Gardening by Month - April
Monthly Tips and Tasks

Category
 
Week
 
Activity 
  1 2 3 4  
 Ornamentals x x x x 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.
  x x x x Enjoy, but do not disturb the many wildflowers blooming in woodlands throughout Missouri.
  x x x x When buying bedding plants, choose compact, bushy plants that have not begun to flower.
  x x x   When crabapples are in bloom, hardy annuals may be transplanted outdoors.
  x x x   Fertilize established roses once new growth is 2 inches long. Use a balanced formulation. Begin spraying to control black spot disease.
  x x     Examine shrubs for winter injury. Prune all dead and weakened wood.
  x       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.
  x       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.
  x       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.
    x x x Look for flowering dogwoods in bloom.
    x x x Break off rims from peat pots when transplanting seedlings, otherwise they can act as a wick to draw moisture away from the roots.
    x x   Transplant Virginia bluebells (Mertensia virginica) after bloom, but before the foliage disappears.
      x x Do not prune boxwoods before April 15.
      x x Evergreen and deciduous hedges may be sheared. Prune the top narrower than the base so sunlight will reach the lower limbs.
      x x Oaks and hickories bloom.
      x x 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.
      x x Apply controls for holly leaf miner when the new leaves are just beginning to grow.
      x x 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.
        x Prune spring flowering ornamentals after they finish blooming.
        x Begin planting out summer bulbs such as caladiums, gladioli and acidanthera at 2 week intervals.
 Lawns     x x x x Start mowing cool season grasses at recommended heights. For complete details, refer to University Extension Guide #6705, Cool Season Grasses.
  x x     Topdress low spots and finish overseeding thin or bare patches.
  x x     Aerate turf if thatch is heavy or if soil is compacted.
  x x     Apply crabgrass preventers before April 15. Do not apply to areas that will be seeded.
 Vegetables     x x x   Finish transplanting broccoli, Brussels sprouts, cabbage, and cauliflower plants into the garden. High phosphorous fertilizers help get transplants off to a quick start.
  x x     Plants started indoors should be hardened off outdoors in cold frames before being transplanted into the garden.
  x x     Start cucumber, cantaloupe, summer squash, and watermelon seeds indoors in peat pots.
  x x     Finish sowing seeds of all cool-season vegetables not yet planted.
  x x     Plastic films can be used to preheat the soil where warm season vegetables are to be grown.
  x x     Asparagus and rhubarb harvests begin.
    x x x Handpick and destroy asparagus beetles.
    x x x Keep your hoe sharp! Don't allow weeds to get an early start in your garden.
    x x x Flower stalks should be removed from rhubarb plants, if they develop.
    x x x Try an early sowing of warm-season crops such as green beans, summer squash, sweet corn, New Zealand spinach and cucumbers.
    x x   Thin out crowded seedlings from early plantings of cool season crops such as beets, carrots, lettuce, onions and radish.
    x x   Sow seeds of luffa and hard-shell gourds indoors in peat pots. Soak seeds overnight before planting.
    x x   Make succession sowings of cool-season crops.
      x x Begin planting lima beans, cucumbers, melons, okra and watermelons.
      x x Begin setting out transplants of tomatoes, eggplants, peppers and sweet potatoes.
 Fruits x x x x 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.
  x x     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.
  x x     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.
  x x     Stink bugs and tarnished plant bugs become active on peaches.
  x x     Leaf rollers are active on apple trees. Control as needed.
  x x     Prune peaches and nectarines now.
  x       Plant bare-root or potted fruit trees as soon as the soil can be worked.
  x       Remove tree wraps from fruit trees now.
    x x x Protect bees and other pollinating insects. Do not spray insecticides on fruit trees that are blooming.
    x     Destroy or prune off webs of eastern tent caterpillars. "B.t." (Dipel) is a safe biological spray.
      x x Orange, jelly-like galls on cedar trees spread rust diseases to apples, crabapples and hawthorns.
      x x Begin sprays for fire-blight susceptible apples and pears using an agricultural streptomycin.
        x Spider mites and codling moths become active on apples.
 Miscellaneous     x x     Termites begin swarming. Termites can be distinguished from ants by their thick waists and straight antennae. Ants have slender waists and elbowed antennae.
  x x     Look for morel mushrooms when lilacs bloom and the forest floor turns green.
  x       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.
    x x x Mole young are born in chambers deep underground.
      x x Honeybees are swarming. Notify a local beekeeper to find a new home for these beneficial insects.
        x Soaker hoses and drip irrigation systems help you save water and money.
        x Hummingbirds return from their winter home in Central America.
        x Wasp and hornet queens begin nesting.
April Pests and Problems


Frost is still possible this month. Do not uncover plants or plant tender plants too early. Little can be done to protect large trees and shrubs but you may be able to give some protection to small plants closer to the ground. Winter burn on broadleaf evergreen may also be noticeable at this time of year.
Click for larger image
Winter Injury: Frost Injury, Ice Damage
This breathable fabric draped around a pot shows one method of protecting tender plants when frost is predicted 
Click for larger image
Winter Injury: Desiccation or Winter Burn
Winter burn on tips of boxwood (Buxus); note undamaged interior leaves 
 

Carpenter bees may be seen buzzing around decks and other wooden structures. Although males appear aggressive when defending their territory they can not sting. Females do not defend their nests but can sting if handled.
Click for larger image
Carpenter Bees
Male carpenter bees (Hymenoptera), identifiable by the white spot between their mandibles, look and act aggressive but actually cannot sting. As with all bees only females have stingers. 
 
