Flavor of oranges may actually get a boost from 'kiss of cold'
Our warmer afternoons have prompted some fruit trees to push out blossoms already, such as on this multi-grafted fruit salad tree, photographed Feb. 11 at the Fair Oaks Horticulture Center. But freezing temperatures could threaten any eventual crop. Kathy Morrison
Our afternoons may feel like spring, but frost danger is still in our forecast. And that creates some challenges for Sacramento-area gardeners: All that tender new growth may need protection.
The National Weather Service warns of “widespread frost” on Thursday and Saturday morning in the greater Sacramento area and foothills. Overnight lows are expected to dip into the low 30s if not below freezing.
Frost threatens not only new shoots but tender blossoms and buds. Sacramento reached 71 degrees on Sunday, Feb. 12. Such warm weather coaxed out early blooms on some fruit trees. Frost can cause those blossoms to fall quickly without setting fruit.
Likewise, frost can burn newly rooted cuttings or transplanted seedlings – even if the temperature stays above 32 degrees. Protect these babies with row covers or “hot caps” – mini-greenhouses made of waxed paper or improvised with plastic milk jugs (with the bottom cut out).
A clear night with no wind can actually produce more frost damage than a windy night at the same temperature. According to university research, foliage temperatures on citrus trees were three to four degrees lower than surrounding air temperature on clear, windless nights. So, 34 degrees could actually feel like 30 to a tender lime or lemon. Young trees are most susceptible to cold damage.
Most citrus is OK down to 30 degrees. Some “chill hours” – time spent under 45 degrees but above freezing – may actually improve the flavor and quality of ripening oranges. That “kiss of cold” brings out the sugars while toughening the skin, extending the fruit’s longevity on and off the tree.
One of the easiest ways to protect sensitive plants: Water. Irrigate your garden before a frost warning; moist soil radiates heat and offers some frost insurance. (The exception are succulents; they soak up that extra moisture and can actually burst if their cells freeze.)
What if a tree or shrub has already suffered frost damage? Leave it on the plant for a few more weeks; it can protect the plant from further damage.
This frost warning is later than usual for Sacramento. After decades of recommending a “last frost” date of mid March, most experts now cut off our frost period at the end of January. According to the Sacramento County master gardeners, our average last frost date is Jan. 27.
But in 2022, Sacramento hit 32 degrees on Feb. 24 and dipped down to 35 degrees on March 6. Our latest ever freeze on record (30 degrees) hit March 27, 1898.
Surrounding communities need to watch out for frost and freeze much later than Sacramento with some areas under threat well into spring. The master gardeners list last frost dates for Marysville (March 16), Lodi (March 31), Woodland (April 1), Auburn (April 13), Davis (April 18), Placerville (May 18) and Nevada City (June 4).
For more tips on frost protection: https://sacmg.ucanr.edu/Frost_Protection/.
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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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