All the Gardening Tasks to Tackle in May

Credit: NikolayTsyu/Shutterstock

May is when all the work you’ve put into your yard over the years starts showing. Suddenly, what looked sparse and barren just five weeks ago is filled out with greenery and signs of life. May is a heavy work month in the garden, but if you put in the time and effort now, you’ll have a summer full of blooms and fruit. 

General garden maintenance

Watering systems may have taken a hit during winter storms, so now is the time to ensure that the controller is working, that none of your underwater pipes have burst, and that all your above-ground connections are intact. Go zone by zone and test each of your lines. If you use a hose bib setup, get it up and running, and then check it. It can still be raining in many parts of the country, but very soon you’ll need your irrigation in place. For plants growing in full sun, you want to aim for one to two inches of water a week by watering in the morning.  

Your established beds can benefit from a layer of compost, which will act as a general fertilizer, as well as create volume back in your beds if they’ve experienced erosion during the winter. Follow the compost with a layer of mulch. Spending this time spreading the compost and mulch will give you the opportunity to size up each part of your garden, so take notes as you go for which areas need weeding, are experiencing pests, or have plants that look like they might not have survived the winter. 

Shrubs, trees and vines

A number of shrubs go through blooming cycles in spring, like lilac and forsythia. Once they’ve bloomed, you can prune them back, and in some cases, like lilac, this may trigger a second bloom later in the season. In either case, it will take one fall task off your list and keep the garden looking tidier. 

This is a good time to plant new woody shrubs and trees—the weather is mild, and the ground should be soft from the rains. For your existing trees, make sure you feed them with a fertilizer that is appropriate for them this month. Your garden center can help identify which fertilizer is best for the trees you have. Each of these trees will be creating shoots this month, and you should prune them back as necessary to maintain the shape of the tree and to keep fruit to an amount the tree can reasonably support. Ensure you are only using clean pruners or loppers—carry diluted bleach or Lysol with you in a spray bottle while outside. 

Climbing perennial vines like clematis, roses and honeysuckle should be coming out of their slumber at this point, and you’ll want to ensure you’re supporting them by tying them loosely to their trellises as they climb. 

Annual flowers

Garden centers should be full of annuals at this point of the year, including petunias, lobelia, marigolds and begonias. Annuals are a bit more tender than perennials, so you want to wait until you are past the risk of freezing to plant. Annuals can fill an area with color in the space and time between perennials blooming, and are ideal for window boxes and planters, where it might be hard for annuals to survive the winter. Most hanging baskets have annuals for the same reason—they’re just too exposed for perennials or anything else to survive winter. You can plant your baskets now, but you might need to wait until it’s warm enough for them to come out; you want to focus on overnight temperatures and soil temperature to determine the right date. 

Perennial flowers

Most people will have tulips in bloom or just completed at this point—remember not to cut them down after bloom. Tulips need their leaves in order to come back next year, so let them compost in place. Once the foliage has yellowed, it’s ok to divide or move the bulbs. Once the tulip has bloomed, it’s a great time for a bulb fertilizer, so they’ll be strong next year. You can also plant summer bulbs like dahlias and cannas now, if the risk of frost is gone.

If you didn’t get new perennials planted in April, you can still do so now, or divide the perennials you have. The ground should be very workable now, and you may be noticing which plants are ready to be divided as you move about the garden. If you’d like them to bloom this summer, you’ll want to get this task done in May. As you plant, ensure you’re using slow release fertilizer in the ground where you plant. 

Your roses need a spring fertilizer and might need some shaping at this point or help attaching to the trellis. Look for signs of stress or pests and ensure you’re treating them with appropriate treatments. Your garden center can help. 

Vegetables

Many zones across the country will start putting vegetables in the ground sometime in May, depending on the soil temperature, overnight temperature and the risk of frost. Begin hardening off vegetables like tomatoes, pepper and eggplant as appropriate.

Perennial vegetables like asparagus and artichokes should be active now. Remember to harvest asparagus daily, taking only spears that are larger than your pinky. Once spears become thinner, it’s time to leave the plant alone for next year. Watch your artichoke plants for ants or aphid infestations, which may be sprayed off, but will return without further treatment like neem oil or nearby trap flowers like nasturtiums. Both asparagus beds and artichokes will benefit from a spring fertilizer. 

By mid to late May, almost all regions should be planting their warn weather crops. Tomatoes, eggplant and peppers, but also beans, corn, cucumber and everything else. Your beans and corn can be direct seeded, as can melon, pumpkin and both winter and summer squash, but using starts will give you a leg up for the summer.

If you planted potatoes in the spring, it’s likely time to hill up earth around the sprouts. 

Thin out your strawberry beds of runners. Strawberry plants can either focus their energy on producing these runners or on fruit, but aren’t very good at doing both. Each spring the beds much be thinned to create better and larger fruit. You can give away the runners or plant them elsewhere.

Pest control

Reduce snail and slug populations by putting out traps and going on regular evening hunts. Doing this now, as the rains cease, will greatly reduce problems later this summer. Hang pheromone traps in your fruit trees now, which will control pests this summer and protect your fruit.