Baptisia australis Blue False Indigo
Baptisia is one of the most reliable, long-lived and easy-to-grow perennials in the landscape. These attributes, combined with its striking garden appeal, has led to its selection as the Perennial Plant Association’s 2010 Plant of the Year. Its common name, blue false indigo, was derived from its use as a substitute for true indigo (Indigofera) from the West Indies, which was used to make blue dye.
Baptisia provides four seasons of interest beginning in mid- to late spring, when foot-long spires of intense indigo-blue flowers arise above the attractive, trifoliate, soft blue-green foliage. Following the impressive display of blooms, it develops numerous 2- to 3-inch-long puffy seed pods that emerge green and turn charcoal black as they ripen in the late summer or early fall. These seed pods remain well into the winter months and provide winter interest sought by numerous gardeners and landscapers. Additionally, baptisia attracts butterflies into the garden and is resistant to deer feeding.
It forms attractive shrub-like clumps reaching 3-4 feet high and up to 6 feet wide at maturity. Baptisia provides a terrific backdrop for other perennials and groundcovers, makes a wonderful specimen plant on its own or can be used effectively in small groupings, or native or meadow plantings. Blue false indigo is a native species of North America and is commonly grown throughout USDA Hardiness Zones 3 to 8. It grows best in full sun but will perform well in locations that receive light shade; avoid placing them under heavy shade as they tend to require staking and may not flower under these conditions.
Baptisia australis can be propagated by seed or with vegetative tip cuttings. Germinating seed can be challenging because of its hard seed coat, providing variable results over time. The best results are obtained when using freshly harvested seed. Older seed can be used but will require stratification or scarification prior to sowing and will usually have a significantly lower germination rate compared to fresh seed. Many growers use a hot water soak over night to soften the seed coat and bypass the need for stratification. Jelitto offers baptisia as Gold Nugget seed, which is pretreated to help improve the germination rate and bypasses the need for stratification.
It is best to sow them in plug trays with large cell sizes (no smaller than 72-cell). Sow one to two seeds per cell when using Jelitto’s Gold Nugget or fresh seed, and sow two to three seeds per cell when using regular (untreated) seed. Do not cover them after sowing; it is beneficial to cover them lightly with growing media after the radical has emerged. Germination will occur over a period of two to three weeks with temperatures of 68-75° F. From sowing, it will take eight to 10 weeks to produce a transplantable plug when grown at 65° F. When propagating them from cuttings, they require a light misting regime for the first seven to 10 days and will reach a transplantable size in six to seven weeks.
Baptisia are best produced in large containers (one gallon or larger) and should be planted even with the soil line of the plug it was previously produced in. Bareroot starting materials are also available and should be planted so the crown is slightly below the soil surface. To promote branching, pinch them prior to transplanting and again several weeks later; it is not necessary to pinch baptisia that was planted from bareroot.
Baptisia performs best in a growing mix with good water-holding characteristics and, more importantly, adequate aeration; many bark-based growing mixes work well. Maintain the media throughout the production cycle with a pH between 5.8 and 6.5. They are moderate feeders requiring a controlled-release fertilizer at a rate equivalent to 1.0-1.2 pounds of nitrogen per yard of growing medium or nitrate levels of 100 ppm under a constant liquid fertilizer program. Baptisia can be grown with slightly below-average amounts of irrigation.
Because of baptisia’s growing habit, it often gets taller than growers would like in container production. There has been limited research done on controlling the height of blue false indigo, with some success when applying a drench of paclobutrazol (Bonzi, Piccolo or Paczol) at 12-18 ppm using the “watering-in” method. Spray applications of paclobutrazol provide less height reduction than a drench application and would require multiple applications using 30-45 ppm. Growth regulator applications are most effective when applied early in production; begin applications when the plants reach 6 inches tall.
Insects and Diseases
Compared to many perennials, the occurrence of insect pests and diseases are usually minimal with baptisia. The primary insect pests are spider mites, and the most common diseases are leaf spots, powdery mildew, rust and root rots. Routine scouting should be sufficient to determine the presence of any pests or diseases. There are a number of good products on the market for controlling these problems once they are detected.
One of the most challenging aspects of growing baptisia in containers is bulking. From plugs, this is not a crop that can be quick cropped easily, as it takes a long time to fill out the container. When plugs are used, plant multiple liners in each container (at least two plugs per one gallon pot and more for larger sizes). Additionally, heavy flowering will not occur until the plants are two to three years old. Therefore, when using plugs or liners, allow adequate time for bulking so the plant can build size and mature. In most cases, baptisia should be considered at least a two-year crop (planting this spring for the following spring’s sales).
However, full-flowering plants of baptisia can be achieved in a short period of time when using bareroot starting materials from Walters Gardens, Inc. Each bareroot contains five to eight buds and will easily fill out gallon-sized containers within weeks of planting.
Blue false indigo does require vernalization for flowering. Spring-planted bareroot does not require vernalization as it received cold treatment in the field before the plants were harvested. After vernalization, baptisia can be grown at natural day lengths. Flowering will occur in seven to eight weeks when they are grown at 68-70° F or nine to 10 weeks at 63-65° F.
Baptisia Gold Nugget seed is available from Jelitto Perennial Seeds (www.jelitto.com); untreated baptisia seeds are available from various seed distributors. Bareroot can be obtained from Walters Gardens, Inc. (www.waltersgardens.com). Plugs and liners can be purchased from propagators throughout the country.