Vail Daily Landscape Logic column: Help plants survive the heat
August 10, 2015
Now that Colorado is finally moving into the hot days of summer, be aware of how warmer temperatures affect edibles — especially our No. 1 homegrown crop, tomatoes.
While people often think tomatoes thrive on warm days, that's not exactly the case. According to the tomato growers at J.W. Jung Seed Co., it takes about five weeks for a tomato flower to become a fully ripe fruit. During the first three weeks it grows to full size and during the last two weeks, it ripens. Temperatures soaring above 90 degrees will slow down this process.
HOW IT AFFECTS TOMATOES
What happens as temps rise?
• When temperatures hit 85 degrees, pollination and fruit set will be affected.
• At 95 degrees and above when nighttime temperatures are higher than 75 degrees, flowers may fall off the plant.
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• Hitting 100 degrees and higher will push the plants into survival mode. The red pigment in the skin may stop forming while the yellow and orange pigments continue to develop. When this happens, growers recommend picking tomatoes when they turn red and then allowing them to ripen indoors at cooler temperatures.
Once those really hot days have passed, it may take five more weeks to begin harvesting tomatoes again. Fortunately, successive 100-degree days are rare along Colorado's Front Range and especially at higher elevations.
TRICKS TO BEAT THE HEAT
Luckily, there are tricks to help protect your crops from the occasional heat spell.
Multiple days of excessive heat can cause cucumbers to drop their blossoms or for developing fruit to become deformed and acquire a bitter flavor. When preparing cucumbers, cut off the stem end and peel off the skin, as this will remove much of the bitterness.
Successive days at 90 degrees and hotter may cause squash, peppers, melons, pumpkins and beans to drop their blossoms and temporarily shut down production.
Cool-season crops such as broccoli, cabbage, lettuce and spinach will bolt in the heat. Wait for cooler days to replant them.
Other heat problems
Blossom end rot is common during hot weather. You'll often see this problem in tomatoes, peppers and squash.
Spider mites like to show up during hot, dry weather and one sign they are active is that leaves that look stressed. The go-to way to check for spider mites is to hold a sheet of white paper under the leaves and tap the plant. You may see the specs move (they are mites) and if you run your hand over the paper, you will see streaks on the paper. To control spider mites, consider applying an insecticidal soap to your plants according to label instructions. Note if there are precautions that apply to edibles.
The good news about hot, dry weather is that it deters fungal diseases such as powdery mildew on impatiens and edibles as well as Ascochyta blight in lawns — all of which have been a problem in some areas of Colorado this season as a result of the prolonged periods of precipitation.
Becky Garber is a member of the Associated Landscape Contractors of Colorado, of which Neils Lunceford, a landscaping company, is a member. You may contact them at 970-468-0340.