Frost, Freeze and Green Tomatoes

 

From Franklin County, PA Master Gardener Facebook Notes (October 2013)

We are fast approaching the last frost free date of October 15 in Franklin County and many home gardeners, eager to either have homegrown tomatoes for Thanksgiving or loath to discard any possible foodstuff, are looking at their green tomatoes.

FROST VS. FREEZE

Frost,“ killing frost,” freeze warnings, a “killing freeze” - what is the difference? In casual conversation the terms frost and freeze are often interchangeable but there is a very real difference. Frost and freeze are two distinct phenomena. These terms take on significance when they are associated with the growing season.

FROST

According to the National Oceanic and Atmospheric Administration (NOAA), frost is the formation of thin ice crystals on the ground or other surfaces in the form of scales, needles, feathers, or fans. Frost develops under conditions similar to dew, except the temperatures of the Earth's surface and earthbound objects falls below 32°F. A frost advisory is issued when widespread frost formation is expected over an extensive area. Surface temperatures are usually in the mid-30’s. If a frost period is sufficiently severe to end the growing season (or delay its beginning), it is commonly referred to as a "killing frost."

Dr. Katharine B. Perry, North Carolina Extension Service, has compared frost and freeze conditions for protection of horticultural crops noting frost and freeze protection methods are based on preventing or replacing radiant heat loss.

Because frost is primarily an event that occurs as the result of radiational cooling - heat loss at night - it frequently occurs with a thermometer temperature in the mid-30’s. A radiation frost happens when a clear sky and calm winds (less than 5 mph) allow an inversion to develop. An inversion occurs when the heat radiating from the earth rises and causes the cooler air above to be pushed down, and temperatures near the surface drop below freezing.

Covering plants before the sun sets may be protection from frost as this can help retain heat near the plants.

 FREEZE

According to NOAA, a freeze is when the surface air temperature is expected to be 32° F or below over a widespread area for a significant period of time. Use of the term is usually restricted to advective situations or to occasions when wind or other conditions prevent frost.

Dr. Perry explains than an advective, or windborne, freeze occurs when a cold air mass moves into an area bringing freezing temperatures. Wind speeds are usually above 5 mph and clouds may be present. Attempts to protect plants are very limited under these conditions.

A "killing freeze" may be used during the growing season when the temperature is expected to be low enough for a sufficient duration to kill all but the hardiest herbaceous crops.

According to NOAA, freeze warning are issued during the growing season when surface temperatures are expected to drop below freezing over a large area for an extended period of time, regardless whether or not frost develops.

GREEN TOMATOES

We are closing in on the first average frost. (Check the date for your area.) Since it takes about six weeks for a tomato to go from flower blossom to ripe fruit, you should have pruned or pinched back your tomato plants in early-to-mid-September (cutting the growing tip off all the vines and any new blossoms to redirect the plant’s energy toward ripening up the existing fruit).

Oops! Okay, you were enjoying the weather and forgot. Now what? There's always fried green tomatoes or you can store them to ripen up later.

Kansas State also suggests roasting them for eating warm or cold, using in side dishes or freezing in small batches to use throughout the winter.

HARVEST AND STORE TO RIPEN

Pick and store your mature green tomatoes and let them ripen up on counter top or windowsill but not in the refrigerator. Ron Wolford, University of Illinois Extension horticulturist, notes that green tomatoes can be harvested before a predicted frost.

“You can tell when a tomato is nearing maturity by its light green, almost translucent, appearance,” according to Barb Fick, horticulturist with the Oregon State University Extension Service. “Tomatoes that are not in this 'mature green' stage won't ripen.”

Kansas State Extension Master Gardeners note that "not all green tomatoes will ripen off the vine. They must have reached a "mature green stage." Look for full-sized tomatoes with a white, star-shaped zone on the bottom end of the green fruit. Also, on maturing green tomatoes, skin at the blossom end may be beginning to change color from green to pink or red." Use immature green tomatoes in recipes such as salsas or fried.

Ron Wolford recommends removing the stems, washing and drying the fruit. Wrap each tomato in newspaper and place them in a single layer on a shelf or in a box. You can also put them in deep straw or just lay them in a box so that they are not touching. Check tomatoes every few days and discard any that show signs of rot.

Tomatoes will ripen satisfactorily in the dark, according to Fick, and sunlight is not needed; however, temperature is important. Storage temperature should range from 60 to 70 degrees. They will ripen over a period of three to four weeks.

Picking and storing the mature green tomatoes in mid-October means there's a good chance you can have some tasty, home-grown tomatoes for the Thanksgiving celebration.

CKagan, Master Gardener

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Look Out for Jumping Earthworms!

