Triple-digit temperatures can affect pollination, tomato development
Extreme heat shuts down production in tomato plants: pollen dries up and the flowers won't set fruit. Kathy Morrison
High heat is on its way – and that’s bound to affect our tomatoes.
First this update from the National Weather Service: Saturday is going to be hot!
A heat advisory is in effect from 11 a.m. to 8 p.m. Saturday, June 22, says the weather service.
“High temperatures 100 to 107 expected. Limited overnight relief with low temperatures in the mid 60s to mid 70s.”
The areas expected to be hardest hit include central Sacramento Valley, Mother Lode, northern Sacramento Valley, northern San Joaquin Valley and southern Sacramento Valley, says the advisory. The warmest overnight temperatures will be in the northern and central Sacramento Valley and foothills.
Saturday’s high temperature in downtown Sacramento is expected to reach 103, says the weather service. That’s 15 degrees above normal.
Be prepared to keep the A.C. running all night. Stay hydrated. Bring pets indoors.
But we can’t bring our vegetable gardens indoors. They have to cope where they’re planted.
So concentrate on keeping them comfortable. Water deeply in the morning before the heat arrives. Make sure there’s mulch (straw, leaves, wood chips, etc.) to help retain that moisture and keep roots cool. Erect some temporary shade (such as an umbrella or shade cloth) over peppers and tender transplants.
Tomatoes and large-leaved vegetables such as squash tend to wilt in the afternoon; that’s a normal coping mechanism. If they’re still wilted in the morning, they need a drink.
Speaking of tomatoes, the top issue right now is lack of pollination. Plants have blooms, but they drop off before they form fruit.
That’s related to heat, too. Tomato flowers won’t set when temperatures stay high – over 90 degrees – for prolonged periods. The pollen dries out. But indeterminate varieties will produce more flowers with new growth.
Tomatoes like some heat; days between 80 and 90 degrees produce optimum growth, according to UC research. But flowers will not set on 100-degree days.
Heat isn’t the only weather factor that can affect tomato pollination. Lack of wind or breeze also can affect tomato set. Tomatoes generally are wind-pollinated. To help with pollination, gently wiggle the tomato’s cage or trellis to shake up and spread the pollen.
For more advice on tomatoes and other summer crops, check out the UC IPM website: https://ipm.ucanr.edu/.
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Garden Checklist for week of Nov. 3
November still offers good weather for fall planting:
* If you haven't already, it's time to clean up the remains of summer. Pull faded annuals and vegetables. Prune dead or broken branches from trees.
* Now is the best time to plant most trees and shrubs. This gives them plenty of time for root development before spring growth. They also benefit from fall and winter rains.
* Set out cool-weather annuals such as pansies and snapdragons.
* Lettuce, cabbage and broccoli also can be planted now.
* Plant garlic and onions.
* Keep planting bulbs to spread out your spring bloom. Some possible suggestions: daffodils, crocuses, hyacinths, tulips, anemones and scillas.
* This is also a good time to seed wildflowers and plant such spring bloomers as sweet pea, sweet alyssum and bachelor buttons.
* Rake and compost leaves, but dispose of any diseased plant material. For example, if peach and nectarine trees showed signs of leaf curl this year, clean up under trees and dispose of those leaves instead of composting.
* Save dry stalks and seedpods from poppies and coneflowers for fall bouquets and holiday decorating.
* For holiday blooms indoors, plant paperwhite narcissus bulbs now. Fill a shallow bowl or dish with 2 inches of rocks or pebbles. Place bulbs in the dish with the root end nestled in the rocks. Add water until it just touches the bottom of the bulbs. Place the dish in a sunny window. Add water as needed.
* Give your azaleas, gardenias and camellias a boost with chelated iron.
* For larger blooms, pinch off some camellia buds.
* Prune non-flowering trees and shrubs while dormant.
* To help prevent leaf curl, apply a copper fungicide spray to peach and nectarine trees after they lose their leaves this month. Leaf curl, which shows up in the spring, is caused by a fungus that winters as spores on the limbs and around the tree in fallen leaves. Sprays are most effective now.
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