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Polemonium caeruleum

Blue Jacob's Ladder · Charity · Greek Valerian

Family PolemoniaceaeGenus Polemonium

Many cupped blue-violet flowers with orange stamens on upright stems with ladder-like leaves
FlowerzebedeugalinhaCC BY 4.0
A painted plate of a stem with ladder-like leaves of paired leaflets, topped by a head of blue bell flowers, with one flower and a seed pod drawn beside it.
IllustrationCarl Axel Magnus LindmanPublic domain

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
Violet, blue-violetFlora of China
Native range
Altay, Austria, Baltic States, Belarus, Central European Russia, China South-Central and elsewhereGBIF 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; Flora of China — Wu Zhengyi, Peter H. Raven and Hong Deyuan (eds.); GBIF Backbone Taxonomy — Global Biodiversity Information Facility.

Worth knowing

Two sources report 6 treatments between them. All are shown.

Protocol 1

DerivedN. C. Deno, 1996

Difficulty Low 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: light

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

84% germination in 7–28 days.

Seed Germination Theory and Practice, 1st Supplement — N. C. Deno, 1996 · 1st Supplement, Polemonium p. 67Public domain
Show the original text
Polemonium (Polemoniaceae). P. coeruleum alba germ. 70L(84% in 1-4 w) and none in 70D. This contrasts with the results reported for P. coeruleum where light if anything was slightly inhibitory. This needs to be reinvestigated particularly in light of a report from KW that P. coeruleum usually germ. at 70 but some forms were 40-70 germinators.
Seed Germination Theory and Practice, 1st Supplement, 1st Supplement, Polemonium p. 67. 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

  1. Sow and cover

    Temperature: 70°F 21°C Light: dark

No stated waiting before sowing.

0% germination.

Nothing germinated at 70.

Seed Germination Theory and Practice, 1st Supplement — N. C. Deno, 1996 · 1st Supplement, Polemonium p. 67Public domain
Show the original text
Polemonium (Polemoniaceae). P. coeruleum alba germ. 70L(84% in 1-4 w) and none in 70D. This contrasts with the results reported for P. coeruleum where light if anything was slightly inhibitory. This needs to be reinvestigated particularly in light of a report from KW that P. coeruleum usually germ. at 70 but some forms were 40-70 germinators.
Seed Germination Theory and Practice, 1st Supplement, 1st Supplement, Polemonium p. 67. Quoted exactly. Every value on this card comes from this record; the step names come from a fixed list.

Protocol 3

DerivedN. C. Deno, 1993

Difficulty Low Rated by us, not by the source.

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

  1. Sow and cover

    Temperature: 70°F 21°C Light: dark

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

82% germination in 14 days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Polemonium p. 195Public domain
Show the original text
Polemonium (Polemoniaceae). The following germ: in 2-5 w at 70: P. coeruleum germ. 70(52% in 1-4w) and 40(none). P. coeruleum ssp villosum germ. 70D(82% in 2nd w), 70L(32% in 2nd w), and 40(8%)-70(4%). Modest differences such as this between 70D and 70L could possibly be a T effect as the seeds unavoidably heat up some because of light absorption.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Polemonium p. 195. 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 Moderate 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

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

52% germination in 7–28 days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Polemonium p. 195Public domain
Show the original text
Polemonium (Polemoniaceae). The following germ: in 2-5 w at 70: P. coeruleum germ. 70(52% in 1-4w) and 40(none). P. coeruleum ssp villosum germ. 70D(82% in 2nd w), 70L(32% in 2nd w), and 40(8%)-70(4%). Modest differences such as this between 70D and 70L could possibly be a T effect as the seeds unavoidably heat up some because of light absorption.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Polemonium p. 195. 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 March 22, 2027 for a May 3 last frost.

  1. Sow and cover

    Temperature: 70°F 21°C Light: light

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

32% germination in 14 days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Polemonium p. 195Public domain
Show the original text
Polemonium (Polemoniaceae). The following germ: in 2-5 w at 70: P. coeruleum germ. 70(52% in 1-4w) and 40(none). P. coeruleum ssp villosum germ. 70D(82% in 2nd w), 70L(32% in 2nd w), and 40(8%)-70(4%). Modest differences such as this between 70D and 70L could possibly be a T effect as the seeds unavoidably heat up some because of light absorption.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Polemonium p. 195. 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 Very high Rated by us, not by the source.

Start around March 15, 2027 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

    4 germinated in this phase.

Steps after step 1 run on after germination.

Germination happens during step 1; time not stated, 21 days assumed.

8% germination.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Polemonium p. 195Public domain
Show the original text
Polemonium (Polemoniaceae). The following germ: in 2-5 w at 70: P. coeruleum germ. 70(52% in 1-4w) and 40(none). P. coeruleum ssp villosum germ. 70D(82% in 2nd w), 70L(32% in 2nd w), and 40(8%)-70(4%). Modest differences such as this between 70D and 70L could possibly be a T effect as the seeds unavoidably heat up some because of light absorption.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Polemonium p. 195. 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

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