April is a great month for working in and enjoying the garden. Danger of frost is past, but the weather and soil are still relatively cool, with a continued opportunity for precipitation. We can plant just about anything this month, and there should be abundant flowers, especially if your garden has a lot of native California and western species.
The state-wide California Native Plant Week is April 15-21, and of course International Earth Day is April 21.
Perennials – Early in the month is the best time to plant manzanita, ceanothus and other western plants that don't like a lot of summer water. While the soil is still moist and cool, you can plant everything from fruit trees to cactus. Any frost-tender plants you did not plant in autumn can be safely planted now, including citrus, native verbena and succulents.
Container plants – If you don't have a lot of space, or if you want to have plants that require better draining soil than your garden offers, why not plant some containers? Use pots that are at least 16 inches in diameter for almost all perennials and sub-shrubs. Use a mix of all-purpose potting soil and cactus mix. Most containers should be placed in the sun during spring and moved to afternoon shade in summer. The containers themselves can add interest and color to the garden, so think about how things will look in September and get creative!
Bulbs – Spring bulbs to plant now are caladium, callas, cannas, dahlia, gladiolus and tuberose. Stagger the planting of gladiolus over several weeks to lengthen the bloom period. Herbs – Plant basil, beebalm, cilantro, chives, parsley, lavender, oregano, sage and thyme. You don't have to have a dedicated herb garden- just mingle a few herbs in your flower beds among your other moderate-to-regular water users. You can still plant some cool season favorites like borage; just tuck them under other larger herbs or right in amongst the vegetables, especially tomatoes.
Houseplants – Rotate your houseplants so they receive sunlight on all sides. Pinch tips of foliage to stimulate new growth and keep plants full, rather than long and leggy. To keep them healthy, remove any spent flowers, dead or yellowing leaves. With the exception of African violets (and any other plants with "hairy leaves") wipe leaves with a damp cloth or give them a shower under the faucet to remove dust. Fertilize with a houseplant food or a time release fertilizer.
Vegetables – You can still plant seeds of beets, lettuce and radishes. In late April after the soil has had time to warm up, plant the heat-loving vegetables: beans, corn, cucumber, eggplant, melons, okra, peppers, tomatillo, squash and tomatoes. You can continue to plant successive crops of greens; just be ready to harvest them as micro or mini, since they will want to flower quickly. The flowers are edible too, and a nice food source for pollinators.
Fertilize roses, shrubs, container plants and trees with a balanced fertilizer. The exception is California native plants; they rarely need fertilizing and over-feeding with nitrogen can shorten their lives by years. Use acid fertilizer on azaleas, gardenias and rhododendrons after they flower.
When spring bulbs finish flowering, snip off old blooms and fertilize. Do not trim or braid foliage leaves—they are taking up nutrients for next year's flowers. Trim after they turn yellow.
If citrus leaves are puny or showing dark green veins with pale middles, then spray them with a liquid cleated iron/zinc mixture. This also works on gardenias, too.
Prune spring flowering shrubs when they finish blooming: azaleas, camellias, forsythia, lilacs, ceanothus, native sage and flowering quince are some examples. You can safely prune as late as mid-summer, but after that you will be cutting off next year's flower buds. Prune citrus and avocado if necessary. You can continue to prune deciduous trees if you haven't yet; it may slow the growth a little but won't hurt them. Pinch annuals and perennials back for dense growth and more blooms.
Thin stone fruits while they are still tiny, to about six-to-eight inches apart.
Mow lawns only to about three inches tall. Fertilize lawns: generally it's best to do two half-strength feedings two months apart, rather than one strong feeding.
Begin your fire clearance: remove dry brush and weeds out to 30 feet from structures, 100 feet if your property is sloped or if you are in fire-prone areas.
Weed control remains important all month. Remove weeds before they set seeds.
Water by need, not by schedule. There is no substitute for observing your garden soil's moisture level. Don't rely on your gardener knowing; most garden care experts tend to over-water, which can lead to an increase in disease and pest issues, as well as wasting our precious resource. Check, flush, repair and renovate your irrigation systems before it gets hot!
Aphids love tender new leaf growth. Spray aphids off with a hose, or use an insecticidal soap. Least toxic first! Eliminate mosquito breeding sites. Drain excess water from gutters, buckets and plant containers. Handpick snails and slugs. They are easier to find in the early morning or early evening. Pesticides with iron phosphate are not toxic to children, pets and wildlife.
Add a bee nesting box or post to your garden to encourage our solitary native bees. Add a birdhouse or birdbath to encourage birds in the garden. Birds devour insects that feast on your plants.
Do not spray insecticides if beneficial insects such as lady beetles are present.
Encourage beneficial insects by planting alyssum, black-eyed Susan, cosmos, dill, fennel, feverfew, fleabane and yarrow. While planting, think about creating an area, or an entire garden, for habitat benefit. Think about how some creatures will enjoy a plant that you otherwise may not find to be that special. Examples may be planting a quail bush, a native sage, a native bunch grass such as deer grass, or having a variety of flower types, including plants with tiny flowers, and leaving some areas for ground-nesting bees.
Consider trying to institute a limited or no-pesticide policy as much as possible. This benefits all creatures, from toads to predatory birds. Tolerate some plant damage. If you farm, consider planting a hedgerow of native buckwheat, sage and other flowering shrubs and perennials.