# Green Alder (Alnus viridis)

> The alder of the far North, a spreading, nitrogen-fixing shrub for stream banks and poor, gravelly ground, with catkins that open with the leaves.

Also called mountain alder, American green alder, Alnus crispa, Alnus alnobetula. Category: Native Shrubs. Grown from seed by Blue Whale Trees. Web version: https://bluewhaletrees.com/plants/green-alder/

![Green alder (Alnus viridis) finely toothed leaves and small young green cones on a branch](https://bluewhaletrees.com/img/plants/green-alder-h1610-800.jpg)
*Photo: Mason Brock, Public domain · [Wikimedia Commons](https://commons.wikimedia.org/wiki/File%3AAlnus_crispa.jpg)*

## Facts

- Type: Shrub
- Mature height: 3 to 14 ft
- USDA hardiness zones: 2 to 8
- Grows wild in: Stream banks, rocky ground and the Appalachians
- Native range: [Alaska](https://bluewhaletrees.com/tools/native/index.html.md?state=AK) and 17 other states, north to [Washington](https://bluewhaletrees.com/tools/native/index.html.md?state=WA), south to [North Carolina](https://bluewhaletrees.com/tools/native/index.html.md?state=NC) and west to [Oregon](https://bluewhaletrees.com/tools/native/index.html.md?state=OR) ([Alaska](https://bluewhaletrees.com/tools/native/index.html.md?state=AK), [California](https://bluewhaletrees.com/tools/native/index.html.md?state=CA), [Idaho](https://bluewhaletrees.com/tools/native/index.html.md?state=ID), [Maine](https://bluewhaletrees.com/tools/native/index.html.md?state=ME), [Massachusetts](https://bluewhaletrees.com/tools/native/index.html.md?state=MA), [Michigan](https://bluewhaletrees.com/tools/native/index.html.md?state=MI), [Minnesota](https://bluewhaletrees.com/tools/native/index.html.md?state=MN), [Montana](https://bluewhaletrees.com/tools/native/index.html.md?state=MT), [New Hampshire](https://bluewhaletrees.com/tools/native/index.html.md?state=NH), [New York](https://bluewhaletrees.com/tools/native/index.html.md?state=NY), [North Carolina](https://bluewhaletrees.com/tools/native/index.html.md?state=NC), [Oregon](https://bluewhaletrees.com/tools/native/index.html.md?state=OR), [Pennsylvania](https://bluewhaletrees.com/tools/native/index.html.md?state=PA), [Tennessee](https://bluewhaletrees.com/tools/native/index.html.md?state=TN), [Vermont](https://bluewhaletrees.com/tools/native/index.html.md?state=VT), [Washington](https://bluewhaletrees.com/tools/native/index.html.md?state=WA), [Wisconsin](https://bluewhaletrees.com/tools/native/index.html.md?state=WI) and [Wyoming](https://bluewhaletrees.com/tools/native/index.html.md?state=WY))
- Sun: Full, Part
- Soil moisture: Average, Wet
- Growth rate: Medium
- Flowers: May to June
- Fruit: Cones, September to November
- First crop: About 2 years
- Mature spread: 15 ft
- Traits: Nitrogen fixing, Wildlife value, Erosion control, Tolerates wet soil
- Sold as: Saplings, Seed

Heights and zones are typical ranges for the species in cultivation; local conditions and seed source shift them.

## Availability

Saplings ship [bare-root](https://bluewhaletrees.com/articles/planting-bare-root-trees-on-arrival/index.html.md) or [in a pot](https://bluewhaletrees.com/articles/a-sapling-in-a-pot/index.html.md), [usually 12 to 18 inches tall](https://bluewhaletrees.com/articles/small-sapling-or-big-transplant/index.html.md), in the dormant season, and their height and age are stated with the price, once available. Live plants ship February to May and October to November. Not priced yet: leave an email on the web page for one email when it is priced, with a code for 10% off the plants in that order, not shipping or tax, or write to captain@bluewhaletrees.com.

