We have been very lucky this year to not have any prolonged heatwaves thus far. The rest of America may laugh at us when we Pacific Northwesterners complain about 85- to 90-degree days as being too hot, but our summer dry climate means constant attention to the garden is required when the weather turns hot.
garden Borders and beyond
The garden in August is in full bloom, with heat loving summer flowers such as dahlias, zinnias and sunflowers strutting their stuff.
Panicle hydrangeas are in flower, taking over the limelight as the mophead hydrangea flowers start to fade. It is time to tidy up early summer blooming plants by deadheading faded blooms and pruning/shaping. Flowering annuals such as petunias, dahlias, cosmos and zinnias will keep blooming till fall if you deadhead the spent flowers. Early summer annuals such as cerinthe, nigella, poppies and alyssum are likely spent and looking drab. It's time to save seeds from these annuals and pull up the plants and designate them to the compost heap. If you are lucky, these annuals will leave seeds in your garden and come back next year.
Don’t prune back shrubs after mid-August to ensure that the new growth will have sufficient time to harden off to survive the winter. Ensure that moisture loving plants are given a deep watering every week, more frequently if your soil is sandy, until the fall rains come.
Bearded irises can be moved and transplanted this month, provided you give them a good watering until they are settled into their new spots. Hold off any transplanting or dividing of plants until the fall, when the weather cools and the rains come, unless you are prepared to water new transplants and divisions daily.
in the vegetable patch
Can one have too many tomatoes?
The weather is now consistently warm enough for the warm weather vegetables such as tomatoes, cucumbers and squash to put on good growth. This is the time to keep up with harvesting your vegetables, unless you want baseball bat sized zucchinis and tough beans. Lettuces that are still in the ground have probably bolted, so it is time to pull them out and start a new crop of lettuces to mature in the cooler fall months.
It is not too late to start another crop of carrots, spinach, radishes, Chinese cabbage and beets and fast maturing salad greens in early August. Late August is a good time to sow arugula, mustards and Asian greens that tend to bolt in hot weather.
Potatoes and onions can be dug up as the foliage dies back. If sowing seeds in the hot weather, make sure the soil is kept moist to ensure good germination. That may mean watering twice a day until the seedlings come up.
For a detailed planting calendar, please refer to:
- Seattle Tilth's "The Maritime Northwest Garden Guide" book
- Oregon Tilth planting calendar
- Oregon extension service 's monthly calendar
- Washington State University extension service's information