Brazilian Waterweed – Egeria densa Not recorded hereInvasive
Invasive in the US, and recorded in no Montana county. Montana lists Brazilian Waterweed under “Priority 3 regulated plant (not a listed noxious weed).”
Montana noxious weeds
Montana (MT) lists 40 plants as noxious weeds under Montana Noxious Weed List (eff. June 21, 2019), ARM 4.5.201. Montana's list is an agricultural noxious-weed law, which governs control and spread on farmland and rights of way rather than what a nursery may sell.
What plants are invasive in Montana?
Montana names 40 plants, including Waterthyme, Brazilian Waterweed and Russian Olive. A noxious-weed listing obliges control and limits movement; it does not by itself ban nursery sale. 36 of the 40 are also flagged invasive by GRIIS, which is an ecological finding rather than a ruling by Montana. Checked against Montana Noxious Weed List (eff. June 21, 2019), ARM 4.5.201 on July 20, 2026.
Cheatgrass – Bromus tectorum IntroducedInvasive
Invasive in the US, and recorded in 51 of Montana’s 56 counties. Montana lists Cheatgrass under “Priority 3 regulated plant (not a listed noxious weed).”
Russian Olive – Elaeagnus angustifolia IntroducedInvasive
Invasive in the US, and recorded in 19 of Montana’s 56 counties. Montana lists Russian Olive under “Priority 3 regulated plant (not a listed noxious weed).”
Waterthyme – Hydrilla verticillata Not recorded hereInvasive
Invasive in the US, and recorded in no Montana county. Montana lists Waterthyme under “Priority 3 regulated plant (not a listed noxious weed).”
Broadleaved Pepperweed – Lepidium latifolium IntroducedInvasive
Invasive in the US, and recorded in 16 of Montana’s 56 counties. Montana lists Broadleaved Pepperweed under “Priority 2A.”
Butter and Eggs – Linaria vulgaris IntroducedInvasive
Invasive in the US, and recorded in 35 of Montana’s 56 counties. Montana lists Butter and Eggs under “Priority 2B.”
Canada Thistle – Cirsium arvense IntroducedInvasive
Invasive in the US, and recorded in 56 of Montana’s 56 counties. Montana lists Canada Thistle under “Priority 2B.”
Common Reed – Phragmites australis NativeListed
Recorded in 3 of Montana’s 56 counties. Montana lists Common Reed under “Priority 1A.”
Common St. Johnswort – Hypericum perforatum IntroducedInvasive
Invasive in the US, and recorded in 27 of Montana’s 56 counties. Montana lists Common St. Johnswort under “Priority 2B.”
Common Viper's Bugloss – Echium vulgare IntroducedInvasive
Invasive in the US, and recorded in 8 of Montana’s 56 counties. Montana lists Common Viper's Bugloss under “Priority 1B.”
Curly Pondweed – Potamogeton crispus IntroducedInvasive
Invasive in the US, and recorded in 2 of Montana’s 56 counties. Montana lists Curly Pondweed under “Priority 2B.”
Dalmatian Toadflax – Linaria dalmatica IntroducedInvasive
Invasive in the US, and recorded in 47 of Montana’s 56 counties. Montana lists Dalmatian Toadflax under “Priority 2B.”
Diffuse Knapweed – Centaurea diffusa IntroducedInvasive
Invasive in the US, and recorded in 39 of Montana’s 56 counties. Montana lists Diffuse Knapweed under “Priority 2B.”
Dyer's Woad – Isatis tinctoria IntroducedInvasive
Invasive in the US, and recorded in 12 of Montana’s 56 counties. Montana lists Dyer's Woad under “Priority 1A.”
Eurasian Watermilfoil – Myriophyllum spicatum Not recorded hereInvasive
Invasive in the US, and recorded in no Montana county. Montana lists Eurasian Watermilfoil under “Priority 2A.”
Field Bindweed – Convolvulus arvensis IntroducedInvasive
Invasive in the US, and recorded in 56 of Montana’s 56 counties. Montana lists Field Bindweed under “Priority 2B.”
Flowering Rush – Butomus umbellatus IntroducedInvasive
Invasive in the US, and recorded in 2 of Montana’s 56 counties. Montana lists Flowering Rush under “Priority 2A.”
Gypsyflower – Cynoglossum officinale IntroducedInvasive
Invasive in the US, and recorded in 39 of Montana’s 56 counties. Montana lists Gypsyflower under “Priority 2B.”
Hardheads – Acroptilon repens IntroducedInvasive
Invasive in the US, and recorded in 56 of Montana’s 56 counties. Montana lists Hardheads under “Priority 2B.”
