By: Ash Lloyd, EcoHouse Green Gardening Volunteer
Often known as “blue false indigo” and “blue wild indigo”, Baptisia australis is a flowering legume native to North America. The plant is a herbaceous perennial that can grow up to 1.5 meters tall and up to a meter across. A mature plant will have a woody base that new growth sprouts from every year until it finally dies. It spreads both through its seeds and through asexual reproduction with its rhizomes beneath the soil. Its flowers are distinctive pea-like flowers that range from light blue to deep violet in hue. Its seeds are formed in large pea-like pods that turn dark brown as they mature and dry out. During the fall season the dried pods can often be heard blowing in the wind, leading to some of its nicknames being “rattleweed” and “rattlebush”. The pods can also break off in the wind and tumble away, taking their seeds with them as a survival strategy for dispersing the seeds.
Uses by Humans
Blue wild indigo has long been used as a dye plant for creating the indigo coloured dye that it gets its name from. While it is considered an inferior plant for dye production compared to true indigo (Indigofera tinctoria), it saw relatively large use in areas where the climate was too cold for true indigo to grow successfully. Some of the first people to use the plant for dye were the Cherokee, though other Indigenous people also used the plant. This practice was picked up by European settlers and continued until the mid-20th century when the introduction of synthetic dyes made many naturally produced dyes less profitable.
Blue wild indigo is a member of the legume family, which means that specially developed nodules on the plant’s roots allow it to release free nitrogen into the soil. This helps increase the fertility of the soil and helps certain plants that require lots of nitrogen to grow. It is typically found along the edges of woods, along streams, or in open fields. It should be noted that while blue wild indigo is a native plant, it is also a fairly persistent plant that can spread quickly due to its deep taproots and rhizomes. With this in mind you should be careful when introducing it to an area of native flora so that it doesn’t dominate everything around it.
Growing Blue Wild Indigo
Blue wild indigo prefers partial to full sun in moist, well drained soils but will tolerate clays and lime. It also prefers an acidic soil for ideal growth but is tolerant of less ideal conditions. The seeds should be lightly abraded to get through their protective seed coating and/or subjected to a couple months of cold stratification for ideal germination rates. Newly planted blue wild indigo will need to be regularly watered during its first year but will become drought resistant after that first year thanks to its deep taproot. It will take 2-3 years before the plant is mature enough to produce its own seed pods but once it does, you’ll be delighted by this charming native addition to your garden.
It should be noted that young shoots of Baptisia australis have been known to resemble young asparagus shoots and so the two should not be planted close together in order to avoid confusion. The plant itself is moderately toxic and the seed pods especially should be kept out of the reach of young children.