Black Adder Agastache

Agastache hybrid ‘Black Adder’

Black Adder Agastache

Agastache hybrid ‘Black Adder’

This product is currently out of stock and unavailable.


How are the heights measured?

All tree, and nothin' but the tree! We measure from the top of the soil to the top of the tree; the height of the container or the root system is never included in our measurements.

What is a gallon container?

Nursery containers come in a variety of different sizes, and old-school nursery slang has stuck. While the industry-standard terminology is to call the sizes "Gallon Containers", that doesn't exactly translate to the traditional liquid "gallon" size we think of. You'll find we carry young 1-gallons, up to more mature 7-gallons ranging anywhere from 6 inches to 6ft.

How does the delivery process work?

All of our orders ship via FedEx Ground! Once your order is placed online, our magic elves get right to work picking, staging, boxing and shipping your trees. Orders typically ship out within 2 business days. You will receive email notifications along the way on the progress of your order, as well as tracking information to track your plants all the way to their new home!

Why are some states excluded from shipping?

The short & sweet answer is: "United States Department of Agriculture Restrictions." Every state has their own unique USDA restrictions on which plants they allow to come into their state. While we wish we could serve everyone, it's for the safety of native species and helps prevent the spread of invasive disease & pests. We've gotta protect good ole' Mother Nature, after all.

About Me


Wonderful colors for months; drought resistant; easy to grow – what’s not to like about the Black Adder Agastache? If you are unfamiliar with growing perennials, here is a great place to start, with a plant that almost thrives on neglect. The 8-inch spikes of violet-blue flowers that top the leafy stalks add lots of interest to all parts of your garden, and they are colorful from mid-summer well into fall. Perfect for growing with other perennials, and a wonderful choice for meadow plantings and other informal ways of growing your garden. The aromatic foliage is pleasant to brush against and the flowers attract butterflies, hummingbirds and bees in abundance. Bring your summer garden to life with this super-easy plant.

  • Long-lasting flower spikes of violet-blue
  • Aromatic gray-green foliage
  • Blooms from mid-summer through fall
  • Attractive to butterflies and hummingbirds
  • Drought tolerant and very easy to grow

Full sun and well-drained soil sum it up for growing the Black Adder Agastache. It loves heat and although it does like some water, established plants take dry conditions well. Plant it in soils of all kinds, from sand to clay, but not in wet areas. Deer and rabbits leave it alone, and it spreads into a wider clump but doesn’t become invasive. Cut back the flower spikes to ground level in fall when they have finished, or leave them up for winter interest and trim in spring.

Plant Hardiness Zones 6-9
Mature Width 1-2
Mature Height 2-3
Sun Needs Full Sun
Zones 6-9

Agastache, also known as Hummingbird Mint, or sometimes as Giant Hyssop, is among our most reliable and easy perennials, and great choices for sunny, drier places in your garden. These are also native plants of North America, and so great choices if you are concerned about the origin of the plants you grow. Many of the best are hybrids between two or more wild species, and that is what we have with the Black Adder Agastache. This plant is medium-sized and self-supporting – it’s an easy perennial that looks almost shrub-like in bloom, with dark-green leaves topped by long spikes of bright-blue flowers open out of dark-purple cups, creating a great two-tone look for many weeks of the summer. Not perhaps as drought-tolerant as some of the others, it is still tough and reliable. Use these plants to attract pollinators to your garden, and hummingbirds too. They are fabulous for a modern, more relaxed gardening style, growing plants where the conditions suit them, and not struggling to make your plants ‘happy’ in unsuitable places. In bloom for weeks and weeks through summer and into fall, Agastache as sure to please.

Growing Black Adder Agastache

Size and Appearance

The Black Adder Agastache is an upright perennial that is a good 4 feet tall when in bloom, forming within a few years a broad bush about 3 feet wide. The oval leaves have serrated edges and a minty, spicy smell when crushed. They cover the stems to the ground and each stem is topped with a spike of flowers, coming into bloom by mid-summer, and continuing right into early fall – one of the longest-blooming perennials you can grow.

The flowering stem has tight-packed whorls of stiff cups with crown-like edges along them, and these are very dark blue – almost black. From them a typical mint-type flower emerges – just a few a day, which is why it is in bloom for so long. The flowers have a prominent upper hood and a broad lower lip – a perfect landing platform for pollinators. This variety doesn’t produce any seeds, so it flowers for longer than wild plants.

Using the Black Adder Agastache in Your Garden

With its clean blue coloring, this desirable perennial is perfect among other perennials, to keep blooms coming when plants like Peonies are over. Grow it among other blues and purples, like Salvia, Perovskia and catmint, with the pinks of Echinacea, or the yellows of Black-eyed Susan. It is also excellent placed among spring flowering shrubs to extend interest in those parts of your garden. Because it is drought-resistant, it’s a natural for slopes and banks, xeric gardens and dry, Mediterranean-style landscaping. Grow it too in its natural habitat – a prairie or meadow garden, among grasses and other prairie plants.


Black Adder Agastache is hardy in zone 6 at least, and probably in zone 5 if the soil is well-drained in winter. It grows well through all warmer zones, including the heat and humidity of the southeast.

Sun Exposure and Soil Conditions

Plant all Agastache in full sun for the best results – these are true sun-lovers. Any well-drained soil is perfect, and good winter drainage is the key to winter survival in cooler areas. It loves poorer soils, especially sandy and rocky soils, and even very alkaline soils.

Maintenance and Pruning

Very little seasonal care is needed. Deer normally leave it alone, not liking the smell, although rabbits can take a nibble, they don’t do much damage. Other pests or diseases are virtually unknown. Plants rarely need staking, unless you need them to take up less room than they naturally do. Removing just the flower spike when early ones finish blooming will keep things looking neater. Some Agastache can be left up for winter, and this provides seeds for small birds. However the Black Adder Agastache is sterile, and produces no seeds, so just cut it to the ground in late fall, once the leaves have begun to yellow. New growth will be back better and stronger next year.

History and Origin of the Black Adder Agastache

There are about 25 species of Agastache, almost all from North America. Agastache foeniculum is the most cold-resistant, growing up into the Arctic Circle, all across the Prairies and midwest, and south to Kentucky and Colorado. The only non-native species is Agastache rugosa, which grows in China and Korea. Called Korean Mint, its leaves make an interesting tea.

In the 1990s the Dutch breeder Coen Jansen crossed Agastache foeniculum with the Agastache rugosa, and grew a batch of seeds. In 1998 he released one whose blue flower color was especially good, naming it ‘Black Adder’.

Buying the Black Adder Agastache at the Tree Center

Almost 25 years since its release, the Black Adder Agastache is still going strong, and still a big favorite among gardeners, so you know it must be good. Make your garden bright without any extra effort, and order now, while we still have plants available.

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Black Adder Agastache

Agastache hybrid ‘Black Adder’