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Know the chill factor before you plant


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Sacramento Digs Gardening
BY Debbie Arrington PUBLISHED SEP 18, 2018
Fuyu persimmons bear more fruit when there's more chill.
(Photo: Debbie Arrington)
Chill hours are a key to success for many fruit trees and shrubs




It’s nature’s cue to take a nap. Lower temperatures in fall signal many plants to wrap things up, drop their leaves and drift off into dormancy. They need to rest.

But it’s the winter cold – measured in chill hours – that really makes a difference in plant performance in the year ahead.

Autumn, which officially starts Saturday, is a wonderful time to plant deciduous trees, shrubs and perennials in Sacramento. They appreciate the lingering warmth of summer while putting down roots and gearing up for a big spring.

Chill hours are an important factor when choosing which varieties to plant. Some need more chill than others.

Chill hours are that kiss of cold that cues blooming and fruiting in a wide range of plants, such as apples, almonds, blueberries, peaches, grapes, persimmons and peonies. Measured from Nov. 1 through Feb. 28 or 29, that chill time is roughly the number of hours below 45 degrees each winter (but above freezing). The total subtracts hours above 60 degrees, which offset the chill effect.

According to the UC Cooperative Extension master gardeners, Sacramento gets on average about 600 chill hours each winter, some communities much more. The Fair Oaks Horticulture Center, home to the Sacramento County master gardeners, recorded 792 hours below 45 degrees last winter; 762 were in that sweet spot above 32 degrees. That also means the Hort Center experienced only 30 hours below freezing.

Chill hours can fluctuate widely, which often accounts in crop changes, too. For example, the Fair Oaks station measured 1,028 chill hours in the winter of 2012, but only 480 in 2014.

The University of California’s Fruit and Nut Research and Information Center developed a very handy set of online tools to calculate chill hours. Its database includes both cumulative chill hours during the current season as well as wealth of historical information. Find it here: https://bit.ly/2NPObh0 . Or got to the center’s website, http://fruitsandnuts.ucdavis.edu/ , and search for “chill calculator.”

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GENERAL GARDENING

An article about gardening.

Keywords:
UCCE master gardeners fall planting gardening peonies Sacramento chill hours Fair Oaks Horticulture Center fruit trees orchards

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Sites We Like

  1.  UCCE Master Gardeners of Sacramento County
  2. Farmer Fred's GardenBasics.net
  3. UC Davis Arboretum and Public Garden
  4. Shepard Garden and Arts Center
  5. Placer County Master Gardeners
  6. El Dorado County Master Gardeners
  7. Yolo County Master Gardeners

Garden Checklist for week of April 21

This week there’s plenty to keep gardeners busy. With no rain in the immediate forecast, remember to irrigate any new transplants.

* Weed, weed, weed! Get them before they flower and go to seed.

* April is the last chance to plant citrus trees such as dwarf orange, lemon and kumquat. These trees also look good in landscaping and provide fresh fruit in winter.

* Smell orange blossoms? Feed citrus trees with a low dose of balanced fertilizer (such as 10-10-10) during bloom to help set fruit. Keep an eye out for ants.

* Apply slow-release fertilizer to the lawn.

* Thoroughly clean debris from the bottom of outdoor ponds or fountains.

* Spring brings a flush of rapid growth, and that means your garden is really hungry. Feed shrubs and trees with a slow-release fertilizer. Or mulch with a 1-inch layer of compost.

* Azaleas and camellias looking a little yellow? If leaves are turning yellow between the veins, give them a boost with chelated iron.

* Trim dead flowers but not leaves from spring-flowering bulbs such as daffodils and tulips. Those leaves gather energy to create next year's flowers. Also, give the bulbs a fertilizer boost after bloom.

* Pinch chrysanthemums back to 12 inches for fall flowers. Cut old stems to the ground.

* Mulch around plants to conserve moisture and control weeds.

* From seed, plant beans, beets, cantaloupes, carrots, corn, cucumbers, melons, radishes and squash.

* Plant onion sets.

* In the flower garden, plant seeds for asters, cosmos, celosia, marigolds, salvia, sunflowers and zinnias.

* Transplant petunias, zinnias, geraniums and other summer bloomers.

* Plant perennials and dahlia tubers for summer bloom.

* Mid to late April is about the last chance to plant summer bulbs, such as gladiolus and tuberous begonias.

* Transplant lettuce seedlings. Choose varieties that mature quickly such as loose leaf.

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