May Tips & Tricks


• Apply slow release nitrogen fertilizer to bluegrass and tall fescue to promote summer growth if watering during the summer. Lower maintenance lawns skip this application. If there are broadleaf weeds you can spot treat with a spray or use a fertilizer that includes a weed killer. Rain or irrigation within 24 hours of application will reduce effectiveness of the weed killer but the fertilizer needs to be watered in. If you are using a product that has both fertilizer and weed killer, wait 24 hours after the application before watering in.
• Keep mower blades sharp for a healthier turf.
• Reduce thatch layers from zoysia by verticutting or core aerating
• Sod or sprig zoysia lawns to fill in bare areas
• Fertilize zoysia lawns with high nitrogen to promote green up and summer growth
• Mow zoysia at 1 to 2 inches tall
• Mow bluegrass and tall fescue at 3 inches
• Withhold early summer watering until needed to promote more drought tolerant lawns


• Remember to fertilize roses with rose formulated fertilizer. Use fish emulsion occasionally to keep the blossoms vibrant with color. Use sparingly because it smells like a dead fish! When used in early May, it will help activate the micro-organisms in the soil so the plant can uptake the soil nutrients. It is great stuff and it will not burn if you accidently use too much.
• The easiest way to fertilize is to use All-In-One Rose Food (Bayer Brand) containing systemic insecticide (only apply every 6 weeks – mark your calendar for the next application). You mix 2 Tablespoons to 1 Quart of water and pour mixture around each bush. Helps prevent mites, leafminers, thrips, aphids, whiteflies and keeps the plant healthy so the leaves are deep colored. It also contains a fungicide, this helps to keep those lower leaves from getting diseased as rain splashes the fungus up on the lower leaves and they soon turn yellow and fall off. It is important to have leaves for the photosynthesis process!
• Hosta problems – the only problem hostas really have is with slugs chewing holes in the leaves at night. Use a product called “Sluggo” or a bait for slugs and sprinkle the pellets under the hosta foliage as soon as it is filled out (which could be early May). It must be re-applied monthly or after a hard rain.

Vegetables and Fruits

• Plant tomato, pepper, and eggplant transplants in early May
• Seed sweet corn, cucumbers, squash, beans, and other warm season vegetables
• Lightly cultivate soil with a hoe to control weed growth
• Mound soil around potato plants to encourage tuber formation
• Harvest fresh asparagus until the spear size decreases
• Remove rhubarb seed stalks to encourage leaf growth
• Plant kitchen herbs for summer use in dishes or food preservation
• Treat fruit trees with needed pesticides to control insects and disease
• Thin heavy fruit set on apples to increase fruit size and next year’s crop


Geraniums are by far one of the brightest annuals there are.
Geraniums are by far one of the brightest annuals there are.

• Plant annual flowers for summer color
• Continue to plant and divide perennials
• Mulch perennial and annual gardens for weed control and moisture retention
• Do not remove foliage from spring bulbs until it dies down naturally, this develops stronger blooms for next year
• Plant container gardens and hanging baskets using a good quality potting mix
• Fertilize perennials now that they are actively growing. Use a balanced fertilizer (Osmocote is slow-release and will last 4 months, through the growing season) to maintain good healthly foliage and flowering. A healthy plant is less likely to be attacked by insects or disease.
• It is safe to plant Summer Bulbs now: Cannas, Dahlias, Glads, Elephant Ear, Oriental Lily. Remember to dig up the tender bulbs in the fall (Cannas, Dahlias, Glads & Elephant Ear).
• Mum Care – trim or pinch every 3-4 weeks to stimulate larger blooms and not such a large bush! Trim back Mums, Asters, tall Russian Sage & tall Sedum also so they do not get leggy and split and fall over when they bloom. Stop trimming after July 4 so the blooms can mature and produce a show for fall.
• Keep a garden journal for permanent reference
• Note: Coreopsis, Plumbago & Hardy Hibiscus are slow to come out of the ground so don’t worry if you don’t see new growth until June. They bloom in July until frost and are worth waiting for!

Trees and Shrubs

• Things should be starting to bloom! Late April to Early May: Time to fertilize all trees & shrubs with Tree & Shrub Fertilizer (Ferti-lome brand) or Osmocote (slow-release fertilizer). Depending on the size of the shrub ½ cup to 1 cup per shrub and water it in well. Viburnum, Sandcherry, White Blooming Spirea, Forsythia, Dogwood Shrubs, Mockorange, Sweetspire, Beautybush, Deuztia, Ninebark, and Lilac will bloom in late April. After these spring-blooming shrubs have bloomed and the bloom has dried up, trim and shape. A good rule of the thumb is to trim a shrub after it is done blooming.
• Hint: Spray for Ash/Lilac Borer when Vanhoutte Spirea is in full bloom (about May 1). Permethrin is labeled for control of this pest. Only spray if you have had problems with this pest in the past or you see holes in the trunk of Lilac shrubs or Ash trees.
• Hint: Spray evergreens for bagworms (use a product that contains BT) when the Catalpa trees are blooming. This should be just after Memorial Day. The best time to kill them is when they first hatch and they are tiny worms. Only spray if you have problems.
• Fertilize with acidic fertilizer once a month: Azaelas, Rhododendrons, Holly, Hydrangeas.
• Hint: Eastern tent caterpillars eggs typically hatch when Magnolia x soulangiana is in full flower. Watch for this pest and only spray if you have problems.
• Plant new trees and shrubs
• Mulch around young trees and shrubs to conserve moisture and control weed growth
• Water young ornamentals as needed
• Remove tree wraps for summer growth
• Remove tree stakes that have been in place more than one growing season
• Fertilize trees to help increase growth rates
• Caution, use line trimmers around trees and shrubs so as not to damage tender bark


• Now is the time to prune Mugo Pine or Globe Blue Spruce. Simply cut the new growth, referred to as “candles”, in half. This will keep the plant dwarf size and not get large in a few years. Treat for bagworms if they have bags hanging on them.
• Prune spring flowering shrubs after bloom to shape plant and encourage flowers next year
• Suckers on Trees – remove sucker growth from the base of trees. Spray with “Sucker Inhibitor” to discourage sucker growth. This is common on fruit trees and crabapples.


• Move plants outdoors for summer by gradually increasing the exposure to sunlight
• Fertilize plants to promote summer development
• Rotate plants to develop a well-rounded plant
• Wash dusty leaves in the shower under room temperature water
• Four to six inch cuttings are a great way to start new plants, root in potting mix under low light
• Repot plants into a one inch larger pot
• Check for insects

This information is brought to you from Nadine Champlin, Designer, Grimms Gardens; and Johnson County K-State Research and Extension.

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