Hoary Alyssum – Berteroa incana IntroducedInvasive
Invasive in the US, and recorded in 25 of Montana’s 56 counties. Montana lists Hoary Alyssum under “Priority 2B.”
Japanese Knotweed – Polygonum cuspidatum IntroducedListed
Recorded in 11 of Montana’s 56 counties. Montana lists Japanese Knotweed under “Priority 1B.”
Japanese Knotweed – Fallopia japonica (potentially invasive weed) IntroducedInvasive
Invasive in the US, and recorded in 11 of Montana’s 56 counties. Montana lists Japanese Knotweed under “Priority 1B.”
Leafy Spurge – Euphorbia esula IntroducedInvasive
Invasive in the US, and recorded in 56 of Montana’s 56 counties. Montana lists Leafy Spurge under “Priority 2B.”
Lenspod Whitetop – Cardaria chalepensis IntroducedListed
Recorded in 10 of Montana’s 56 counties. Montana lists Lenspod Whitetop under “Priority 2B.”
Meadow Hawkweed – Hieracium caespitosum IntroducedInvasive
Invasive in the US, and recorded in 8 of Montana’s 56 counties. Montana lists Meadow Hawkweed under “Priority 2A.”
Medusahead – Taeniatherum caput-medusae Not recorded hereInvasive
Invasive in the US, and recorded in no Montana county. Montana lists Medusahead under “Priority 1A.”
North Africa Grass – Ventenata dubia Not recorded hereInvasive
Invasive in the US, and recorded in no Montana county. Montana lists North Africa Grass under “Priority 2A.”
Orange Hawkweed – Hieracium aurantiacum IntroducedInvasive
Invasive in the US, and recorded in 12 of Montana’s 56 counties. Montana lists Orange Hawkweed under “Priority 2A.”
Oxeye Daisy – Leucanthemum vulgare IntroducedInvasive
Invasive in the US, and recorded in 29 of Montana’s 56 counties. Montana lists Oxeye Daisy under “Priority 2B.”
Paleyellow Iris – Iris pseudacorus IntroducedInvasive
Invasive in the US, and recorded in 2 of Montana’s 56 counties. Montana lists Paleyellow Iris under “Priority 2A.”
Purple Loosestrife – Lythrum salicaria IntroducedInvasive
Invasive in the US, and recorded in 8 of Montana’s 56 counties. Montana lists Purple Loosestrife under “Priority 1B.”
Rush Skeletonweed – Chondrilla juncea IntroducedInvasive
Invasive in the US, and recorded in 4 of Montana’s 56 counties. Montana lists Rush Skeletonweed under “Priority 1B.”
Scotch Broom – Cytisus scoparius IntroducedInvasive
Invasive in the US, and recorded in 1 of Montana’s 56 counties. Montana lists Scotch Broom under “Priority 1B.”
Spotted Knapweed – Centaurea stoebe IntroducedInvasive
Invasive in the US, and recorded in 56 of Montana’s 56 counties. Montana lists Spotted Knapweed under “Priority 2B.”
Stinking Willie – Senecio jacobaea IntroducedInvasive
Invasive in the US, and recorded in 4 of Montana’s 56 counties. Montana lists Stinking Willie under “Priority 2A.”
Sulphur Cinquefoil – Potentilla recta IntroducedInvasive
Invasive in the US, and recorded in 33 of Montana’s 56 counties. Montana lists Sulphur Cinquefoil under “Priority 2B.”
Tall Buttercup – Ranunculus acris NativeListed
Recorded in 25 of Montana’s 56 counties. Montana lists Tall Buttercup under “Priority 2A.”
Tansy – Tanacetum vulgare IntroducedInvasive
Invasive in the US, and recorded in 35 of Montana’s 56 counties. Montana lists Tansy under “Priority 2B.”
Whitetop – Cardaria draba IntroducedInvasive
Invasive in the US, and recorded in 53 of Montana’s 56 counties. Montana lists Whitetop under “Priority 2B.”
Yellow Star-Thistle – Centaurea solstitialis IntroducedInvasive
Invasive in the US, and recorded in 6 of Montana’s 56 counties. Montana lists Yellow Star-Thistle under “Priority 1A.”
No plant on Montana’s list matches that.
Want to check a plant by photo or county?
Use our “Is it native” tool for free.Compiled from the rule itself, retrieved July 20, 2026. Law changes; if you spot a listing we have wrong or stale, tell us at support@getezina.com.
