Philadelphus coronarius
Genus Philadelphus
This source reports 6 treatments. All are shown.
Protocol 1
DerivedN. C. Deno, 1993Difficulty Moderate 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 · Temperature: 70°F 21°C
- 2
Cold moist stratification
Duration: 90 days · Temperature: 40°F 4°C
- 3
Warm moist stratification
Duration: 90 days · Temperature: 70°F 21°C
about 12 months from start to sowing. Germination time not stated; 21 days assumed.
68% germination.
Protocol 2
DerivedN. C. Deno, 1993Difficulty Moderate Rated by us, not by the source.
Start around September 13, 2027 for a May 3 last frost. Too late for spring 2027 — that needed starting on September 12, 2026.
- 1
Dry storage
Duration: 180 days · Temperature: 70°F 21°C
- 2
Sow and cover
Temperature: 70°F 21°C
about 6 months from start to sowing. Then 25 days to germinate.
58% germination in 5–25 days.
Protocol 3
DerivedN. C. Deno, 1993Difficulty Moderate Rated by us, not by the source.
Start around March 22, 2027 for a May 3 last frost. Too late for spring 2027 — that needed starting on March 21, 2026.
- 1
Dry storage
Duration: 180 days · Temperature: 70°F 21°C
- 2
Cold moist stratification
Duration: 90 days · Temperature: 40°F 4°C
- 3
Warm moist stratification
Duration: 90 days · Temperature: 70°F 21°C
about 12 months from start to sowing. Then 20 days to germinate.
57% germination in 3–20 days.
Protocol 4
DerivedN. C. Deno, 1993Difficulty High 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
Warm moist stratification
Duration: 90 days · Temperature: 70°F 21°C
2 germinated in this phase.
- 2
Cold moist stratification
Duration: 90 days · Temperature: 40°F 4°C
- 3
Warm moist stratification
Duration: 90 days · Temperature: 70°F 21°C
about 9 months from start to sowing. Germination time not stated; 21 days assumed.
41% germination.
Protocol 5
DerivedN. C. Deno, 1993Difficulty 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 days · Temperature: 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.
16% germination.
Protocol 6
DerivedN. C. Deno, 1993Difficulty 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
Cold moist stratification
Duration: 90 days · Temperature: 40°F 4°C
- 2
Warm moist stratification
Duration: 90 days · Temperature: 70°F 21°C
- 3
Cold moist stratification
Duration: 90 days · Temperature: 40°F 4°C
- 4
Warm moist stratification
Duration: 90 days · Temperature: 70°F 21°C
Steps after step 2 run on after germination.
about 6 months from start to sowing. Germination time not stated; 21 days assumed.
14% germination.