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Know the chill factor before you plant


Sacramento Digs Gardening logo
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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  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
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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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