As much as I love the freshness of a June garden, September is my favorite month. Some visitors seem surprised that we “still” have so much color but I can’t imagine it any other way. The gentle light and the beautiful cool blue days demand that we be outside reveling in exuberant color. We definitely plan for this time of year (in truth, for the whole summer into fall season) to be stupendous but it doesn’t take much – a few annuals like zinnias, ageratum, and alyssum; and a handful of tender perennials like dahlias, salvias, angelonia, and plectranthus and you’re golden. Or the garden is in any case, especially in the slanted light of September. Even with roses, delphinium, asters, and euphorbia (re)blooming in the Rose Garden, it wouldn’t be nearly as spectacular without the annuals and tender perennials giving them a boost. I know a lot of gardeners choose not to buy plants that won’t survive the winter outside but I think those plants are worth every penny (and seed annuals like zinnias really do just cost pennies) because they’re the ones that carry the garden so effortlessly past its usual early summer peak well into the prettiest months of all.

And of course, some of them can survive the winter and carry whatever we spent on them into the next season too (and the next after that and the next…) We’ve started taking cuttings of some of our favorites like porterweed (Stachytarpheta mutabilis), cigar plant (Cuphea spp.) and heliotrope. We’re lucky to have the greenhouse for overwintering them but sunny windowsills would work too.

Is your garden as colorful as you’d like it to be this month? Do you use annuals and tender perennials too or do rely on late-blooming hardy perennials and shrubs? For a look at a whole world of colorful September blooms, check out May Dreams Gardens Garden Bloggers Bloom Day (September 15).

Our Tuesday volunteer group has been known for years — for ever? — as the “Deadheads” because they work in the Display Garden and traditionally, the biggest summer chore in these gardens has been to deadhead flowers to keep them from quitting and going to seed. While we still ask for help deadheading the annuals in the cutting garden to keep them blooming gangbusters, in recent years we have not deadheaded the other beds as rigorously. Now when the Deadheads ask if we want echinacea deadheaded in the pollinator bed we say, “No… let’s leave their seeds for the birds.” And when they ask if they should deadhead the betony, beebalm, cardoon, teasel, and eryngium, we say, “Nah, don’t those look cool?! Let’s leave them up for the winter.” Perhaps the Tuesday group needs a new name…

I know the betony (Stachys monnieri ‘Hummelo’) wouldn’t have bloomed again because we cut a couple of clumps back last year as a test, but the beebalm (Monarda fistulosa ‘Claire Grace’) might have rebloomed, and there are still buds opening along the echinacea stems. But right now I wouldn’t trade any of those seedheads for their flowers. Not only are they beautiful (in the eye of this beholder) but there is more wildlife activity in that garden than I ever remember seeing before. It’s positively mesmerizing – I’ve been so distracted that visitors have caught me gawping instead of working. Goldfinch, wrens, and sparrows are all vying for seeds and hummingbirds, bees and butterflies are still zinging around working all of the flowers that aren’t ready to go to seed yet.

But there’s a fine line between letting the garden go to seed and letting the garden go. Some gardeners and visitors might think the cardoon seedheads look more like the undead than the simply un-deadheaded. And I imagine that it might make some people nervous to watch them self-destruct and send helicopters wheeling on the wind to float with the butterflies and catch in the grass and on bare patches of soil. But that doesn’t make me nervous. As long as the stalks are still standing upright, surrounded by a colorful garden that looks tended (it’s been meticulously weeded and propped, if not deadheaded) rather than abandoned, and the birds are happy, then I figure we gardeners are as golden as the light that falls this time of year.

Do you deadhead everything up until the bitter end or do you leave seedheads standing for their looks and for the birds? Have you found a happy medium? (Have we? – All opinions welcome!)

I am as fickle as any gardener. I’ll pick a new favorite color, fragrance, leaf, flower, and plant habit every other week (or day) and reserve the right to change my mind over the slightest disappointment. That said, the hyssops, which have been blooming since June, are vertically eye-catching, and smell like candy, have managed to stay at the top of my favorites list for months now. I also think they deserve the  “Most Attractive Plant” award in the 2012 Blithewold yearbook superlatives.

Agastache, which is pronounced ah-GAH-stah-kee or aga-STAK-ee depending on who says it (tomato, tomahto), is Greek for very much (agan) spike (stachys) according to Allen J. Coombes’ The Hamlyn Guide to Plant Names. (He pronounces it the first way.) Very much spike is right. And probably because their native habitat is sharply drained hillsides they’re fairly sturdy, unfussy, and drought tolerant. They are also hardier than I ever thought. Around here anyway, wet winters and poor drainage are more likely to do them in than cold temperatures.

