Traditionally a bright blue or purple, delicate annual widely used in hanging baskets, containers or as edging plants, the lobelia family has a few varieities that will survive over winter in Climate Zones 3 to 9 as perennials. Lobelia cardinalis, or Cardinal Flower, is a bright red blooming perennial form.
Lobelia siphilitica, the Great Blue Lobelia, is a vivid blue version of the cardinal flower, with tall spikes of small, hooded blooms. Appearing in June and lasting throughout the growing season, with regular maintenance and proper winter protection, your perennial lobelia will be a favorite bedding plant for many seasons.
Choose the bedding site for your perennial lobelia carefully. These plants crave moisture, so ensure that there is a water source nearby. Partial shade is a must since these special lobelia will remain in the same location yearly and need protection from harsh, direct sunlight.
Prepare the perennial lobelia bed in the spring for best winter results. Provide a 2-inch layer of organic mulch, such as composted pine bark, around obelia plants. Do not allow the mulch to touch the base or crowns of the plant, as this can encourage rot and disease spread.
Maintain the mulch cover at the 2-inch level yearly, ensuring the mulch is evenly distributed and not crowding the crowns.
Leave the spikes intact on spent summer lobelia foliage unless disease is present. The University of Illinois horticulture experts suggest that the foliage will help protect the plant crown over winter, and provides a marker for spring identification and maintenance.
If the plant is infected with disease, however, cut back the spikes and foliage leaving 2 to 3 inches above the ground. Remove all discarded or diseased plant material.
Divide lobelia plants in spring to ensure continued health and viability. Perennials show reduced flowering, leggy foliage, and general lack of performance as visual cues when division is necessary.
Dig around the root system of the plant and lift the root ball. Gently cut the clump into smaller sections with clean tools. Re-plant the lobelia 18 to 24 inches apart to allow for mature growth.