The last week of June through the first week of July is the sweet spot for Zone 8b. That gives transplants 6 to 8 weeks of indoor or shaded growth before going into the ground by mid to late August, which lines up heads with the cool October weather brassicas want. Sow later than mid July and you risk immature heads when the light fades in November.

Brassica seed germination drops sharply above 85 degrees F, and a sunny Portland windowsill or greenhouse easily hits 90 degrees F this time of year. Move trays to a shaded outdoor bench or the cool north side of the house, keep the soil surface consistently damp, and you should see cotyledons in four to six days.

Look for fine yellow stippling on the tops of leaves and a dusty webbing on the undersides, especially on beans, cucumbers, and tomatoes during heat spells. Confirm by tapping a suspect leaf over a sheet of white paper and watching for moving specks the size of pepper grains. Insecticidal soap on the undersides of the leaves at dusk, repeated in five days, knocks them back without harming bees.

This is the final week. Rhododendrons and other spring blooming shrubs set their flower buds for next year in early to mid July, so any pruning after the first week of July trades away April 2027 flowers. If you still need to shape a rhododendron, do it now and stop before the calendar flips.