It's time for planting fall color, such as mums and asters, as well as sprucing up planter boxes. You also may be surprised to learn that it's the best time of year to plant perennials and shrubs (trees, too!) while plants still have an opportunity to establish their root systems before the ground freezes.
Flowers to plant in September
English marigold (Calendula) has deep orange petals, which are perfect for a hot border or for cutting. It's easy to grow – from an autumn sowing it should flower from May. Sow direct into shallow drills or on the surface of moist peat-free compost, in pots.
Autumn is a great season for annuals, low-maintenance perennials and evergreen shrubs to shine. In fact, some of the most popular flowers, like colorful mums, roses, dahlias, purple pansies and yes, even bright yellow sunflowers, all bloom around September and October.
Late summer or early fall is an excellent time to plant mums, one of the symbolic flowers of the season. Practically any time in September that strikes your fancy is a good bet, so long as it's at least six weeks before the year's first frost.
Vegetables to plant in September: Beets, broccoli, bush beans, pole beans, carrots, cauliflower, collards, cucumbers, kale, kohlrabi, lettuce, onions (seed & sets), radishes, summer squash and turnips.
Planting in September
Plant now beets, broccoli, Brussels sprouts, carrots, cauliflower, celery, fava beans, kale, kohlrabi, leeks, both head and leaf lettuce, mustard greens, onions, parsley, peas, potatoes, radishes, rutabagas, spinach, Swiss chard, and turnips.
The latest time to plant for most vegetables would be the second week in June with a short harvest time. If planting crops that mature within 50 days, you could plant those as late as the last week in June, but keep in mind the weather will be turning cooler, especially at night. Cool crops are best for late plantings.
Think about ways to add color and draw beneficial insects to your fall gardens. Consider planting nasturtiums, marigolds, asters, cosmos, mums, and anemones. Plan out your fall pots and planters. Summer blooms are fading, but there are many opportunities to add color and visual interest to your landscape.
For this Blooming Period, we're highlighting some late summer/fall favorites: callas; China asters; lisianthus; perennial sunflowers; and zinnias.
Tip. Mid- to late-August is often an excellent time to plant fall flowers, as long as the weather isn't still so hot that the plants will suffer heat stress. But don't wait too late to plant, or you'll have a very short window to enjoy your flowers. Check the growing requirements for each plant.
Some fast growing fall crops like lettuce and radishes can be planted into late September, but many desirable fall crops like broccoli and carrots need several months of prime-growing conditions to mature before frost and low light levels set in. When in doubt, plant your fall crops a little early.
September Plant of the Month: Epilobium.
Most flowers should be planted after your region's last frost date. Planting flowers in spring is the most popular time, but perennials do fine if planted in early fall in the North and late fall in the South.
October is the season to plant spring-blooming bulbs, wildflowers, and many standard gardening favorites. The flowers that don't blossom this winter can spend the cold season in the ground, strengthening their root systems in preparation for a springtime bloom.
Asters (Aster Spp.)
One very popular variety is Aster 'Celeste', which forms a clump covered with dense purple daisy-like flowers in late summer and early fall.
For those planning big changes in the garden, perhaps to a more water thrifty plants, October is definitely the time to get started so plants are well-established by next summer. This is just about the only time you can plant California natives, and most drought-resistant plants do best planted in the fall.
For April, May or June blooms, plant seed directly outdoors August-October. For June, July, August and/or September blooms, plant your seed outdoors March-June. Seedlings normally tolerate a light frost.
Starting too soon can result in a weak, lanky plant, while starting too late can give you one that is just not ready for the outside world—both will struggle to survive!
Late summer planting
Choose quick-maturing crops. Spinach, lettuce and greens, beets, carrots, peas, and beans can be sown now. Most seeds will readily germinate in the garden now because the soil holds heat well into autumn; warm soil (in the 70°s) is ideal for seed starting, as long as the weather is not too hot.