How to Use Lobelia

Written by laura reynolds
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  • Introduction

    How to Use Lobelia

    The image of lobelia that comes to mind for most gardeners is of the carpets of tiny intensely blue flowers that we use to fill spaces and provide contrast in our gardens. Hundreds of species of lobelia grow all over the world in hot, cool, wet and dry conditions. There are annual forms and perennial forms. How you use this remarkable group (or "genus") of plants depends on where you live and how much care you want to give to it.

    (DRW & Associates Inc, USDA-NRCS Plant Database, Wikimedia Commons)

  • 1 / 5

    Use "Edging Lobelia" (lobelia erinus) in the garden as an edging plant along walks and borders. This delicate native of South Africa provides "pop" in the garden, in pots and in window boxes and grows best in cool weather. Edging lobelia is an annual and may reseed itself in the fall. Plant seeds in fall for spring bloom. Since seeds require specific conditions and take up to 20 days to germinate, you will probably prefer to buy these popular, easy-to-grow plants in shades of blue, white and pinks at garden centres. Keep them out of direct sun in hot weather---they grow most aggressively and blossom most profusely in part shade and cool weather.

    Annual "lobelia erinus" is a favourite, carefree form of this versatile plant group. ()

  • 2 / 5

    Plant "Great Blue" (lobelia siphilitica) in garden borders. This North American native is perennial in growing zones 4 to 8. Like its more delicate cousin erinus, it has lance-shaped leaves and blue flowers but unlike edging lobelia who wanders, Great Blue lobelia blooms on an upright stalk, or raceme, above a mound of flowers. Use Great Blue in a woodland garden or marshy spot in a border. These native specimen plants prefer partial shade and do not tolerate full sun or high heat well.

    Great Blue is a common woodland flower ()

  • 3 / 5

    Enlist "Cardinal Flower" (lobelia cardinalis) to attract butterflies but place it carefully---its brilliant red flowers will out shine other reds. This flower and scarlet "Bee Balm" monarda are two of the most reliable butterfly and hummingbird attractors for the midsummer garden. Plant it in part shade near rivers, streams or "water features." Another North American native perennial, it flourishes in boggy or marshy areas and will tolerate full sun for part of the day. Its growth habit is similar to Great Blue lobelia and flowers have the same two-part shape as any lobelia. Cardinal flower sports longer lower parts in more tubular flowers than other lobelias.

    Cardinal Flower loves boggy or riverside locations. ()

  • 4 / 5

    Incorporate "Indian Tobacco" (lobelia inflata) in wild flower gardens in its eastern North American range. Its natural habitat is pastures, meadows and cultivated fields, so it's a good choice for areas requiring more sun and drought-tolerant plants than its American cousins. Like many wildflowers, it is biennial in habit---it takes two years to flower but reseeds itself if you've planted it in the "right" place. Indian tobacco is available in many garden centres; it grows from a mound of lance-shaped flowers, putting up a raceme of tubular white flowers in late summer. It grows taller than its cousins---up to 3 feet tall---but its blooms are smaller and less showy. Its seed pods and milky sap was used by native peoples for herbal cures from skin salve to emetics.

    Lobelia inflata is also called "pukeweed" for its emetic qualities. ()

  • 5 / 5

    Try more exotic lobelias if your garden is in a tropical or alpine region. The Giant Lobelia and lobelia telekii flourish on the cool mountainsides of eastern Africa. Those with tropical gardens might consider startling Hawaiian native lobelias. Wherever you garden, there is a lobelia that can match your garden's conditions.

    Lobelia aberdarica grows on a Kenyan mountainside. ()

  • Checklist

    Things you will need

    • Plants
    • Pots, hangers, boxes or garden
    • Hand trowels and gardening gloves
    • General garden (5-10-5) fertiliser
    • Water
  • More information

    Tips and warnings

    There are enough varieties of lobelia to match any garden's environment. Always check the cultural requirements of a lobelia before purchasing to make sure it can survive in your backyard's habitat.

    Some exotic lobelias are endangered. They should not be on the market because they will not survive except in very specific climatic conditions that most backyard gardeners cannot replicate. "Indian tobacco" has been used in alternative medicine to treat coughs, asthma and smoking cession. The herb contains contain toxic alkaloids that cause nausea, vomiting and seizures and interact adversely with common substances like nicotine. Researchers at Sloan-Kettering hospital report that they have found no medical value in the herb and have found a number of harmful effects. Do not plant them--or Great Blue or Cardinal Flower--where children or pets may decide to taste them.

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