How To Choose The Best Perennial Plants For Your Garden
Without a doubt‚ the best perennials for your garden are those best suited to your hardiness zone‚ soil drainage‚ and light conditions․ Get those three conditions right, and in most cases‚ any perennial you select will do just fine and require relatively little care for many years․
Tennessee's periphery is easy to garden in․ The huge majority of the state sits in USDA Zones 6b and 7b‚ with a few highest-elevation spots in East Tennessee sitting in USDA Zone 6a․ It is a very large range‚ much larger than gardeners anywhere in the Deep South or the upper midwest ever get to work with․ The trick isn't finding perennials that will grow here‚ but finding those that make sense for your garden in particular․
Start With Your Hardiness Zone‚ Not Your Wish List
It's very easy to read about a plant in a magazine and try to make it fit‚ but that is not the right way․ Find out what your zone is (a zip code search on the USDA site takes thirty seconds) and shop within that zone․
In Tennessee‚ the winter low may be 10°F (−10°C) in January and the summer high may be 95°F (35°C)‚ with meaningful humidity making the air feel even warmer․ The temperature and humidity range eliminates many plants not tolerant of both extremes․ Lavender‚ for example‚ does not suffer from the cold‚ but from our very hot and humid summer climate with heavy clay soil that stays wet․ Echinacea‚ or coneflower‚ listed as being hardy from Zones 3-9‚ grows very well in Tennessee‚ better than it does in the cooler part of its range․
Know Your Soil Before You Dig
While most of Middle Tennessee is clay with limestone not far beneath the surface‚ the soils of the mountains of East Tennessee are largely rocky and acidic‚ and the soils of West Tennessee along the Mississippi River are sandy and alluvial․ These differences are enormously important for success․
Clay soil retains water‚ so plants requiring well-drained soil are unlikely to succeed in your garden: peonies and lavender‚ for example‚ or most Mediterranean herbs․ But don't despair․ There are plenty of perennials that like moisture if you are not prepared to try to change your soil․ Astilbe‚ Cardinal Flower‚ and most native Ferns are more than happy with wet feet․
For a few bucks, your county extension office can run a simple soil test, giving you pH and nutrient content․ Tennessee soil is generally a bit on the acidic side of neutrality, and that's perfect for most natives, which evolved here․
Match Light Levels To The Right Zones In Your Yard
Seasonal changes in sun angles can affect available sunlight levels between seasons․ Before planting your garden‚ monitor the amount of sun exposure over a week's time․ What is six hours of sunshine in June can be only three hours in September when the trees fill in or the sun angle changes․
Deep shade under established hardwoods․ In many areas of Tennessee where deep shade is provided by established oaks and maples‚ Hostas and Ferns are best plant choices․ Space filler plants require little maintenance and generally prefer protection from the hot afternoon sun․ Astilbe and Bleeding Heart do well in dappled or morning-only sun․
Black-Eyed Susan‚ Coneflower‚ and most of the ornamental grasses can survive in full sun․ Not only will they bloom during this season‚ but their stems will remain strong and not flop over in August․
Think About Bloom Timing‚ Not Just Bloom Color
One of the things that a lot of garden advice sort of doesn't stress is that you need to stagger the bloom times‚ so that there's something blooming at all times throughout your garden beds․ If you just buy a whole bunch of plants that all bloom in May‚ that won't be very effective․ So our garden will look great for three weeks and flat the rest of the season․
A rough calendar might place Bleeding Heart and early Iris in early spring․ During the summer months‚ coneflower and Black-Eyed Susan typically dominate‚ while ornamental grasses and asters dominate in-between and late in summer and autumn․ This can take an amount of planning‚ of course‚ but the result is a garden that has something worth looking at from March through October․
Plan For Division Before You Even Plant
Perennials do not remain static‚ but instead spread and clump and become too crowded‚ so most should be divided every 3 to 4 years․ Others, such as daylilies, can be left longer‚ and others, such as some Sedum‚ which quickly outgrow their spaces‚ need dividing every second year․
Common signs that a clump is ready to divide include the center of the clump dying off and the plant forming that donut shape so many gardeners complain about․ Decreased flowering signals the same․ In Tennessee‚ the best time to divide is the spring‚ as new growth emerges‚ and early fall‚ after the heat of summer has broken․ Don't divide in the heat of summer․ When it's 90 degrees out‚ the roots have a hard enough time being dug up․
For division‚ dig up the plant's entire rootball‚ and cut it into pieces with a sharp spade or knife so that each has some healthy roots and at least a growth point or two‚ and replant immediately; do not let it dry out in full sun while you ponder where its new home will be․
Space Plants For Their Mature Size‚ Not Their Current Size
But nursery pots can be misleading․ A perennial that looks small in a one-gallon container can spread three feet in two seasons․ Check the plant tag for the mature spread of each plant‚ and position them according to this (it may look sparse the first year)․
Crowded perennials compete for moisture and nutrients‚ are more prone to disease‚ and produce smaller flowers․ The first year of empty-looking spacing requires patience‚ but is worth it in year 2 or 3 when the plants fill in․
Building Cohesion‚ Not Just A Collection
An individual garden bed full of beautiful plants can still look untidy if there is no relationship between them․ Look at the existing perennials․ Look at their height‚ their bloom color, and their habit (spreading or clumping)․ Repeating a few colors or shapes throughout a bed creates a visual rhythm and prevents hodgepodge․
If you're starting from scratch (or filling in space in a mass planting for other beds)‚ TN Nursery carries established perennials for the Southeast such as Ferns‚ Hostas‚ Coneflower‚ and other types established for the region rather than shipped in from a growing zone that's completely inappropriate for our soil and climate․ Starting with regionally appropriate stock removes a lot of the guesswork this guide just walked through․
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