Things to do in your garden in May.
Taken from the Ontario Master Gardener Calendar
by John Hethrington, Master Gardener Emeritus
Past President, Master Gardeners of Ontario
Please contact John for more information!
May Garden Tips: There’s lots to do in your garden In May, now that Spring is finally here!
- If not done already, clean up winter debris in the garden as soon as the soil is dry enough to work. The little insects that wintered in your garden, that you have been protecting, will have flown away. Cut off dead plant stalks. Rake the leaves etc. and put them on your compost pile.
- Dig in manure and/or compost around perennials and shrubs and weed well. An extra hour weeding now, will save 3 days later in the summer!
- Use a string line and cut sharp, straight edges for your beds. For curved edges, run hot water through a hose to soften it up and lay out a smooth curve. Watch you don’t chop the hose!
- Take coloured pictures of your spring bulbs in each of your gardens so you will know where there are any gaps and where existing bulbs are, when you order more bulbs to plant in the fall. Save the pictures in a safe place.
- Plan now to plant lots of early blooming bulbs like snowdrops and crocus in the fall at places close to where you come in and out of the house. It’s nice to be greeted by early signs of spring.
- Add 3 to 4 inches of mulch to flowerbeds and shrubs to conserve moisture and discourage weeds. Shredded cedar bark is best, but expensive. Try 13/Forty Landscape Supply who have 3 types of mulch: Cedar, Pine, Black and Utility. It’s the cheap stuff I use.
- Don’t walk on or roll lawns that are still wet and full of water. If you can see your footprint, stay OFF the lawn. You will compact the soil.
- If your lawn is already compacted, rent an aerator which will dig out small plugs. Let the plugs dry and rake them back into the lawn as a top dressing. Add grass seed to bare patches.
- When dry, rake lawns vigorously to remove dead grass and thatch.
- Spread weed-free topsoil on thin patches in your lawn. Apply grass seed, roll and water with a mist setting. Keep seeded areas moist, but don’t flood.
- If you find moss in your lawn, the soil is too acidic. Apply dolomite lime before a rain. You may need a second application.
- If you have pots or planters that are very big or deep, put some empty plastic water bottles with lids in the bottom of the pot to take up the space the roots will never get to. It makes the planter or pot lighter and easier to move.
- Prepare containers and pots for planting. Fill with a mixture of compost and potting soil. Add peat moss, or better still, coconut coir to retain the moisture.
- Place pots with a selection of culinary herbs close to the kitchen door for easy access.
- Harden off seedlings for at least a week before planting outside. Google the last frost date for your area (June 1 in the Blue Mountains) and allow at least 1 week more before planting tender transplants such as annuals and tomatoes.
- Walk around your garden and look for perennials that have grown and should be divided, are in the wrong place, or you don’t like anymore. Pot them up for spring plant sales at least 3 weeks before the sale. Add compost, not garden soil to the pots. To be really fancy, add a little bone meal to the pot before you put in the plant. Add plant labels with the name (Botanical and/or common), colour, sun exposure, height, bloom time, etc. Water well and keep in the shade.
- If you dig, pot-up and donate 15 or more perennials to the St. George’s Church annual Plant Sale, you will receive an Income Tax Donation Receipt for the price your plants sell for. Register as a donor online at www.stg.plantsale.com. Bring them to the church Wednesday, May 9 AM to 3 PM. It’s a win-win for everyone.
- The giant annual St. George’s Plant Sale is Sat May 24, 2025 on the church grounds in Clarksburg. It starts at 8 am. Come early for best selection.
- Plant beans now directly into the garden, as they germinate quickly and will grow as long as the soil is warm. Maybe mid-May this year.
- Install peony rings before the plants start to grow.
- Monitor for the presence of slugs, cutworms, earwigs and tent caterpillars. The best solution is to pick them off.
- Control weeds in the lawn by hand pulling. Use nematodes to control grubs, which eat the grass roots, leading to brown patches in the lawn in summer.
- Prune roses according to type.
- Deadhead (cut the blooms off) tulips, daffodils and other spring bulbs but do not cut or pull out the leaves until they are brown, shriveled and decayed. The green leaves are needed to nourish the bulbs for next year’s bloom.
- If you have any fritillaria or Asian lilies, now is the time to watch for the red lily beetle (adult, larva and eggs). It seems that removal by hand is the best and only way to reduce this problem. At least, day lilies are beetle free.
- And finally, another call-out to students who like to work in the garden. There are lots of jobs, after school and all summer long. Contact John Hethrington at casacarolejohn@gmail.com
John Hethrington,
Master Gardener Emeritus,
Past President, Master Gardeners of Ontario
Beaver Valley Probus Club