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Front Range Gardening Tips for the Fourth Week of May

Tips & News

• The lilacs were beautiful this year and the blossoms seemed to survive our May snowstorm. Once they have finished blooming, it’s time to prune before next year’s buds have formed. Remove the flower stem to prevent it from going to seed. You can also prune out any dead, damaged or diseased branches. To rejuvenate the whole shrub, remove up to 1/3 of the larger branches for the next 3 years. Trim these branches back to the ground.
• Bacillus thuringiensis, Bt, is a naturally occurring bacterium common to soils around the world. Its insecticidal properties were discovered in 1911. The caterpillars on your cabbage and broccoli plants are usually the cabbage worm and can be controlled with Bt (Kurstaki strain). This strain of Bt is also effective on tomato and tobacco hornworm. San Diego strain (Trident, Foil) can be used to kill Colorado potato beetle and elm leaf beetle. Bt rapidly disintegrates in sunlight and should be reapplied weekly if worms are present. Bt is essentially non-toxic to people, pets and wildlife. Read and follow the directions on the container when applying any insecticide.
• Cool season grasses like Kentucky blue grass and turf-type tall fescue need about 1” of water (rain and irrigation) a week during May and June. Pop-up sprayer heads will deliver about 1” — 2.5” of water per hour. Rotor heads only deliver ¼” — ¾” of water per hour, so zones with rotor heads will need to run longer to deliver the same amount of water.
• Tomato seedlings with 5-7 leaves are ready to transplant into the garden. They will benefit from deep planting with only a few leaves above ground. Lay the plant in a shallow trench, carefully bending the stem so only the top of the plant is out of the ground. Remove any of the leaves below soil level and fill in the trench. New roots will sprout along the stem.

<Tips & News written by Mitzi Davis, Colorado State University Extension Master Gardener in Larimer County>