The Flower Garden in Late Summer: Transition, Pests, and Early Winter Prep

Late summer ornamental garden work mirrors mid-summer but with less volume overall. Daylight noticeably decreases; long-day plants peak and fade. Short-day autumn plants — dahlias, early chrysanthemums, Michaelmas daisies — show bud color and open first flowers. Annuals get straggly and less floriferous; biennials long finished — rely on bedding plants and half-hardy annuals for seed-grown display.

Days shorten but weather may stay very hot and wet with frequent thunderstorms — fast growth for some (including weeds), lots of tying up and restoring after heavy rain, summer gales, possible hail. Wet conditions = watch for grey mould on many-petalled flowers (dahlias) and greenhouse plants (high humidity).

Dry weather brings mildew problems on many plants; some gardens also see rust. Major outdoor pest: earwig. Indoors: whitefly may have built large colonies if not watched.

Some sowing/planting for winter/spring greenhouse displays can start now. Gardeners fallowing soil for new lawn seed can finish prep except final seed-bed tilth. Autumn-sown annuals give earlier summer display next year — soil for them can be prepped in late summer too.