Portland garlic planting season opens this week, and the ideal window runs from September 20 to October 10 for hardneck varieties in Zone 8b. The wrinkle: Wednesday and Thursday are forecast near 85 degrees F with zero rain, so anything freshly planted or transplanted needs real water, not wishful thinking.
This Week's Action List
- 1
Prep garlic beds now for planting the weekend of September 19 or the following week. Work 2 to 3 inches of finished compost into the top 6 inches of soil, aim for pH 6.5 to 7.0, and choose hardneck cultivars like Music, German Red, or Chesnok Red that reliably size up in Portland winters. Break heads into cloves the day you plant, not before, and set cloves pointy end up, 2 inches deep, 6 inches apart.
- 2
If the forecast holds and Wednesday hits 85 degrees F, run drip on any shrubs planted in the last three weeks for 45 to 60 minutes at dawn Tuesday and again Thursday. Newly planted rhododendrons, camellias, and hydrangeas have not rooted out yet and will scorch fast in dry 85 degree air, even in mid September.
- 3
A common September mistake: turning off irrigation because the calendar says fall. Rain is not forecasted this week at all, and daytime highs of 81 to 85 from Wednesday through Saturday will pull moisture out of fall transplants and freshly sown spinach. Keep timers running through Sunday, then reassess when the next front actually shows up.
- 4
Sow overwintering spinach (Giant Winter, Tyee, Winter Bloomsdale) and mache directly this week, but shade the seedbed with a length of 30 percent shade cloth or a floating row cover through Thursday. Soil surface at 80 degrees F will cook spinach germination; keep the bed evenly moist with a light morning sprinkle until you see true leaves.
- 5
The single highest value disease task of the year is happening right now under your rose bushes. Rake every fallen leaf, strip any remaining blackspotted foliage off the canes, and bag it for the yard debris bin, not the home compost. Overwintering spores in this leaf litter are what seed next April's infection, and the dry week ahead makes cleanup easy.
- 6
Pull spent tomato and squash vines completely and get them out of the garden this week. Any plant that showed late blight, powdery mildew, or septoria goes in yard debris, never the compost pile. With dry weather through Saturday, the debris is light and easy to haul, do not wait for the next rain to mat everything down.
- 7
Watch dahlias for botrytis on cool nights in the mid 50s followed by warm afternoons. Mushy brown petals or fuzzy gray patches on stems mean pinch off the affected bloom immediately and thin surrounding foliage to improve airflow. Keep cutting blooms for the vase, that removes spent tissue before it turns.
- 8
Order spring bulbs this week if you have not already. Tulips, daffodils, and alliums from Portland Nursery or Cornell Farm are in stock now, and the best cultivars sell out by early October. Hold off on planting until soil drops below 60 degrees F, typically mid October, but stage the bulbs in a cool dark spot until then.
Frequently Asked Questions
When is the best time to plant garlic in Portland Oregon?
The reliable window in Zone 8b is September 20 through October 10 for hardneck varieties, which need a cold period to form good heads. Planting in this window gives cloves enough time to root before hard freezes but not so much top growth that leaves get frost damaged. Softneck varieties can push a week or two later.
Should I still be watering my Portland garden in mid September?
Yes, when the forecast is dry. This week runs zero measurable rain with highs reaching 85 degrees F midweek, so newly planted shrubs, fall vegetable seedlings, and containers all need active irrigation. Turn timers off only when weekly rainfall reliably exceeds 0.5 inches, which usually starts in the last week of September or early October.
Why should I remove rose leaves in the fall?
Blackspot fungus overwinters in fallen rose leaves and reinfects new growth the following spring, which is why Portland roses often start the season already spotted. Raking every leaf out from under the bush and bagging it in yard debris, not home compost, breaks the cycle. Doing this cleanup in dry September weather is far easier than trying to rake soggy leaves in November.
Can I plant rhododendrons and camellias in September in Portland?
Yes, September through October is the prime planting window in the Pacific Northwest because soil is still warm, air is cooling, and winter rains will handle most of the establishment watering. Just apply a 3 inch mulch ring after planting and keep drip irrigation running until the rains take over. This week's 85 degree spike means water new plants deeply Tuesday and Thursday.