Posts Tagged: chill
No-Chill Bulbs for Spring Blooms
At this time of year bulbs are appearing at nurseries and big retail stores as well as in the...
Pomegranates.
By Susanne von Rosenberg, UC Master Gardener of Napa County Fig trees are among a small...
Fresh pomegranates. (norin.co.in)
Pomegranate blossoms. (monrovia.com)
Bowl of pomegranates. (photos.hgtv.com)
Growing pomegranates. (gardening-forums.com)
They -do- crack. (straythreads-straythreads.blogspot.com)
Parfianka pomegranate. (naturehills.com)
Eversweet pomegranate. (louiesnursery.com)
Wonderful pomegranate. Looks like other red ones. Note the longer petals. (almansifresh.com)
Pomegranate growing in garden. (gardeningknowhow.com)
A.maz.ing Pomegranates! (richfarming.com)
Warm winter renews concerns about orchard chill
National Public Radio highlighted a growing concern for San Joaquin Valley tree fruit and nut farmers - diminishing winter chill in an age of climate change. "Warm winters mess with nut trees' sex lives," reported Lauren Summer on Morning Edition.
For example, adequate winter chill allows female and male pistachio trees to wake up simultaneously, which is ideal for pollen to be available for wind to carry it to blooms on female trees.
Fresno State agriculture professor Gurreet Brar, a former UC Cooperative Extension advisor, is testing whether horticultural spray application at different chill-hour intervals will trick trees into thinking they've been colder. Normally, the spray is used on fruit and nut trees to control insects, but it's also known to alter the tree's dormancy period.
"It's supposed to help the tree and buds wake up normally and have a normal bloom," Brar said.
Summer also spoke to Katherine Jarvis-Shean, UC Cooperative Extension orchard systems advisor in Yolo County.
"We're on this (climate change) march and it's really just a matter of how bad it's going to be, not whether it's happening or not," Jarvis-Shean said. "Threatening those crops is really threatening the livelihoods of a lot of Californians."
Fruit and nut trees that require the most winter chill will run into trouble by mid-century, when experts predict consistently warmer weather, Summer reported.
"Bing cherries, which is really the marquee variety in California, won't get enough chill," Jarvis-Shean said. "We'll need to be breeding new varieties that still have that rich ruby flesh and that juicy flavor that can do well under those low chill conditions."
Better-adapted trees may be the only strategy in the long-run, she said. Efforts are already underway to breed new varieties of pistachios that can handle warmer winters.
Choosing a Fruit Tree?
By Susanne von Rosenberg, UC Master Gardener of Napa County Have you been thinking about adding a...
The EVERYTHING book about fruit trees: The Home Orchard (UC ANR) Available online from UC ANR Publications. https://anrcatalog.ucanr.edu/Details.aspx?itemNo=3485
Delving Deeper into the Concept of Supplemental Chill
Supplemental chill, also known as cold conditioning, takes place after harvest of the transplants, which have gone dormant because of their exposure to the decreasing daylength and lower temperatures of the nursery fields of Northern California where they are grown. Postharvest supplemental chill occurs in a constant near freezing temperature, in the dark and when the transplant has no to very few leaves left on it.
What supplemental chill is actually doing is breaking (reversing) plant dormancy, which sets into motion a series of metabolic events in the plant resulting in a promotion of vegetative growth and inhibition of new inflorescence formation. Petioles grow longer, leaf blades get bigger and more runners are formed as dormancy is broken through supplemental chill. All of this is consistent with the industry understanding that a longer period of supplemental chill results in more plant vigor, again meaning more vegetative growth and less fruiting. The challenge for the berry grower is to strike a balance between the vigor of vegetative growth and the fruiting which is greatly desired.
Growers already know this, but berry cultivars vary greatly in their sensitivity to the dormancy breaking supplemental chill. Generally speaking, short day strawberry varieties need very little – something on the order of one to three days - to break dormancy and in fact most become tremendously vegetative when chilled in excess over the recommended few days. In contrast, day neutral varieties need substantially more days of chill, most often in the range of one to two weeks, to develop the normal balance of vigor and fruiting following planting. Since longer periods of chill are associated with greater vegetative vigor, organic growers tend to chill their plants longer before planting, in the range of 30% longer, so as to enable the plant to handle less hospitable soil environments.