Mendel’s Gardens

Oenothera brachycarpa

Shortfruit Evening Primrose

Family OnagraceaeGenus Oenothera

About the plant

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

Habit
Perennial, Forb/herb
Native range
Native to the lower 48 states

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

Source: PLANTS Database — USDA NRCS.

This source reports 4 treatments. All are shown.

Protocol 1

DerivedN. C. Deno, 1993

Difficulty Low 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. Dry storage

    Duration: 180 daysTemperature: 70°F 21°C

  2. Cold moist stratification

    Temperature: 40°F 4°C

about 6 months from start to sowing. Germination time not stated; 21 days assumed.

77% germination.

The best result by far, and an odd one: store it dry warm, then sow it cold.

This source doesn't state how long.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, OenotheraPublic domain
Show the original text
Oenothera (Onagraceae). While many species germ. well in dark treatments, 0. biennis has an absolute light requirement so that photorequirements have to be considered in this genus. 0. brachycarpa germ. 70(39% largely in 2-3 d) and 40(33% in 1-10 w)-70(49% in 1-5 d) for fresh seed and 70(11%) and 40(77%) for seed DS 6 m at 70..
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Oenothera. 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 Moderate Rated by us, not by the source.

Start around December 31, 2026 for a May 3 last frost.

  1. Cold moist stratification

    Duration: 90 daysTemperature: 40°F 4°C

    33% germinated at 40 itself, over 1-10 weeks. Deno gives no length for this period; three months is his standard cycle.

  2. Warm moist stratification

    Temperature: 70°F 21°C

    A further 49%, in 1-5 days.

about 3 months from start to sowing. Then 5 days to germinate.

49% germination in 1–5 days.

33% comes up in the cold itself, then 49% within days of the move.

This source doesn't state how long.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, OenotheraPublic domain
Show the original text
Oenothera (Onagraceae). While many species germ. well in dark treatments, 0. biennis has an absolute light requirement so that photorequirements have to be considered in this genus. 0. brachycarpa germ. 70(39% largely in 2-3 d) and 40(33% in 1-10 w)-70(49% in 1-5 d) for fresh seed and 70(11%) and 40(77%) for seed DS 6 m at 70..
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Oenothera. 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 3

DerivedN. C. Deno, 1993

Difficulty Moderate Rated by us, not by the source.

Start around April 2, 2027 for a May 3 last frost.

  1. Sow and cover

    Temperature: 70°F 21°C

No stated waiting before sowing. Then 3 days to germinate.

39% germination in 2–3 days.

Fresh seed at 70 is quick but partial: 39%, most of it in two or three days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, OenotheraPublic domain
Show the original text
Oenothera (Onagraceae). While many species germ. well in dark treatments, 0. biennis has an absolute light requirement so that photorequirements have to be considered in this genus. 0. brachycarpa germ. 70(39% largely in 2-3 d) and 40(33% in 1-10 w)-70(49% in 1-5 d) for fresh seed and 70(11%) and 40(77%) for seed DS 6 m at 70..
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Oenothera. 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 4

DerivedN. C. Deno, 1993

Difficulty High 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. Dry storage

    Duration: 180 daysTemperature: 70°F 21°C

  2. Sow and cover

    Temperature: 70°F 21°C

about 6 months from start to sowing. Germination time not stated; 21 days assumed.

11% germination.

Dry storage then warmth is the worst of the four: 11%, against 77% sown cold.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, OenotheraPublic domain
Show the original text
Oenothera (Onagraceae). While many species germ. well in dark treatments, 0. biennis has an absolute light requirement so that photorequirements have to be considered in this genus. 0. brachycarpa germ. 70(39% largely in 2-3 d) and 40(33% in 1-10 w)-70(49% in 1-5 d) for fresh seed and 70(11%) and 40(77%) for seed DS 6 m at 70..
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Oenothera. 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.