Always knowing the when to plant, prune, and harvest.
All you need is the right checklist.
What To Do In Your Vegetable Garden This May (Late Spring)
May is the month when the vegetable garden begins to look more and more like the summer garden we’ve been waiting for all winter.
Vegetable Gardening Tasks for May
- Harden off all homegrown vegetable seedlings before transplanting, bringing them in and out for a week before planting.
- Place cutworm collars around young transplants if cutworms are a problem where you live. Collars are easily made from cardboard strips. Cut strips of cardboard two inches wide by eight inches long, staple them into circles and place them around the plants. Press the collar about one inch into the soil. These collars will fence out the cutworms and protect the stems of the vegetable plants.
- Grow lettuce under shade cloth to slow bolting and extend your harvests into hotter weather.
- If slugs are a problem place a board over damp ground. Slugs will hide under it. Check each morning and destroy any slugs that have gathered on the underside of the board.
- Direct-sow herbs: dill, cilantro, chervil, fennel, and parsley and thin out seedlings.
- Keep asparagus harvested. Control asparagus beetles as needed by handpicking and destroying.
- Begin planting sweet corn when your soil is warm enough.
- Isolate sweet, super sweet, and popcorn varieties of corn to prevent crossing.
- Thin plantings of carrots and beets to avoid overcrowding. Thin them using a pair of scissors, to avoid disturbing the young roots.
- Control caterpillars on broccoli and cabbage plants by handpicking or use biological sprays such as B.t.
- Set out tomato, peppers, and eggplants once your soil warms up. They’ll do best when the soil has warmed to 60° (F). Place support stakes or structures alongside each plant at planting time.
- Keep soil moisture even to minimize blossom-end rot on your tomatoes. Contrary to popular belief, adding more calcium to your soil probably won’t fix the problem. Most garden soils have plenty of calcium. The lack of consistent (and proper amounts of) water makes the calcium unavailable to your plants.
- Plant sweet potatoes now.
- Place a stake by seeds of squash and cucumbers when planting in hills so you can locate the root zone – for watering the plants after the vines have run.
- Remove rhubarb seed stalks if they appear.
- Harvest rhubarb when it’s young.
- Watch for striped and spotted cucumber beetles now. Both may spread wilt and mosaic diseases to squash and cucumber plants.
- Set out Brussels sprouts starts this month for summer-to-fall harvest. Keep plants growing vigorously by keeping the soil evenly moist.
- Sow main-crop carrots in May. Sow successive crops at three-week intervals.
- Watering newly sown seeds and seedlings is very important. Normal growth depends upon an even supply of water. Check the garden daily to make sure the soil stays evenly moist. Put your finger in the soil; if it comes away just moist, the moisture level is good, if your finger comes away from the soil dry, water.
- Aphids will reappear this month. Knock them off plants with a stream of water. This works because aphids are soft-bodied insects and are physically torn apart by a blast from your hose.
- Set out basil seedlings when the danger of frost has passed. Set seedlings 12-15 inches apart and water well in the early stages until the plants are established.
- Take cuttings, 3 to 4 inches long, of pot marjoram, rosemary, sage, and thyme from last year’s growth.
- Divide and replant mint and thyme that has overgrown pots or have become straggly in the garden.
- Make succession sowings of salad crops–lettuces and spinach–to maintain a continuous harvest. Sow lettuce and spinach every two weeks until about eight weeks before maximum daytime temperatures are expected to average about 80°F.
- Cabbage loopers and imported cabbage worms are green worms. They leave large holes in the leaves of plants in the cabbage family. For control, caterpillars can be picked off by hand or sprayed with Bt (Bacillus thuringiensi).
- Monitor for slugs and snails. These pests thrive in moist, cool areas of the garden.
- Mulch your vegetable beds with straw.
Fruit Garden To-Dos for May
- Mulch blueberries.
- Don’t spray any fruits while in bloom. Refer to local Cooperative Extension publications for fruit spray schedules for your area.
- Prune unwanted shoots as they appear on fruit trees.
- Spread bird netting over trees and row crops, and fasten the seams well with clothespins or binder clips.
- Treat grape leaf skelotonizer. Kill the caterpillars by spraying the leaves, especially the undersides, with Bacillus thuringiensis. Check for new damage in 10 days; respray if needed.
- Fasten grape stems to training wires.
- Treat for powdery mildew on apples beginning when leaves are emerging (at 1/2 inch green)
- until June.
- Watch for insect pests in raspberries from mid-May thru early June.
- Continue to remove flowers from newly planted strawberries.
- Thin fruit on apples, peaches, pears, and plums when marble-size.
- Replace mulches removed last month.
- Prune suckers and water sprouts from trees, and weak shoots from brambles.
- Control Codling moth in apples and pears to reduce wormy fruit.