Discolored berries are another example of crops affected by intense summer heat
This close-up on two blackberries shows the white-to-tan drupelets that can develop in hot, dry weather. Courtesy UC Integrated Pest Management
Add another crop to our list of heat victims this summer: Blackberries.
Throughout the Sacramento region, blackberries are developing odd white or tan discoloration. The little drupelets – the juicy sacs that make up the berry – turn white or tan. It’s not just cosmetic; they generally don’t taste so good either. Often, the discolored drupelet withers to nothing but a dried seed.
I noticed these weird drupelets on my own Baby Cakes blackberries as well as the wild blackberries that grow near our home. Was it the heat?
Thanks to Farmer Fred Hoffman (and UC research), we know why: Excess UV radiation. (And yes, that’s related to the heat.)
Hoffman, host of “Garden Basics with Farmer Fred” podcast, solved this mystery in response to an Oroville listener who saw her berries go from pink to tan to yuck.
In his column, Hoffman recapped heat-related problems with other crops such as tomatoes.
“And now, you can add blackberries to the list of crops that develop problems when it gets too sunny, too hot, dry and windy, especially because of extended heatwaves. The problem is known as White Drupelet Disorder (WDD),” Hoffman wrote.
It’s not just a matter of adding shade; the berry plants need humidity.
According to the UC Integrated Pest Management Guidelines for Caneberries:
"White drupelet is a tan-to-white discoloration of one to many drupelets on the fruit. Most often, white drupelets will appear when there has been an abrupt increase in temperature accompanied by a drop in humidity; it is especially pronounced when there is wind. ...
“While white drupelets may seem to be directly caused by weather, they are actually caused by ultra-violet (UV) radiation,” note the UC experts. “Weather conditions modulate this by the effect they have on penetration of UV radiation into the fruit. Cool, humid air scatters and absorbs UV radiation, while hot dry air has the opposite effect and allows more direct UV rays to reach the fruit.
“The movement of humidity away from the canopy by wind only heightens the effect of hot dry air. Additionally, as humidity is moved away from the plant canopy, more UV rays penetrate the canopy and damage fruit that may not even have been exposed to the sun. Fruit inside of the canopy is not acclimatized to UV radiation and is subsequently more susceptible when it reaches them.”
How do you combat WDD? Make your own fog.
“Some growers of caneberries in the Willamette Valley of Oregon, where rapid changes from a normally mild climate to temperatures up to and above 100 degrees occur through the summer, use overhead irrigation to minimize fruit loss to white drupelet,” say the researchers. “This is not merely to mist the fruit; instead, large amounts of water are applied to thoroughly wet the canopy and maintain cool temperatures and high canopy humidity for as long as possible. Sprinkling is not done too late in the evening to allow fruit to dry before nightfall.”
Learn more here: https://ipm.ucanr.edu/agriculture/caneberries/white-drupelet/#gsc.tab=0
Hoffman also cited other university researchers. As other berry-growing regions get hotter and drier, WDD will only become a bigger problem.
Meanwhile, Hoffman offered tips for berry success in his “Beyond the Garden Basics” segment, plus reasons why taking time to smell the roses (and other aromatic plants) really is good for you in his Friday podcast, “Stressed? Your Garden Can Help.” (And who isn't this summer?)
Find Hoffman’s podcasts and more here: https://gardenbasics.net/.
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Flowers in My Back Yard Series
May 12: Know your coreopsis from your bidens
May 5: Mums the word on Mother's Day weekend
April 28: Majestic Matilija poppy is worth a look
April 21: Celebrate roses, America's favorite flower
April 14: Small flowers with outsized impact
April 7: Calendulas do double duty
April 3: Make Easter lilies last for years to come
March 31: In praise of a pollinator magnet (small-leaf salvias)
March 24: Azaleas brighten shady spots
March 17: The perfect flower for beginners? Try zonal geraniums
March 10: Keep camellias happy for years to come
March 3: Fruit tree blossoms are a fleeting joy
Feb. 27: Are your roses looking rusty?
Feb. 24: Treasure spring daffodils now and for years to come
Feb. 17: How and why to grow wildflowers
Feb. 10: Let's talk Valentine's Day roses
Feb. 3: Why grow flowers?
