Caring for Perennials Throughout the Seasons: A Tennessee Gardener's Guide
Perennials' life cycle changes with the seasons‚ with dormant roots in winter becoming spring's rapid shoots‚ with bloom-increasing summer perennials going dormant in fall‚ storing energy for the next spring's fast growth․ This includes the forcing of growth too early in the fall with fertilizer when it should be done in spring‚ and the overall weakening of the perennial over the years․ For us‚ in Tennessee‚ USDA zones 6b to 8a on your gardening map‚ this also depends on our erratic late frost and humid summer months․
This guide gives you exactly what your perennials need‚ season by season, including information specific to gardens in the Southeast․
March to May‚ Spring: Wake-Up Call
Tennessee springs are tricky․ Once you've had a week of warm weather in late February‚ you think winter's done‚ but then in early April we get a hard frost and that takes care of that․ Don't rush your perennials awake․
Remove winter debris (old leaves‚ matted plant material) from the crowns and stems‚ since this can harbor slug eggs‚ fungal spores, and insects that overwinter in the debris․ Wait for 2-3 inches of new growth before removing last year's dead growth‚ which will help protect perennials in those questionable April nights when frost can appear․
Divide dense clumps․ When hostas‚ daylilies‚ or coneflowers become so congested they stop blooming‚ divide them in the spring․ Once new shoots are 3-4 inches (7․6-10․2 cm) tall‚ dig up the entire clump and cut it into pieces with a sharp spade․ Each piece should have at least 2-3 growth points․ Replant the daffodil immediately with amended soil; for the clay-heavy soils of middle Tennessee adding compost is essential․
Don't fertilize until new growth appears․ A slow-release granular fertilizer incorporated into the top layer provides nutrients at a steady rate‚ allowing plants to grow well all season rather than surge and slump as with liquid fertilizers․ Use package rates; more is not necessarily better․
As a general rule‚ pay attention to soil moisture over the calendar․ If in doubt‚ it is probably not necessary to water anything in April in Tennessee․ Stick a finger in the soil 2 inches (5․1 cm) deep․ When dry‚ water thoroughly in the morning․
After the soil warms‚ in early May or so‚ add two or three inches of shredded bark or leaf mulch to retain moisture and suppress weeds․ Mulching the soil too early keeps the ground cool and slows germination․
Summer: Maintenance Mode (June through August)
Tennessee summers are not great for plants․ High temperatures (90+ degree days) and high humidity stress out even the heartiest of perennials․ Most garden failures occur during this period because of inconsistent watering․
Water less frequently but deeper․ One inch of water a week‚ applied in one or two deep soakings‚ encourages roots to grow where the soil is cooler and moister‚ rather than on the superficial surface․ Watering early (before 9 AM) is best․ This allows the leaves to dry before the humidity rises in our sticky Southern evenings‚ which is ideal for mildew and other fungi․
Other plants that benefit from deadheading include coneflowers‚ salvia‚ daylilies․ It prevents the plants from wasting energy creating seeds instead of flowers․ This is enough difference to convert wide varieties from a three-week-long bloom to a three-month-long bloom
As a rule‚ stake before you need to because tall perennials like garden phlox‚ delphiniums‚ and certain asters flop after our frequent summer thunderstorms․ Tie up stakes or grow-through supports in late spring before the plants are high and top-heavy; a flop in July is a battle that cannot be won․
Japanese beetle can be a major pest of gardens in Tennessee during mid-June through July‚ especially on roses, and members of the hibiscus family․ Hand-picking beetles into soapy water may only be effective for small populations․ For larger infestations‚ targeted treatment will avoid pollinator harm․
To avoid fighting summer battles with unwanted pests‚ you can plant native pest-resistant plants in your beds․ Southeast problem pest populations have evolved with local varieties of Bloodroot‚ Lily of the Valley‚ and native Poppy‚ which shrug off the pest problems other outdoor ornamentals experience․ TN Nursery offers several native perennials that have been bred for the rigors of the Tennessee climate and minimize the need for pest control․
Fall: Preparation Season (September through November)
Fall matters more than most gardeners realize; decisions now determine how well plants make it through winter‚ and how quickly and vigorously they return in spring․
Do not cut everything back․ Herbaceous perennials that die back completely to the ground (such as hostas‚ daylilies‚ and peonies) can be cut back to 2 to 3 inches above ground after a hard frost blackens the leaves․ The seed heads of coneflowers and black-eyed Susans are left for winter interest and to feed goldfinches and other birds․
This is prime division/planting time for Tennessee․ The fall is mild until the end of October‚ allowing 6-8 weeks for roots to establish before the ground freezes․ This is actually easier on many perennials‚ as roots are not competing with vegetative growth for resources during root establishment․
After they have experienced their first light frost‚ cover perennials with a thicker mulch (3 to 4 inches) to protect them․ The cover doesn't keep them warm‚ but it does prevent the freeze-thaw cycles that heave roots out of the ground‚ a much greater danger than cold weather to perennials in Tennessee․
Winter: dormant‚ planning (December to February)
Winter in Tennessee is a period of erratic weather‚ and dormant is not the same as ignore․ Deep freezes alternating with warmer periods can trick plants into resuming growth․
Marginally hardy perennials‚ such as zone 7 plants being pushed in a 6b microclimate‚ may be protected with straw‚ burlap wraps, or frost cloth․ Tender crowns may also be protected with evergreen boughs from your Christmas tree․
Watering is usually reduced‚ but not eliminated․ If there is no snow cover for long periods (more frequent than one might expect in the Tennessee winter)‚ check for moisture and water if the soil is bone dry․
Use this break to plan‚ though․ Order bare-root perennials now when selection is good‚ as nurseries often sell out of popular varieties around March․ Hence, this is also when TN Nursery ships many bare-root perennials because transplanting while the plants are dormant reduces transplant shock, which allows roots to get a head start on spring․
The Bottom Line
Caring for your perennials is not that complicated‚ but conditions and requirements change month to month․ That same plant in July is not the same as that plant in January․ Match the care calendar that makes sense to Tennessee's climate and not to a county elsewhere with a different climate, and you'll spend less time fixing and more time enjoying․
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