The same list as a table
| Plant | Scientific name | Status | Plant instead |
|---|---|---|---|
| Brazilian Waterweed | Egeria densa | RestrictedInvasiveMontana says “Priority 3 regulated plant (not a listed noxious weed)” | — |
| Cheatgrass | Bromus tectorum | RestrictedInvasiveMontana says “Priority 3 regulated plant (not a listed noxious weed)” | — |
| Russian Olive | Elaeagnus angustifolia | RestrictedInvasiveMontana says “Priority 3 regulated plant (not a listed noxious weed)” | Silver Buffaloberry, Smooth Sumac, Snowbrush Ceanothus |
| Waterthyme | Hydrilla verticillata | RestrictedInvasiveMontana says “Priority 3 regulated plant (not a listed noxious weed)” | — |
| Broadleaved Pepperweed | Lepidium latifolium | ListedInvasiveMontana says “Priority 2A” | — |
| Butter and Eggs | Linaria vulgaris | ListedInvasiveMontana says “Priority 2B” | — |
| Canada Thistle | Cirsium arvense | ListedInvasiveMontana says “Priority 2B” | — |
| Common Reed | Phragmites australis | ListedMontana says “Priority 1A” | — |
| Common St. Johnswort | Hypericum perforatum | ListedInvasiveMontana says “Priority 2B” | — |
| Common Viper's Bugloss | Echium vulgare | ListedInvasiveMontana says “Priority 1B” | — |
| Curly Pondweed | Potamogeton crispus | ListedInvasiveMontana says “Priority 2B” | — |
| Dalmatian Toadflax | Linaria dalmatica | ListedInvasiveMontana says “Priority 2B” | — |
| Diffuse Knapweed | Centaurea diffusa | ListedInvasiveMontana says “Priority 2B” | — |
| Dyer's Woad | Isatis tinctoria | ListedInvasiveMontana says “Priority 1A” | — |
| Eurasian Watermilfoil | Myriophyllum spicatum | ListedInvasiveMontana says “Priority 2A” | — |
| Field Bindweed | Convolvulus arvensis | ListedInvasiveMontana says “Priority 2B” | — |
| Flowering Rush | Butomus umbellatus | ListedInvasiveMontana says “Priority 2A” | — |
| Gypsyflower | Cynoglossum officinale | ListedInvasiveMontana says “Priority 2B” | — |
| Hardheads | Acroptilon repens | ListedInvasiveMontana says “Priority 2B” | — |
| Hoary Alyssum | Berteroa incana | ListedInvasiveMontana says “Priority 2B” | — |
| Japanese Knotweed | Polygonum cuspidatum | ListedMontana says “Priority 1B” | — |
| Japanese Knotweed | Fallopia japonica (potentially invasive weed) | ListedInvasiveMontana says “Priority 1B” | — |
| Leafy Spurge | Euphorbia esula | ListedInvasiveMontana says “Priority 2B” | — |
| Lenspod Whitetop | Cardaria chalepensis | ListedMontana says “Priority 2B” | — |
| Meadow Hawkweed | Hieracium caespitosum | ListedInvasiveMontana says “Priority 2A” | — |
| Medusahead | Taeniatherum caput-medusae | ListedInvasiveMontana says “Priority 1A” | — |
| North Africa Grass | Ventenata dubia | ListedInvasiveMontana says “Priority 2A” | — |
| Orange Hawkweed | Hieracium aurantiacum | ListedInvasiveMontana says “Priority 2A” | — |
| Oxeye Daisy | Leucanthemum vulgare | ListedInvasiveMontana says “Priority 2B” | — |
| Paleyellow Iris | Iris pseudacorus | ListedInvasiveMontana says “Priority 2A” | Rocky Mountain Pond-Lily, Western Water Hemlock, Broadleaf Arrowhead |
| Purple Loosestrife | Lythrum salicaria | ListedInvasiveMontana says “Priority 1B” | Canada Goldenrod, Cutleaf Waterparsnip, Common Cowparsnip |
| Rush Skeletonweed | Chondrilla juncea | ListedInvasiveMontana says “Priority 1B” | — |
| Scotch Broom | Cytisus scoparius | ListedInvasiveMontana says “Priority 1B” | Mallow Ninebark, American Black Currant, Sticky Currant |
| Spotted Knapweed | Centaurea stoebe | ListedInvasiveMontana says “Priority 2B” | — |
| Stinking Willie | Senecio jacobaea | ListedInvasiveMontana says “Priority 2A” | — |
| Sulphur Cinquefoil | Potentilla recta | ListedInvasiveMontana says “Priority 2B” | — |
| Tall Buttercup | Ranunculus acris | ListedMontana says “Priority 2A” | — |
| Tansy | Tanacetum vulgare | ListedInvasiveMontana says “Priority 2B” | — |
| Whitetop | Cardaria draba | ListedInvasiveMontana says “Priority 2B” | — |
| Yellow Star-Thistle | Centaurea solstitialis | ListedInvasiveMontana says “Priority 1A” | — |
Where this comes from
- Montana listings
- Montana Noxious Weed List (eff. June 21, 2019), ARM 4.5.201. Read the rule.
