St John Indiana Garden Club Garden Selfie

Hot Temps & Plants

The plant temperature at which tissue dies is around 115°F. Normally, plant temperature is just above air temperature. However, plant temperature can rise to a critical level under certain conditions.

Plants have three major ways in which they dissipate excess heat: long-wave radiation, heat convection into the air and transpiration.

If transpiration is interrupted by stomatal closure due to water stress, inadequate water uptake, injury, vascular system plugging or other factors, a major cooling mechanism is lost. Without transpiration, the only way that plants can lose heat is by heat radiation back into the air or wind cooling. Under high temperatures, radiated heat builds up in the atmosphere around leaves, limiting further heat dissipation.

Dry soil conditions start a process that can also lead to excess heating in plants. In dry soils, roots produce Abscisic Acid (ABA). This is transported to leaves and signals to stomate guard cells to close. As stomates close, transpiration is reduced. Without water available for transpiration, plants cannot dissipate much of the heat in their tissues. This will cause internal leaf temperatures to rise.

Vegetables can dissipate a large amount of heat if they are functioning normally. However, in extreme temperatures, there is a large increase the water vapor pressure deficient (dryness of the air). Rapid water loss from the plant in these conditions causes leaf stomates to close, again limiting cooling, and spiking leaf temperatures, potentially to critical levels causing damage or tissue death.

Very hot, dry winds are a major factor in heat buildup in plants. This causes rapid water loss because leaves will be losing water more quickly than roots can take up water leading to heat injury. Heat damage is most prevalent in hot, sunny, windy days from 11 am to 4 pm when transpiration has been reduced. As the plants close stomates to reduce water loss, leaf temperatures will rise even more. In addition, wind can decrease leaf boundary layer resistance to water movement and cause quick dehydration. Wind can also carry large amounts of advected heat.

Photosynthesis rapidly decreases above 94°F so high temperatures will limit yields in many vegetables. While daytime temperatures can cause major heat related problems in plants, high night temperatures have great effects on vegetables, especially fruiting vegetables. The warmer the night temperature, the faster respiration processes. This limits the amount of sugars and other storage products that can go into fruits and developing seeds.

Heat injury in plants includes scalding and scorching of leaves and stems, sunburn on fruits and stems, leaf drop, rapid leaf death, and reduction in growth. Wilting is the major sign of water loss which can lead to heat damage. Plants often will drop leaves or in severe cases will “dry in place” where death is so rapid, abscission layers have not had time to form.

Those who use black plastic mulch, surface temperatures can exceed 150°F. This heat can be radiated and reflected onto vegetables causing tremendous heat loading. This is particularly a problem in young plants that have limited shading of the plastic. This can cause heat lesions just above the plastic. Heat lesions are usually first seen on the south or south-west side of stems.

Herbs & Vegetables 4 Hot Weather

Here is a list of some herbs and vegetables that can tolerate drier conditions and higher temperatures.

  • Amaranth (harvest and eat leaf amaranth like spinach)
  • Arugula
  • Asian Greens (a wide selection here)
  • Beans (bush and pole)
  • Broccoli (Sun King Hybrid)
  • Cabbage
  • Chards
  • Chinese Cabbages
  • Cowpeas
  • Cucumbers
  • Dandelion
  • Eggplant
  • Endive
  • Garlic
  • Leeks
  • Lettuces (leaf varieties, harvest young and early in the season)
  • Melons (cantaloupe, honey-dew, watermelons, etc.)
  • Okra
  • Onions (sets and plants)
  • Peppers* (sweet and hot peppers)
  • Pumpkins
  • Rhubarb
  • Spinach (New Zealand, Malabar)
  • Squash (summer and winter)
  • Sweet Corn (white, yellow, yellow and white)
  • Sweet Potatoes (Georgia Jet, Vardaman, Wakenda)
  • Tomatoes (i.e. Solar Fire, Sun Leaper, Sunmaster, Equinox, many cherry varieties)
  • Woody stemmed herbs (Oregano, Rosemary, Sage, Thyme, Winter Savory)

Sweet Corn

Sweet corn takes between 60 and 100 days to mature, but the window when ripe corn is at its prime, sweet flavor doesn’t last long. The ears of sweet corn display signs that they are ready for picking. The ripe corn tastes sweetest when cooked shortly after being harvested before the natural sugars convert to starch.

Knowing when to pluck the ears from the corn stalks maximizes your harvest and rewards you with the best possible flavor. Estimate the date of maturity for the sweet corn based on the variety and planting date. Many varieties take 75 to 85 days, some varieties only take 60, while others require closer to 100 growing days. Review the maturity date for the specific sweet corn variety you plant to get a general idea of when to harvest.

