Deno’s GardenMy Garden

Alnus glutinosa

Alder · Black Alder · Black Elder · European Alder

Family BetulaceaeGenus Alnus

Green unripe woody cones and blackened older ones on the same branch, among rounded toothed leaves
FruitAEngelhardtCC BY-SA 3.0

About the plant

What it is and where it grows — not part of any germination protocol.

The plant

Habit
TreeExtension Gardener Plant Toolbox
Habit
treePlants of the World Online
Height
40-60 ft12-18 mExtension Gardener Plant Toolbox
Spread
20-40 ft6-12 mExtension Gardener Plant Toolbox
Flower
Brown/Copper, Red/BurgundyExtension Gardener Plant Toolbox
Blooms
SpringExtension Gardener Plant Toolbox
Native range
Albania, Algeria, Austria, Baltic States, Belarus, Belgium and elsewhereGBIF Backbone Taxonomy
Hardiness zones
4-7Extension Gardener Plant Toolbox

Growing conditions

Sun
Full sun; Partial ShadeExtension Gardener Plant Toolbox
Soil
Clay, Loam (Silt), SandExtension Gardener Plant Toolbox
Soil pH
Acid (<6.0), Neutral (6.0-8.0)Extension Gardener Plant Toolbox
Moisture
Good Drainage, Moist, Occasionally WetExtension Gardener Plant Toolbox
Watering
Drought tolerance: MediumPLANTS Database

Toxicity is noted only where a source states it. No note here is not a finding of safety.

Sources: Extension Gardener Plant Toolbox — NC State Extension; Plants of the World Online — Royal Botanic Gardens, Kew; GBIF Backbone Taxonomy — Global Biodiversity Information Facility; PLANTS Database — USDA NRCS.

Worth knowing

  • Nodules on its roots hold a bacterium, Frankia alni, which fixes nitrogen from the air, so the tree improves the soil it grows in. Wikipedia: Alnus glutinosa
  • Under water the wood is very durable. The piles beneath the Rialto in Venice, and the foundations of several medieval cathedrals, are alder. Wikipedia: Alnus glutinosa

This source reports two treatments. Both are shown.

Protocol 1

DerivedN. C. Deno, 1996

Difficulty Moderate Rated by us, not by the source.

Start around March 27, 2027 for a May 3 last frost.

  1. Sow and cover

    Temperature: 70°F 21°C Light: light

No stated waiting before sowing. Then 9 days to germinate.

65% germination in 7–9 days.

Seed Germination Theory and Practice, 1st Supplement — N. C. Deno, 1996 · 1st Supplement, Alnus p. 18Public domain
Show the original text
Alnus (Betulaceae). All samples were received in March, and had already undergone at least 6 m of DS and probably more. Since DS was clearly detrimental in A. glutinosa germ. 70L(65% in 7-9 d) and 70D(20% in 1-4 w). A prior 3 m at 40, OT, GA-3, or DS 6 m had little effect.
Seed Germination Theory and Practice, 1st Supplement, 1st Supplement, Alnus p. 18. Quoted exactly. Every value on this card comes from this record, except the difficulty rating, which is ours; the step names come from a fixed list.

Protocol 2

DerivedN. C. Deno, 1996

Difficulty High Rated by us, not by the source.

Start around March 8, 2027 for a May 3 last frost.

  1. Sow and cover

    Temperature: 70°F 21°C Light: dark

No stated waiting before sowing. Then 28 days to germinate.

20% germination in 7–28 days.

Seed Germination Theory and Practice, 1st Supplement — N. C. Deno, 1996 · 1st Supplement, Alnus p. 18Public domain
Show the original text
Alnus (Betulaceae). All samples were received in March, and had already undergone at least 6 m of DS and probably more. Since DS was clearly detrimental in A. glutinosa germ. 70L(65% in 7-9 d) and 70D(20% in 1-4 w). A prior 3 m at 40, OT, GA-3, or DS 6 m had little effect.
Seed Germination Theory and Practice, 1st Supplement, 1st Supplement, Alnus p. 18. Quoted exactly. Every value on this card comes from this record, except the difficulty rating, which is ours; the step names come from a fixed list.

How each step is done, in Deno’s words, and what Verified and Derived mean.

Germination trials

Readers’ own records of sowing this species, published after review. Share your trial · All trials

Add to My Garden

View species page