- Invasive status
- GRIIS, the Global Register of Introduced and Invasive Species, via GBIF, covering the lower 48 states. A scientific register with no legal force; it is cited separately from the statute above because the two disagree far more often than they agree. Garden crops it flags only for spreading from cultivation are left out after review.
- Status wording
- The Prohibited / Restricted / Listed chips are Ezina’s normalisation across 44 states and are not the legal term. Where Montana’s own word for a plant differs from the chip, it is quoted verbatim beneath it.
- Nativity
- USDA PLANTS county distribution layer, surfaced through the county checker.
Regulated next door, but not in Montana
Plants that two or more states bordering Montana regulate, and Montana does not. A listing is a legal act rather than an ecological one, so a plant can be a documented problem here and still be sold here.
- Absinthium Artemisia absinthium regulated in North Dakota, South Dakota
- Field Sowthistle Sonchus arvensis regulated in Idaho, South Dakota
- Nodding Plumeless Thistle Carduus nutans regulated in Idaho, North Dakota
Questions
Is there an official Montana invasive species list?
Not under that name. Montana's legal list is a noxious-weed list: 40 plants named under Montana Noxious Weed List (eff. June 21, 2019), ARM 4.5.201, an agricultural noxious-weed law, which governs control and spread on farmland and rights of way rather than what a nursery may sell. GRIIS, the Global Register of Introduced and Invasive Species, flags 36 of these 40 as invasive in the lower 48 states. That is an ecological finding, not a ruling by Montana. This page shows both side by side.
What plants are illegal to sell in Montana?
Montana's list is an agricultural noxious-weed law, which governs control and spread on farmland and rights of way rather than what a nursery may sell. 40 plants are named under Montana Noxious Weed List (eff. June 21, 2019), ARM 4.5.201. A noxious-weed listing does not automatically ban nursery sale, so check the rule itself before assuming a plant cannot be bought or sold.
Is my plant invasive in Montana?
Search the table on this page for Montana's legal determination, then look for the Invasive chip beside it, which is a separate ecological finding from GRIIS rather than a ruling by Montana. A plant can carry one, both, or neither. For an address-level answer, enter the plant's name in Ezina's checker to get its Montana status alongside whether USDA records it as native to your specific county. Every answer links the record it came from.
Is it illegal to plant these in Montana?
Not necessarily, and the distinction matters. Montana's list is an agricultural noxious-weed law: it obliges landowners to control these plants and restricts moving them, rather than making the act of planting one an offence in itself. Montana Noxious Weed List (eff. June 21, 2019), ARM 4.5.201 is the text that says what is actually required of you, and it is linked beside every plant here.
Does a plant missing from this list mean it is safe to plant in Montana?
No. This page reproduces what Montana regulates, and a state list is a legal instrument rather than an ecological verdict. Plenty of plants spread aggressively without ever being listed, and states add species years after the problem is documented.
Grow natives easily with Ezina
How it works
We provide the tools you need to succeed.
010.1Identify
Add a plant
Snap a photo or type the name. Ezina matches it to a library of about 40,000 species and starts a care plan tailored to your zone, the local weather, and the time of year.
010.2Care
Get a care plan
A schedule built from local rain, temperature, and sun, not a fixed weekly cadence. You get a single notification when a plant actually needs water. Easily add treatments for diseases and pests.
010.3Plan
Explore new options
Our garden planner Dig helps you understand what works best for your location and makes suggestions based off your long term goals.
Add a plant
Snap a photo or type the name. Ezina matches it to a library of about 40,000 species and starts a care plan tailored to your zone, the local weather, and the time of year.
Get a care plan
A schedule built from local rain, temperature, and sun, not a fixed weekly cadence. You get a single notification when a plant actually needs water. Easily add treatments for diseases and pests.
Explore new options
Our garden planner Dig helps you understand what works best for your location and makes suggestions based off your long term goals.
Compiled from peer-reviewed research, USDA documentation,
and direct scientific observation across the United States.