Ornamentals, Trees, Shrubs
Most bedding plants, summer flowering bulbs, such as gladiolus and dahlias, and annual flower seeds can be planted after danger of frost is past (around mid-April).
Let spring flowering bulb foliage remain as long as possible before removing. As long as the foliage is green it is feeding the bulbs for next years growth..
Remove any winter-damaged branches or plants that have not begun to grow. Prune spring blooming shrubs after blooming is complete, but prune only if you have a reason to do so. See our pruning section in the trees and shrub general information section.
Watch for Cedar-Apple rust. When the orange jelly galls have formed on junipers following a rain, begin treating apple and crabapple trees with a fungicide. Nearby native cedars make control difficult. See OSU Pub. 7611 – Cedar-Apple Rust.
Gather and review OSU information for control of Pine needle diseases. See OSU Pub. 7618 – Common Diseases of Conifers in Oklahoma.
Fire blight is a bacterial disease common in trees and shrubs in the rose family this time of year. Most commonly involved are pears, apples, crabapples, pyricantha and others. For information as to control, see OSU information sheet here..
Powdery mildew (white coating on leaves) may occur during wet seasons on crapemyrtle, lilac, roses and many other plants. Early detection and treatment are necessary to remedy the problem. See OSU Pub. 7617 – Powdery Mildews of Ornamentals & Fruit Shade & Nut Trees.
Turfgrass See also — Oklahoma Turfgrasses-Characteristics/Maintenance
Mow cool season grasses at 2 1/2 to 3 1/2 inches high, warm season 1 1/2 to 2 inches. Mowing should be frequent enough to remove not more than one-third of the leaf blade per cutting.
Water mature grass to wet soil 4-6 inches deep when footprint impressions remain after walking over lawn.
Fertilize warm season grasses on quick release program with one pound of nitrogen (only) per 1000 square feet. Fertilize warm season grasses on the slow release program with 1 2/3 pounds of slow release nitrogen per 1000 square feet.
Start vegetative planting of warm season lawns in late month. Sod or sprig as appropriate for the grass variety desired. See OSU Pub. 6419 – Establishing a Lawn in Oklahoma.
Damage from Spring Dead Spot(SDS) becomes visible in Bermudagrass this month. SDS can be confused with winter kill in Bermuda.For help in diabnosis and control, see OSU Pub. 7665 – Managing Spring Dead Spot Disease of Bermudagrass in Oklahoma.
Watch for grub damage in lawns. See OSU Pub. 7306 – Ornamental and Lawn Pest Control for control.
Make preparations to set out tomato plants when the soil temperature is greater than 60 degrees, usually the last of the month or early May. Don’t rush it, be aware of a late freeze. See OSU Pub. 6012 – Growing Tomatoes in the Home Garden. Also see our tomato section on this web site.
Please read the label when using pesticides. Verify the use of the chemical for that particular plant. Also note the “days to harvest” waiting period before the vegetable can be harvested and consummed.
Be alert for both insect pests and predators. Hand pick if possible. Only use a pesticide if there are too few predators to be effective.