What to Plant, Weed and Prune in May
If you’re a gardener in the Northern Hemisphere, the month of May is an excellent time to refresh your garden after its winter sleep. Don’t know where to start? Try some of these simple steps to prepare your garden for a smooth growing season ahead.
Whether you’ve been stockpiling packages of seeds or have trays of young seedlings waiting around, May is the perfect month for getting the majority of your plants in the ground.
1. Vegetables and Annuals
- At the beginning of May, start hardening off any seedlings and potted plants you’ve kept in the house. Put them outside during the day so they get used to direct sun and cooler temperatures. Always bring them back inside at night if the temperatures are below freezing.
- Young vegetable and ornamental annual seedlings can be planted out as soon as the risk of frost has passed in your area. This includes onion sets and seed potatoes.
- Sow cold-tolerant vegetable seeds directly in the soil in early May or late April. Examples are green peas, lettuce, mustard greens, kale, arugula, spinach and root vegetables like carrots, parsnips, beets and radishes.
- After your frost-free date later in May, you can direct seed warm season veggies like cucumbers, beans, squash, melons, pumpkins and herbs including basil, dill, parsley, marjoram and oregano.
- Direct-sow ornamental annual seeds after the risk of frost has passed. Annuals like alyssum, lobelia, poppies, sunflowers, cosmos, marigolds and nasturtiums all grow well from direct seeding.
2. Perennials, Shrubs and Trees
- Select what types and varieties you want in your yard, and pay close attention to the maximum size they will reach when mature. Trees and shrubs in particular can outgrow their space quickly if you’re not careful.
- If you’ve been storing any potted perennials inside, harden them off the same as annual seedlings.
- Prepare your planting site by digging a hole about twice as large as your pot. Mix some compost in around the edges and make sure the soil level comes up to the bottom of your plant’s pot. Remove the plant’s pot and brush your hand lightly against the outside of the root ball to loosen it, taking apart any circling roots. Place it in the prepared hole, fill in with soil, tamp down with your hand or foot, and water it in well. Cover the soil surface with mulch for better moisture retention.
- If you bought any bareroot perennials, shrubs or trees from mail-order catalogues, plant these as soon as they arrive in a similar way.
- May is also a good time to plant summer-flowering bulbs, such as lilies, dahlias, alliums, canna lilies and gladiolas. You can buy fresh bags of bulbs and plant them directly in the ground. Or plant out any non-hardy bulbs you’ve overwintered and stored from last year.
- Planting perennial vegetables are another option this time of year. Try experimenting with eatable plants such as asparagus, rhubarb, horseradish, or herbs like oregano, thyme, sage or lovage.
Unfortunately, the explosive May growth you see in your garden also applies to weeds. An important first step is to never let weeds go to seed. Deal with them as soon as they start. These are some of the worst types of weeds to watch out for and how to keep them under control.
- Weeds with tap roots. Some of the hardiest weeds fall into this category, including dandelions, thistles and docks. Their strength lies in the nutrients and energy stored in the tap root. Repeatedly digging up the tap roots by hand will weaken the weeds over time until they eventually die. You can also spray the plants individually with an organic herbicide or treatment such as vinegar, boiling water or a small flame thrower.
- Annual weeds. These often come up in large groups of fresh seedlings in May. They can be hand-weeded if there aren’t too many. Smothering is an option for larger areas. This involves covering the weeds with newspaper, cardboard or other organic mulch in a thick enough layer to block out all light reaching the ground. Keep the covering layer moist and leave it in place to decompose during the growing season. Plant what you want around it.
- Creepers. Weeds that spread through underground roots can be especially invasive, such as grasses and bindweed. Hand-dig any smaller patches that have started, taking care to remove shoots that have grown sideways. You can solarize an affected area by covering it with a heavy plastic sheet and leaving this in place for a few weeks until the weeds underneath have all died from the heat.
- Other Intruders. Keep an eye out for unwanted tree or shrub seedlings that might have drifted into your yard from invasive neighbors. You might also have to remove perennials you planted previously, but have since shown their ugly sides.
It’s best to prune trees and shrubs at the end of the dormant season just before they start to grow their first leaves. This is often in April or May, depending on your location and the individual plants. Keep these tips in mind as you plan your spring pruning.
- Early spring-flowering shrubs should be pruned immediately after flowering because the shrub will start to set flower buds for the next year. This includes shrubs like forsythia, lilacs, magnolias, ornamental cherries and apricots, and azaleas.
- Berry bushes like raspberries and blackberries should be pruned as early as possible to remove any old, non-productive branches. This will encourage new fruiting growth.
- Prune hedges as they start to grow in the spring and a second time in mid-summer to keep the growth even and compact.
- For multi-stemmed shrubs, such as forsythia or hazelnuts, you can remove one-third of the main stems in spring to control growth and improve the shape.
- If you haven’t already, make sure to cut the dead growth from last year off any herbaceous perennial plants. These include perennials like daisies or ornamental grasses that die down to the ground each year. You can also divide and move around any perennials that need it.
- Fruit trees are typically pruned during late winter or summer. Spring weather conditions can promote the spread of bacteria, so avoid pruning trees like apples, peaches, cherries or pears.
- Avoid pruning hardwood trees in May for the same reason, such as oaks, maples, walnuts or birch.
- You can prune off dead, diseased or insect-infested branches at any time of year.