✨ Tomato leaves under a magnifier, roses on a five day loop, fall brassicas already on the bench.
Portland late blight prevention in June is not a maybe, it is the single most important habit standing between a full tomato harvest and a compost pile of bagged plants by August. Warm days, cool nights in the low 50s, and any lingering morning dew give Phytophthora infestans exactly the conditions it wants. This week the job is to inspect, water at soil level, deadhead the roses that are hitting peak bloom, and get fall brassica seeds started before the solstice.
This Week's Action List
- 1
Inspect every tomato plant, every leaf, twice this week. Late blight starts as olive to brown water soaked spots on lower leaves, often with a faint white fuzz on the underside in humid mornings. Any plant showing the classic lesions comes out today in a sealed contractor bag, roots and all, straight to the trash, not the compost.
- 2
Switch tomatoes from any overhead watering to drip or soaker hose at soil level, running 45 to 60 minutes between 5 and 8am every 2 to 3 days. Wet foliage overnight is how blight spreads across a bed in 72 hours.
- 3
Deadhead roses on a 5 day loop this week. Cut down to the first outward facing 5 leaflet leaf, use bypass pruners wiped with rubbing alcohol between plants, and drop spent blooms straight into a bucket rather than the mulch below where black spot spores overwinter.
- 4
Feed dahlias with a low nitrogen, high phosphorus fertilizer this week, something in the 5 10 10 range at label rate. Too much nitrogen right now buys you tall leafy plants and delays the first bloom into August.
- 5
Start fall brassica seeds indoors by Friday: broccoli, cabbage, kale, and Brussels sprouts. Transplants need 6 to 8 weeks under lights before going out in mid to late July, and starting late is the number one reason Portland fall brassicas underperform.
- 6
Thin apple and pear fruit clusters to one fruit every 6 inches along the branch. It feels brutal, but unthinned trees give you hundreds of ping pong ball sized fruit and a broken scaffold limb in August.
- 7
Scout cucurbit leaves (zucchini, cucumber, pumpkin, squash) for the first dusty white patches of powdery mildew. Thin interior vines for airflow and spray affected leaves with potassium bicarbonate at the first sign. Waiting until half the leaf is coated means you are already losing the plant.
- 8
Trim boxwood, privet, and laurel hedges this week for their main seasonal shaping. Cut on a dry morning, sterilize shears between plants if you have any suspicion of boxwood blight, and avoid shearing in direct afternoon sun which scorches the freshly exposed interior leaves.
- 9
Cut lavender flower stems back by half as blooms fade, staying well above the woody base. Lavender does not resprout reliably from old wood, and one aggressive cut into the gray woody stems can kill a five year old plant.
Frequently Asked Questions
How do I know if my Portland tomato plant has late blight?
Look for olive brown to nearly black water soaked lesions on lower leaves and stems, often with a fuzzy white ring on the leaf underside in cool damp mornings. Fruit develops greasy brown patches that stay firm rather than soft. Once confirmed, the plant must come out in a sealed bag the same day, because spores travel by wind and rain splash and can take out a whole bed in under a week.
When should I start fall broccoli and cabbage seeds in Portland?
Start seeds indoors under lights between June 5 and June 25 for transplants going into the garden mid to late July. That gives brassicas 6 to 8 weeks of cool root establishment before the September temperature drop, which is when the heads actually size up. Direct sowing in July usually fails because the soil is too warm for good germination.
How often should I deadhead roses in June in Portland?
Every 3 to 5 days during peak bloom, which for most Portland gardens means now through early July. Cut each spent bloom back to the first 5 leaflet leaf with an outward facing bud below it, using clean bypass pruners. Skipping a week lets the plant put energy into hips instead of the next flush, and you lose the July repeat bloom entirely.
Can I still prune my rhododendron in June?
This week is the last safe window. Rhododendrons and azaleas set next year's flower buds in late June, so any shaping cuts after roughly June 25 remove the flowers you want to see next April. Deadhead spent trusses by snapping them off just above the new leaf whorl, and save any real size reduction for right after bloom next spring.