✨ Late blight patrol, fall brassica seed trays, drip lines on the clock, roses in full showoff mode.
The first week of June is the pivot point in the Portland Zone 8b June garden: warm season crops are settling in, roses are hitting peak bloom, and the dry season is here even if the sky hasn't fully committed yet. Fall planning starts now, not in August, because brassicas need eight to ten weeks indoors before their late July transplant window. This week is about setting the systems that carry you through August: irrigation, disease scouting, and the first fall seed trays.
This Week's Action List
- 1
Start fall brassica seeds indoors this week. Sow broccoli (Belstar, Marathon), cabbage (Farao, Ruby Perfection), and kale (Winterbor, Lacinato) in 4 inch pots under lights at 65 to 70°F. They need six to eight weeks before their late July transplant date, and starting now beats the August heat that fries direct sown seedlings.
- 2
Water soaked spots the size of a pencil eraser on lower tomato leaves are the opening move of late blight, Portland's number one tomato killer. Walk the tomato patch every three days, look at the undersides of leaves, and bag any suspect plant whole rather than composting it. Spores travel by rain splash and wind, so one hesitant week can take out the whole bed.
- 3
Switch tomato and pepper watering to drip or soaker hose now, before the first 85°F stretch. Overhead sprinklers wet the foliage and set up both late blight and powdery mildew; a drip line at soil level delivering two to three gallons per plant every two to three days keeps fruit sizing up without the disease pressure.
- 4
Deadhead roses every three to five days by cutting back to the first five leaflet leaf with an outward facing bud. That single cut resets the plant for another flush and keeps June's peak bloom running into July. Skip the pruners for a week and you get one show instead of four.
- 5
Side dress tomatoes, corn, and winter squash with a nitrogen source (blood meal, feather meal, or a balanced 5 5 5) as soon as the first fruit sets or plants hit knee high. Scratch it into the top inch of soil six inches out from the stem, then water it in. Hungry plants in June turn into stunted plants in July.
- 6
Feed dahlias with a low nitrogen, high phosphorus fertilizer (something like 5 10 10) as buds form, and stake any variety over three feet now while stems are still flexible. Waiting until July means wrestling a five foot plant into a cage without snapping laterals.
- 7
Powdery mildew shows up on zucchini and cucumber leaves as pale dusty patches, usually starting on the oldest leaves. Thin the interior vines for airflow, and spray potassium bicarbonate (Milstop or similar) at the first white speck. Once it coats the whole plant, you're managing decline, not curing anything.
- 8
Container plants are the first casualties of Portland's dry June. A 12 inch pot in full sun can go from moist to bone dry in 24 hours once daytime highs cross 80°F, so check every container by lifting or finger testing at soil level daily. Water until it runs from the drainage holes, not just until the surface looks damp.
- 9
This is the last clean week to prune spring flowering shrubs like rhododendrons, lilacs, and forsythia. Next year's flower buds set in late June, and cuts after roughly June 25 remove blooms you were counting on. If the shrub bloomed in April or May and you haven't touched it, do it now.
Frequently Asked Questions
When should I start fall broccoli and cabbage seeds in Portland?
Start fall brassica seeds indoors in early to mid June for transplanting out in late July. That gives seedlings six to eight weeks under lights and lets them mature into the cooler September and October weather, which is when brassicas actually taste their best in Zone 8b.
How do I know if my Portland tomatoes have late blight?
Late blight starts as irregular dark green or brown water soaked spots on leaves, often with a pale halo, and it moves fast during humid or damp weather. Within days you'll see white fuzzy growth on leaf undersides and stem lesions. Any tomato showing these signs needs to come out whole in a sealed bag, not composted, because spores travel by wind and rain to every solanaceous plant nearby.
How much water do Portland tomatoes need in June?
Established tomatoes need consistent deep watering every two to three days in June, roughly one to two gallons per plant per session depending on soil and mulch. Inconsistent watering causes blossom end rot and cracked fruit, and overhead sprinklers invite blight. Drip or soaker hose at soil level in early morning is the right delivery.
Is it too late to prune my rhododendron in June?
Early June is your last clean window. Rhododendrons and other spring bloomers set next year's flower buds in late June, so cuts after roughly June 25 remove next spring's flowers. If you missed the post bloom window in May, prune this week and stop by month's end.