Peony stems pushing up red through cold spring soil are a welcome sign that winter did its job. Idaho gives peonies the cold rest they need to flower, so the choice comes down to type, planting depth and a little patience.
Best Peonies to Grow in Idaho
Herbaceous peonies and tree peonies suit Idaho because peonies need winter chilling to bloom and Idaho winters provide it. In the USDA hardiness system, the state runs from zone 3b to 7b, so conditions vary greatly across Idaho, while peonies may flower poorly in mild-winter climates. Idaho is not that kind of place.
Herbaceous Peonies
These are the classic garden peonies. They die back to the ground each year and come up again in spring, with blooms in May and June, making them a familiar choice for Idaho yards.
They grow better in full sun. Plant them in fall, keep the eyes near the soil surface, and expect no flowers the first spring after planting.
Tree Peonies
Tree peonies (Paeonia suffruticosa) are deciduous shrubs, not true trees. Their woody stems stay through winter and are never cut to the ground.
They tend to bloom earlier than herbaceous peonies, and the flowers are larger. Choose a protected spot in light shade, which shelters those big early blooms from harsh weather.
Doubles and Other Flower Forms
Peony flowers come as single, double, bomb and anemone forms, in whites, pinks, reds, corals and yellows. Doubles are showy, but they hold a lot of water, and heavy blooms can flop after rain.
Pick a form you like and plan a support ring for the heavy ones. Early, mid and late varieties stretch the bloom season across the yard.
Tall Shrub Types
A mature tree peony develops into a shrub. Its woody branches hold up the large flowers, so staking is not usually needed once it is established.
Give it room from the start, since a shrub that size crowds a narrow bed quickly.
Idaho — the year and the numbers
- State
- Idaho
- USDA zones
- 3b-7b
- Last spring frost
- April 23 to May 7
- First fall frost
- October 7 to October 21
- Annual rain
- 12 in
- Lawn zone
- transition-season
- Source
- NOAA NCEI 1991-2020 Climate Normals, 32F freeze probabilities · Boise
How to Choose a Peony for an Idaho Garden
Idaho has cold winters, so the match depends less on survival and more on space, shade and how much work you want to do each year. Herbaceous peonies need a fall cutback, while tree peonies need a sheltered spot.
Pick by the conditions in your own yard, then plant in September or October.
| Your situation | What suits it in Idaho | Why |
|---|---|---|
| Very cold winter | Herbaceous peony | It dies back each year and needs a cold winter rest to flower |
| Need for winter chill | Any peony | Peonies require winter chilling in order to bloom |
| Little time for upkeep | Tree peony | No fall cutback, and it usually needs no staking once mature |
| Small space | Herbaceous peony | Tree peonies mature into shrubs |
| Sheltered, lightly shaded corner | Tree peony | It prefers light shade and a protected location |
| Open, sunny bed | Herbaceous peony | It grows better in full sun |
Cutting peonies for a vase is its own question. Choose varieties recommended for cut flower production rather than just landscaping.
Which Peonies Suit Different Parts of Idaho
Idaho covers a lot of ground, and the right peony shifts with how cold your corner gets.
- Boise and the Treasure Valley: This is a low valley, with a last spring frost between April 23 and May 7. A tree peony suits a protected spot, while an herbaceous peony benefits from Idaho’s cold winter rest.
- The high country and mountain towns: Winters are colder and seasons shorter. Herbaceous peonies die back and rest underground through winter.
- Southern and eastern Idaho: Cold winters give plenty of chilling. Herbaceous peonies bloom well here, and tree peonies want a sheltered, lightly shaded site.
Wherever you garden, a tree peony prefers a protected location.
Peony Buying Mistakes to Avoid in Idaho
Planting Too Deep
A peony set too deep may bloom poorly or not come up at all. That can leave you waiting for flowers.
Keep the eyes near the soil surface when you plant in September or October.
Expecting Quick Flowers
A newly planted or transplanted peony may not bloom the first spring. Digging it up in frustration only restarts the clock.
Leave it in place and let the roots settle before the cold arrives.
Buying Without Knowing Size
A small potted tree peony can mature into a shrub. Crowded against a walkway or a house corner, it ends up moved or cut hard.
Check the adult size on the tag and leave room. If you want cut flowers, pick varieties recommended for that use.
Where to Get Peony Advice in Idaho
Local help can answer questions about soil, shade and timing.
- The University of Idaho Extension offers plant guidance for the state, and it is a good first stop before fall planting.
- Your county extension office can speak to your local elevation and soil, so call it ahead of a September or October planting.
Common Questions
When Should You Cut Back Peonies in Idaho?
Cut herbaceous peonies back in October or November, after a hard freeze has killed the foliage. Cut stems down to within a couple inches of the ground, and destroy the debris instead of composting it to help prevent disease.
When Do Peonies Bloom in Idaho?
Peonies bloom in June, and some years flowers open in May. Tree peonies tend to bloom earlier than herbaceous ones.
Can You Divide Peonies in Idaho?
Yes, divide them in September or October, in fall, before the ground freezes. Replant with the eyes near the surface.