Illustration
Montgomery
Astilbe japonica 'Montgomery'
Montgomery blooms from June through July.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Montgomery
Plant it in part shade. It prefers high water. It is hardy in USDA zones 3–8. Expect it to reach about 24 in tall and 20 in wide at maturity, in roughly 2 years (checked).
No toxicity note is on file for Montgomery. That is not a clearance: check its safety for people and pets before planting.
What was checked
Fifteen fields were checked against named botanical sources, each recorded beside the sources that carried it, with every unsettled point written down and decided: mature height and spread, hardiness zones, sun, water, bloom months and color, the trait tags, soil, diseases, pests, toxicity, the plant's own names, and years to mature size, which rests on a recorded house rule where no publisher states one and is marked so. Each fact above carries its own mark. The planting, spacing and size sections are derived from these checked facts by a fixed rule, not checked separately, and the plant type is the library's own classification.
When to plant Montgomery
Plant Montgomery in early spring as soon as the soil is workable, or in early fall at least six weeks before your first frost, so roots establish in cool weather. In zone 5, the middle of its hardy zones 3 to 8, spring means April to June and fall means August or September. Once settled, it blooms from June to July.
Month-by-month timing for your zone is on the planting calendar; if you garden near zone 5, the middle of this plant's hardy range, start with zone 5 in April. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Montgomery get?
24 intall5 ft 7 inan adult20 inwideSee Montgomery in a garden plan: the planner shows it in 3D beside everything else you add, growing toward this size over the years.
How far apart to plant Montgomery
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Montgomery about 20 in apart, center to center, so each plant has room to reach its full width.
Add Montgomery to a garden plan and the planner draws it at its full width, so you see the spacing before you buy.
Where these facts come from
Montgomery's height, spread, hardiness zones, sun, water, bloom months and color, years to mature size, trait tags, soil, diseases, pests and toxicity were checked against 10 published sources on August 24, 2026. Each one is linked below with every fact it carried, which can include a fact this page still marks as not yet checked, because a source carrying a value is not the same as the value being held to the standard. Facts not in that list, and the planting, spacing and size sections, are not covered by these sources.
- Missouri Botanical GardenPlant Finderheight, spread, hardiness zones, sun, water, bloom months and color, trait tags, soil, diseases and pests
- Chicago Botanic GardenPlant Finderheight, hardiness zones, sun, water, bloom months and color, trait tags, soil and pests
- RHSsun, water, bloom months and color, years to mature size, soil, diseases and pests
- NC State ExtensionPlant Toolboxspread, sun, soil, diseases, pests and toxicity
- Clemson Home and Garden Information CenterClemson Cooperative Extension, Home & Garden Information Centersun, water, soil, diseases and pests
- Iowa State University Extensionand Outreach, Yard and Gardenwater, bloom months and color and soil
- thegardenct.comDietrich Gardens / The Garden CTheight, spread and hardiness zones
- Proven Winnersheight and hardiness zones
- ASPCAAnimal Poison Control Center, Toxic and Non-Toxic Plant List, Dogstoxicity
- ASPCAAnimal Poison Control Center, Toxic and Non-Toxic Plant List, Catstoxicity
How the checking works, and what each standard covers, is on the verified plants page.
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Design a garden with this
Drop this plant onto a 3D plan, see how it fills in, and watch your whole garden bloom across the year.