Agastache Scrophulariifolia
Purple Giant Hyssop for Monarch Butterflies and More…
Agastache Scrophulariifolia common names: Purple giant hyssop, Purple giant-hyssop
Agastache Scrophulariifolia Plant Specs
- Perennial: USDA hardiness zones 3-8 (lows -40 °C or -40 °F)
- Native Plants: Eastern US and Eastern Canada (Ct, DC, De, Ga, Ia, Il, In, Ks, Ky, Ma, Md, Mi, Mn, Mo, NC, Ne, NH, NJ, NY, Oh, Pa, SC, SD, Tn, Va, Vt, Wi, WV)
- Full sun to part shade
- Average water needs; do not over water
- Height: 5 to 8 feet
- Spacing: 1 to 2 ft
- Blooms: purple, pink, or white flower spikes
- Deep Green Leaves: 4 inches wide, 2 inches long at maturity, round base with pointed tip
- Blooms summer to early fall: late June, July, September into early October
Agastache Scrophulariifolia Pros
- Top attractor during summer and the monarch migration
- Long blooming flowers up to 2 months
- High nectar content to nourish butterflies, hummingbirds, bees, and more..
- Height makes it easy to view butterflies feeding
- Can grow in poor soils
- Insect Pest, rabbit, deer, and disease resistant
Agastache Scrophulariifolia Cons
- Doesn’t bloom until late summer, but worth the wait
- Spring planted seeds and small seedlings won’t flower first year
- Not commonly sold in nurseries. Anise hyssop is not a good substitute for attracting butterflies
Purple Giant Hyssop Plant Propagation
- Sow seeds directly outside in fall- November is a good option for most regions
- Start seeds indoors before final frost
- Sow seeds directly after final frost
- Divide large clumps in fall or spring with a sharp knife or shovel
- Winter sowing is a good option for controlling plant placement
This member of the mint family grows reliably once established…
Agastache Scrophulariifolia Growing Tips
- Plant at least 3 together for max monarch attraction
- Once your agastache plants eclipse 6 feet, use stakes and plant support clips to keep the stalks from flopping over, allowing you to better see the feeding frenzy.
- Good for back perennial borders
- Purple Giant hyssop can be planted/divided in spring or fall– we divided in fall with great results.
- Once established, plants put out multiple stalks. You can add more plants through division of mature perennial plants and letting plants seed.
- Cut- if you prefer bushier growth and less height, cut back stalks 25% to 50% in late spring…experiment to see which height you (and the butterflies) prefer.
Pollinator Plus
Besides monarchs, purple giant hyssop is popular with American ladies, bumble bees, hairstreak butterfly, honey bees, hummingbirds, native bees, painted lady butterfly, red admirals, sulphur butterflies, eastern tiger swallowtails. Goldfinches and other birds love the seeds.
Please comment below if you’ve seen other butterflies sipping nectar from Agastache Scrophulariifolia. This type of info is rarely listed so your input can help others make the best decisions for their precious butterfly garden space.
Buy Agastache Scrophulariifolia Plants and Seeds
Always purchase seeds and plants by botanical (scientific) name. There are many agastache species that don’t attract butterflies so be sure you search for, and purchase Agastache scrophulariifolia by species name to avoid buying the wrong variety:
5 Questions about Purple Giant Hyssop
How big do Agastache scrophulariifolia get?
This will likely be one of the tallest plants in your butterfly garden and our tallest have towered to 10 feet high. The good news is they are not top-heavy so they will require little staking compared to other tall plants like Mexican Sunflowers. They can be cut back in late spring for bushier growth.
Does purple giant hyssop spread?
It can spread through seeding. In both of our Minnesota garden locations it has been minimal and unwanted seedlings are easy to pull. If you want to avoid any seeding, you can cut off flower heads before they go to seed.
Is A. Scrophulariifolia an invasive plant?
In our northern garden (zone 5a), it has not been invasive or even aggressive.
Does giant hyssop come back every year?
In our northern garden (hardiness zone 5a) it has come back reliably year after year.
Do you cut back purple giant hyssop?
It dies back to the ground in winter. Each spring we cut back stalks to the ground and new shoots emerge.
Find More butterfly favorites on our Butterfly Plants Page
Agastache scrophulariifolia in your butterfly garden:
Have you ever grown Agastache foeniculum – Anise Hyssop. That is the native form that gets 3-5 foot tall. I can buy it from Wild Roots Native farm. I wonder if it would attract as many butterflies as the Purple Giant Hyssop?
Hi Terry, A. foeniculum does not attract butterflies like A. Scrophulariifolia does, but it does attract a good number of bees.
Have you grown the pink or white? Do you prefer pink, white or purple?
Hi Terry, I think the purple ones are a little ‘showier’ but they both attract butterflies and pollinators. In my experience, the purple ones bloom a little earlier so having both on hand gives you a longer bloom period
Hi Tony,
You have a link to some plant clips. Do you tie your Purple giant Hyssop up? Do they have more than one stem/branch that need tied/clipped? I have a Windwalker Royal Red Sage and a Common Iron weed that I tie up, but they have more than one stem/branch so I am not sure if 1) a dowel rod like Amazon shows in the picture with the clips, would be strong enough or tall enough. 2) would the clips work if the flower has more than one stem that needs supported?
the flowers aren’t top-heavy so the stalks (mostly) stay upright. We don’t need to stake these very often…some even grow to 7-8 feet in our northern garden. We use stakes with clips, cables ties, or garden twine.
How wide does it get? I planted Windwalker Royal Red sage and Common Iron weed this year, and do not want it to be too wide. I don’t want the width to block those perennials. Heighth is not an issue as they are back of the border against a tall fence. The butterflies and hummingbirds like them.
Hi Terry, not very wide…about 1 to 2 feet.