To be sure, I’ve grown the old-fashioned lovely Agastache (pronounced Aga- sta -cheee) before all over my garden as it self-sows with abandon but I’ve not yet grown most of the more modern hybrids as perennial flowers.
Let me give you a heads-up and a warning about these lovely plants because you’re going to be seeing them more and more on garden centre shops in the next few years.
Some you can grow and overwinter and many you’ll kill as they are too tender. The problem will be some confusion in the nursery trade about which are which and some retailers may indeed try to sell the tender ones as hardy because of the common name Hyssop and its reputation for hardiness. See below for guidelines.
I’ve already seen this happening so be aware of what you’re getting.
How To Grow Agastache
The Agastache that you’re likely familiar with is commonly called Hyssop. It is a lovely plant with blue flowers that thrives in full sun and well-drained soils.
So while I apologize to all who have clay soils for describing this plant, (clay kills Agastache) you can grow it quite nicely in raised beds because it isn’t a water-hog and will grow quite nicely in dry gardens once it is established.
- Bloom time: Early summer to midsummer
- Height: 24” to 36”
- Sun needed: Full
- Bloom color: Purples, white
- Planting space: 12” to 18” apart
- Soil preferred: Open, Well-drained
- Propagation method: Seed, Division
A. cana. Grows 12-36 inches tall. Hardy to USDA 7
A. foeniculum Grows 20-30 inches tall. Hardy to USDA 6
A. rugosa Grows 24-30 inches tall. Hardy to USDA 5
A. rupestris Grows 36-48 inches tall. Hardy to USDA 5
This means if you’re in a USDA 4 – you’re going to treat most Agastache (certainly the modern hybrids) as annuals.
Agastache foeniculum or Anise-Hyssop has graced almost every garden I’ve ever grown. This licorice tasting plant is easy to grow from seed and is quite hardy in our local gardens.
It is indeed a wonderful plant with its blue flower spikes and if happy, it will self-sow.
In this way, you’ll never lack for this plant even if the short-lived mother plant dies off after a few years.
The leaves make a soothing tea and are welcome additions to my kitchen herb garden.
Drying the plant is quite simple; all I do is take a few branches and hang them upside-down in the kitchen for a week.The leaves curl and brown and once fully dried, they go into a glass jar (I use old sealer-jars) for storage and use in teas during the winter.
A. rugosais a much taller form and is sometimes called ‘Giant Hyssop’.
This plant too is hardy and fun to grow. It will easily top 4-feet tall in the garden and the blooms in early summer are rose to white coloured depending on the plant.
While it is a little tender, it will take -10C with little apparent damage.
If you can find the seed, it is easily sown and started with no heat mat or other fancy equipment as long as you keep the soil temperatures about 60F.
Sow them indoors in May and transplant outdoors in July for blooms the following year.
I doubt you’ll find this plant in garden shops but you will find it in seed catalogues or the Internet.
Agastache urticifoliais the other hardy form (again to -10C) that you might find in seed catalogues.
This one tops out around 6-feet tall and will grow in exactly the same conditions as the previous two. The flowers on this delightful plant are rose to violet shades.
Annual Hyssop Confuses The Issue
Where we get into difficulty with tender plants is when we add A. mexicanato the breeding mix. This plant is quite tender as it is a tropical species but the flower colours are wonderfully blended and varied ranging from bright reds through to pale pink-whites.
This gives the plant breeders a red gene and a blue gene to play with and as you can guess, the resulting rainbow of plants is fantastic. These heavy blooming southerly plants are fantastic and the trials I saw last year were magnificently in bloom in a hot spot in small containers.
I confess the plant collector in me lusted after them.
Note from Doug:
At this point, I have not tried to grow any of the above so I have no trials to report. When I do, the report will be included at the bottom of this page.
Unfortunately The Brighter The Bloom The More Tender The Plant
But the brighter the colour of the bloom, the more tender the plant. When you see Agastache on the plant benches this spring, make sure you know what you’re buying. Do not think you’re buying a perennial when in fact you’re really getting an expensive annual.
And yes, the annual forms will be priced pretty close to perennials if the wholesale numbers I saw are any indication of the retail pricing that we’re all going to see.
Having passed along this warning, let me also say that if I can find them on the benches this spring, I’m going to pick up a few, grow them in the garden all summer and try to overwinter them in the fall.
Getting More: Propagation
In the meantime, I’ve got some seeds started of a golden-leaved annual variety (start at 70F soil temperatures and they germinated in 5-7 days) and while it is tender, it will at least let me ease the pangs of plant-lust for this family of lovely Hyssops.
Other species and varieties start equally easily from seed. Cuttings can also be taken as can early spring divisions.
Notes from Doug
2012: The gold leaved Agastache were magnificent and oh so full of promise in their first year. See where this is going? 🙁
2013: Didn’t make the winter. Oh well…
Other Interesting Notes about Agastache:
Hummingbirds love this plant – among others. It’s also one of the longest blooming plants in the perennial garden (some of this ability is due to the annual species in the breeding) And to top it off, butterflies love it as well.