New Zone Map
MONROE - The U.S. Department of Agricultural Research Service and Oregon State University recently released a new, more detailed version of the USDA Plant Cold Hardiness Zone Map, replacing the 1990 version. The new map uses Geographic Information System technology and data from a greater number of weather observation stations across the country, allowing for a higher degree of accuracy and resolution than the old map.
An online interactive map can be found at www.planthardiness.ars.usda.gov/PHZMWeb/.
MONROE - It's not just recent warm temperatures making the trees and flowers pop early this spring - it's the day-after-day-after-day duration of warm temperatures.
Farmers and gardeners use a measure of heat accumulation, called growing degree days (GDD), to determine when a daffodil will bloom or the corn will reach maturity.
This year, not only is the weather warmer, but the ground is also drier than average. Together, that's making soil temperatures rise. So much so that the daffodils and apple trees think it's about mid-May.
Only humans, with their man-made calendars, know it's late March and a chance of frost and snow is still possible. May 5 is considered the last frost date in southern Wisconsin.
"The apple trees and magnolias are right on time with growing degree days," said Mark Mayer, University of Wisconsin Extension agent. "But if the apple tree is in blossom, and the temperature drops quickly, the apple crop will be gone."
Mayer has been receiving calls from local farmers asking his opinion about when to start to plant.
The soil is warm enough to germinate corn seed, but Mayer said he can't predict the weather, and there is a whole host of factors to consider before planting - most of it boils down to knowing how the plants grow.
Farmers can get corn into the ground about mid-April, because the corn's growing point is underground until it reaches about 5 or 6 inches. After that, the growing point comes above the ground surface and is subject to a killing frost before May 5.
Mayer said if farmers take advantage of the warmth and the chance to plant early, they expose themselves to voiding their crop insurance. Insurance companies don't want to see any planting until April 11, he said.
Protecting the corn crop is easy to do; Mayer said, "just don't plant it" yet. Crops already in the ground are harder to protect.
Winter wheat is ready to green up, but Mayer cautions farmers not to apply a boost of nitrogen yet.
"It just pushes the plant toward the dangers of a potential frost," he said. Winter wheat can take temperatures down to about 29 degrees, but temperatures below mid-20s cause damage.
Farmers with fields of alfalfa, a perennial, just have to hold their breath and hope an early frost doesn't kill it off. Alfalfa stands with southern exposure is already 4 to 5 inches high.
Mayer said the alfalfa will grow up to 10 to 12 inches high using the carbohydrates reserved in its roots as food before switching to photosynthesis to make food through its leaves. But if a hard frost touches the tips, killing its tender leaves, the plant has no root reserves left to try again.
Mayer does not rule out a hard frost yet this year.
Plants are not the only ones thinking its mid-May. Mayer said farmers need to watch out for diseases, fungus and pests. If an April frost doesn't do them in, the early flush of insects, rejoicing in the warmth, is waiting to finish them off.
Alfalfa weevils could do some damage and probably have planted their eggs already, he said.
Weevil larvae eat small holes in the leaves at the growing tip usually during April and May. But Mayer is advising farmers to start scouting for damage by April 10 this year.
A nice last snow fall could help, he added. A wet snowfall in 29- to 30-degree temperatures would kill the weevil and push a little nitrogen into the winter wheat and alfalfa and newly planted oats.
And check the grain bins, he said. With the cooler mass of grains, this unprecedented early warming period will cause condensation inside bins, leading to mold formation. Aeration fans will help warm up the bins inside, Mayer said.
Without a hard frost, most plants should be OK. "We'll just have a longer growing period," he said.
Except for the maple syrup-making season, cut short when the trees began to bud.
"That season's over," Mayer said.
Farmers and gardeners use a measure of heat accumulation, called growing degree days (GDD), to determine when a daffodil will bloom or the corn will reach maturity.
This year, not only is the weather warmer, but the ground is also drier than average. Together, that's making soil temperatures rise. So much so that the daffodils and apple trees think it's about mid-May.
Only humans, with their man-made calendars, know it's late March and a chance of frost and snow is still possible. May 5 is considered the last frost date in southern Wisconsin.
"The apple trees and magnolias are right on time with growing degree days," said Mark Mayer, University of Wisconsin Extension agent. "But if the apple tree is in blossom, and the temperature drops quickly, the apple crop will be gone."
Mayer has been receiving calls from local farmers asking his opinion about when to start to plant.
The soil is warm enough to germinate corn seed, but Mayer said he can't predict the weather, and there is a whole host of factors to consider before planting - most of it boils down to knowing how the plants grow.
Farmers can get corn into the ground about mid-April, because the corn's growing point is underground until it reaches about 5 or 6 inches. After that, the growing point comes above the ground surface and is subject to a killing frost before May 5.
Mayer said if farmers take advantage of the warmth and the chance to plant early, they expose themselves to voiding their crop insurance. Insurance companies don't want to see any planting until April 11, he said.
Protecting the corn crop is easy to do; Mayer said, "just don't plant it" yet. Crops already in the ground are harder to protect.
Winter wheat is ready to green up, but Mayer cautions farmers not to apply a boost of nitrogen yet.
"It just pushes the plant toward the dangers of a potential frost," he said. Winter wheat can take temperatures down to about 29 degrees, but temperatures below mid-20s cause damage.
Farmers with fields of alfalfa, a perennial, just have to hold their breath and hope an early frost doesn't kill it off. Alfalfa stands with southern exposure is already 4 to 5 inches high.
Mayer said the alfalfa will grow up to 10 to 12 inches high using the carbohydrates reserved in its roots as food before switching to photosynthesis to make food through its leaves. But if a hard frost touches the tips, killing its tender leaves, the plant has no root reserves left to try again.
Mayer does not rule out a hard frost yet this year.
Plants are not the only ones thinking its mid-May. Mayer said farmers need to watch out for diseases, fungus and pests. If an April frost doesn't do them in, the early flush of insects, rejoicing in the warmth, is waiting to finish them off.
Alfalfa weevils could do some damage and probably have planted their eggs already, he said.
Weevil larvae eat small holes in the leaves at the growing tip usually during April and May. But Mayer is advising farmers to start scouting for damage by April 10 this year.
A nice last snow fall could help, he added. A wet snowfall in 29- to 30-degree temperatures would kill the weevil and push a little nitrogen into the winter wheat and alfalfa and newly planted oats.
And check the grain bins, he said. With the cooler mass of grains, this unprecedented early warming period will cause condensation inside bins, leading to mold formation. Aeration fans will help warm up the bins inside, Mayer said.
Without a hard frost, most plants should be OK. "We'll just have a longer growing period," he said.
Except for the maple syrup-making season, cut short when the trees began to bud.
"That season's over," Mayer said.