We are growing North American native anise hyssop (A. foeniculum, zone 4-11) because it seeds itself all over the Display Garden. Its spikes start out a lovely dusty blue and deepen over the season and are more slender than its hybrid child ‘Blue Fortune’ (zone 6-9; crossed with Korean A. rugosa). That’s the one we’re growing in the Rose Garden this year and the bees can’t get enough of it. My personal favorite, planted in the Display Garden and North, is ‘Black Adder’ (zone 6-9). The deep indigo bracts are spectacular especially now that every plant is also decorated with its own klatch of a half-dozen or more American Lady butterflies. (At least I think that’s what they are.) All 3 are standing a good 4-5′ tall now and need propping – particularly top-heavy ‘Blue Fortune’ even though we lopped them back by half in late May or early June. In my own garden, I grew ‘Golden Jubilee’ (zone 5-9), which has brilliant chartreuse foliage through mid-summer and pale grey-blue spikes. The best thing about that plant is that its seedlings have already started to pop up. The more the merrier. We have no intention of deadheading any of these because we’re looking forward to their structure over the winter, but we have used some stems in flower arrangements.

I always though that the cultivars of hummingbird mint like ‘Heatwave’, ‘Acapulco Orange’, and ‘Summer Glow’ were tender but they’re at least as hardy as ‘Black Adder’ and ‘Blue Fortune’. Both ‘Heatwave’ (zone 5-10) and A. mexicana ‘Acapulco Orange’ (zone 5-9) came back for us this year but last winter was unusually dry and mild so it probably wasn’t a good test. We have our fingers crossed for ‘Summer Glow’ (zone 6-9) in the North Garden, which in its first year isn’t as outstanding as the others but certainly could be the prettiest of all with one more season’s growth. We’ll probably take cuttings and overwinter a stock plant in the greenhouse just in case it doesn’t make it outside. The slightly contrasting bracts on ‘Acapulco Orange’ and ‘Summer Glow’ make those my faves over ‘Heatwave’ (plus they’re orange) but the hummingbirds probably have no preference at all.

Are you as in love with agastache as I am? Which ones do you grow?

I finally bought my very own copy of Ken Druse’s latest book Natural Companions: A Garden Lover’s Guide to Plant Combinations and if you don’t have a copy yet, it’s worth dropping everything else – plant those annuals later! – to pick it up. (I ordered mine from my favorite local bookstore and beat feet to get it as soon as it came in.) Truly, you might never look at your garden and the plants in it the same way again. I appreciated Ken’s reminder to pick flowers and foliage to see what would look well together but Ellen Hoverkamp’s digital scans of those pickings are exquisite. And then Ken takes it several steps further to illuminate plants that not only look well together but go together in various other ways, whether they’re related by “blood”, color, place, habit, use, and so on and on for well over 200 beautifully written and photographed pages.

I don’t have Ellen’s patience – or her brilliant artistic eye – or her equipment – to ever be able to create such amazing compositions but I have already started to notice the garden’s own arrangements and natural companions with a fresh eye. Some of these combinations (related more by good looks and cultural requirements than anything more thought-provoking) were planned but I think most were either lucky guesses or pure wind-blown serendipity. (Mouse over for captions, click on for larger views.)

What combinations of plants go well together in your garden? Do you think about different kinds of plant relationships when you’re working on your garden’s design?

This week we just about finished planting 300-something new perennials – with the garden volunteers’ help, thank goodness! – and that meant it was time to pick up another order. One of the highlights of Gail’s and my year is our spring trip to Avant Gardens in N. Dartmouth, MA to grab our order and see if there are maybe a few other things we can’t garden without. We found a lot this year. We should have brought the truck.

The owners, Kathy and Chris Tracey have a love of plants that is obvious and totally infectious and their nursery is like a fabulously curated art gallery. — But less fancy-pants; it’s as comfortable as a kitchen. They grow and sell plants that they know are awesome performers and they trial every new plant that intrigues them in their own garden, which is attached to the nursery. They’re also famous for fabulous pot combinations and the most sublime trough gardens. Seeing their plants so artfully planted and growing gangbusters just makes us want everything even more.

The nursery is well off the beaten track but so easy to find. Just head north (away from the mall) from the Faunce Corners exit off 195 in North Dartmouth and follow the road until it Ts. Take a left there and go winding along the shady country road until you just begin to wonder if you’ll ever get there. Card carrying Blithewold members who visit Avant Gardens will be richly rewarded with a 10% discount but they also have a fabulous online catalog here. If you aren’t already hooked to her feed, Kathy writes one of the most read-ably fun and informative blogs with the best name: Garden Foreplay. The plants she sells are definitely seductive…

Have you been to Avant Gardens yet? Did you find treasures too?