Hummingbird mint, also known as agastache, is a perennial plant that produces aroma-filled foliage and spikes of lavender, orange, or pink tubular flowers that attract hummingbirds. It’s gained popularity as an ornamental plant that adds visual interest to gardens with its vibrant colors and vertical form. But an important question for any gardener considering adding hummingbird mint to their landscape is whether it spreads aggressively like its notorious relative, regular culinary mint. This article will examine the growth habits and spread potential of hummingbird mint to help determine if it will make a well-behaved garden plant or weedy nuisance.
Growth Habits of Hummingbird Mint
Hummingbird mint is a herbaceous perennial in the Lamiaceae or mint family. Like regular mint, it emerges in spring and produces upright, multi-branched stems reaching 1-4 feet tall depending on variety. The light green leaves are ovate to lance-shaped with toothed edges. Plants produce flowers on tall spikes that continue blooming from midsummer into fall. Hummingbird mint spreads via both rhizomatous roots and self-seeding in ideal growing conditions. Here is a table comparing the main growth habits of hummingbird mint and regular mint:
| Growth Habit | Hummingbird Mint | Regular Mint |
|---|---|---|
| Plant Type | Herbaceous perennial | Herbaceous perennial |
| Mature Size | 1-4 feet tall depending on variety | 1-3 feet tall depending on variety |
| Leaf Shape | Ovate to lance-shaped | Ovate to lance-shaped |
| Flowers | Summer to fall spikes | Summer to fall spikes |
| Spreads by | Rhizomes and self-seeding | Vigorous rhizomes |
This table shows that hummingbird mint shares many growth similarities with culinary mint varieties. Both are herbaceous perennials with upright, branched stems and spikes of flowers. They have similar leaf shapes and bloom seasons as members of the same plant family. But while regular mint is known for spreading rampantly via underground rhizomes, hummingbird mint has a reputation for more restrained spread through rhizomes. The other key difference is that hummingbird mint can spread by self-sown seeds while regular mint does not.
Spread Potential Through Rhizomes
The most notorious trait of regular mint is its vigorously spreading rhizomatous roots which allow it to quickly colonize areas of the garden. The species Mentha spicata, or spearmint, is particularly aggressive in sending out lateral roots that creep along the soil surface. Any piece of root that detaches can form a new plant, allowing mint to spread far beyond its original planting site. Many gardeners plant mint in containers or restrict the roots via buried barriers to prevent rampant spread.
While hummingbird mint produces rhizomes and will expand its footprint over time, it does not spread with the same voracity as regular mint. One reason is that different varieties have different inherent tendencies when it comes to the vigor of their rhizomes. For example, the species Agastache foeniculum is noted for spreading more aggressively than some other types like Agastache rugosa which have shown less tendency to spread rapidly via rhizomes. So plant selection plays a role in spread potential, with some varieties of hummingbird mint spreading faster than others.
In general though, hummingbird mint spreads via rhizomes at a much slower rate than the most aggressive mint species. While mint’s rhizomes may travel several feet in a single season, hummingbird mint progresses at the pace of several inches per year. This makes it much easier to control by containment or dividing congested plants. For gardeners who want the vertical accent of hummingbird mint but not the headache of managing its spread, less aggressive varieties are recommended. Or planting in containers always provides maximum control.
Spread Potential Through Self-Seeding
While rhizomes enable both mint and hummingbird mint to expand via vegetative reproduction, hummingbird mint has another way to spread that regular mint lacks – self-sowing from seed. Hummingbird mint produces small brown seeds within its flower spikes. When the flowers fade and dry up, these seeds may drop to the ground and germinate the following spring to produce new plants. Self-sowing is nature’s way of propagating desirable plants. But it can also lead to seedlings popping up in unwanted places.
The potential for hummingbird mint to spread through self-seeding depends on several factors:
- Flower production – Plants that bloom heavily will shed more seed than light bloomers
- Seed viability – Fresh, healthy seeds have higher germination rates
- Site conditions – Seeds need proper conditions like consistent moisture to sprout
- Weather – Significant rain, wind, or animals can disperse seeds farther
- Removal – Deadheading flowers before seed set reduces spread
In ideal circumstances with abundant seed production and dispersal, hummingbird mint can sow itself over an area of several square feet per year. To restrict self-sowing, gardeners should deadhead spent flowers. Plants can also be cut back substantially after bloom. Aggressive self-seeders should be sited away from paths and beds where seedlings are not desired. As with rhizomes, some hummingbird mint varieties spread more readily by seed than others. Selecting types with restrained seeding habits is recommended for easier management.
Best Practices for Planting Hummingbird Mint
Here are some tips for planting hummingbird mint in ways that minimize the potential for unchecked spread:
Select Less Invasive Varieties
Seek out compact hummingbird mint varieties with better behaved rhizomes and less prolific self-seeding. Some examples include:
- Agastache aurantiaca ‘Apricot Sprite’ – compact at 10-12 inches tall with low reseeding
- Agastache ‘Blue Boa’ – non-aggressive roots and slower to self-sow
- Agastache ‘Desert Sunrise’ – forms a tidy clump that resists spread
Allow Enough Space
Give each plant adequate space to grow to its expected mature size without crowding neighbors. Cramped conditions encourage hummingbird mint to spread outward seeking space and light.
Grow in Containers
Choose pots or planters at least 12-16 inches wide and deep to restrict roots. This prevents any potential spread via rhizomes.
Use Physical Barriers
Plant in beds divided by sturdy edging or sink a vertically oriented barrier 1-2 feet deep around roots to keep rhizomes contained within bounds.
Remove Spent Flowers
Deadhead plants before seeds form to minimize self-sowing around the garden.
Cut Plants Back After Flowering
Removing significant top growth after bloom also reduces opportunities for self-seeding.
Site Carefully
If allowing natural reseeding, keep plants away from borders, paths, and beds where seedlings are unwanted.
Conclusion
Hummingbird mint has less potential to become aggressively invasive in the garden compared to its notorious mint relatives. While it can spread via rhizomes and self-sowing under ideal conditions, its moderate rate of spread is easier to control with proper siting, adequate spacing, containment, removal of spent flowers, cutting back after bloom, and choosing less aggressive varieties. With some simple practices, it can make a well-behaved, colorful addition to gardens that also attracts desirable pollinators.
