August: Combining Annuals and Perennials

Kip finds a way to make annuals work in the Victory Garden's perennial border
by Kip Anderson

This year our long perennial border is looking better than it ever has in the four years of its existence. You might be tempted to think, "Of course it does," going on the assumption that it has taken a bit of time for the plants to mature — but both the assumption and the conclusion would be incorrect. We started out with many hefty plant divisions and employed other techniques (see February, 2005, the Bluestone Perennials section) to promote strong early growth, and in fact the border looked better in its first year than in the second and third due to the depredations of voles and perhaps due also to our high expectations. In any case, Michael expressed his disappointment and suggested we use some annuals to fill gaps and provide pockets of summer-long bloom. At first, maybe because of my purist bent, I was reluctant to go along with this idea, but finally I gave in.

The key to combining annuals with perennials without creating awkward incongruities is to choose annuals that resemble perennials. Marigolds and petunias, for instance, simply will not sit well next to border perennials — they would look like doilies on a rustic picnic table. The following are the particular annuals that have made the difference in our mixed border this season. (See February, 2006 for our main plant and seed sources.)

• Euphorbia 'Diamond Frost'
  Produces small white flowers endlessly and is reminiscent of baby's-breath.
• Angelonia 'Angelface Blue'
  Spikes of deep blue all season, suggesting delphinium or penstemon.
• Ageratum 'Artist Blue'
  A good edging plant with flowers nearly identical to those of Eupatorium coelestinum.
• Lavatera 'Novella Rose'
  Resembles mallow (malva spp.); for this species to succeed, extreme care must be taken when transplanting.
• Foxglove (digitalis) 'Camelot Cream'
  An award winner now available in individual colors; started from seed in late winter, it will bloom in its first season, and unlike biennial or perennial foxgloves it will not come through the winter.
• Verbena bonariensis
  Purple/violet flowers on tall spindly plants for massing in the back of the border; easy to grow from seed, and should be planted close together, no more than 6" to 8" apart.
• Delphinium 'Summer Nights' & 'Summer Blues'
  Flowers in its first season from a late winter sowing; like the verbena above, it is actually considered a perennial, but here in zone 5/6 it rarely comes back the following spring.
• Salvia longispicata x farinacea 'Mystic Spires Blue'
  Only hardy to zone 7, we treat it as an annual; imagine a taller, more robust Salvia 'Victoria' with super-sized flower spikes.

The best annuals are unapologetic profligates that spend their blooms as though there were no tomorrow — which, for them, there really isn't. But an elite cadre of true hardy perennials bloom profusely for months on end and yet somehow manage to put by sufficient reserves to repeat the performance year after year:

• Penstemon 'Red Rocks'
  Short plants with spikes bearing rose pink flowers.
• Dianthus amurensis 'Siberian Blues'
  Easy from seed, with flowers as close to a true blue as can be found in the genus.
• Geranium 'Rozanne'
  An astounding plant which will spread to five feet and ramble through adjacent perennials; one-inch blue flowers from late June through October.

If anyone out there can think of other great annuals that look like perennials, or other perennials that perform like annuals, then please let us know what they are. Power to the flower!

Kip Anderson has been the Victory Garden's head gardener for over 20 years.

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