As September unfolds in the garden, it can feel a bit like watching a time-lapse video of summer itself: from the height of the season at the start of the month to its demise only weeks later. Days are still warm (if not as long) in early September, and flowers are blooming prodigiously—many dahlias are just starting to come into their own. But by mid-month, cool gusts and rain showers have arrived, and all of a sudden you can feel the flowers starting to fade. It's the change of the season, my least favorite of the year.
And yet...a look around our garden just last week revealed loads of annuals still in bloom and also still producing new flowers. This isn't the first time I've been "surprised" by how much is still in bloom right now, but it is the first September I've decided to take notes on it: which annuals are going strong, which are adding color and interest to a garden that otherwise would be only brown seedheads or greenery by now, and which are so outstanding I need to plant them again next year. Below is a list of 5 of the annuals I'll be sure to seed again next spring for a September/October showing. (Not including the ultimate star of the September garden, of course: the dahlia.)
We can't pick just one variety of Cosmos to recommend, because there are so very many good ones. Our favorite whites at the moment are: 'Cupcakes White,' (the flower with fused petals that makes everyone stop in their tracks), the ruffly, ultra-feminine 'Double Click Snow Puff' (pictured above), and the cottage garden classic 'Purity.' For more drama, I love the dark frills of 'Double Click Cranberries', as well as 'Rubenza,' which starts out a deep berry and fades beautifully to shades of rose and terra cotta. (A flower that looks just as lovely at its height as during its decline is a true keeper.)
2) HELIANTHUS DEBILIS 'VANILLA ICE'
We love a good sunflower for the birds to feast on, but for the cutting garden, we wanted something more refined in color and smaller in size. These pale yellow sunflowers are exactly what we had in mind, and extremely easy to start from seed. (We seeded ours outside with no issue.) Growing to about 6'5" in height (with no staking required), and with a lovely branching habit, they'd also be ideal in the back of a border, filling late-season gaps. The soft yellow looks gorgeous with just about anything, but we've been pairing them with rusts and mellow oranges like those in Rudbeckia 'Sahara' (another September favorite), the sweet lime of Nicotiana alata 'Lime Green," and blue/purples like Pincushion Flower 'Oxford Blue' or 'Fama Deep Blue.'
3) AMARANTH 'OPOPEO'
This was the first year I grew Amaranth from seed, and now that I've witnessed the full effect of this statuesque beauty in my garden, I'll never be without it. I first saw 'Opopeo' at Great Dixter, where it's a staple in their beds, interplanted with everything from dahlias and eupatorium to salvias and sanguisorba. 'Opopeo' is an intense oxblood red (it reminds me of a beet, actually), with gorgeous purple-green leaves that have striking red veins. (The leaves are tasty when picked young, and the whole plant is edible if you want to harvest the seeds.) This is one of those plants that makes you feel like a child, marveling at how fantastic it is that one tiny seed can produce something so substantial. Amaranth runners-up: the warm brown of 'Hot Biscuits,' the green fringe of 'Emerald Tassels,' and the bright buttons of globe amaranth 'QIS Purple.'
4) FLOWERING TOBACCO
Like Cosmos, it's impossible to pick just one Nicotiana (Flowering Tobacco) to recommend for the garden. They are such prolific bloomers all summer and into the fall that I have 5 different varieties in my garden, each of which still looks and smells amazing right now. So it's more a matter of planting for color—and space. Nicotiana alata 'Lime Green' has a permanent spot in my garden—its acid green flowers look surprisingly good with everything—but it can get a bit thuggish and I have to cut it back several times a season. The same goes for the classic white 'Jasmine.' Her smell can't be beat, but she seeds like crazy and gets so large that I've had to move her to a more isolated spot where she won't take over. My personal favorites this year are the soft pink variations of Nicotiana mutablis (which also has an airy branching habit); the chocolatey-rose Nicotiana 'Tinkerbell'; and 'Starlight Dancer,' a more delicate and dainty white.
5) ZINNIA 'QUEEN LIME WITH BLUSH'
Picking the last must-have September annual isn't easy (or fair), but I'm going with Zinnia 'Queen Lime with Blush.' Not only are zinnias quick starters from seed, but they've been blooming since mid-summer by now and still look pristine. (Also, have you ever forgotten/been too lazy to pick or deadhead a zinnia and seen what happens? Nothing! The flowers and foliage seem to be preserved in time, ageless, except for maybe a little elegant fading of their color. So basically zinnias are no-brainers for gardening beginners on up.) By those merits, you could argue for any zinnia to be on this list, but the uniquely lovely coloring of 'Queen Lime with Blush' has made it a particular favorite of mine. This plant contains so much color and variation, it's as if you've planted 8 different zinnias instead of just one. 'Queen Lime with Blush' produces singles, doubles and semi-doubles, some that are mostly pink, others mostly lime, still others are lilac, dark pink or touched with salmon. Many a bedside arrangement has been inspired by this pretty palette.