In gardening, as in everything else, one needs to try to imagine what the future holds. Think about whether you are planting a garden or landscape for immediate use or for the long-term.
If this planting is for next week (a party? The real estate agent is coming?) or next June, pack in the plants. If you're planning for the mature garden in five years, that's an entirely different design.
Whether you're a DIY gardener, or you're hiring a professional, decide now: When must this garden or landscape bed look full and fabulous?
*What plants become: People who want widely spaced plants, with lots of visible mulch between them, look at a mature garden and call it "overgrown." The criticism might be leveled at even a well-tended, full border, with large clumps of plants bumping against each other and some spikes or "weavers" rising above them. Some people are uncomfortable with lushness or abundance.
*But here is the reality of most perennials: If they are healthy, they will spread. "Clumpers" expand as the original plant gradually sends shoots outward from the center. Black-eyed Susans, coneflowers and hostas do that.
Some perennials send out runners or rhizomes (and a few, such as gooseneck loosestrife, should come with a warning). Some drop seeds that produce new plants nearby. When you look at any mature garden, you will see most perennials in clumps 2 to 4 feet wide. At some stage the gardener decides, "That's enough of a good thing" and divides the clump and discards, shares or places some elsewhere.
*Plan for it: So what do you do once you know that your new Filipendula or Japanese anemone wants to form a 3- to 5-foot diameter colony? It depends upon your patience and your goal for the garden.
Let's imagine an area, say, 10 by 5 feet, where you envision a sunny, colorful island of late summer flowers. (You will see it from the patio as you sit on summer evenings sipping a cool drink.)
You have chosen butterfly and bumblebee favorites: black-eyed Susans, Culver's root (Veronicastrum), New York ironweed 'Iron Butterfly' (Vernonia) and liatris. For the front edge you'll use the short aster 'Snow Flurry.'
Now, how many to buy and how to space them?
For a full garden in three years: The larger the garden area you tend, the more you'll want to space plants according to the size they will become. You want less work, and don't want to be dividing and replanting sooner than three to five years. Remember the old adage: "The first year they sleep. The second year they creep. The third year they leap!" So design for years three to five.
Fortunately, plant tags or labels make this easy to do. They tell the width of the ultimate plant or the recommended spacing. If the tag says "H 24", W 36" " place the plants 3 feet apart.
For our example, if you stick with the spacing recommended on the labels, you might buy two black-eyed Susans, three Culver's root, two Vernonia, six liatris and seven asters. That's 20 plants over 50 square feet.
Since the seven plants across the front will be just 18 inches apart, the rest of the plants will average 3 feet apart in all directions. The planting will look sparse and puny at first, but it will fill out.
Now let's take the same approach with a landscape bed, in front of the house.
If you're using low-growing Chamaecyparis (tag reading "W 5' "), tall pointy junipers (W 4') and a Japanese maple (W 8'), just one of each would span 17 feet of bed.
Yet how many times do we see that same 17 feet crammed with 10 plants that are small -- now. Somebody oversold that homeowner, or nobody read the plant tags.
Or maybe the landscaper knew it was too many plants for the space, but the client insisted on that look for immediate impact. (It's also typical that plants labeled "Height 6 feet" are placed in front of windows.)
Perhaps the client will retain the landscaper for frequent thinning, and drastic pruning in order to force those plants into staying small. Eventually many of the plants will look terrible. It would be so much better for the trees and shrubs (your largest plant investments) if they were spaced to allow them to acquire their natural sizes.
*Don't believe your eyes: It's difficult to fight what your eyes are telling you when you are placing plants.
The little lamb's ears in a 4-inch pot looks modest next to the tall balloon flower in a gallon pot, so it's counterintuitive to allow the lamb's ears three times more space than the balloon flower. Similarly, the doublefile viburnum will grow to 10 by 10 feet and the 'Endless Summer' hydrangea will only be about 3 1/2 feet tall and wide, but now they're the same size.
The newly planted bed can -- and perhaps should -- look all wrong. The mature heights and spread of the plants you're buying have nothing to do with their appearance now. Fight it.
*Smart compromise: You can have immediate satisfaction and still practice intelligent horticulture.
Annuals provide one answer. You might plant your perennials and shrubs at proper distances, and fill in with as many annual flowers as needed to make it look full and amazing during those first years. In the future you won't need the annuals. (Or you've grown to love them so you widen the bed!)
Or you can fill out an island of shrubs with perennials for the first years, knowing that someday you'll have to move them out.
If you're planting a young tree, why not design an island of flowering perennials around it, and plan to transplant them out in a few years, or widen the island? Just don't plant large woody plants so close that they cannot thrive or survive for long. You're wasting your money, and they will grow up to be deformed, high-maintenance or they will die.
Plants aren't furniture. Plants grow and change. What you see is not what you get. But you can take control of your garden or landscape with one simple trick: Read the tag!
Sally Cunningham is a garden writer, lecturer and consultant.