- Fertilize established trees and shrubs in early May. Do not fertilize newly planted trees and shrubs until they start growing.
- At the beginning of the month be prepared to cover annuals and warm-season vegetables if frost is predicted.
- Remove spent flowers from spring blooming bulbs, allow foliage to die back naturally. Leaves absorb the energy from the sun, which is stored in the bulbs for next year, this will promote healthier plants for next spring.
- Depending on the temperature, you could plant summer blooming bulbs mid to late May (Dahlia, canna, calla lilies, freesia, gladiolus, caladium, begonia, gladiolus, etc.)
- Once the risk of frost is over, usually after mid-May, plant transplants of tomatoes, peppers, herbs and eggplants. Choose disease-resistant varieties. Provide support with stakes or cages and allow proper spacing.
- Plants seeds or transplant of cucumbers, watermelon, and squash. Train the vining vegetables to some type of support, fences, poles, wire cages or trellises.
- Prune out twigs and branches that have not leafed out, and consider removing plants that have been extensively damaged by the winter. Keep in mind that some plants such as butterfly bush and rose of Sharon leaf out late, it is good to wait and give them a chance to leaf out before you remove them.
- Apply 2 inches of mulch around plants in late May, keep mulch pulled away from plant crowns to prevent insect or disease problems.
- When the fall blooming plants, such as chrysanthemums, asters, phlox and sedum reach 6 inches tall, pinch off half an inch of the stems and continue pinching back shoots through mid-June.
- Prune spring-flowering shrubs right after they bloom, before next year’s buds are being formed.
- Water the garden deeply once a week. Frequent, shallow watering is not beneficial and will promote shallow roots. The rule of thumb is 1 to 1 1/2" of water a week. Take into consideration rain.
- Avoid wetting leaves when watering, this a good way to prevent leaf fungi. Except when watering tropical plants with large leaves, such as bananas, elephant ears, cannas, palms, etc.
- When planting garden containers mix a slow release fertilizer in the soil. The fertilizer is released each time the plant is watered.
- Core-aerate when lawn is actively growing.
- If you have problems with weeds on your lawn, apply post-emergence broadleaf weed control to actively growing weeds. Killing weeds before they set blooms is a great way of controlling weeds.
- Apply lawn fertilizer containing slow-release or controlled-release nitrogen. Apply about 1 pound of nitrogen per 1,000 square feet. Water the lawn after application.
- Towards the end of the month, move house plants outdoors to a shady area once the night temperatures are steady above 60° F.
Ana graduated with an Associate’s Degree in Ornamental Horticulture from the College of DuPage. She continued her studies in Horticulture through the outreach program at the University of Illinois. In 2014 Ana completed the Horticultural Therapy Certificate Program through the Chicago Botanical Garden.