the state.”


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