LSU AgCenter's Weekly Message

Not Just the Blues: Indigos and Wild or False Indigos

When I think about wisterias, which were discussed in last week’s article, I sometimes think of the indigo plant – Kirilow’s or Chinese indigo (Indigofera kirilowii) – that’s cultivated under tree canopies in Louisiana. This wisteria relative produces pinkish flower clusters (racemes) similar in size to those of American wisteria. It begins flowering in the spring and produces some blooms in summer and fall, too.

Kirilow’s indigo is a deciduous plant that remains short, growing approximately 2 to 3 feet tall, rather than climbing like wisterias do. Where conditions are good for its growth, it often spreads but is not considered invasive. It grows well in partial shade.

Despite the name, Kirilow’s indigo is not one of the indigos that was a major historic source of dye. Those species include true indigo (I. tinctoria) and anil de pasto or bush indigo (I. suffruticosa). The latter is native to Louisiana but more common in the west-central part of the state than the Florida Parishes. A third major source of indigo dye was not an Indigofera species at all but a mustard family plant called woad (Isatis tinctoria).

Besides Kirilow’s indigo, there are wild or false indigos in the Baptisia genus that are grown as ornamental plants in the southeastern US. Like Indigofera species, these are in the bean family, and some have historically been used to produce dye. Wild indigos support bees and butterflies.

Blue wild indigo (Baptisia australis) was used to make dye in North America before true indigo was cultivated here. The Perennial Plant Association named it the Perennial Plant of the Year for 2010. It produces blue flowers in spring and grows to approximately 3 to 4 feet tall and wide. It’s native to much of the eastern US though not to Louisiana.

Like blue wild indigo, white wild indigo’s (B. alba) name reflects its flower color. This one is native to Louisiana, including the Florida Parishes.

Other Baptisia species found in Louisiana include several yellow-flowered species: longbract or nodding wild indigo (B. bracteata), Nuttall's wild indigo (B. nuttalliana), and yellow wild indigo (B. sphaerocarpa). The yellow wild indigo variety ‘Screamin’ Yellow’ performed well at the Hammond Research Station.

Plant wild indigos on sites with full to partial sun exposure and well-drained soil, but provide adequate moisture while they’re getting established.

Let me know if you have questions.

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Dr. Mary Helen Ferguson is an Extension Agent with the LSU AgCenter, with horticulture responsibilities in Washington and Tangipahoa Parishes. Contact Mary Helen at mhferguson@agcenter.lsu.edu or 985-277-1850 (Hammond) or 985-839-7855 (Franklinton).