Keep up with the watering and the deadheading. Water early in the morning to cut down on evaporation. Weeds shouldn’t be too bad right now.
Be sure to stake tall, top-heavy plants like sedum and Shasta daisies. You can put a few bamboo stakes behind them and loop garden twine around the stakes and in front of the plants. In future, if you have a lot of floppy fall-bloomers, pinch them back in early summer to reduce height.
If crashing thunderstorms are predicted, you’ll be better off just picking your flowers for bouquets.
Fertilize your roses for their fall bloom. You’ve been fertilizing them every month, right?
Start thinking about spring bulbs! Catalogues will start arriving soon and there are sometimes discounts if you get your order in early. I use John Scheepers or, for larger quantities, their sister company Van Engelen.
Now is also a good time to prepare any orders of daylilies, hostas and peonies. Planting rhizomes and tubers in the fall is cheap and easy, and the selection is great. I use Gilbert H. Wild and Son.
Yank out yellowing foliage on daylilies and grasses. Daylilies do well if you chop them short once the foliage is completely a disaster; they regenerate from the base and you’ll have nice little tufts of green until snowfall. Grasses will need cutting down too, but wait as long as you can because you’ll be left with an unpromising thatchy stub. Or you can let the grasses stay up over the winter – some find this provides “winter interest” – I think it’s usually just a mess.
Clean up fallen rose and peony leaves and put them in the trash (not your compost). These leaves could harbor diseases and/or pests.
This is a good time to do snip-pruning on boxwoods, yews, or whatever else you have that’s looking shaggy. Your pruning will stimulate new growth, but there’s still enough time before winter for that growth to harden off. Snip off the leggy pieces of forsythia that have sprung up over the summer, too.
Indoor plants: protect them from strong sunlight that can cause foliage burn. You might not want to leave them on a blazing-bright windowsill. You should also make sure they aren’t getting blown on by the air conditioning vents.
When watering tropical house plants, use room temperature water. Some plants have delicate root hairs that can be damaged by cold water. Letting water sit out for a day before using it in your plants will also allow any chemicals that may be in the water to dissipate into the air.