Advice for the Home Gardener from the Home Gardener from the
Help Desk of the UC Master Gardener Program of Contra Costa County
Help Desk Response: Thanks for contacting the UC Master Gardener Program Help Desk with your question about the “white spots” on your blackberries.
What you see happening on the fruit of your blackberry vine is an abiotic disorder (damage not caused by insects or disease) called “White Drupelet”. A “drupelet" is the individual seed on fruits like blackberries and raspberries (the “bump”).
White Drupelet will appear as a tan-to-white discoloration on the drupelets of caneberry fruit, and it can effect one drupelet or many. As you have described, the drupelet's often appear brown and hard at first, then become soft and take on a tan-to-white coloration.
This disorder happens when there is a sharp increase in the heat and a drop in humidity, often caused by wind. This is exactly the weather pattern we have had lately -- lots of wind with high heat and low humidity. Although this condition is weather related, the actual cause of the “whitening” is UV radiation. Ordinarily, 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. You may be observing this condition more in the canopy of the vine, or on the berries exposed to the sun, while the fruit tucked in under the leaves lower on the vine may be unaffected. When the heat subsides, and the humidity increases the condition will correct itself. The berries are safe to eat but you will want to remove the damaged part of the fruit. This UC Pest Note provides some more detailed information on White Drupelet disease: http://ipm.ucanr.edu/PMG/r71800111.html.
There is some debate about shade cloth being used to protect the vines but we found no conclusive scientific information indicating that shade cloth will prevent this condition.
If you were to experiment using shade cloth you must be careful to leave a good space between the shade cloth and the vine for proper air circulation or the shade cloth will just exacerbate the problem, creating more of a greenhouse effect rather than a shade structure.
Note: If you were to see the pale colored drupelets ONLY on the back side of the fruit (away from the sun) this could be caused by thrips, red mites or stinkbugs. More information on growing caneberries can be found searching for “caneberries” at http://ipm.ucanr.edu/GENERAL/search.html
Thanks for contacting the Master Gardener Program with your question. If we can be of further help, don't hesitate to contact us.
Help Desk of the UC Master Gardener Program of Contra Costa County (BHD)
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925)646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (http://ucanr.edu/blogs/CCMGBlog/).
/span>Home Gardening Advice from the Help Desk of the
UC Master Gardener Program of Contra Costa Cunty
Client's Request: I have 2 different berry bushes in my backyard. One berry bush is a thornless blackberry and the other an olallieberry, and they are 2 years old. I am quite confused as to how to prune them. Can you explain the fruiting canes, the old canes, the canes for next crop of berries, etc. None of the informative videos I've reviewed make anything any clearer.
Pruning berry canes yearly encourages more fruit production and makes cultivation easier. Both of your berry bushes are considered to be grown and pruned as “blackberries”. We agree that pruning blackberries can be a bit overwhelming at first, but once you understand how they grow and get the plants trellised and trained, the task will become much easier for you!
There are two names for a blackberry cane, depending on whether the cane is in its first or second year of growth:
Primocanes: First year of growth: most types produce no fruit on these canes.
Floricanes: Second year of growth; these canes produce flowers and fruit and then die.
When to Prune With blackberries, primocanes create new stems, while floricanes produce flowers and after pollination, blackberries. It's important to know the difference because each type of cane is pruned at a different time of year and at a different point in the plant's growth cycle.
How to tell the difference? Just look carefully at the canes. Primocanes don't produce flowers or fruit and may have a flush of new growth at the tip, they may also tend to grow on the ground. Floricanes produce blossoms in the spring and berries in early to midsummer. Prune primocanes or stems without fruit and berries in June and July, but wait to prune the floricanes until after berries are picked. Another helpful hint for identifying the type of cane is that the floricanes will have remnants of bloom/berry clusters.
How Much to Prune When pruning blackberries, cut the primocanes down to about 48 inches, measuring from the ground up to the tip of the cane. Shoots develop off the main stem. These are called lateral shoots. They jut out to the sides. You can prune these back to around 18 inches towards the end of the summer. Floricanes are pruned differently. After all the fruit is harvested, wait until the end of the summer or into the early fall. Prune branches that bore fruit down to the ground, or at least as far down as you can reach comfortably.
Here is an excellent video on blackberry care and pruning from Peaceful Valley Farm & Garden Supply:
http://www.groworganic.com/blackberryolallieeach.html
Here are additional helpful links from UC sources about blackberry care:
http://cesonoma.ucanr.edu/files/27140.pdf
http://cagardenweb.ucanr.edu/Berries/Blackberries/
Good luck with your pruning project! Please let us know if you have any additional questions.
... and apologies for the blog title... I just couldn't help myself... editor
Help Desk of the UC Master Gardener Program of Contra Costa County (SLH)
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (http://ucanr.edu/blogs/CCMGBlog/).
Advice for the Home Gardener from the Contra Costa Master Gardeners' Help Desk
Client's Problem and Questions:
Advice from the CCMGs' Help Desk
"Researchers around the world are investigating approaches for controlling Bermuda buttercup. Some suggest covering infestations with stiff cardboard, then covering the cardboard with a thick layer of organic mulch to kill the plants and weaken the bulbs, making them less capable of competing with desirable plants. Keep the mulch on the infestation until the mulch and cardboard have rotted, then plant competitive ornamentals into the soil-mulch mixture."
The Contra Costa Master Gardener article, "Oxalis: From Ornament to Nuisance" will give you even further insight on controlling Oxalis per-caprae. http://ccmg.ucanr.edu/files/83817.pdf
I know that the management of these weeds is a big challenge and wish you all the best in dealing with it!
Contra Costa Master Gardeners' Help Desk
Note: The Contra Costa Master Gardener Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/