False indigo 'Purple Smoke'

Questions about false indigo 'Purple Smoke'

Does false indigo 'Purple Smoke' need sun or shade?

False indigo 'Purple Smoke' grows in full sun (6 or more hours of direct sun a day).

It wants ordinary well-drained soil, on the lean side, with no feeding, and little watering once settled.

What zones does false indigo 'Purple Smoke' grow in?

USDA zones 4 to 9. It is hardy to zone 4, which means it survives winter nights down to about −20 °F (−29 °C).

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

When does false indigo 'Purple Smoke' flower in my zone?

In zone 5 it flowers mid 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 false indigo 'Purple Smoke' 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 false indigo 'Purple Smoke' 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 false indigo 'Purple Smoke' 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 false indigo 'Purple Smoke'?

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

• Goat's beard: the same job in a bed; 12 in taller, flowers early June to late June.
• Bluestar: the same job in a bed and the same flowering time; belongs in the middle, not at the back, 12 in shorter.
• Willowleaf sunflower 'First Light': the same job in a bed; 10 in narrower, flowers mid September to mid October.

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

What flowers after false indigo 'Purple Smoke'?

False indigo 'Purple Smoke' 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 false indigo 'Purple Smoke' look like in winter?

False indigo 'Purple Smoke' 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.