Warmer-than-normal soil temperatures have given more than lawns, shrubs and trees a jump on the growing season.
Crabgrass, grubs and other scourges of the landscape also are ahead of schedule, throwing off-kilter normal regimens for applying pesticides.
Zac Reicher, a professor of turf grass science at the University of Nebraska-Lincoln, said soil temperatures have climbed as much as 22 degrees above normal this spring, based on readings at university's John Seaton Anderson Turf Center near Mead.
Soil temperature measurements at 4 inches of depth, where seeds germinate, have averaged above-normal since at least the first of the year, he said.
There's little that landscapers can do right now, he said. Even though the first of May is normally when pre-emergence herbicides are applied, it's too late now, he said. Instead, a mix of pre- and post-emergence herbicides can be used sequentially to control the seeds yet to sprout.
People should keep their lawns mowed no shorter than about 3 inches of grass height.
“I know it sounds boring, but that's the best thing you can do,” he said. “Mow it to 3 inches and keep it there all year.”
Mowing shorter than that deprives grass of sufficient leaf to maximize the photosynthesis essential for healthy lawns. Mowing shorter, to 2 inches or so, actually causes grass to grow faster.
Kathleen Cue, horticulturist for the UNL Extension in Sarpy and Douglas Counties, said tomatoes recently planted should be fine. Soil temperatures below 50 degrees can damage roots, leaving a plant that looks normal but has less vigor, she said. Even though overnight temperatures may dip below 50 degrees, soil temperatures should remain warm enough, she said.
Cue said most shrubs and trees can still be pruned. The exception, she said, are oak trees. Those should not be pruned until winter, when they return to dormancy. Otherwise, the tree is more susceptible to oak wilt.
Contact the writer: