Blue false indigo

Questions about blue false indigo

Does blue false indigo need sun or shade?

Blue false indigo grows in full sun (6 or more hours of direct sun a day) and part sun (4 to 6 hours of sun, including some afternoon sun).

It wants ordinary well-drained soil, of average fertility, and little watering once settled. Once settled in, it stands drought.

What zones does blue false indigo grow in?

USDA zones 3 to 9. It is hardy to zone 3, which means it survives winter nights down to about −30 °F (−34 °C).

Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.

When does blue false indigo flower in my zone?

In zone 5 it flowers late May to mid June. As a spring flower it moves about a week for every zone: earlier where it is warmer, later where it is colder.

Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.

How far apart should blue false indigo be planted?

3½ ft (100 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 4 ft (120 cm), so a group knits into one patch.

It grows 4 ft (120 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.

How many blue false indigo plants do I need?

At 3½ ft apart, set out in staggered rows:

• 1 to fill 10 square feet (about 1 m²)
• 4 for a single row 10 ft (3 m) long
• 3 to fill a 4 × 8 ft bed on its own

In a mixed border, plant it as one, with clear ground around it: a feature plant is seen as an object, and a group of them is a thicket.

In the bed above, the planner used one in one group.

Is blue false indigo poisonous to dogs and cats?

Yes: mild toxicity to people, dogs and cats. May cause mild stomach upset if eaten.

Rated from NC State Extension. Where references disagree, the more cautious rating is used.

Is there a pet-safe plant like blue false indigo?

These come closest to doing what blue false indigo does, and no toxicity is recorded for them:

• Bluestar: the same job in a bed, the same flowering time and the same colour; belongs in the middle, not at the back, 12 in shorter.
• Goat's beard: the same job in a bed and the same flowering time; 12 in taller, cream, not blue.

Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.

Do deer eat blue false indigo?

Mostly not. NC State lists it as resistant to deer and rabbits. No plant is proof against a hungry deer in a hard winter, but this one is low on the menu.

What flowers after blue false indigo?

Blue false indigo is over by mid June. These start as it finishes and carry the same spot on, so it never goes flat:

• Bee balm: from early July to early August, 3 ft tall, to stand in front of it and cover its fading stems.
• Purple coneflower: from late June to early September, 3 ft tall, to stand in front of it and cover its fading stems.
• Daylily: from late June to early August, 2½ ft tall, to stand in front of it and cover its fading stems.

What does blue false indigo look like in winter?

Blue false indigo dies down, but leave the stems standing: the seed heads stand through the winter. Cut them down in early spring, before the new shoots come.

Is blue false indigo good for bees and butterflies?

Blue false indigo is visited by pollinators, bees, butterflies and hummingbirds.

It is a host plant: the caterpillars of eastern tailed-blue, frosted elfin, wild indigo duskywing, hoary edge, orange sulphur and clouded sulphur feed on its leaves. A butterfly can only lay its eggs on its host plants, so these do more for it than any nectar flower.

It is native to the United States.