Deno’s GardenMy Garden

Primula japonica

Japanese Cowslip · Japanese Primrose

Family PrimulaceaeGenus Primula

Tiers of magenta flowers with dark red eyes around an upright stem, above broad crinkled green leaves.
FlowerStan ShebsCC BY-SA 3.0

About the plant

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

Habit
perennialPlants of the World Online
Habit
Perennial, Forb/herbPLANTS Database
Flower
PurpleWikipedia
Native range
Japan, Kuril Is.GBIF Backbone Taxonomy

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

Sources: Plants of the World Online — Royal Botanic Gardens, Kew; PLANTS Database — USDA NRCS; Wikipedia — Wikipedia contributors; GBIF Backbone Taxonomy — Global Biodiversity Information Facility.

Worth knowing

  • The Japanese primrose, also called queen of primroses, likes shady, damp, poorly drained places such as the edges of streams and ponds. Its cultivars 'Miller's Crimson' and 'Postford White' have won the RHS Award of Garden Merit. Wikipedia: Primula japonica

This source reports 10 treatments. All are shown.

Protocol 1

DerivedN. C. Deno, 1993

Difficulty Moderate Rated by us, not by the source.

Start around October 4, 2027 for a May 3 last frost. Too late for spring 2027 — that needed starting on October 3, 2026.

  1. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C

  2. Cold moist stratification

    Duration: 90 daysTemperature: 40°F 4°C

  3. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C

about 6 months from start to step 3. Germination happens during step 3, in 4 days.

100% germination in 2–4 days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Primula p. 197Public domain
Show the original text
Primula. (Primulaceae). The discovery of a photorequirement in P. japonica (Can) is largely a 40-70 germinator. Fresh seed germ; 70-40- 70(100% in 2-4 d), 70 GA-3(45% in 2nd w), and 40-70(50%).. Seed DS 6 m at 70 or 40 germ. 70(1%)-40-70(50%) and 40(30%).-70(70%). The increasing effect of DS at 70 was shown by DS for 0, 1, 3, and 6 m. The respective germinations were 40- 70(50%), .40(1%)-70(97%), 40(20%)-70(80%), and 40(30%)-70(70%). The lOnger the DS at 70 the faster the germination at 40. However, seed DS at 70 for 2 y was dead.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Primula p. 197. 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 15, 2026 for a May 3 last frost.

  1. Cold moist stratification

    Duration: 90 daysTemperature: 40°F 4°C

    1 germinated in this phase.

  2. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C

about 3 months from start to step 2. Germination happens during step 2; time not stated, 21 days assumed.

97% germination.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Primula p. 197Public domain
Show the original text
Primula. (Primulaceae). The discovery of a photorequirement in P. japonica (Can) is largely a 40-70 germinator. Fresh seed germ; 70-40- 70(100% in 2-4 d), 70 GA-3(45% in 2nd w), and 40-70(50%).. Seed DS 6 m at 70 or 40 germ. 70(1%)-40-70(50%) and 40(30%).-70(70%). The increasing effect of DS at 70 was shown by DS for 0, 1, 3, and 6 m. The respective germinations were 40- 70(50%), .40(1%)-70(97%), 40(20%)-70(80%), and 40(30%)-70(70%). The lOnger the DS at 70 the faster the germination at 40. However, seed DS at 70 for 2 y was dead.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Primula p. 197. 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 December 15, 2026 for a May 3 last frost.

  1. Cold moist stratification

    Duration: 90 daysTemperature: 40°F 4°C

    20 germinated in this phase.

  2. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C

about 3 months from start to step 2. Germination happens during step 2; time not stated, 21 days assumed.

