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Missouri Environment & Garden


Missouri Botanical Garden

April Gardening Calendar

Missouri Botanical Garden

Published: March 1, 2012


  • Weeks 1-4: 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.
  • Weeks 1-3: Fertilize established roses once new growth is 2 inches long. Use a balanced formulation. Begin spraying to control black spot disease.
  • Weeks 1-2: Examine shrubs for winter injury. Prune all dead and weakened wood.
  • Week 1: 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.


  • Weeks 1-4: Start mowing cool season grasses at recommended heights. For complete details, refer to University Extension Guide #6705, Cool Season Grasses.
  • Weeks 1-2: Topdress low spots and finish over seeding thin or bare patches.
  • Weeks 1-2: Aerate turf if thatch is heavy or if soil is compacted.
  • Weeks 1-2: Apply crabgrass preventers before April 15. Do not apply to areas that will be seeded.


  • Weeks 1-3: Finish transplanting broccoli, Brussels sprouts, cabbage, and cauliflower plants into the garden. High phosphorous fertilizers help get transplants off to a quick start.
  • Weeks 1-2: Plants started indoors should be hardened off outdoors in cold frames before being transplanted into the garden.
  • Weeks 1-2: Start cucumber, cantaloupe, summer squash, and watermelon seeds indoors in peat pots.
  • Weeks 1-2: Asparagus and rhubarb harvests begin.
  • Weeks 2-4: Try an early sowing of warm-season crops such as green beans, summer squash, sweet corn, New Zealand spinach and cucumbers.
  • Weeks 2-3: Thin out crowded seedlings from early plantings of cool season crops such as beets, carrots, lettuce, onions and radish.


  • Weeks 1-4: 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.
  • Weeks 1-2: 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.
  • Weeks 2-4: Protect bees and other pollinating insects. Do not spray insecticides on fruit trees that are blooming.
  • Weeks 3-4: Orange, jelly-like galls on cedar trees spread rust diseases to apples, crabapples and hawthorns.


  • Weeks 1-2: Look for morel mushrooms when lilacs bloom and the forest floor turns green.
  • Week 1: 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.
  • Week 4: Soaker hoses and drip irrigation systems help you save water and money.
  • Week 4: Hummingbirds return from their winter home in Central America.
  • Week 4: 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)

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REVISED: May 29, 2012