With Tuesday and Wednesday forecast to hit the upper 90s and no rain in sight for seven days, the job this week is... watering!
This Week's Action List
- 1
Move containers into afternoon shade before Tuesday, since anything in a black nursery pot on a west facing deck will hit root zone temperatures near 110°F when the air reaches 97°F. Twelve inch and smaller pots may need watering both at dawn and again around 6pm through Wednesday.
- 2
Deep soak established shrubs, hydrangeas especially, on Monday evening before the peak heat lands. Run a slow trickle from a hose at the base for 30 to 45 minutes per plant, delivering roughly 5 to 10 gallons, so the water reaches 8 to 12 inches down where roots can actually use it.
- 3
Scout tomato foliage every three days this week, starting Monday. Late blight shows as olive gray blotches with a fuzzy white underside near the leaf margin, and with lows of 69 to 72°F Tuesday through Thursday paired with any morning dew from irrigation, spores move fast. Pull affected leaves into a bag, not the compost.
- 4
Skip overhead watering entirely through Sunday. Drip lines and soaker hoses at the soil surface keep foliage dry, which is the single most useful late blight prevention on a week with 99°F afternoons and warm humid nights.
- 5
Check drip emitters on tomatoes and peppers Monday morning. A clogged one gallon per hour emitter during a 99°F Wednesday is a split fruited tomato and a blossom end rot problem by Friday. Flush the lines and replace any emitter that reads dry after a five minute run.
- 6
Harvest zucchini, cucumbers, and beans early each morning this week. Fruit left on the vine in 97°F afternoon heat turns bitter, develops tough skin, and signals the plant to slow flowering. Daily picking through the heat wave keeps production moving into August.
- 7
Direct sow fall carrots and beets on Saturday or Sunday, once highs drop back into the mid 80s. Pre soak the seed furrow, sow at a quarter inch depth, and cover with a board or shade cloth for four days to keep the soil surface below 85°F until germination.
- 8
Saturday, July 25 is the hard stop on structural pruning for shrubs and trees. Any cuts after this weekend push tender new growth that will not harden before November frost. Deadheading roses, dahlias, and perennials continues all summer and does not count.
- 9
Spray water forcefully on the undersides of bean, rose, and strawberry leaves Wednesday and Friday mornings. Spider mite populations double every three days at 95°F and above, and a strong water blast disrupts their webs and knocks off adults before stippling turns into full leaf collapse.
Frequently Asked Questions
How much should I water my vegetable garden during a 99 degree heat wave?
In ground vegetables need about 1.5 to 2 inches of water per week during temperatures above 95°F, delivered in two or three deep soakings rather than daily shallow watering. Containers need daily watering minimum, and small pots on a hot deck may need it twice, once at dawn and once after 6pm. Always water at the soil, never overhead, to keep late blight and powdery mildew in check.
Can I still prune my rhododendron or hydrangea in late July in Portland?
Stop all structural pruning of shrubs and trees by Saturday, July 25. Cuts made after this date push new growth that will not harden off before Portland's first frost around November 15, leaving tender shoots vulnerable to dieback. Deadheading spent blooms is fine and encouraged all summer, since it removes only the flower, not living wood.
What does late blight look like on tomatoes in July?
Late blight starts as irregular olive gray or brown blotches on leaves, often at the margins, with a faint white fuzzy growth on the underside in humid morning conditions. Stems develop dark brown lesions and fruit shows greasy brown patches that harden and spread. Remove affected leaves immediately into a sealed bag for the trash, never the compost, and keep foliage bone dry going forward.