The Garden Guru: This fall, hit the blue notes in the garden

Want to let your garden stand out from the rest? One of the best ways in autumn is to go against the grain and showcase colors other than traditional rusts, reds, oranges and yellows. Do blue, which is an amazingly rich shade in the fall, and we’ve been blessed with several blue-flowering plants that are stellar performers this time each year.

Of course, those warmer shades of yellow and orange are the traditional fall colors, and you’ll see them almost anywhere you look. Any other colors you use will still have to look good against them. The good news about blue is that it goes with almost anything. Second to green, it’s our most neutral shade. We see it in the sky, and it’s reflected in large and small bodies of water.

You’ll find a wide range of blues, from light blues in Cape plumbago and 'Heavenly Blue’ morning glories earlier in the fall, to deep, twilight blues in 'Indigo Spires’ salvias. If you broaden the color wheel ever so gently, you’ll also pick up a bunch of great lavenders and purples, and most of them are equally at home in the fall garden.

If you’re going to get maximum value out of your blue- and purple-flowering plants, you’ll want to use them either combined with one another, or you’ll need to provide a stark contrast. Dark blues, for example, won’t show very well against deep green foliage, but they’re usually good with orange, tan, gray or yellow.

Best of the blues

Fall asters are the stalwart blue flowers of the season. Our grandmas told us this was a great plant, but many of us refused to believe it. Then, 15 or 20 years ago, it staged a big comeback, and now you’ll see it in the best-dressed gardens in town. It grows to 18 to 20 inches tall, so it’s the perfect backdrop for shorter, more spreading plants. Its leaves are tiny, almost inconspicuous all through the growing season. It’s a perennial, so it comes back from its root systems each spring. Give it one light shearing in May to keep it compact. Otherwise, the plants will become leggy and uneven. Dig and divide it in late fall, as soon as it has finished its flowering.

Indigo Spires salvia is upright, to 24 to 36 inches, with deep blue spikes all summer and through the fall. It’s one of the most common of the blue-flowering perennial salvias, and it’s also one of the darkest floral shades available. It’s been in the trade since the late 1970s, and it’s a hybrid between two salvia species. It’s a magnet for butterflies.

Mexican bush salvia (Salvia leucantha) grows to 36 to 48 inches tall, but it’s prettier when sheared lightly a couple of times during the summer to keep it compact. It has blue-gray foliage, the perfect complement to its purple flower spikes. All-purple selections are available, the compact form 'Santa Barbara’ being most common, but the standard species is still a favorite with its purple and white flower parts. The selection called 'Midnight’ is standard height and very dark-flowering. All varieties flower about the same time the monarch butterflies are making their annual migration through our area.

Chrysanthemums don’t come in a true blue, but some of the light purples come close. Used in combination with shades of yellow and orange, they’re absolutely stunning in the cool fall garden. Choose garden mums if you want the small, globe-form plants and multitudes of flowers. Florist mums will succeed in the garden, but they tend to get leggy, and they’ll almost always require staking. They also bloom several weeks later than garden mums.

Selected varieties of pansies pick up from mid-October, and they carry the blue theme all through the winter. They’re our most winter-hardy annuals, and all that they ask is good drainage, highly organic soil and ample nitrogen to keep them growing actively. Nurseries are well-stocked with pansies right now. Small- and medium-flowering types give the best landscaping show, and the look is even more dramatic if you choose types without the traditional dark pansy faces.

As we head into the slower, cooler months of the winter, this is a great time to consider which plants you want to include in your garden next season. Then, as next fall rolls around, you can have blue on deck and waiting.