Portland garlic planting prep begins this week. Mornings are getting cool enough to fog, watch for signs of blight pressure on tomatoes.
This Week's Action List
- 1
Source hardneck seed garlic this week from Portland Nursery, Territorial Seed, or Filaree Garlic Farm. Music, Chesnok Red, and German Extra Hardy all overwinter reliably in Zone 8b. Grocery store garlic is a bad idea, most is treated to inhibit sprouting and often carries the wrong varieties for our winters.
- 2
Scout tomato plants every morning this week for late blight. The tell is olive brown lesions on leaves with a pale fuzzy underside, plus greasy dark patches on stems. Wednesday's 75°F high paired with a 64°F low is exactly the fog window blight loves, bag and trash infected material, never compost it.
- 3
Take dahlia cuttings from healthy peak bloom plants before Friday's heat spike. Snip a 4 inch shoot with two leaf nodes, strip the bottom leaves, and root in moist perlite in bright shade. Cuttings taken now root in 3 to 4 weeks and give you free stock for 2027.
- 4
Direct sow spinach, mache, and arugula in a bed shaded from afternoon sun until Sunday. Soil temperatures above 75°F will make lettuce and spinach seed go dormant, a shade cloth or the north side of a taller crop keeps germination rates above 70 percent this week.
- 5
Water deeply Thursday evening ahead of Friday's 91°F peak, aiming for 1 inch total across established vegetable beds. Skip overhead watering on tomatoes and dahlias entirely, wet foliage overnight is the fastest way to seed blight and botrytis.
- 6
Order spring bulbs this week if you have not already. Tulip and daffodil supply from Brent and Becky's or John Scheepers thins out fast by mid September, and October is the planting window for Portland. Alliums and species tulips are the most reliable perennializers in our wet winters.
- 7
- 8
Rake up fallen rose leaves twice a week from now through leaf drop. Black spot spores overwinter on debris and reinfect canes next spring, a clean bed floor in August and September is worth more than any fungicide spray next May.
Frequently Asked Questions
When should I plant garlic in Portland Oregon?
Plant hardneck garlic cloves between late August and mid October in Zone 8b, with mid September being the sweet spot. Cloves need 4 to 6 weeks of root development before hard frost, then vernalize through winter for a July harvest. Order or buy seed garlic in August because the best varieties sell out by early September.
How do I identify late blight on Portland tomatoes?
Look for irregular olive brown to black lesions on leaves, often starting at the edges, with a pale gray fuzzy growth on the underside in humid mornings. Stems develop dark greasy patches, and fruit shows firm brown blotches that spread fast. Once you see it, remove the entire plant and bag it, spraying rarely saves a heavily infected tomato in August.
Can I still prune shrubs in August in Portland?
No, the pruning window is closed for woody shrubs and trees until November. Cuts made now push tender new growth that will not harden before the first frost around November 15, leaving damaged tissue that invites disease. Deadheading annuals, dahlias, and roses is fine, structural pruning waits for full dormancy.
How much should I water Portland gardens in mid August?
Established vegetable beds need about 1 to 1.5 inches per week from irrigation, with zero help from rain this week. Reduce frequency compared to July, aim for 2 deep soakings rather than daily shallow ones. Woody shrubs and trees should get one deep soaking of 5 to 10 gallons per week and no more, hardening off for fall matters now.