May in the Garden

May in the Garden

While April is often cool and rainy here in the Pacific Northwest, by the time May rolls around, it starts to really feel like spring — even if the weather can still be a bit unpredictable. Portland gardeners are no strangers to making a mad dash out between rain clouds to admire our flowers, pop in a few perennials, or pull a weed or two. There’s simply too much going on to stop for the weather around here! As the days continue to warm and the skies clear, the gardening season only continues to ramp up as more and more plants explode into flower and leaf out in a vibrant display.

Breaking Out the Shovel

If you’re looking to add color — and pollinator value — to your garden, there’s no time like the present to plant annuals, perennials, shrubs, and trees. Although we enjoy months of beautiful planting weather in the Pacific Northwest, spring is one of our favorite times to plant because the rains are here to help us with the task of watering while our plants get established.

As you seek to fill any fill any visual “holes” you may notice in your garden beds, we encourage you to consider what plants might fill any temporal gaps in your garden’s bloom time, as well. Missing something flowering in the fall? Consider adding asters! Need a pop of color for that mid-summer lull? A few echinaceas or agastaches might just do the trick! Plus, when you plant a combination of plants that flower year-round, you can increase the pollen and nectar available to native insect pollinators and hummingbirds at critical points in the year, which is a worthy pursuit if you ask us.

In this month when we celebrate Mother’s Day, graduations, and more, many gardeners are looking for quick and easy ways to brighten up their patio, deck, or front porch before company arrives, and hanging baskets and container gardens are where it’s at! In May, there are even more options available to gardeners as warm-weather annuals like impatiens, petunias, geraniums, coleus, heliotrope, fuchsias, and cuphea expand the palette of colors and textures available for gardeners to play with. And they aren’t limited to use in containers! By mid-May, it is time to plant for summer color with plants such as gladioli, begonias, and dahlias. While other summer favorites like zinnias may take a bit more waiting until warmer temperatures arrive at the end of the month, blink twice and it will be here.

Kitchen Gardening

Pass the peas, please! Vegetable gardening season is now officially upon us, although some of the earliest crops of the year — like the snow peas we planted back in March — are very nearly at the point of harvest already. Even so, we’re already jumping forward to the bounty of summer, when the veggies, fruits, and herbs we set out in the coming days and weeks will be ripe for the picking.

We can often plant tomatoes and other warm season crops in May, but keep in mind that things may still be a bit cool for warm-season crops towards the beginning of the month. The minimum sustained soil temperature for planting tomatoes, melons, and squash starts in the ground is 50°F; however, you can get away with planting such crops during cooler weather if you choose varieties that have been grafted onto a hardier root stock. We offer grafted tomatoes, cucumbers, peppers and melons that offer increased disease resistance, earlier planting and harvest times, and 30 to 50% higher yields! Our Kitchen Garden staff is happy to show off our selection of these amazing grafted varieties.

We highly recommend using E.B. Stone Tomato and Vegetable Food, as well as a product like Bonide Rot-Stop in order to prevent blossom end-rot and encourage the growth of healthy tomato plants.


May is also an excellent time to prune any rhodies, azaleas, and camellias that you need to keep on the smaller side. Ideally, you want to make your selective cuts just as the blooms on these shrubs fade in order to give them as much time to sprout new growth and set buds for next year.

If you haven’t pruned your roses yet, we get it; sometimes life just gets away from us! It’s not necessarily too late to do so, but know that you will delay your plants’ bloom time the later in the season you prune. If you have thick growth that limits air flow or an excess of dead wood and crossing branches, it’s a good idea to bite the bullet and do it now for the health of the plant. (If you’re starting with a new rose from Cornell Farm, we’ve already done this year’s pruning for you so that you can enjoy those beautiful, fragrant summer bouquets without breaking out the loppers!)

It’s always a good idea to give your new plants a bit of a boost from an organic fertilizer like E.B. Stone Sure Start to help them as they leaf out, flower, and put on new growth. For existing plants, you can just sprinkle a bit of fertilizer around the plants’ drip line and water everything in. Watering deeply and feeding plants before the heat of summer gives them a stronger position to withstand stress — like a runner preparing for a marathon. This is especially true for rhododendrons and azaleas; the dreaded Azalea Lace Bug targets plants stressed by summer sun and drought.

Preventing Pests

Speaking of bugs, while you always want to be on the lookout for signs of insect damage, May is a critical month for pest and weed control. Your future self will thank you for keeping an eye out for emerging pest problems and staying on top of weeds while our clay soils are still soft enough to easily pry them up. Whenever possible, we recommend taking physical measures to deal with weeds and pests rather than pursuing chemical solutions, but here’s a few pests to be on the lookout for, and what you can do about them if you can’t control them by hand:

  • Cabbage Worms: Those dainty white moths fluttering around your brassicas may be cute, but they lay eggs that hatch into ravenous little caterpillars. To treat affected plants, apart from picking off the worms yourself, you can spray BT or Spinosad. These are both forms of beneficial bacteria that paralyze the insects, but neither is absorbed by the plant or poses any threat to humans or pets.
  • Cutworms: Holes in the middle of leaves or plants exhibiting wilted tops could be due to cutworms. If you notice young plants sawed off at the soil line, inspect the surrounding ground  for tiny, pellet-shaped black droppings. Sluggo Plus is a good option to deal with these pests, but be careful not to let your pets ingest it, as it contains additional ingredients that basic Sluggo doesn’t.
  • Slugs and Snails: These common garden visitors leave a telltale slime trail — not to mention foliar damage on the edges of leaves — in their wake. They can be safely treated with basic Sluggo, which isn’t harmful to people or pets if used as recommended. 
  • Aphids: These tiny brown, black, yellow or — most commonly — green, soft-bodied insects show up on tender new growth and flower buds to suck the sap from plants. They usually occur in colonies as they are born pregnant and can reproduce within hours. It’s best to catch the first few, as heavily infested leaves can wilt or turn yellow upon losing too much sap. You can deal with aphids by dislodging them with a strong stream from the watering hose, introducing beneficial insects like ladybugs, squishing them by hand, or spraying with Captain Jack’s Dead Bug Brew as a last resort.
  • Spittlebugs: If you notice a glob of spittle on the stems of your plants with a tiny green bug inside, don’t fret! These little guys generally aren’t harmful to your plants unless there are many on one plant, which is rare. They are fun to show young children by taking one up on your finger and examining their large eyes — before gently letting them go, of course!

Nature is full of wonders great and small, so be sure to find time to get outside and do a little exploring of your very own this May.