## Notes

Green alder is the alder of the far North, a spreading shrub of stream banks, lakeshores, rocky slopes and bog edges from Alaska to Greenland. Unlike our smooth alder, it opens its catkins with the new leaves rather than before them. Its roots fix nitrogen, so it is among the first shrubs on bare gravel and on soil left by glaciers. It helps hold stream banks and slopes against erosion. Pennsylvania lists it as endangered. Grow it on a poor, gravelly bank or along a stream edge.

## Size, growth and what to expect

Green alder grows at a medium pace, about a foot and a half a year in our growth estimator. It makes a spreading, many-stemmed shrub 3 to 14 feet tall, and it can form dense thickets. Its leaves stay green until they drop in fall. Its roots fix 18 to 55 pounds of nitrogen an acre a year.

Slender male catkins hang from the twig tips in May and June, as the leaves unfold, beside small, upright red female catkins. The female catkins turn into small woody cones that ripen from September to November, and the winged seed blows away on the wind. Moose, hares and beavers browse it. Many birds eat its seeds, buds and catkins, and its thickets shelter nesting birds.

It grows wild across the far North of the world. In North America it ranges from Alaska and Greenland south to New England, New York, Pennsylvania and the upper Great Lakes. An outpost grows on Roan Mountain, on the North Carolina and Tennessee line. In the West its Sitka alder form grows south to California, Idaho, Montana and Wyoming.

## How to grow Green Alder

Green alder grows in full sun or part shade, but not under a dense canopy. It wants a moist, acid soil, sandy, gravelly or rocky, near some source of water. Set plants 6 feet apart and keep them 8 feet from a wall. At its size it can go within 15 feet of overhead wires.

Saplings ship bare-root or potted. Plant dormant saplings in fall or early spring, in a hole wider than the roots and no deeper, and put the native soil back in. It needs no fertilizer, since its roots fix nitrogen. Much of the seed is often empty or dead, so sow it thickly. Chill it damp in the refrigerator for one to two months, then sow it in spring an eighth of an inch deep and keep it moist. Seed can also go outdoors in fall on moist, bare soil.

Water it weekly through the first summer unless the ground stays moist. It needs no pruning, and a clump cut back in winter or spring sprouts again from the base.

It carries male and female catkins on the same shrub, and the wind carries the pollen. Green alder sets some seed with its own pollen, but most of its seed comes from another plant's pollen, so plant two seedlings from different parents for seed. Like other alders, it can get leaf spots, cankers and powdery mildew.

## Sources

- [USDA Forest Service, Fire Effects Information System: Alnus viridis subsp. crispa, Matthews 1992](https://research.fs.usda.gov/feis/species-reviews/alnvirc)
- [USDA Forest Service, Woody Plant Seed Manual: Alnus chapter, Harrington and others](https://research.fs.usda.gov/download/treesearch/32626.pdf)
- [Flora of North America, vol. 3: Alnus viridis](http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500041)
- [USDA NRCS Plant Guide: Sitka alder, Alnus viridis ssp. sinuata](https://plants.sc.egov.usda.gov/DocumentLibrary/plantguide/pdf/pg_alvis.pdf)
- [Oregon State University, Landscape Plants: Alnus alnobetula subsp. crispa](https://landscapeplants.oregonstate.edu/plants/alnus-alnobetula-subsp-crispa)
- [Trees and Shrubs Online: Alnus alnobetula](https://www.treesandshrubsonline.org/articles/alnus/alnus-alnobetula/)
- [Minnesota Wildflowers: Alnus viridis, green alder](https://www.minnesotawildflowers.info/shrub/green-alder)
- [Go Botany, Native Plant Trust: Alnus viridis](https://gobotany.nativeplanttrust.org/species/alnus/viridis/)
- [Lady Bird Johnson Wildflower Center: Alnus viridis](https://www.wildflower.org/plants/result.php?id_plant=ALVI5)
- [Michigan Flora: Alnus viridis](https://michiganflora.net/species.aspx?id=549)
- [NatureServe Explorer: Alnus viridis](https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.149029/Alnus_viridis)
- [State lists: Pennsylvania, 17 Pa. Code 45.12](https://www.pacodeandbulletin.gov/Display/pacode?file=/secure/pacode/data/017/chapter45/s45.12.html&d=reduce)

