Green Industry Resources
Hort Update- Seasonal Information for the Green Industry
April Garden Activities
Protect honeybees. Use caution when applying insecticides to flowering plants.
- Plant cole crops, lettuce, onions, spinach, and parsnips as soon as the ground is dry and workable.
Plant carrots in early to mid April.
- Plant successive crops of cool season vegetables.
- Plant dormant strawberry and asparagus crowns.
- April 1-30, aerify Kentucky bluegrass and tall fescue lawns that are in high traffic areas and/or on compacted soil to alleviate compaction, improve rooting, and increase irrigation efficiency. Power rake or aerate Kentucky bluegrass lawns if the thatch layer exceeds 0.5 inches. Apply leafspot fungicide to common Kentucky bluegrass lawns after power raking. Thatch is seldom a problem on tall fescue lawns.
- Overseed thin Kentucky bluegrass lawns from April 1-30 with improved cultivars at .75 to 1.0 lb. seed per 1,000 sq.ft. Spring overseeding can be accompanied by an application of siduron to prevent crabgrass competition.
- April 15 to June 15, overseed thin tall fescue lawns with improved turf-type cultivars at 4-6 lbs. per 1,000 sq.ft. When seeding, apply a starter fertilizer at 1 lb. N/1,000 sq.ft. Spring overseeding can be accompanied by an application of siduron to prevent crabgrass competition.
- April 10 to June 15, control leafspot on common Kentucky Bluegrass lawns. Apply according to label directions. Diseases are seldom a problem on tall fescue lawns. Leafspot susceptibility is often related to spring fertilization (April & May) and the use of fast release fertilizers.
- Earthworms move close to the soil surface in spring and their activity often creates a rough, uneven soil surface. Earthworms are beneficial, increasing air and water movement in soil and increasing thatch decomposition. There are no pesticides labeled for earthworm control. Although some pesticides and fertilizers are known to have an impact on earthworms, none can be recommended as controls. Core aerifying, power raking and verticutting will break down some of the castings and reduce bumpiness. Use of a heavy roller is not recommended due to creation of soil compaction.
- Water Kentucky bluegrass lawns as needed to prevent wilting and drouight, about 1.0 inches of water are needed per week in spring and fall. Deep water every two to three days, but avoid daily, light watering. Water tall fescue has a very deep root system which helps it survive prolonged dry periods. With timely rains in central and eastern Nebraska it may not required any supplemental irrigation in spring and fall.
- Mow lawn at 2.0 inches. Mowing frequency should be dictated by growth rate. Never remove more than 1/3 of the turf's height at any mowing. Alternative and preferrred- throughout the growing season maintain Kentucky Bluegrass lawns at 2.5-3.5 inch height and return clippings to promote rooting and stress tolerance.
- Make your first application of pre-emergence herbicides to control warm-season annual grassy weeds, like crabgrass and foxtail, between April 20-May 5. Repeat as needed based on the residual strength of the herbicide used.
- Watch for "cool season" spruce spider mite damage on spruce, juniper and pine now through May. Tap a suspect branch over a white piece of paper to spot the mites. If mites are a problem make two applications of insecticide at 7-10 day intervals for control. Control spruce spider mite on with a dorman oil/ horticultural oil application on affected spruce, juniper and pine. (Oil will remove the blue needle color of blue spruce.)
- In the dormant season just before bud break, make a dormant oil/horticultural oil application on white, Scotch and Austrian pine to control pine bark adelgid.
- Watch for popcorn-like masses of dried sap at the base of branches or branch breakage caused by tunneling of Zimmerman pine moth in Austrian, Scotch and Pondersona pine. Apply an insecticide to the trunk and major branches of affected trees. Use the insecticide rate for borers and repeat the second week of August.
- Watch for pine and spruce sawflies on conifers now through the end of April.
- Spray for honeysuckle aphids when buds begin to open.
- Fertilize established asparagus and rhubarb plants.
- April 20 to May 10, fertilize Kentucky bluegrass and tall fescue with 1 lb. of actual nitrogen per 1,000 sq.ft. using slow release fertilizer products. Apply preemergence herbicide for crabgrass, goosegrass and foxtail control.
- As early spring strawberry flowers begin to bloom, remove the row covers or mulch from existing plantings to allow for pollination, but recover the plants at night when frost is predicted. Be sure to remove only enough mulch to expose the leaves. Place this excess mulch in the walkways between the plant rows. Partial removal of the mulch allows for plant development but delays blooming by keeping the soil cooler and slowing plant growth.
- After forsythia and flowering quince blooms have faded, prune plants as needed.
- Apply first fungicide application on apples and crabapples for control of cedar-apple rust, beginning at bud break; plan to make 3 or 4 additional fungicide applications at 7-10 day intervals.
- Apply first fungicide application on apples and crabapples for apple scab from pre-bloom through the rainy periods of the spring growing season at 7-14 day intervals; plan to make five or more applications.
- Apply first streptomycin spray at the pink bud stage on apples, crabapples and pears for fireblight; repeat applications every 5-7 days until petal drop.
- At bud break make the first fungicide application to ash trees to prevent ash rust; repeat applications 2 or 3 times at 10-14 day intervals.
- At bud break make the first fungicide application for anthracnose, if necessary on sycamore, ash, maple, oak and walnut; repeat applications 2-3 times at 7-14 day intervals. (Anthracnose damage is seldom serious enough to warrant control.)
- First application of copper fungicide on long needle pines, such as Austrian and Ponderosa pine, to control Sphaeropsis tip blight.
- Watch for grape flea beetles damaging expanding grape buds. Spray if necessary.
- Begin dividing fall-blooming perennials, such as chrysanthemums and asters, as soon as new growth begins.
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