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Garden checklist for week of May 10
Take it easy during that high heat – then get to work! Your garden is calling.
* Remember to irrigate your tender transplants. Seedlings need consistent moisture. Deep watering will help build strong roots and healthy plants. Water early in the morning for best results.
* Plant, plant, plant! It’s prime planting season in the Sacramento area. Time to set out those tomato transplants along with peppers and eggplants. Pinch off any flowers on new transplants to make them concentrate on establishing roots instead of setting premature fruit.
* Direct-seed melons, cucumbers, summer squash, corn, radishes, pumpkins and annual herbs such as basil.
* Harvest cabbage, lettuce, peas and green onions.
* In the flower garden, direct-seed sunflowers, cosmos, salvia, zinnias, marigolds, celosia and asters. (You also can transplant seedlings for many of the same flowers.)
* Plant dahlia tubers. Other perennials to set out include verbena, coreopsis, coneflower and astilbe.
* Transplant petunias, marigolds and perennial flowers such as astilbe, columbine, coneflowers, coreopsis, dahlias, rudbeckia and verbena.
* Keep an eye out for slugs, snails, earwigs and aphids that want to dine on tender new growth.
* Feed summer bloomers with a balanced fertilizer.
* For continued bloom, cut off spent flowers on roses as well as other flowering plants.
* Put your veggie garden on a regular diet. Set up a monthly feeding program, and keep track on your calendar. Make sure to water your garden before applying any fertilizer to prevent “burning” your plants.
* As spring-flowering shrubs finish blooming, give them a little pruning to shape them, removing old and dead wood. Lightly trim azaleas, fuchsias and marguerites for bushier plants.
* Don’t forget to weed! Those invaders are growing fast.
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Food in My Back Yard (FIMBY) Series
Lessons learned during a year of edible gardening
WINTER
Is edible gardening possible indoors?
Hints for choosing tomato seeds
Why winter is the perfect time to plant fruit trees
When to plant? Consider staggering your transplants
How to squeeze more food into less space
Plant a fruit tree now -- for later
Win the weed war by tackling them in winter
Tips for planting bare-root trees, shrubs and vegetables
Time to give vegetable seedlings some more space
Ways to win the fight against weeds
FALL
Dec. 16: Add asparagus to your edible garden
Dec. 9: Soggy soil and what to do about it
Dec. 2: Plant artichokes now; enjoy for years to come
Nov. 25: It's late November, and your peach tree needs spraying
Nov. 18: What to do with all those fallen leaves?
Nov. 11: Prepare now for colder weather in the edible garden
Nov. 4: Plant a pea patch for you and your garden
Oct. 27: As citrus season begins, advice for backyard growers
Oct. 20: Change is in the autumn air
Oct. 13: We don't talk (enough) about beets
Oct. 6: Fava beans do double duty
Sept. 30: Seeds or transplants for cool-season veggies?
Sept. 23: How to prolong the fall tomato harvest
SUMMER
Sept. 16: Time to shut it down?
Sept. 9: How to get the most out of your pumpkin patch
Sept. 2: Summer-to-fall transition time for evaluation, planning
Aug. 26: To pick or not to pick those tomatoes?
Aug. 19: Put worms to work for you
Aug. 12: Grow food while saving water
Aug. 5: Enhance your food with edible flowers
July 29: Why won't my tomatoes turn red?
July 22: A squash plant has mosaic virus, and it's not pretty
July 15: Does this plant need water?
July 8: Tear out that sad plant or baby it? Midsummer decisions
July 1: How to grow summer salad greens
June 24: Weird stuff that's perfectly normal
SPRING
June 17: Help pollinators help your garden
June 10: Battling early-season tomato pests
June 3: Make your own compost
May 27: Where are the bees when you need them?
May 20: How to help tomatoes thrive on hot days
May 13: Your plants can tell you more than any calendar can
May 6: Maintain soil moisture with mulch for garden success
April 29: What's (already) wrong with my tomato plants?
April 22: Should you stock up on fertilizer? (Yes!)
April 15: Grow culinary herbs in containers
April 8: When to plant summer vegetables
April 1: Don't be fooled by these garden myths
March 25: Fertilizer tips: How to 'feed' your vegetables for healthy growth
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