## Read before planting

- [Ten planting mistakes that quietly kill trees](https://bluewhaletrees.com/articles/ten-planting-mistakes/index.html.md)
- [Transplanting young trees: timing, water and protection](https://bluewhaletrees.com/articles/transplanting-young-trees/index.html.md)
- [Protecting young trees from voles, rabbits, deer and squirrels](https://bluewhaletrees.com/articles/protecting-trees-from-animals/index.html.md)
- [How fast every tree and shrub we grow gets tall: growth rate, A to Z](https://bluewhaletrees.com/articles/growth-rates/index.html.md)
- [The habitat around a tree is part of the tree](https://bluewhaletrees.com/articles/habitat-around-a-tree/index.html.md)
- [Invasive vines and shrubs are what is killing your woods](https://bluewhaletrees.com/articles/invasive-vines-and-shrubs/index.html.md)

## Related

- Other alders (Alnus) we grow: [Seaside Alder](https://bluewhaletrees.com/plants/seaside-alder/index.html.md), [Smooth Alder (Swamp Alder)](https://bluewhaletrees.com/plants/smooth-alder/index.html.md)
- Trees to plant it under: [Eastern Hemlock](https://bluewhaletrees.com/plants/eastern-hemlock/index.html.md), [Northern White Cedar](https://bluewhaletrees.com/plants/northern-white-cedar/index.html.md) and [Yellow Buckeye](https://bluewhaletrees.com/plants/yellow-buckeye/index.html.md)
- [Planting-site check](https://bluewhaletrees.com/tools/site-check/index.html.md): for a thrive, struggle or fail verdict on Green Alder, add ?species=green-alder with zone (2 to 10), sun (full, part, shade) and moisture (dry, average, wet) to that address; for example, the verdict for zone 2, part sun and average soil as Markdown is at https://bluewhaletrees.com/tools/site-check/index.html.md?species=green-alder&zone=2&sun=part&moisture=average
- [Companion species for Green Alder](https://bluewhaletrees.com/tools/companions/index.html.md?species=green-alder): the natives that share its ground and the plants that pair with it in a yard.
- [Growth estimator](https://bluewhaletrees.com/tools/growth/index.html.md): how the height and trunk projections are made; the estimate for Green Alder as Markdown is at https://bluewhaletrees.com/tools/growth/index.html.md?species=green-alder (add height=, years= and site= poor, average or good)
- [Seed sowing planner](https://bluewhaletrees.com/tools/sowing/index.html.md): how Green Alder is sown, in the chart for every species (treatment, cold days, depth, timing); the dated plan for it as Markdown is at https://bluewhaletrees.com/tools/sowing/index.html.md?species=green-alder (add state= and zone= for your own frost dates, method=fridge for the refrigerator route)
- [Pollination planner](https://bluewhaletrees.com/tools/pollination/index.html.md): what Green Alder needs for a crop and how many to plant, in the table for every species; the verdict for 2 of them as Markdown is at https://bluewhaletrees.com/tools/pollination/index.html.md?plants=green-alder:2
- [Planting-window tool](https://bluewhaletrees.com/tools/planting-window/index.html.md): when to plant Green Alder where you live, as a fall and a spring window from the local frost dates; the windows as Markdown are at https://bluewhaletrees.com/tools/planting-window/index.html.md?species=green-alder&state=MO&zone=6 with your own state and zone in place of those
- [Planting-distance tool](https://bluewhaletrees.com/tools/distance/index.html.md): how far Green Alder goes from a house, a septic field, a walk, wires, a property line and the next tree; the distances as Markdown are at https://bluewhaletrees.com/tools/distance/index.html.md?species=green-alder&near=house,septic,pavement,wires,boundary,tree
- [Bloom and fruit calendar](https://bluewhaletrees.com/tools/calendar/index.html.md): the months Green Alder flowers and fruits, in the grid for every species; its own row and the gaps of a planting with it as Markdown at https://bluewhaletrees.com/tools/calendar/index.html.md?plants=green-alder