Zones for Verbena Bonariensis

About Tall Verbena

• Sometimes called Brazilian vervain or purple-top verbena, tall verbena (Verbena bonariensis) earns its name by growing to heights of 4 to 6 feet, crowned by tiny yet vibrant purple flowers beloved by butterflies and hummingbirds. Its loose, open branches rarely spread more than 2 feet. As one of its common names implies, the plant is native to South America, and prefers to be planted in full sun, though in warmer climates it will appreciate some light shade during the hottest parts of the afternoon. It will grow in virtually any soil, but because it needs good drainage, verbena may suffer on clay soils during unusually rainy periods. Tall verbena is drought tolerant once established, though blooms and foliage may look tattered after long stretches with too little water. To look its best in the garden, tall verbena should receive at least 1 inch of water weekly.

Verbena Hardiness

• Tall verbena grows best in areas with hot summers and relatively mild winters, and can be grown as a perennial in U.S. Department of Agriculture plant hardiness zones 7 through 10. With additional winter protection, such as a deep mulching after plants enter dormancy in the late fall, verbena may sometimes overwinter as a perennial down through zone 6, though this is the absolute extent of the plant’s hardiness. If you live in zone 5 and below and think you cannot grow tall verbena, take heart: the ease with which tall verbena resprouts from seed in a single season makes it suitable to use as a self-seeding perennial outside of its normal hardiness zones.

Self-seeding

• From seedlings to flowering plant to seed again in the fall, tall verbena readily self-seeds, which makes it both a boon as well as a bother, depending on who you’re asking. Its free re-seeding makes it an excellent choice for areas intended for naturalizing, but also marks the plant as a potential invasive when it continually comes back in areas where it’s unwanted. It is officially listed as an invasive plant in Oregon and Georgia, as well as in individual counties throughout many Southwestern and Southern states, as of 2013. If you want to confine this plant to one spot, be diligent in removing the hundreds of seedlings that appear each spring, or assent to live with tall verbena’s roaming nature.

Pests and Problems

• Tall verbena is relatively healthy in the garden, attracting few insect pests and unfazed by any serious plant diseases. Powdery mildew can be a problem when verbena is planted in humid areas where it receives less than full sun, or is stressed by long periods of drought. Whiteflies and mites may attack drought-stressed plants, as well. Tall verbena may also develop root rot or botrytis blight when planted in consistently soggy soils.