April Gardening Calendar
Published: March 17, 2020
- Study your landscape for gaps that could be nicely filled with bulbs. Mark these spots carefully and make a note to order bulbs next August.
- Enjoy, but do not disturb the many wildflowers blooming in woodlands throughout Missouri.
- When buying bedding plants, choose compact, bushy plants that have not begun to flower.
- When crabapples are in bloom, hardy annuals may be transplanted outdoors.
- Fertilize established roses once new growth is 2 inches long. Use a balanced formulation. Begin spraying to control black spot disease.
- Examine shrubs for winter injury. Prune all dead and weakened wood.
- Groundcovers can be mowed to remove winter burn and tidy plants up. Raise mowers to their highest settings. Fertilize and water to encourage rapid regrowth.
- Shrubs and trees best planted or transplanted in spring, rather than fall, include butterfly bush, dogwood, rose of Sharon, black gum (Nyssa), vitex, red bud, magnolia, tulip poplar, birch, ginkgo, hawthorn and most oaks.
- Winter mulches should be removed from roses. Complete pruning promptly. Remove only dead wood from climbers at this time. Cultivate lightly, working in some compost or other organic matter.
- Look for flowering dogwoods in bloom.
- Break off rims from peat pots when transplanting seedlings, otherwise they can act as a wick to draw moisture away from the roots.
- Transplant Virginia bluebells (Mertensia virginica) after bloom, but before the foliage disappears.
- Do not prune boxwoods before April 15.
- Evergreen and deciduous hedges may be sheared. Prune the top narrower than the base so sunlight will reach the lower limbs.
- Oaks and hickories bloom.
- Easter lilies past blooming can be planted outdoors. Set the bulbs 2 to 3 inches deeper than they grew in the pot. Mulch well if frost occurs.
- Apply controls for holly leaf miner when the new leaves are just beginning to grow.
- Balloon flower (Platycodon), hardy hibiscus, gasplant (Dictamnus albus) and some lilies are slow starters in the spring garden. Cultivate carefully to avoid injury to these tardy growers.
- Prune spring flowering ornamentals after they finish blooming.
- Begin planting out summer bulbs such as caladiums, gladioli and acidanthera at 2 week intervals.
- Start mowing cool season grasses at recommended heights. For complete details, refer to University Extension Guide #6705, Cool Season Grasses.
- Topdress low spots and finish overseeding thin or bare patches.
- Aerate turf if thatch is heavy or if soil is compacted.
- Apply crabgrass preventers before April 15. Do not apply to areas that will be seeded.
- Finish transplanting broccoli, Brussels sprouts, cabbage, and cauliflower plants into the garden. High phosphorous fertilizers help get transplants off to a quick start.
- Plants started indoors should be hardened off outdoors in cold frames before being transplanted into the garden.
- Start cucumber, cantaloupe, summer squash, and watermelon seeds indoors in peat pots.
- Finish sowing seeds of all cool-season vegetables not yet planted.
- Plastic films can be used to preheat the soil where warm season vegetables are to be grown.
- Asparagus and rhubarb harvests begin.
- Handpick and destroy asparagus beetles.
- Keep your hoe sharp! Don't allow weeds to get an early start in your garden.
- Flower stalks should be removed from rhubarb plants, if they develop.
- Try an early sowing of warm-season crops such as green beans, summer squash, sweet corn, New Zealand spinach and cucumbers.
- Thin out crowded seedlings from early plantings of cool season crops such as beets, carrots, lettuce, onions and radish.
- Sow seeds of luffa and hard-shell gourds indoors in peat pots. Soak seeds overnight before planting.
- Make succession sowings of cool-season crops.
- Begin planting lima beans, cucumbers, melons, okra and watermelons.
- Begin setting out transplants of tomatoes, eggplants, peppers and sweet potatoes.
- Blemish-free fruits unmarred by insect or disease injury can rarely be produced without relying on regular applications of insecticides and fungicides For special information, consult University Extension Guide Sheet #G6010, Home Fruit Spray Schedule.
- Wooden clothespins make useful spreaders for training young fruits limbs. Place pins between the trunk and branch to force limbs outward at a 60 degree angle from the trunk.
- A white interior latex paint may be brushed on the trunks of newly planted fruit trees to prevent sunburn. This will gradually weather off in time.
- Stink bugs and tarnished plant bugs become active on peaches.
- Leaf rollers are active on apple trees. Control as needed.
- Prune peaches and nectarines now.
- Plant bare-root or potted fruit treesÂ as soon as the soil can be worked.
- Remove tree wraps from fruit trees now.
- Protect bees and other pollinating insects. Do not spray insecticides on fruit trees that are blooming.
- Destroy or prune off webs of eastern tent caterpillars. "B.t." (Dipel) is a safe biological spray.
- Orange, jelly-like galls on cedar trees spread rust diseases to apples, crabapples and hawthorns.
- Begin sprays for fire-blight susceptible apples and pears using an agricultural streptomycin.
- Spider mites and codling moths become active on apples.
- Termites begin swarming. Termites can be distinguished from ants by their thick waists and straight antennae. Ants have slender waists and elbowed antennae.
- Look for morel mushrooms when lilacs bloom and the forest floor turns green.
- Mount a rain gauge on a post near the garden to keep track of precipitation so you can tell when to water. Most gardens need about 1 inch of rain per week between April and September.
- Mole young are born in chambers deep underground.
- Honeybees are swarming. Notify a local beekeeper to find a new home for these beneficial insects.
- Soaker hoses and drip irrigation systems help you save water and money.
- Hummingbirds return from their winter home in Central America.
- Wasp and hornet queens begin nesting.
Gardening Calendar supplied by the staff of the William T. Kemper Center for Home Gardening located at the Missouri Botanical Garden in St. Louis, Missouri. (www.GardeningHelp.org)