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Starting Jan. 1, some insecticide ingredients commonly used to treat ornamental plants, trees, turf and other plants will no longer be available to buy off the shelf in California. Neonicotinoid, a class of pesticides found in more than 100 insecticide products, will no longer be allowed for sale at retail nurseries and garden centers under a new set of laws aimed at protecting birds, bees, aquatic insects and humans from their potential harmful impacts.
This class of pesticides will only be available for sale at licensed pest control dealers and limited for use by licensed professionals. The insecticide imidacloprid and the related active ingredients acetamiprid, clothianidin, dinotefuran, and thiamethoxam, belong to the neonicotinoids group. To find out whether you may have insecticides on your shelf that are now prohibited, look for these active ingredients, or check the California Department of Pesticide Regulation’s list of neonicotinoid products.
For more information about these restricted pesticides, the University of California’s Integrated Pest Management (UC IPM) is hosting a free webinar on Jan. 16 that will cover which ingredients have been restricted and how to protect pollinators and wildlife with the new laws that just came into effect in California.
The program is part of the group’s monthly webinars about pest identification, prevention and management around the home, garden and landscape.
The webinar is free, but advanced registration is required. All webinars will be recorded and posted to their YouTube channel.
Your gardening questions answered
Why are the leaves on my citrus tree turning yellow?
While there are several possible causes for yellow citrus leaves, the most likely one in winter/early spring is that citrus roots do not absorb nitrogen efficiently from cold, wet soils. There may be adequate nitrogen in the soil, but the roots aren’t able to take it up. However, if the tree doesn’t green up when the weather warms, give it some nitrogen fertilizer, up to 1 pound of nitrogen per year for a mature, full-size tree. Dwarf trees or ones in containers require less fertilizer, a 1/2 pound of nitrogen or less. Do not overfertilize since that may cause other problems.
More information: Growing Great Citrus
January gardening tips
Prune (some) California native plants
If your landscape includes California native plants, you may wonder if you should prune them. It depends. Some don’t respond well to shaping or shearing to control size. But they do like careful pruning at the proper time, which is when they are dormant. That could be either summer or mid-winter. Natives that do well with winter trimming include California buckeye (Aesculus californica), honeysuckle (Lonicera hispidula), and salvia species. California fuchsia (Epilobium canum) and lilac verbena (Verbena lilacina) can be cut almost to the ground. But wait until summer for grasses and broadleaf evergreen shrubs and trees.
More information: How to Prune California Native Plants
Plant blueberries for spring harvest
The best time to plant blueberries is from late fall to winter, using 2- to 3-year-old plants. Varieties that do well in Santa Clara County include Southern Highbush and Northern Highbush. These varieties bloom from late January to March, with their flowers turning into berries from late May to early September.
January gardening events
Several UC Master Gardener gardening events are happening all over Santa Clara County this month. Here are some of them; more are listed on our events page.
- National Seed Swap Day – Saratoga, Jan. 25
Blueberries require acidic soil with a pH between 4.5 and 6.5. If you have clay soil, amend it with organic matter, preferably peat moss, and add sulfur during the wet season to help maintain acidic soil conditions. Oregon State University has useful information on acidifying soil for blueberries.
New branch and leaf growth starts after berry harvest and continues until fall colors appear from September to November. Not all blueberry varieties are deciduous; some drop their leaves in late November or December. The plants go dormant from December to January. Blueberries need annual pruning to maintain the right balance of new and previous season growth. If you want to increase your blueberry crop, you’re in luck! We’re offering a hands-on workshop on blueberry (and rose) pruning on Feb. 1 at our Palo Alto Demonstration Center. Bring your pruning tools.
For more information on successfully growing blueberries, visit our Master Gardeners site.
Do you have a gardening question? The UC Master Gardeners of Santa Clara County can help. Our volunteers are part of the University of California’s Cooperative Extension program and we are trained to use research-based information to educate our fellow residents on sustainable gardening and landscaping practices specific to our area.Our monthly “Ask a Master Gardener” column will answer your questions and offer tips. Have a question? Email lifestyle@embarcaderopublishing.com.
You can also subscribe to our monthly Tips and Events newsletter. San Mateo residents can also find gardening advice on the UC Master Gardeners of San Mateo and San Francisco website.
