10 Neat Things about Verbena bonariensis

January 28, 2026 Canada's Local Gardener 376 Views

Lovely, purple-topped flowers that float and sway in the breeze on tough, wiry stems are the magic of Verbena bonariensis. Sometimes (rarely) called purpletop vervain, this plant has been quietly climbing must-have lists because it manages to be both solid and ethereal at the same time. Once it starts flowering, it keeps going for months, often right into fall. Here are ten neat things about Verbena bonariensis.

1. It makes a garden look designed

Those tall, slender stems topped with small purple flower clusters create height without mass. The effect is airy and layered, lifting the eye through the planting instead of stopping it, which is why it slips so easily into mixed borders.

2. Designers quietly rely on it

Garden designers often describe it as a secret weapon because it fills space without competing. Its see-through habit allows other plants to shine while still providing structure, movement, and cohesion.

3. It is a perennial that will not overwinter here

Botanically, Verbena bonariensis is a perennial, but in most of Canada its roots are killed once the soil freezes deeply. Any apparent winter survival is misleading and should not be counted on. But wait… this is an annual that deserves another look.

4. What comes back is almost always seed

When plants reappear the following year, they are nearly always seedlings. The seeds are far more cold-tolerant than the roots, allowing them to survive winter and germinate when conditions improve.

5. The seed is surprisingly hardy

Dry, dormant seed can withstand soil temperatures that living plant tissue cannot. This explains why Verbena bonariensis can reseed even in Prairie climates where winter soil temperatures drop well below the plant’s survival threshold. Some people even recommend cold stratification for your seeds.

6. Seedlings know when to grow

Self-sown seedlings often outperform those started indoors because they emerge when soil temperature, moisture, and light are aligned. This timing advantage is well documented in annuals adapted to variable climates.

7. Starting from seed indoors takes patience

When started indoors, germination can be slow and early growth underwhelming. It often sits for weeks looking unimpressive, which can tempt gardeners to give up too soon.

8. Do not give up on slow seedlings

Once summer heat arrives, growth accelerates dramatically. Flowering then continues steadily from mid-summer until hard frost, far longer than many faster-starting annuals.

9. It thrives on neglect more than care

Average to poor soil produces sturdier plants than rich soil. Extra fertility leads to lush, floppy growth, while lean conditions keep stems wiry and upright.

10. It earns its keep until the very end

Because it flowers for so long and asks for so little, Verbena bonariensis is one of the most rewarding long-season annuals you can grow. Once it finds a foothold, it often becomes a quiet regular in the garden, whether you plant it or not.