April in the Contra Costa Garden
April Garden To Dos
General Garden Care
- Adjust irrigation controller programming. Check soil moisture around plant roots, and if dry, start increasing watering frequency.
- Program irrigation start times for early a.m. to reduce evaporative loss.
- Empty & remove all sources of standing water to reduce mosquito habitat.
- Weed: remove summer weeds while still small.
- Amend the soil with finished compost prior to planting and water deeply after planting.
- Cover compost piles with damp burlap bags if it has stopped raining.
- Group new plantings according to water requirements. Don’t fertilize until plants have been in a couple of weeks and are showing signs of new growth. Top-dress with compost to fertilize (preferable) or use a slow-release source of Nitrogen.
- Fertilize turf if needed. Compost is best, or use a slow-release fertilizer.
Fruits & Vegetables
- Sow vegetable seeds in outdoor beds where the soil has warmed: beets, broccoli, corn, cucumbers endive, kohlrabi, lettuces, onions, parsley, parsnips, peas, potatoes, radishes, spinach, Swiss chard, squash and turnips.
- Fertilize citrus - follow directions.
- Thin most fruit when dime-sized to about 6” apart or one per cluster.
- Place hot caps on tomatoes if the weather is cool.
Flowers & Landscaping
- Mow the following groundcovers : Achillea tomentosa, Baccharis pilularis, Cotoneaster dammeri, Euonymus fortunei ‘Colorata’, Hedera helix, Hypericum calycinum, Juniperus spp., Lonicera japonica ‘Halliana’, Mahonia repens, Pachysandra terminalis, Rosa banksiae (Lady Banks Rose), and ground cover roses.
- Prune spring-blooming shrubs that have finished flowering, such as Spirea, Philadelphus, Viburnum, Cercis (redbud), Ribes, lilac, Ceanothus, Chaenomeles (quince), Genista, Acacia, Forsythia.
- Pinch back: chrysanthemums, euryops, fuchsias, geraniums, impatiens, petunias, snapdragons and zinnias.
- Plant: heat loving annuals if the weather has warmed up, such as ageratum, amaranth, celosia, cosmos, dahlia, globe amaranth, impatiens, lobelia, marigolds, petunias, phlox, portulaca, salvia, sanvitalia, statice, sweet alyssum, verbena, and zinnias.
- Plant drought-tolerant perennials; try something new this year like Euphorbia characias wulfenii, E. myrsinites, E. rigida.
- Plant sub-tropicals in protected sites: e.g., Bougainvillea, Hibiscus, Jacaranda, Mandevilla, Plumeria. They may only live till winter in colder microclimates.
- Take cuttings from azaleas, carnations, chrysanthemums, fuchsias, geraniums and succulents for propagation.
- Anthracnose in Modesto ash and other landscape trees: The leaves look scorched, turn brown, and drop. Dry weather can sometimes arrest the disease. Prune out and get rid of infected twigs and branches. Fertilize tree to stimulate vigorous growth if needed.
- Ants: Control with baits or use barrier products such as Tanglefoot.
- Aphids: Spray off with water before populations build up.
- Control snails and slugs with hand-picking, traps or iron phosphate bait.
- Lots of other pests can show up in April, including the following: Codling Moth, Powdery Mildew, Rose Mosaic Virus, Rust, and Brown Rot on peaches, plums, apples, and pears. See the links below for information on controls.
For More Information
Local Weather Information
Linked data is from the California Irrigation Management Information System (CIMIS) weather stations. Visit CIMIS web site.
Contra Costa County Stations
USDA zones range from 8-9B
Sunset zones range from 7-17
Average max. temp. 69.4°F, 17.4°C
Average min temp. 43.8°F, 6.56°C
Average rainfall 1.58”, 4.01 cm.