To save seeds from your favorite open-pollinated annuals or vegetables, take the seeds only from the healthiest, best specimens. Harvest fully mature seeds, then make sure they are clean and completely dry. Label and store in a cool, dry place.
Don't Treat Mildewed Lilacs
Many lilac cultivars have poor or no mildew resistance, and so the foliage becomes discolored with a white or gray powdery coating by late summer. This is not very attractive but it does not harm an otherwise healthy plant so it does not need to be treated.
Dahlias will keep blooming until frost if the flowers are picked often. Of course you can cut them to enjoy in bouquets in the house or to share with friends. But when left to be enjoyed in the garden, you still need to remove the spent blooms from the plant when they fade. This is called deadheading.
Divide Old Iris
Dig and divide older plantings of bearded iris. Cut back the foliage to about 6 inches. Replant only healthy, vigorous rhizomes. Plant them shallowly in well-prepared garden soil. The traditional spacing is in groups of three facing outward to eventually form a clump.
Woody plants should not be pruned any more this season. Late summer or fall pruning can result in excess winter damage. Pruning stimulates new growth that may not have time to harden off before the cold winter weather.