How to Design a Beautiful Perennial Border (That Actually Blooms Every Season)
The secret to a great perennial border is threefold: a tiered arrangement with high‚ mid-height and low plants; a succession of bloom times to ensure something is in flower at any given time; and good soil that has been well prepared․ Get those three things right and the rest is really just picking plants you love․ If you get them wrong‚ you'll have a bed that looks great in June and bare by August․
Tennessee is generally USDA hardiness zones 6b to 7b․ That is a longer growing season than most of the rest of the United States․ It also means clay soil‚ warm humid summers, and the occasional frost in April that catches everyone off-guard․ It's what shapes every decision we make here․
What Exactly Is a Perennial Border?
In old British garden design‚ long rectangular borders of perennials were planted along the boundaries of properties where the hedge or fence lines were the border․ Now‚ the term is widely used to mean any perennial bed‚ and this can include freestanding island beds in the middle of a lawn․ Even so‚ the best example of a perennial border is still the customary one‚ in backdrop‚ mid-ground and front edge‚ which support each other․
They are a practical choice because‚ unlike annuals‚ perennials come up on their own every spring‚ and with the passing years become a little bigger‚ taller‚ and more established․ Once established‚ they require little care‚ with the only major chores being dividing overgrown clumps every few years and cutting back old leaves in the fall․
Step 1: Pick the Right Spot
Most old-fashioned perennials such as coneflowers‚ black-eyed Susans‚ phlox‚ and daylilies want six or more hours of sun each day, so check the site where you want to dig all day․ The amount of shade from a tree or your house changes more in the summer as the leaves fill in․
Another big issue is drainage․ Tennessee red clay is famously good at retaining water․ Soggy roots kill more perennials than drought ever does․ It's as simple as this: if you dig a foot-deep hole for a plant‚ fill the hole with water‚ and the water is still there an hour later‚ you have a drainage problem․ This can be solved by digging in a few inches of compost‚ installing a French drain‚ or building the bed up to 6-8 inches with a raised border․ If that is not possible‚ then any other spot you can find is good; nothing will out-compete standing water․
Step 2: Mark Out the Bed and Break Ground
For straight‚ rectangle-shaped borders‚ use garden stakes and mason's string to mark the boundaries․ To outline curvilinear borders or an island bed‚ place a garden hose on the ground‚ walk around until satisfied‚ and dig out the sod․ It's much easier to adjust the hose than to redig the border․
Once you've got your outline‚ strip all the sod‚ don't just till it in․ Grass and weed roots left in the soil will come back up through your perennials for years and be far harder to remove once they've got tangled around established root systems․
Step 3: Fix the Soil Before You Plant Anything
This is the step most people rush‚ but it's also the most important step in creating a border that will flourish‚ rather than limp along․ Work 3 to 4 inches of compost‚ aged manure into the soil of top 8 to 10 inches․ In heavy Tennessee clay‚ this isn't optional‚ it is what allows roots to actually spread instead of hitting a wall of compacted clay six inches down․ If your soil test is acidic (as is common for most of the state)‚ a light application of garden lime will raise the pH to the 6․0-7․0 range most perennials prefer․
Step 4: Plan the Layout Before You Buy a Single Plant
It is also often recommended that the height of plants is arranged to create back‚ middle‚ and front rows․ Tall plants are nearest the back‚ middle-height plants in the center‚ and low‚ spreading plants are in front․ As a rule of thumb‚ back-row plants may be 3-4 ft tall‚ center row 18-24 in, and front row under a foot․
Within that frame of mind‚ think bloom succession․ A border that looks terrific in May and bare in July is unfinished․ If you choose spring-bloomers‚ summer-perennials‚ and a few fall-blooming plants‚ you can have color from April to October․ Follow the golden rule of three in landscaping‚ groupings in threes‚ fives‚ or sevens of the same variety․ This reads as more deliberate and gives the eye a place to rest․
Make a plant list before you visit a nursery․ It's easy to get swept up in what's in flower in a pot that day‚ and you are unlikely to pick the right color or bloom time just by chance․
Step 5: Planting Day
If possible‚ plant on an overcast day or in the evening‚ since disturbed roots are vulnerable to exposure to sunlight․ Make sure to arrange the pots on the soil surface according to your design․ Do not place them too closely together as it might look congested․ Allow for the mature spread of each plant․ Plant them at the same depth they were in their pot‚ firming up the soil around the stem and watering in deeply‚ immediately․
A few starter plants to build around:
Most Dianthus grow well in full sun to partial shade․ They are tolerant of both drought and wet‚ making them ideal plants for a beginner's border or perennial garden․ Their mat-forming habit means they make good front border plants‚ and they flower and hold their color from late spring to summer․
The coneflower (Echinacea) is as Tennessee-hardy as perennials get: full sun‚ drought-tolerant after becoming established‚ and blooms from June through September․
Daylilies fit comfortably within that middle ground‚ and they shrug off our humid summers better than almost any other plant․
Gardeners who decide to start their borders from scratch will be pleased to hear that TN Nursery ships fully-grown‚ established perennials instead of seed packets‚ which means that your plant comes equipped with a root structure that will see it through a Tennessee summer with roots that can sustain steadier moisture levels․ It can take a full year or more off the time it takes a border to fill in․
New perennial beds take two years to get established․ During the first year‚ the plant is mostly growing its root system․ Now‚ by year two‚ you've actually got that world‚ that sandbox‚ that you designed for․
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