How to Grow Physostegia (Obedient Plant)
Physostegia virginiana
Physostegia is a vigorous, upright perennial native to North America that produces spikes of tubular pink to lavender flowers from mid-summer to autumn. It thrives in full sun to partial shade and moist, well-drained soil. Plants spread readily by rhizomes and may need dividing every 2-3 years to stay contained. Fully hardy in zones 3-9, it attracts bees, butterflies, and hummingbirds. Cut back dead growth in late autumn or early spring. Pinch tips in late spring for bushier plants.
Yearly Lifecycle
Care Essentials
Apply a balanced general-purpose fertiliser in early spring as new growth emerges. Physostegia is not a heavy feeder; avoid over-fertilising which promotes lush foliage and excessive spreading at the expense of flowers.
Watch For
- Rust on foliage in humid conditions
- Slug and snail damage on young shoots
- Powdery mildew in dry spells
- Aphids on flower buds
Care Requirements
Light
Full sun to partial shade
Grows best in full sun with at least 6 hours of direct light. Tolerates partial shade but may become leggy and require staking. Afternoon shade is beneficial in hot climates.
Watering
Moist but well-drained
Prefers consistently moist soil, especially during the first year. Once established, tolerates short dry spells but flowers best with regular moisture. Avoid waterlogged conditions.
Fertilizing
Light annual feed in spring
Apply a balanced general-purpose fertiliser in early spring. Avoid over-feeding which promotes excessive leafy growth and rhizome spread at the expense of flowers.
Pruning
Cut back in autumn, pinch in spring
Cut dead stems to ground level in late autumn or early spring. Pinch growing tips by one-third in late spring for bushier plants that need less staking.
Spacing
45-60 cm apart
Space plants 45-60 cm apart to allow for spreading habit. Divide clumps every 2-3 years to control spread and maintain vigour.
Support
May need staking if not pinched
Tall varieties in exposed positions may need support. Pinching tips in late spring reduces the need for staking by producing shorter, bushier growth.
Growing Tips
Control rhizomatous spread
Physostegia spreads aggressively by underground rhizomes, especially in rich moist soils. Divide clumps every 2-3 years in spring or install root barriers to keep plants contained.
Pinch for compact growth
Pinch back growing tips by one-third in late spring when plants reach 30 cm. This produces bushier, more compact plants that are less likely to need staking.
Excellent pollinator plant
The tubular flowers are highly attractive to bees, butterflies, and hummingbirds. Plant in groups of three or more for maximum pollinator impact.
Good cut flower
Cut stems when the lower flowers on the spike are open. They last well in water for 7-10 days and the buds continue to open up the spike.
Spacing & Planting
| Plant spacing | 50 cm |
| Row spacing | 50 cm |
| Mature height | 120 cm |
| Mature spread | 75 cm |
Space 45-60 cm apart to allow for spreading rhizomatous habit. Divide clumps every 2-3 years to control spread and maintain vigour.
