MAY
FIRST WEEK
- Blackspot infection on roses occurs primarily during wet weather in May and June. Fungicide sprays during this time are essential for roses susceptible to blackspot. For highly susceptible cultivars, begin applying fungicides as leaves expand. (BP-139) (HO-128) (Link to Purdue PPDL)
- Prune spring-flowering trees and shrubs after the blossoms fall. Do not leave stubs and do not prune flush. Make proper pruning cuts next to the branch collars. (HO-4)
- Treat honeylocust trees for honeylocust plant bug only if the population grows to at least one bug per compound leaf. Avoiding a spray now may reduce chances of a mite infestation later. (Link to Purdue Entomology) (Link to PA)
- Remove faded blooms on flowers through the season to keep them attractive and/or encourage more flower development. (HO-61) (HO-99)
- Wait until the soil temperature is at least 50 degrees F before planting sweet corn. "Extra sweet" varieties prefer soil temperatures of 60 degrees F or warmer. (HO-98)
- Remove dead or dying birch trees and branches before bronze birch borer adults emerge. This will help reduce borer populations in the area. (E-50)
- Systemic soil insecticides containing dinotefuran kill armored scales and soft scales. Apply to the soil according to the label no earlier than 3 weeks before crawler emergence. (E-29)
SECOND WEEK
- The average frost-free date for Marion County is May 10 (light frost, average last 36 degree temperature). Plant tomatoes when danger of frost is past. You can plant earlier if you cover the plants when frosts are forecast. (HO-26) (Indpls Airport Freeze Probability Data 1971-2000)
- Continue planting trees and shrubs through the end of the month. (HO-100)
- Plant snap beans. For a continuous supply, make a planting every 2 to 4 weeks until August 1. (HO-175)
- Plant warm season annual flowers after danger of frost. (HO-80) (HO-99)
- Maintain good weed control in the strawberry bed through the season by hoeing and cultivating. This will result in additional production next year. (HO-46)
- Read sweet corn seed packages carefully before planting. Some extra sweet cultivars must be isolated from other sweet corn by distance or planting date to prevent cross-pollination. (HO-98) (Link to IL)
THIRD WEEK
- Fertilize the lawn in mid- to late May with a slow release high nitrogen fertilizer if no fertilizer was applied in April. Most of your lawn fertilizer should be applied in the fall.(AY-22)
- Plant cucumbers and related crops when soil temperatures warm to 60 degrees F. To prevent bacterial wilt disease, apply an insecticide if spotted or striped cucumber beetles are detected. (HO-8) (E-30)
- Spray white birch trees between mid-May and mid-June to control bronze birch borers. A soil drench of a systemic insecticide can also be used. (E-50)
- Finish transplanting new asparagus crowns this month. (HO-96)
- Watch for red thread disease in slow growing lawns. A fertilizer application can minimize red thread infections. (BP-104)
- Peppers do not grow well in cold, wet soil so plant them 1-2 weeks after tomatoes. (Link to IL)
FOURTH WEEK
- Most house plants can be moved to their summer home outside as soon as night temperatures stay above 55 degrees F. (HO-39)
- Leaf galls are common on oak trees. No control is necessary for the health of the plant. (E-56)
- Check euonymus shrubs and ground covers for tiny crawlers of the euonymus scale insect. If present, treat with a summer oil or other labeled insecticide. (E-29)
- Transplant slips of sweet potato plants to the garden. (HO-136)
- Canada geese can be a nuisance around suburban ponds. Do not make the problem worse by feeding them. (FNR-FAQ-8)
- If you enjoy cooking or garnishing with flowers, plant an edible flower garden. However, plan carefully as some flowers are toxic. (Link to Purdue News) (Link to MN) (Link to NC) (Link to IA) (Link to CO) (Link to NE) (Link to ATTRA)
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