Clusterspike Indigobush

Size, growth and what to expect

No source rates its growth, so our growth estimator treats it as a slow grower, like our leadplant, about a foot a year. It makes a shrub 2 to 4 feet tall and 3 to 4 feet wide, and a few reach 5 feet. Its gray, downy leaves carry up to 45 small leaflets, and the foliage has a faint smell of cat urine.

Four to twelve slender spikes, each 4 to 7 inches long, cluster at the top of the stems from May into July. The small flowers range from white to blue violet, with yellow to orange anthers. Like other amorphas, it bears tiny pods with a single seed each, which ripen brown in mid to late summer.

It grows wild on the Coastal Plain from North Carolina to Florida and west into Alabama, and now and then in the Piedmont. Its home is dry, open woods, sandhills, scrub and savannas. It is the most widespread of the low indigobushes of the Southeast.

How to grow Clusterspike Indigobush

Clusterspike indigobush wants full sun or light shade and a sandy soil that drains well. Once rooted it takes long dry spells, but not standing water or salt spray. Set plants 3 feet apart and 2 feet from a wall. At its size it can go within 15 feet of overhead wires.

Saplings ship bare-root or potted. Plant them dormant, in a hole wider than the roots and no deeper. Set the crown at the soil line, put the native soil back in, and keep the mulch thin and clear of the stems. Seed sprouts best when it is rubbed out of its pod first. Sow it about a quarter inch deep in spring. Cleaned seed keeps well in the freezer.

Water weekly through the first summer, then only in long droughts. Heavy shade stunts it, so keep taller plants from closing over it.

Each flower carries both male and female parts. A lone plant sets some seed with its own pollen and more with pollen from another plant, so plant two or more seedlings from different parents. Native bees work the flowers, and it feeds the caterpillars of the silver-spotted skipper and the southern dogface.