If ever a season could be called bittersweet, fall is that season. Not the scientific fall, which occurs this year on Sept. 22, but just before then, when the nights come noticeably earlier and are definitely cooler. Mosquitoes are on the wane, humidity is down (now referred to as “damp.”), and it’s much more pleasant to work in the garden.

If your garden lacks the charm it had in July, it’s time to rethink your choices. Plants that carry the garden through until frost and even beyond should be introduced. While it’s best to plant most of them in spring, now is the time to clear out the garden to make room for them.

There are dozens of plants that will pick up the color pace in September. Here are six to start with.

Mum Was the Word

Chrysanthemums are now in the genus Dendranthema, but for purposes of this feature, we’ll refer to them as mums. I’ve grown several, and I always plant them in the spring. This year I’m growing two varieties in the Igloo series. They’re both new on the market and were sent to me by Rozanne and Friends to test in my garden. I pinched them back just once, removing about an inch or so from each stem around July 1.

This series of mums is bred to be compact, and are described as needing no pinching. Because I don’t have the six hours plus of full sun that mums prefer, they tend to grow taller than shown on the tag, stretching toward the sun. They now are no more than around 18 inches tall and smothered in buds just waiting to pop. In their first year after spring planting, mums in the Igloo series (like ‘Harvest Igloo’) bloom later in the season than they will in subsequent years.

Asters

Asters also have had a name change, and it’s a doozy. Symphyotrichum is the botanical moniker for the flower that is often in the blue range as far as color goes. It’s a diverse group, from rangy and shade-loving to perky, stiff-stemmed sun worshippers. I’ve grown a variety of hybrids that run the gamut in size and even color. For small gardens and gardeners who prefer a low growing mound, ‘Wood’s Light Blue’ is amazing. Growing no more than 20 inches tall and smothered in bloom, this hybrid also is available in blue, purple and pink. The name “Wood’s” refers to the hybridizer, an apple grower in Portland, Oregon named Ed Wood.

One of the problems with some of the taller asters is that, by the end of summer, the leaves on the lower part of the plant die, leaving ugly bare stems. The plant goes on to bloom just fine at the uppermost stems. The best way to prevent or at least mitigate the damage is to avoid overhead watering, divide the plant every three years, and make sure it is watered about an inch a week during droughts.

The Chicago Botanic Garden’s plant evaluation manager, Richard G. Hawke, published an extensive evaluation report on cultivated asters that lists dozens of different varieties, rating them for bloom coverage and disease resistance.

Dahlias

Whether you plant them as tubers (a swollen root like a potato) or buy them as potted plants, Dahlias will wow you from August through frost. If you have at least six hours of direct sun each day, it’s certainly worth it to try these outstanding flowers. When you have Dahlias growing—especially those that are taller than three feet—the rest of your garden fades into the background.

For the best choice, order tubers from specialty nurseries. Several online retailers sell dahlia tubers in the very early spring in bags containing three tubers for around $10 to $15. It’s best to order them online as early as December to assure you will get what you want the following March or April. Longfield Gardens opens their online shop in December. They offer a great video How to Plant Dahlias.

Specialty growers like Swan Island Dahlias offers single tubers that range in price from $6 to $35. But Dahlias are all they do, so they know their stuff. There are other retailers that specialize in bulbs of all kinds, also good sources for Dahlia tubers. Two are Old House Gardens and Brent and Becky’s Bulbs.

More and more garden centers are offering Dahlias in pots. The shorter the variety, the easier they are to transplant into your garden. They also are good in containers.

Salvia: A Hummingbird’s Last Buffet

If you’ve enjoyed hummingbirds in your garden throughout the summer, there is no better farewell party plant than Salvia. In the sage family, decorative Salvia comes in a wide array of sizes, forms and colors.

Four varieties that have stood out as hummingbird magnets are tall and loosely-formed. Some have even required staking. They are:

‘Amistad’

One of the best Salvias for large blooms in a deep shade of blue. In my partly sunny garden, I’ve used stakes to keep it from laying all over its neighbors. It grows around four feet tall and at least five feet across by the end of summer.

‘Wendy’s Wish’ and ‘Love and Wishes’

I’ve grown both of these Australian-bred beauties, and have been amazed at their bloom power. Like most of the Salvias, they don’t do much until it gets hot. Then you can’t stop these brawny 4’ by 5’ stunners from blooming. They don’t hold back when the nights cool down; in fact, they increase bloom production as if they know it’s their last chance before a heavy frost takes them down. The sales of both plants benefit Australia’s Make-a-Wish Foundation.

Burgundy Scarlet Sage (Salvia splendens ‘van Houttei’)

These can be grown in partial to full shade, and like the others, really puts on a show from late summer through frost. For me it grew up to nearly four feet tall, and the hummingbirds loved its huge burgundy and scarlet flowers.

Salvia ‘Playin’ the Blues’

A newcomer in the world of Salvias, ‘Playin’ the Blues’ was one of the sample plants I received this spring from Proven Winners. From mid-July, each spike has remained colorful even after the individual flower dries up, providing some of the most long-lasting color in my garden. As its name indicates, flowers are blue, and the plant, for me, has reached just around three feet tall. It’s in a container by the window so I can see the hummingbirds fight over its nectar.

Goldenrod: It Doesn’t Make You Sneeze

Goldenrod (Solidago) has gotten a bad rap. It’s been thrown into the same bin with ragweed, a rampant plant that keeps a much lower profile. I wonder if part of the confusion stems from ragweed’s botanical name, which is Ambrosia, the same term used to mean “food of the gods.” Go figure. A more likely cause for its reputation as a major sneeze-inducer is that it’s the most visible candidate during the same time ragweed is spewing its pollen. Both plants are native to North America, and therefore can be found in just about any field come September. Guess which one is more visible, and therefore, gets fingered for respiratory unrest.

I love Solidago for its prowess as a cut flower. Its gracefully bright presence in an otherwise colorless scheme, and its easy-care nature. The variety I’ve enjoyed the most is called ‘Fireworks’, an upright grower with stems that curve downward for a fireworks look. The only warning I’d offer for planting goldenrod in your garden is that it spreads quickly.

Marigolds? Really?

It’s amazing what you will find in all of those catalogs that come around Christmas. The ones that offer seeds, bulbs, perennials, and all sorts of unusual plants. I was intrigued by a Marigold I’d never heard of called ‘Cinnabar’ (more correctly Tagetes erecta ‘Cinnabar’). Its common name is Cinnabar African Marigold, but it’s no big-headed, look-at-me lollipop flower. It won’t get lost in the garden, though. That’s because its stems grow two to three feet tall.

‘Cinnabar’ is one of those plants they call “see-through,” its stems thinly-clothed in finely dissected foliage that allows a plant behind it to show through. Its flowers, about the size of a quarter, are a spicy deep red with a gold center, and seem to float in the air. It looks especially good with Salvia, Solidago, and any of the mums and asters. And it’s just as easy as any marigold to start from seed.