Monitor the growth of the corn ears. Watch for the ears to plump and fill out to indicate they are finished growing. Inspect the appearance of the ears. Ripe sweet corn ears have dark green leaves covering them. The silk on the ears turns brown as the corn ripens. Squeeze the tip of the ears gently. Feel for a rounded end to the ear. If the end still feels pointed, the corn is likely still growing and not ready for harvesting. Peel back the husk slightly to inspect the corn kernels. Ears with plump, full kernels that are soft indicate ripeness. Puncture a kernel with your finger to evaluate the juice inside. Harvest the corn when the juicy has a milky appearance. Let it continue growing if the juice appears watery. A thick, pasty texture indicates the corn is too ripe.

Time 2 Pick

Vegetable When to harvest How to store Expected shelf-life Comments
basil when leaves are still tender at room temperature 5 days keep stems in water; will discolor if kept in refrigerator for 10 days
beans, snap about 2-3 weeks after bloom when seeds still immature cold and moist 1 week develop pitting if stored below 40°
beets when 1.25-3 inches in diameter cold and moist 5 months store without tops
broccoli while flower buds still tight and green cold and moist 2 weeks
brussels sprouts when heads 1 inch in diameter cold and moist 1 month
cabbage when heads compact and firm cold and moist 5 months
carrots when tops 1 inch in diameter cold and moist 8 months store without tops
cauliflower while heads still white, before curds “ricey” cold and moist 3 weeks
corn, sweet when silks dry and brown, kernels should be milky when cut with a thumbnail cold and moist 5 days
cucumbers for slicing, when 6 inches long cool spot in kitchen 55°F in perforated plastic bags; storage in refrigerator for a few days okay 1 week develops pitting and water-soaked areas if chilled below 40°F; do not store with apples or tomatoes
eggplant before color dulls like cucumbers 1 week develops pitting, bronzing, pulp browning if stored for long period below 50°F
kohlrabi when 2-3 inches in diameter cold and moist 2 months store without tops
lettuce while leaves are tender cold and moist 1 week
muskmelons (cantaloupe) when fruits slip off vine easily, while netting even, fruit firm cold and moist 1 week develops pitting surface decay with slight freezing
onions when necks are tight, scales dry cold and dry 4 months cure at room temperature 2-4 weeks before storage, do not freeze
parsnips when roots reach desired size, possibly after light frost cold and moist 4 months do not wax or allow roots to freeze; sweetens after 2 weeks storage at 32°F
peas when pods still tender cold and moist 1 week
peppers when fruits reach desired size or color like cucumbers 2 weeks develops pitting below 45°F
potatoes when vine dies back cold and moist; keep away from light 6 months cure at 50-60°F or 14 days before storage, will sweeten below 38°F
pumpkins when shells harden, before frost cool and dry 2 months very sensitive to temperatures below 45°F
radishes when roots up to 1.25 inches in diameter cold and moist 1 month store without tops
rutabagas when roots reach desired size cold and moist 4 months do not wax
spinach while leaves still tender cold and moist 10 days
squash, summer when fruit 4-6 inches long like cucumbers 1 week do not store in refrigerator for more than 4 days
squash, winter when shells hard, before frost cool and dry 2-6 months, depending on variety curing unnecessary; do not cure Table Queen
tomatoes, red when color uniformly pink or red like cucumbers 5 days loses color, firmness and flavor if stored below 40°F; do not refrigerate!
turnips when roots reach desired size, possibly after light frost cold and moist 4 months can be waxed
watermelons when underside turns yellow or produces dull sound when slapped like cucumbers 2 weeks will decay if stored below 50°F for more than a few days

Before & After

St John Indiana Garden Club

St John Indiana Garden Club

Bluebird Feeding

Bluebirds forage small insects and fruit, so they are not often seen visiting traditional feeders that offer seed. They can, however, learn to eat from a feeder, and they will quickly learn to use one in order to spend their energies on caring for their young instead of foraging for food. Their feeder favorites are mealworms and small pieces of fruit or berries, including raisins. When insects and other natural food supplies are scarce, they will also eat small peanut and sunflower kernels, as well as suet. Bluebird feeder types range from dish-style to the predator-resistant, house-style.

Mealworms are available live, roasted or canned. Live mealworms are obviously the closest match to a bluebird’s native diet, while roasted mealworms have a longer shelf life and do not require refrigeration. Canned mealworms are processed in a way that locks in their nutrients and juices. If you choose to offer fruit, you can cut fresh fruits, or offer a number of varieties of dried fruit such as blueberries, cranberries, raisins and cherries. Some owners use a seed blend with fruit in hopes of attracting bluebirds to feed at their traditional feeders.