 

Apply crabgrass preventer by mid-April or by the time forsythia is blooming. If you decide to use a weed and feed product, do not use a fertilizer high in nitrogen.
Click for larger image
Crabgrass Control
Large crabgrass (Digitaria sanguinalis) in zoysia grass lawn (Zoysia japonica
 
 

Scout for and remove tent caterpillar webs. Treat now to help control lacebugs if they were a problem on azaleas or other plants last year.
Click for larger image
Eastern Tent Caterpillar
Eastern tent caterpillar (Lepidoptera) inside their web on crabapple (Malus
Click for larger image
Eastern Tent Caterpillar
Close-up of egg mass of eastern tent caterpillar (Lepidoptera) on flowering quince (Chaenomeles
Click for larger image
Lace Bugs
White flecking on upper leaf surface on azalea (Rhododendron) caused by feeding of lace bugs (Hemiptera); heavy infestation 

Observe indoor seedlings closely for signs of damping off. Treat if necessary.
Click for larger image
Damping-off
Damping-off of snapdragon seedlings (Antirrhinum) caused by Rhizoctonia sp. Note constriction of stems at the soil line. R. K. Jones, NCSU, Bugwood.org 
 
 

Harden-off seedlings before planting in open ground to reduce or prevent transplant shock.
 
 
 

Don’t plant tomatoes or other warm-season annuals such as petunias and vinca until the weather warms, usually in mid-to late May.
 
 
 

Fluctuations in temperature can result in damage to flower buds of plants such as hydrangeas and magnolias.
 
 
 

Remove mulch from roses in mid-April to limit damage from stem canker diseases.
 
 
 

Do not prune boxwood until all chance of a hard frost is past, usually in late April. In late April or early May, inspect for and treat boxwood leafminers as new leaves emerge.”
Click for larger image
Boxwood Leafminer
Blistered, puckered tissue on the underside of boxwood leaves (Buxus) due to boxwood leafminer (Diptera) 
 
 

In late April or early May, inspect for and treat holly leafminers as new leaves emerge.
Click for larger image
Holly Leafminer
Tunneling damage in holly (Ilex) leaf caused by holly leafminer, a fly maggot (Diptera) 
Click for larger image
Holly Leafminer
Holly leafminer maggot (Diptera) between layers of leaf tissue on inkberry holly (Ilex glabra
 

Collect and dispose of cedar-apple and cedar-hawthorn galls on junipers before the orange spore-producing structures emerge from the galls.
Click for larger image
Cedar-Apple Rust
Galls of cedar-apple rust on juniper (Juniperus
Click for larger image
Cedar-Hawthorn Rust
Cedar-hawthorn rust on hawthorn leaves and fruit (Crataegus
 

Scout for and control common spring insect pests such as aphids, spruce mites, and pine sawflies.
Click for larger image
Aphids - Outdoors
Aphids (Hemiptera) come in many colors; sometimes they blend into the background and are difficult to see; other times, they stand out, as do these red aphids 
Click for larger image
Spruce Spider mite
Spruce spider mite damage (Acari) on spruce (Picea
Click for larger image
Pine Sawflies
This pine sawfly larva (Hymenoptera) has eaten only the older needles of a Mugo pine (Pinus mugo) leaving new growth for next year's meal 

Weed whips can be deadly to plants, especially small trees when they girdle them by killing the bark at the base of the tree. Keep weed whips away from the base of trees and other plants.
Click for larger image
Mechanical Damage
Scars on tree trunk from use of a weed whip 
 
 

Resist the temptation to prune fruit trees including ornamental pears and oak trees now as they may be more subject to disease and insect damage at this time.
Click for larger image
Fireblight
Fireblight canker and twig dieback on crabapple (Malus
 
 

Cool-season grasses are best fertilized in fall. If you do apply fertilizer in spring, make sure it is low in nitrogen. Nitrogen applied in spring encourages excess growth, which is more susceptible to disease. Hold off until May to fertilize zoysia or other warm-season grasses.
 
 
 

Be on the look out for sycamore anthracnose.
Click for larger image
Sycamore Anthracnose
Sycamore anthracnose on sycamore leaf (Platanus); note that the spots are along the veins and angular in shape rather than round 
 
 

Be on the lookout for asparagus beetles.
 
 
 

Do not harvest and eat rhubarb that has been damaged by a late frost.