Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
The first time that I saw baptisia, I fell in love with it. Such pretty flowers, such interesting seedpods. Even the leaves are attractive. Then I was told that it is invasive. Very invasive. I’ve watched it year after year gradually take over a garden, crowding out other pretty flowers on its march to world domination.
What is Baptisia?
Baptisia (Baptisia australis) is a flowering perennial plant that is a member of the legume family which includes peas and beans. It is native to Eastern and Central North America. Another name for baptisia is false indigo because its flowers produce a blue dye that was once used as a cheap alternative to true indigo (Indigofera tinctoria), an Asian plant that was more expensive.
Baptisia is hardy in zones 3 – 9. In the wild, it can be found in meadows and open woods and along streams. The plants are quite tall, 3 – 4 feet in height and 3 – 4 feet in width. The leaves are a lovely blue-green. They are trifoliate meaning they grow in groups of three along the stem.
The flowers appear in the late spring. They are a striking blue color and look a lot like pea flowers. They grow on racemes (long flower stalks) like lupines. Newer hybrids have flowers that are yellow or purple. The flowers can be cut and used in arrangements.
Also used in flower arranging are the seed pods which appear after the flowers. They grow to 2 – 3 inches and look like pea pods but turn dark as they ripen. The seeds inside rattle in the breeze resulting in other common names for baptisia: rattle bush and rattle weed.
How to Grow Baptisia
Baptisia grow best in full sun but will tolerate a little shade. The plants often need support when grown in partial shade because the stems are not as strong. Well-drained soil that is on the dryer side is best. Established plants are drought tolerant. Soil pH should be neutral to slightly acidic. It is not necessary to fertilize these plants. Like all legumes, they are nitrogen fixing plants which means that they produce their own nitrogen in the soil.
Space your plants 24 – 36 inches apart. Don’t worry, the gaps will fill in rapidly. Baptisia spreads via underground rhizomes. Don’t let them get out of hand. They have long tap roots making them hard to dig up if you wish to remove plants that are overgrowing their place in your garden.
In the colder parts of their range, the foliage dies in the fall. You can cut it down to the ground in the fall or in the spring before the new growth begins.
How to Divide Baptisia
Baptisia is difficult to divide because it has a long taproot. It is usually best to divide the plants when they are still young and their taproot is not as long. Division should be done in the spring as the new growth is starting.
Using a spade, dig 6 inches around your plant. Once you are down about 12 inches, start digging under the root ball. At this point, you will encounter the taproots. Cut them using pruners or loppers if they are particularly large.
Once you have the entire root ball out of the ground, brush away as much soil as you can. Then use something sharp like a saw to cut the crown into pieces. Each piece, or division, should be at least 6 inches in diameter and have both leaves and roots.
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Replant your divisions 24 – 36 inches apart and water well.
How to Grow Baptisia From Cuttings
If you don’t want to go to all of the effort of digging up your baptisia, you can propagate it from cuttings as long as the plant is not patented. Some of the newer cultivars have been patented which means that you cannot legally grow them from cuttings or tissue culture because you are making an exact copy or clone of the plant.
If your plant is an older cultivar and not patented, you should make your cuttings in the spring when the plant is actively growing but before it flowers. Your cuttings should be at least 6 inches long. Strip the leaves from the bottom 3 inches, dip them in rooting hormone which will promote growth of the roots, and gently press it into a container filled with pre-moistened soil. Put the container and cutting into a plastic bag to create a humid environment.
Check your cutting periodically to make sure that the soil is still moist. Gently water it if the soil starts to dry out. Your cutting should develop roots in about 8 weeks. You will know that roots have grown because you will see new growth developing. Plants with no roots cannot grow new stems and leaves.
How to Grow Baptisia From Seed
Baptisia can be grown from seed but it will take 3 – 4 years before the plants will bloom. The easiest way to grow baptisia from seed is to sow the seed in your garden in the fall. Baptisia seed has a hard shell. Leaving the seed outdoors exposed to winter weather will soften the shell enough that the seeds can germinate the following spring.
If you wish to start your seeds indoors in the spring, you will need to cold stratify them. This is to fool them into thinking that winter has come and gone. Chill the seeds, unplanted, for 6 – 12 weeks in your refrigerator.
After chilling, you will need to scarify the seeds. This is a way to soften the shell so that the seeds can germinate. You can scarify in one of two ways, either by lightly filing the shell or by carefully nicking it with a sharp knife. You have to be careful though not to damage the embryo inside. With seeds that have hard shells, I prefer to soak them overnight. This softens the shell enough that the embryo will be able to break through and germinate.
Plant the seeds ¼ inch deep in a container filled with pre-moistened soil. A heat mat set to 75⁰F will speed up germination by fooling the seeds into thinking that spring has arrived and the soil is warm. Germination should occur in about 2 weeks.
You can transplant your seedlings into your garden after your last frost. Space them 24 – 36 inches apart.
© 2020 Caren White
Caren White (author) on June 12, 2020:
This is a plant that is native to North America so you may only find it in the UK in nurseries that specialize in rare plants. I hope that you can find it. They are lovely.
Imogen French from Southwest England on June 12, 2020:
It looks very pretty, lovely coloured flowers. I'm not sure I've seen this plant in the UK, but will look out for it - thanks for the info.