Deno’s Garden

Clethra alnifolia

Genus Clethra

This source reports two treatments. Both are shown.

Protocol 1

DerivedN. C. Deno, 1993

Difficulty Moderate Rated by us, not by the source.

Start around September 17, 2027 for a May 3 last frost. Too late for spring 2027 — that needed starting on September 16, 2026.

  1. Cold moist stratification

    Duration: 90 daysTemperature: 40°F 4°C

  2. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C Light: light

about 6 months from start to sowing. Then 21 days to germinate.

60% germination in 21 days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Clethra p. 121Public domain
Show the original text
Clethra (Cletharaceae). Both species required light for germination. C. alnifolia germ: 40-70L(60% in 3rd w), 40-70D(none), 70L(10% in 5th w), and 70D(none). Seed DS 6 m at 70 gave the same results, but seed DS 12 m was dead.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Clethra p. 121. 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, 1993

Difficulty High Rated by us, not by the source.

Start around March 1, 2027 for a May 3 last frost.

  1. Sow and cover

    Temperature: 70°F 21°C Light: light

No stated waiting before sowing. Then 35 days to germinate.

10% germination in 35 days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Clethra p. 121Public domain
Show the original text
Clethra (Cletharaceae). Both species required light for germination. C. alnifolia germ: 40-70L(60% in 3rd w), 40-70D(none), 70L(10% in 5th w), and 70D(none). Seed DS 6 m at 70 gave the same results, but seed DS 12 m was dead.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Clethra p. 121. 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.