Nope, not Oster, Waring or Hamilton Beach, these are plants that are called into service for the purpose of unifying a planting of individual elements and to give it coherence. Homeowners and professional garden designers devote hours to planning landscapes that will be interesting and attractive throughout the growing season and beyond.  Much is attention is given to the “bones” of a garden –  plants that provide structure and give the landscape interest into the bleak mid-winter. Secondary plants contribute the seasonal interest, texture and rhythm. Then there is a third tier, those varieties that serve the valuable function of tying the whole composition together.

Poppy 'Queen Alexandra' and Cranesbill, McInnis photo

Annuals that self-sow are often the star performers in this category; they can be selectively thinned or transplanted for the desired effect.  They run the gambit from the delicate and well-behaved Nigella to downright coarse and aggressive – the purple form of Perilla, for example. Cosmos and cleome contribute cheerful interest toward the back of a border and will soften the heavy appearance of shrubs. Each plant weaves its unique character through a planting, often with a result that looks more carefully planned than it really was.

Purchased annuals can be used to achieve the same informal effect. Since contemporary gardens rarely adhere to the rigid formality of Victorian carpet bedding designs, weaving annuals through established shrubs and perennials is an attractive way to display their assets, prevent them from flopping, and create a lush display. These workhorses provide a long season of color, and when they do fade, tend to drop out of sight.

Many perennials will return in the spring with a new generation of seedlings in tow. The list is endless, but some personal favorites are: Verbena bonariensis, pops of purple bloom randomly scattered about; Bronze Fennel (Foeniculum vulgare ‘Purpureum’) with its gossamer smoke; Rose campion, (Lychnis coronaria) a vigorous biennial well-adapted to hostile sites; Johnny Jump-Ups (Viola cornuta) , always a welcome surprise in the spring; Snapdragons (Antirrhinum majus) and Columbine (Aquilegia canadensis). Remember that plants that self-sow may not always come true from seed, particularly the hybrids. But, an advantage to this is that the undesirable forms can be culled and preferred ones encouraged.

A bed unifier can double as a living groundcover, such as Speedwell (Veronica spicata) or Cranesbill (Geranium sp.) that will allow taller plants to emerge and harmonize.

Dense groundcovers, such as the sedums, Moss Phlox (Phlox subulata) and Dianthus species serve as a living mulch that discourages weeds and add interest.

Liatris emerging through sedum, McInnis photo

Then there are the happy accidents; the bird-delivered False Solomon’s Seal (Smilacina racemosa), the Lady’s Mantle (Alchemilla mollis) that arrived as a stowaway in a container-grown hydrangea, or a Joe Pye Weed (Eutrochium purpureum) whose seeds were deposited by October breezes the previous year. Consider keeping these volunteers who are already thriving in conditions they themselves have chosen.

A word of warning – some species in some locations cross the line from welcome additions to the party to obnoxious trespassers. Some consider Perilla a noxious weed, for others it’s a simple matter of pulling unwanted plants and cooking them in a Japanese-inspired stir fry. Over time, Rose campion or Bugleweed (Ajuga reptans) can consume a bed, invade a lawn, snuggle into the cracks of a sidewalk and from there scout out new locations to conquer.

Ajuga invading a lawn, McInnis photo

What about mulch? For this gardener, mulch (natural color, PLEASE – and NO cocoa mulch – it’s lethal to dogs!) is merely a temporary placeholder to discourage weeds and add organic matter to the soil while the surrounding plants are filling in.

James McInnis