Purple flowers sit in all three groups, so the answer is both. Purple perennial flowers such as coneflower, lavender, catmint and salvia live for years and push up new growth every spring. Petunia and heliotrope are sold as annuals, and you get one season of bloom before you pull the plants out. A third set comes back from bulbs you plant in fall. Color tells you nothing about which group you are buying.
Nine coneflower seedlings came up in my gravel path one spring, about 6 feet (1.8 m) from the plants that dropped the seed. Purple coneflower self-seeds, and the seed needs cold, moist stratification before sprouting, which a winter of wet gravel handed over for free. Seed that lands in fall sits through the cold months and shows up as plantlets once the ground warms. I dug four out for the bed and left the rest in the path.
Whether a plant returns comes down to surviving winter, and the hardiness zone on the tag settles that. A perennial rated to zone 5 dies in a zone 3 winter, so you get one summer of flowers and an empty spot in April. Purple flowers that come back for a gardener one zone warmer can fail in your yard for that reason alone. Self-seeding blurs the line from the other side. A true annual that drops viable seed fills the same patch next year, so you see flowers again without ever owning a perennial.
Purple perennial flowers give you the longest list to shop from, and the group is a deep one. Coneflower, lavender, catmint, Russian sage, salvia, iris and aster all bloom in purple and hold ground for years. Give full sun and soil that drains, and you get thicker clumps each season until the middle of a clump starts to thin out. Coneflower takes root division in early spring or late fall, so you can turn one plant into three without spending a dollar.
Purple annual flowers do one job better than any perennial. Petunia, heliotrope, zinnia and sweet alyssum bloom from planting until frost with no gap in the middle. You pay for that long run with a fresh purchase every spring. I've grown all four in pots and along the front edge of a bed, where your perennials can come and go behind them without leaving a hole.
Bulbs and corms are the third answer, and you get perennial behavior without a perennial label. Crocus, tulip, hyacinth and allium sit underground through winter and come up on their own clock, with crocus out before most perennials have broken dormancy. You plant once in fall and the show arrives on its own. Bulbs cost little each, so a wide drift runs cheaper than you would guess.
Check the zone range on the tag against your own before you look at the price. Sources do not always agree, and coneflower shows the problem. University of Vermont Extension rates the plant hardy in zones 4 to 9, with some varieties good to zone 3, while NC State Extension lists 3a to 8b. If your garden sits at the edge of either range, buy one and watch a full winter before you buy five more.
A perennial rated one zone warmer than your garden is an annual with a perennial price tag. Buy one if you love the flower, but plan on replacing the plant each spring.
Read the full article: 10 Purple Flowers Worth Planting
