Gardening by Month in the PNW-May

I’m here again, ready to share my “gardening by month” tips for May. These are based on zone 8, with an average last frost date of April 18th. If you live in a different zone, make sure to confirm the frost dates in your area, and plan accordingly.

May is warming up and raining less, which makes it so much more pleasant to work in the yard. Transplanting my seed starts, that are currently growing in the greenhouse, into the garden will be the most important task in the month of May. This is the PNW’s prime time for planting annuals.

GARDEN PLANTING IN THE MONTH OF MAY

If you have started annuals from seed, be sure to start hardening them off this month. Start this process by leaving them outside for an hour the first day, and then extend the time their outside each day, for about a week. This will help to acclimate your fragile plants to the outdoors. To read more about acclimating your seedlings, visit my blog post on Seed Starting Basics.

Once your seedlings are hardened off, transplant them into the garden beds. There are certain annuals that need to be pinched back when they have reached 4-6 inches high. This helps to promote bushier growth. Some of these annuals include zinnias, petunias, salvia, sweet peas and dahlias.

I will be transplanting the following annual varieties into the garden this month from the greenhouse: Cosmos, Zinnias, Marigolds, Strawflowers, Snapdragons, Bee Balm, Orach, Stock, Larkspur, Nasturtium, Dill, Phlox, Sweet Peas and Globe Amaranth.

If at all possible, transplant when it is a calm and cloudy day. Strong sun and wind are hard on transplants and can cause much stress on the plant. Mulching can also help with the process, since it lowers the rate at which water evaporates from the soil, and controls the soil temperature.

Plant seeds or starts of warm-season crops like peas, beans, sweet corn, cucumbers, eggplants, melon, pumpkins and summer squash in the garden this month. Carrots, lettuce, potatoes, tomatoes and peppers can also be planted in May.

As for tomatoes, you can move hardened-off plants outside, once the nighttime temperatures hit 50 degrees. If you will be transplanting starts, smaller 4 inch plants are recommended, rather than a gallon sized plant. The smaller plants establish and transplant better than the larger ones. For more information on tomatoes, Houzz.com has a great blog post, with great information.

MONTHLY GARDEN MAINTENANCE

WATERING

Check your irrigation system, if you have one, to make sure it is in good working order. Test and run each system manually, for at least five minutes, to make sure there are no leaks or repairs that may be needed.

Newly planted trees and shrubs should be watered deeply, every week or two until the fall rain begins.

Make sure your flowers and shrubs get an inch of water each week.

CUTTING BACK SPENT FLOWERS

Remove any wilting seed heads from rhododendrons and azaleas once they have bloomed, in order to provide more energy to those plants. Removing spent flowers from camellias and roses will help to lengthen the flowering time for each plant.

Remove spent flowers from spring bulbs, such as tulips and daffodils. This will help preserve the energy for next year’s bloom. Cut each finished flower stalk at the base, but do not cut down the foliage. The plant will naturally die back, and will build food reserves to support next year blooms. Plant hardy annuals in areas where spring bulbs will die back. Daffodils may be divided and moved when finished blooming.

Prune spring-flowering shrubs and vines after they have finished blooming, and the flowers have faded. Make sure you do this immediately after flowering, so you’re not cutting into next years blossoms.

SOIL

Mulching soil will prevent weeds, keep the soil cooler and require less water for plants. Spread 1-3 inches of bark chips, compost, wood shavings or other organic material under shrubs, trees, annuals and vegetables.

FERTILIZING AND FEEDING

Feed lilacs with 10-10-10 fertilizer after blooming. Feed roses after their first bloom, then repeat feeding every 4-6 weeks. Try a complete fertilizer like a 10-10-10 granular or liquid soluble. You can basically fertilize annuals, fruit trees, fuchsias, perennials and shrubs.

Feed spring-flowering shrubs like azaleas, camellias and rhododendrons with an acid based fertilizer as soon as they have finished flowering.

For hydrangeas, work lime in soil for the color pink, and Aluminum Sulfate for blue blooms.

WEED AND PEST CONTROL

Use either a strong stream of water or use safer soap products, if you see aphids in your garden.

Slugs are in full force this time of year. Plants that are most susceptible to slugs, such as marigolds, hostas, dahlias and zinnias, and can all benefit from slug bait. I use Sluggo in my garden, which is pet and wildlife safe. However, there are more natural alternatives available as well.

Hopefully, I have given you some tips you can use in the garden for the month of May. As most of us isolate in our homes right now, the garden can be a place of peace. I hope that the weather is warming up for you and you are able to take advantage of the great outdoors!

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