80% germination.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Primula p. 197Public domain
Show the original text
Primula. (Primulaceae). The discovery of a photorequirement in P. japonica (Can) is largely a 40-70 germinator. Fresh seed germ; 70-40- 70(100% in 2-4 d), 70 GA-3(45% in 2nd w), and 40-70(50%).. Seed DS 6 m at 70 or 40 germ. 70(1%)-40-70(50%) and 40(30%).-70(70%). The increasing effect of DS at 70 was shown by DS for 0, 1, 3, and 6 m. The respective germinations were 40- 70(50%), .40(1%)-70(97%), 40(20%)-70(80%), and 40(30%)-70(70%). The lOnger the DS at 70 the faster the germination at 40. However, seed DS at 70 for 2 y was dead.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Primula p. 197. 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 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 days

  2. Sow and cover

    Temperature: 70°F 21°C

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

70% germination.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Primula p. 197Public domain
Show the original text
Primula. (Primulaceae). The discovery of a photorequirement in P. japonica (Can) is largely a 40-70 germinator. Fresh seed germ; 70-40- 70(100% in 2-4 d), 70 GA-3(45% in 2nd w), and 40-70(50%).. Seed DS 6 m at 70 or 40 germ. 70(1%)-40-70(50%) and 40(30%).-70(70%). The increasing effect of DS at 70 was shown by DS for 0, 1, 3, and 6 m. The respective germinations were 40- 70(50%), .40(1%)-70(97%), 40(20%)-70(80%), and 40(30%)-70(70%). The lOnger the DS at 70 the faster the germination at 40. However, seed DS at 70 for 2 y was dead.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Primula p. 197. 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 5

DerivedN. C. Deno, 1993

Difficulty Moderate Rated by us, not by the source.

Start around December 15, 2026 for a May 3 last frost.

  1. Cold moist stratification

    Duration: 90 daysTemperature: 40°F 4°C

    30 germinated in this phase.

  2. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C

about 3 months from start to step 2. Germination happens during step 2; time not stated, 21 days assumed.

70% germination.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Primula p. 197Public domain
Show the original text
Primula. (Primulaceae). The discovery of a photorequirement in P. japonica (Can) is largely a 40-70 germinator. Fresh seed germ; 70-40- 70(100% in 2-4 d), 70 GA-3(45% in 2nd w), and 40-70(50%).. Seed DS 6 m at 70 or 40 germ. 70(1%)-40-70(50%) and 40(30%).-70(70%). The increasing effect of DS at 70 was shown by DS for 0, 1, 3, and 6 m. The respective germinations were 40- 70(50%), .40(1%)-70(97%), 40(20%)-70(80%), and 40(30%)-70(70%). The lOnger the DS at 70 the faster the germination at 40. However, seed DS at 70 for 2 y was dead.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Primula p. 197. 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 6

DerivedN. C. Deno, 1993

Difficulty Moderate Rated by us, not by the source.

Start around December 15, 2026 for a May 3 last frost.

  1. Cold moist stratification

    Duration: 90 daysTemperature: 40°F 4°C

  2. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C

about 3 months from start to step 2. Germination happens during step 2; time not stated, 21 days assumed.

50% germination.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Primula p. 197Public domain
Show the original text
Primula. (Primulaceae). The discovery of a photorequirement in P. japonica (Can) is largely a 40-70 germinator. Fresh seed germ; 70-40- 70(100% in 2-4 d), 70 GA-3(45% in 2nd w), and 40-70(50%).. Seed DS 6 m at 70 or 40 germ. 70(1%)-40-70(50%) and 40(30%).-70(70%). The increasing effect of DS at 70 was shown by DS for 0, 1, 3, and 6 m. The respective germinations were 40- 70(50%), .40(1%)-70(97%), 40(20%)-70(80%), and 40(30%)-70(70%). The lOnger the DS at 70 the faster the germination at 40. However, seed DS at 70 for 2 y was dead.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Primula p. 197. 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 7

DerivedN. C. Deno, 1993

Difficulty Moderate Rated by us, not by the source.

Start around June 19, 2027 for a May 3 last frost. Too late for spring 2027 — that needed starting on June 18, 2026.

  1. Dry storage

    Duration: 180 daysTemperature: 70°F 21°C

  2. Cold moist stratification

    Duration: 90 daysTemperature: 40°F 4°C

  3. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C

about 9 months from start to step 3. Germination happens during step 3; time not stated, 21 days assumed.