 

From the Penn State Extension Article (August, 2018) by Nancy Knauss

Asian jumping worms are a relatively new invasive species but they are rapidly spreading across the United States. They can be found in the Southeast, along the Eastern Seaboard, and in mid-Atlantic, Midwest, and some Northwestern states.

There are still native species of earthworms in a few areas of North America, but in states where glaciation occurred the native species were wiped out. Forests developed without them, but in time European earthworms appeared and began to burrow through the soil. As the tunnels were created, the earthworms mixed soil components and improved air and water movement. Unfortunately, European nightcrawlers are now being displaced by the destructive Asian jumping worms.

These invasive worms are members of the genus Amynthas and live in the organic matter or the topmost layer of soil. This upper layer of organic matter protects the soil from erosion. It is in this duff layer of the forest floor where many of the tree roots establish and wildflowers grow. Asian jumping worms are ravenous feeders and they quickly consume the organic matter and degrade the soil. Nutrients from their castings are rapidly released with a small amount actually reaching the roots of plants. During heavy rainstorms, the nutrients are quickly lost and the soil may be unable to support plant growth. Where there was once lush vegetation and wildflowers, there is only bare soil. When such a disturbance happens, it provides an opportunity for an invasive plant species such as garlic mustard or stilt grass to move in. The structure of the soil is also damaged and often there will be voids under tree roots that are near the surface of the soil.

Asian jumping worms are an annual species—the adults die after the first freeze. The cocoons, which are about the size of a mustard seed, will survive the winter and hatch in mid-April after temperatures reach 50°F for a consistent period. One worm can produce many cocoons without mating. While the cocoons can survive the winter temperatures, the hatchlings cannot survive freezing temperatures.

Worm hatchlings (PSE MG Program)

How do you know if you have Asian earthworms?

One telltale sign of an infestation is a very uniform, granular soil created from worm castings, the nutrient-rich soil that the worms leave behind. The texture of this soil is often compared to coffee grounds.

When you scratch the top layer of soil, you will see the worms thrashing about with an erratic, snakelike movement. These worms, which can reach 6 inches in length, are much more active than European nightcrawlers.

If you examine a worm close-up, you will notice the prominent band around the body of the worm called the clitellum, where cocoons are produced. On a jumping worm, the band completely encircles the body, is milky white to light gray, and is flush with the body. On European nightcrawlers, the clitellum is raised and reddish-brown color and does not wrap entirely around the body

What can you do to prevent jumping worms from invading our forest and landscapes?

It is very difficult to remove an invasive species once it is well established in an ecosystem, so the focus must be on preventing the spread of Asian earthworms. The cocoons, which are very small and difficult to see, can be easily introduced to your garden in compost, bark, or leaf mulch, or when swapping plants with friends.

Consider reducing the amount of organic matter that you add to your garden each year. Most importantly, when purchasing bulk mulch or compost, use a reputable producer that has heat-treated the material to a temperature of 130°F for at least three days to destroy the cocoons. The other option is to purchase bagged mulch.

Check any plants that you bring into your garden for the distinctive coffee ground like soil. If present, throw out the plant, or remove all soil and rinse the roots thoroughly before bringing the plant into your garden.

Coffee ground-like soil (PSE MG Program

What to do to control jumping worms?

Research is currently being conducted on invasive worms at the University of Wisconsin and several practices do show some promise of control. Once you have identified jumping worms in your landscape, you will need to eliminate both the cocoons and the worms.

If you have a small population of jumping worms, handpick and destroy adult worms by bagging them and throwing them in the trash. Brad Herrick, an ecologist, and researcher at the University of Wisconsin Arboretum recommends making a mustard solution of one-third cup dry mustard in one gallon of water and drenching the area. The solution will irritate the worms and bring them to the soil surface where you can easily remove them.

While research is ongoing, abrasive materials such as biochar (ground up charcoal) and diatomaceous earth (fossilized diatoms) may show some promise in killing adult jumping worms. Incorporate one of these products into the infested soil to a depth where the worms are located. Worms that come in contact with the materials and will be adversely affected.

In addition, an organic fertilizer used by golf course managers has been effective in eliminating jumping worms. The fertilizer made from tea seed meal irritates and eventually kills these worms when applied to the soil. Two applications are recommended, one in late April or early May to target the young hatchlings and again in the summer to suppress the remaining worms.

It is important to also destroy Asian jumping worm cocoons. The cocoons are sensitive to heat and can be destroyed with clear plastic solarization. In late spring or summer, cover moistened soil with a sheet of transparent polyethylene for two to three weeks or until the soil temperature exceeds 104°F for at least three days.

Diligence in following the preventive measures and implementing control methods for both the cocoons and adult worms can impact the health of your soil by eliminating these destructive invasive worms.

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