A Guide to Choosing Annuals versus Perennials in Tennessee
Perennials are cheaper and easier to maintain in your Tennessee garden than annuals‚ but annuals will pack a bigger‚ prettier punch to liven up the landscape in one season‚ so perhaps the better answer is knowing when to use each‚ depending on your growing zone and the swampy heat of a Tennessee summer․
Tennessee has plant hardiness zones 6a through 7b․ One small area near Memphis has climate zone 8a․ This matters more than most articles say․ For example‚ a plant that is a perennial in Nashville's zone 7a might not survive the freezes of the Cumberland Plateau‚ and a plant that is marketed at a Georgia big-box store as perennial might be annual in Tennessee․
The Actual Difference (Not the Textbook Version)
Annual plants germinate‚ flower‚ produce seeds and die in one growing season․ A perennial plant survives and regrows from its root system each year over the course of several growing seasons‚ usually many years․ Another important aspect of annuals and perennials is that while a plant might be perennial in one zone‚ it might be an annual plant in another zone․ Lantana is perennial in zone 8‚ but in winters in Tennessee with hard freezes it dies all the way to the ground‚ except in (sheltered) locations where it is heavily mulched․
This is why perennial vs․ annual‚ is not a fixed category but rather a regional question․
Where Perennials Win in Tennessee, Specifically
We have heavy clay soil‚ and we get humid summers․ This makes it hard for shallowly-rooted plants to thrive‚ but perennials become well-established and tend to do well․ Here are some examples․
Year one: roots are establishing‚ with modest top growth․ Occasional wilting can occur between watering, even with proper watering․ The average person will give up on perennials by this time‚ but not for lack of effort․
At year two‚ most perennial species reach 12-18 inches deep roots․ Drought tolerance is improving, and more growth is taking place․
Year three onward: The perennials are now established‚ having deep roots and needing less water as they mature․ Many perennials fill in as they spread or self-seed into the cracks and gaps․
Coneflowers‚ black-eyed Susans, and daylilies are workhorses in Tennessee because they tolerate our clay soil without a lot of heavy amendment․ If you're creating a perennial flower bed in Tennessee‚ TN Nursery's native perennial collections are designed around this kind of regional hardiness instead of with generic zone-9 plants that happen to survive here for a season or two before fading out․
Where Annuals Actually Make More Sense
However‚ annuals aren't a step down․ If you just moved into a house with bare dirt and you want flowers by June‚ annuals can be ready for you literally in weeks․ The petunias‚ marigolds‚ and zinnias are going to bloom from the time they are planted until frost‚ providing instant curb appeal that most perennial beds do not have in their first year․
Annuals also make sense for:
- Rental properties where you won't be able to build roots - Filling gaps in a perennial bed during that slow first year - Container gardens on porches or patios‚ where winter survival is not the goal - Testing out color combinations before committing to permanent plantings
One thing that the other articles make little or no mention of is that annuals planted in the heat of July and August in Tennessee need way more water than you'd expect․ Hanging baskets and container plantings need watering every day; the roots don't get a chance to reach the moist soil․ Without commitment‚ annuals will disappoint quickly in the garden․
The Cost Comparison‚ With Real Numbers
If you buy a flat of annuals (about 18-24 plants) for $20-40 each year‚ you could cover a small bed for a season․ Multiply that by five years of spring planting‚ and you're looking at $100-$200‚ plus the effort to till and replant each spring․
The initial cost of a similar-sized perennial bed is $150-300‚ and after year 3‚ an additional $20-30 is spent on mulch and occasionally dividing the plants․ By year 5‚ perennials are often the less expensive option․ However‚ at year 10‚ the perennials become by far the best․
If you want constant color‚ the mathematics are different․ As each perennial blooms in mass for only two to six weeks‚ you will have a gap between blooms unless you include species with staggered bloom periods in the same perennial bed․ Annuals do not have that problem and keep growing until frost․
The Combination Approach (What Actually Works)
Most experienced Tennessee gardeners don't belong to either camp‚ but choose both․ Perennials are the backbone of the garden: shrubs like coneflower, phlox, and hosta take up space and are there year after year․ Annuals are interplanted to fill in gaps as the perennials take hold‚ but are reduced in number once the bed is filled in year three․
If you're on a budget‚ the best thing you can do is to start out with fewer perennials than you want‚ and then use annuals to fill gaps for a couple of years․ As your perennials fill out‚ you'll need fewer and fewer annuals to fill up the bed․
TN Nursery Recommendations for Tennessee's Specific Growing Conditions
We prefer using native or near native perennials that have already adapted to our clay soil and humidity change․ Purple coneflower‚ black-eyed Susan‚ and ferns for shaded areas of the garden are able to take care of themselves during the Tennessee summer without the constant babying non-natives require․
Annuals such as the zinnia and vinca do far better in August than the cooler-climate pansy‚ which grows better in Tennessee's Fall and early Spring․
The Bottom Line
Low-maintenance perennials are the best investment for plants that you want to keep for at least 10 years or more․ These plants grow more slowly during years 1 and 2 but last longer․ Annuals are for gardeners who want color more quickly or mainly garden in containers‚ or who are uncertain how long they will live in one home․ Most yards in Tennessee need both‚ and that's not compromise; that's just the reality of how growing conditions in Tennessee work․
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