50% germination.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Primula p. 197Public domain
Show the original text
Primula. (Primulaceae). The discovery of a photorequirement in P. japonica (Can) is largely a 40-70 germinator. Fresh seed germ; 70-40- 70(100% in 2-4 d), 70 GA-3(45% in 2nd w), and 40-70(50%).. Seed DS 6 m at 70 or 40 germ. 70(1%)-40-70(50%) and 40(30%).-70(70%). The increasing effect of DS at 70 was shown by DS for 0, 1, 3, and 6 m. The respective germinations were 40- 70(50%), .40(1%)-70(97%), 40(20%)-70(80%), and 40(30%)-70(70%). The lOnger the DS at 70 the faster the germination at 40. However, seed DS at 70 for 2 y was dead.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Primula p. 197. 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 8

DerivedN. C. Deno, 1993

Difficulty High Rated by us, not by the source.

Start around March 21, 2027 for a May 3 last frost. Too late for spring 2027 — that needed starting on March 20, 2026.

  1. Dry storage

    Duration: 180 days

  2. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C

    1 germinated in this phase.

  3. Cold moist stratification

    Duration: 90 daysTemperature: 40°F 4°C

  4. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C

about 12 months from start to step 4. Germination happens during step 4; time not stated, 21 days assumed.

50% germination.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Primula p. 197Public domain
Show the original text
Primula. (Primulaceae). The discovery of a photorequirement in P. japonica (Can) is largely a 40-70 germinator. Fresh seed germ; 70-40- 70(100% in 2-4 d), 70 GA-3(45% in 2nd w), and 40-70(50%).. Seed DS 6 m at 70 or 40 germ. 70(1%)-40-70(50%) and 40(30%).-70(70%). The increasing effect of DS at 70 was shown by DS for 0, 1, 3, and 6 m. The respective germinations were 40- 70(50%), .40(1%)-70(97%), 40(20%)-70(80%), and 40(30%)-70(70%). The lOnger the DS at 70 the faster the germination at 40. However, seed DS at 70 for 2 y was dead.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Primula p. 197. 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 9

DerivedN. C. Deno, 1993

Difficulty Moderate Rated by us, not by the source.

Start around March 22, 2027 for a May 3 last frost.

  1. Gibberellic acid soak

  2. Sow and cover

    Temperature: 70°F 21°C

No stated waiting before sowing. Then 14 days to germinate.

45% germination in 14 days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Primula p. 197Public domain
Show the original text
Primula. (Primulaceae). The discovery of a photorequirement in P. japonica (Can) is largely a 40-70 germinator. Fresh seed germ; 70-40- 70(100% in 2-4 d), 70 GA-3(45% in 2nd w), and 40-70(50%).. Seed DS 6 m at 70 or 40 germ. 70(1%)-40-70(50%) and 40(30%).-70(70%). The increasing effect of DS at 70 was shown by DS for 0, 1, 3, and 6 m. The respective germinations were 40- 70(50%), .40(1%)-70(97%), 40(20%)-70(80%), and 40(30%)-70(70%). The lOnger the DS at 70 the faster the germination at 40. However, seed DS at 70 for 2 y was dead.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Primula p. 197. 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 10

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. Dry storage

    Duration: 180 days

  2. Cold moist stratification

    Temperature: 40°F 4°C

about 6 months from start to step 2. Germination happens during step 2; time not stated, 21 days assumed.

30% germination.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Primula p. 197Public domain
Show the original text
Primula. (Primulaceae). The discovery of a photorequirement in P. japonica (Can) is largely a 40-70 germinator. Fresh seed germ; 70-40- 70(100% in 2-4 d), 70 GA-3(45% in 2nd w), and 40-70(50%).. Seed DS 6 m at 70 or 40 germ. 70(1%)-40-70(50%) and 40(30%).-70(70%). The increasing effect of DS at 70 was shown by DS for 0, 1, 3, and 6 m. The respective germinations were 40- 70(50%), .40(1%)-70(97%), 40(20%)-70(80%), and 40(30%)-70(70%). The lOnger the DS at 70 the faster the germination at 40. However, seed DS at 70 for 2 y was dead.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Primula p. 197. 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