Colusa County
University of California
Colusa County

Master Gardeners


 Science based solutions for Colusa County's gardening communities.

This is what we do!

Click here for a short video!



Preparing for a Frost




Before a frost

  • Identify cold spots in the landscape by monitoring with thermometers
  • Identify plants at risk: citrus, succulents, tender perennials, tropical and subtropical plants.
  • Have supplies ready: sheets, blankets or frost cloths, lights, wraps for trunks, thermometers, stakes or framework to hold covers off foliage. Frost cloths come in different weights that can provide 4 to 8 degrees of protection. Because the frost cloth allows some light and air to penetrate, it can stay on plants for a few days at a time. Frost cloth can lie directly on plant foliage.
  • Prepare tender plants: avoid fertilizing and pruning after August to minimize tender new growth.
  • Rake away mulch to allow soil to warm up during the day and radiate heat into the plant at night.
  • MONITOR weather forecasts and note how low temperatures will be and for how long.

o   Local frost: clear, dry nights, usually warms during the day.

o   Hard freeze: temperature inversion or Arctic front, can last for days or weeks, are very damaging.

When a frost is forecast

  • Move plants to a warmer spot next to the house or under a patio cover, especially on the south side.
  • Check that plants are well watered because dry plants are more susceptible to damage, and moist soil retains heat better than dry soil.
  • Cover plants before sunset to capture ground heat radiating upward at night. Remove sheets, blankets and other covers daily if it is sunny and above freezing to allow soil to absorb heat.
  • Add heat by using outdoor lights: hand 100 watt drop lights or holiday string lights to interior of plant. Use the old C7 or C9 large bulbs, not new LED lights which do not give off heat. Old style holiday lights that give off heat can provide up to 3 degrees of protection. Use lights, extension cords, and multi-outlets or power strips that are rated for outdoor use and grounded (3-prong). Avoid connecting together more than three light springs in a line.
  • Wrap trunks of tender trees if a hard freeze is expected, using towels, blankets, rags, or pipe insulation. Also wrap exposed pipes the same way.
  • Harvest ripe citrus fruit. Generally both green and ripe fruit are damaged below 30 degrees, but there is some variation by species.


For more information, click here to visit the UC Master Gardeners of Sacramento County page on frost protection.

Thank you, UC Master Gardeners of Sacramento and San Joaquin Counties for the information.


January in the Garden

In the Garden:

  • Plant rhubarb, strawberries, and cane berries. Plant seeds for broccoli, cabbage, parsley, turnips, peas, radishes, lettuce, and spinach.
  • This is the time to plant bare root roses, trees, artichoke crowns, grapevines, and other vines.
  • You can still plant pansies, violas, snapdragons, and fairy primroses.
  • Plant gladiolus every 2 weeks for a succession of blooms.
  • Later in the month you can divide Shasta daisies, daylilies, chrysanthemums, and other perennials.


NOTE: Beware of digging in soggy soils. All plantings should be well-drained; the new plants might rot if soil is soggy.



  • Roses, fruit trees and other perennials can be pruned this month.
  • Do not prune spring flowering shrubs until after they bloom.
  • Prune berry canes that bore fruit last year to the ground.
  • Prune grapevines back, leaving 2 to 3 buds per side shoot.


Pest and Disease control:

  • Spray horticultural oil on pruned fruit trees to control scale, mites and aphids. Thorough coverage will kill over-wintering eggs.
  • Later in the month, spray neem oil on roses to control mildew, rust, and black spot. Do not apply oils unless there will be 24 hours of dry weather following application.
  • Be sure to clean up debris (leaves and twigs) around roses and fruit trees to help prevent disease.


Order seeds for this year’s vegetable and flower garden.


Asian Citrus Psyllid

Asian Citrus Psyllid is an insect that carries a devastating disease in Citrus trees and there is no cure. The insect and disease is usually detected in home citrus first. Click here to read more about the Asian Citrus Psyllid and the Huanglongbing disease.

The Asian Citrus Psyllid has been found in San Joaquin County.

Click here to read about the Asian Citrus Psyllid from the UCCE Master Gardeners of San Joaquin County.

Click here for Spanish


UC Master Gardeners of Colusa County

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The University of California Master Gardener Program provides the public with UC research-based information about home horticulture, sustainable landscape and pest management practices. The program is administered by local University of California Cooperative Extension (UCCE) county offices that are the principal outreach and public service arms of the University’s division of Agriculture and Natural Resources.

The UC Master Gardener program supports sustainable gardening practices that protect the environment, conserve natural resources, and take into consideration each gardener's lifestyle and goals.


What do UC Master Gardeners do?

UC Master Gardeners are trained to help residents of California become better gardeners. Using a variety of activities such as workshops, lectures, and garden hotlines these volunteers answer questions about home horticulture, sustainable landscaping, and integrated pest management using University of California research-based information.

After their training UC Master Gardeners are qualified to help the public with problems in areas such as:

  • Weed Control
  • Plant Problem Diagnosis
  • Integrated Pest Management (insect and pest control)
  • Soils, fertilizers and irrigation
  • Selecting and caring for fruit and landscape trees
  • Growing annuals, perennials and food crops
  • Lawn care
  • Vegetable Gardening
  • Plant Pathology
  • Composting


Each county develops programs to address local needs. Some typical activities are:

  • Using mass media to disseminate gardening information
  • Teaching workshops, or lecturing on gardening practices
  • Participating in research activities with academics within UC
  • Answering gardeners’ questions via email or helplines
  • Speaking to the public on horticultural and gardening topics
  • Manning county fair information booths
  • Consulting with gardeners to improve their landscape practices


Find us on Facebook



Event Name



Winter Fruit Tree workshop

Saturday January 10, 2015, 1-3pm

Click here for flyer



Rose Pruning workshop

Sunday January 25, 2015, 1-3pm

Click here for flyer


Featured Plant


California fescue


Medium size

California native




Master Gardener Blog

It's a Butterfly Week!

Ulysses butterfly (Papilio ulysses) collection in the Bohart Museum of Entomology. These are all males. The females have barely any blue on their wings. (Photo by Kathy Keatley Garvey)

When the week is about butterflies instead of guerrilla attacks, murderous rampages, measles outbreaks, and deflated footballs, it's a good week. Butterflies draw smiles instead of scowls, pleasure instead of pain, glee instead of grief. So, here's...

Posted on Friday, January 23, 2015 at 9:37 PM

Rose pruning workshop

Rose prunig

Rose pruning workshop Saturday January 24 1-3pm Colusa County Fairgrounds, grandstand area Bring pruning shears This is a hands-on workshop Hope to see you there.

Posted on Friday, January 23, 2015 at 9:03 AM

Waiting for the Bees

A queen black-tailed bumble bee, Bombus melanopygus, foraging on pansies on Jan. 22, 2014. (Photo by Kathy Keatley Garvey)

Where, oh where, is that first bumble bee of the year? It's about this time of the year when the queen black-tailed bumble bee, Bombus melanopygus, and the queen yellow-faced bumble bee, Bombus vosnesenskii, emerge.  One of our area readers asked...

Posted on Thursday, January 22, 2015 at 9:19 PM
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