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Phlox speciosa

Bush Phlox · Showy Phlox

Family PolemoniaceaeGenus Phlox

A single thin stem carrying two pink notched-petal flowers, standing among narrow leaves on a floor of dry pine needles.
The whole plantWalter Siegmund (talk)CC 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/herb, SubshrubPLANTS Database
Flower
White, pinkWikipedia
Native range
Canada, lower 48 statesPLANTS Database

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.

Two sources report 4 treatments between them. All are shown.

Protocol 1

DerivedN. C. Deno, 1996

Difficulty Moderate Rated by us, not by the source.

Start around November 17, 2026 for a May 3 last frost.

  1. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C

  2. Cold moist stratification

    Duration: 90 daysTemperature: 40°F 4°C

about 3 months from start to step 2. Germination happens during step 2, in 49 days.

50% germination in 21–49 days.

Seed Germination Theory and Practice, 1st Supplement — N. C. Deno, 1996 · 1st Supplement, Phlox p. 65Public domain
Show the original text
Phlox (Polemoniaceae). Several species germinated over a number of cycles. Phlox glaberrima was one of these. It is now found that P. speciosa data is now more complete. Seeds germ. 70-40(50% in 3-7 w).
Seed Germination Theory and Practice, 1st Supplement, 1st Supplement, Phlox p. 65. 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 October 21, 2027 for a May 3 last frost. Too late for spring 2027 — that needed starting on October 20, 2026.

  1. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C

  2. Cold moist stratification

    Duration: 90 daysTemperature: 40°F 4°C

about 3 months from start to step 2. Germination happens during step 2, in 77 days.

50% germination in 21–77 days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Phlox p. 191Public domain
Show the original text
Phlox (Polemonlaceae). Phlox seed is hard to collect as there are only a few seed in each spherical capsule and these capsules roll away as soon as ripe. As a result seed of Phlox is not readily available except for the annual P. speciosa germ. 40-70(2/5 in 3rd w). A second sample germ. 70-40(10/20 in 3-11 w) and 40(3/18 in 3-11 w)-70(5/18 in 1-12 w).
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Phlox p. 191. 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

  2. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C

about 3 months from start to step 2. Germination happens during step 2, in 21 days.

40% germination in 21 days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Phlox p. 191Public domain
Show the original text
Phlox (Polemonlaceae). Phlox seed is hard to collect as there are only a few seed in each spherical capsule and these capsules roll away as soon as ripe. As a result seed of Phlox is not readily available except for the annual P. speciosa germ. 40-70(2/5 in 3rd w). A second sample germ. 70-40(10/20 in 3-11 w) and 40(3/18 in 3-11 w)-70(5/18 in 1-12 w).
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Phlox p. 191. 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 October 14, 2027 for a May 3 last frost. Too late for spring 2027 — that needed starting on October 13, 2026.

  1. Cold moist stratification

    Duration: 90 daysTemperature: 40°F 4°C

    3/18 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, in 84 days.

28% germination in 7–84 days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Phlox p. 191Public domain
Show the original text
Phlox (Polemonlaceae). Phlox seed is hard to collect as there are only a few seed in each spherical capsule and these capsules roll away as soon as ripe. As a result seed of Phlox is not readily available except for the annual P. speciosa germ. 40-70(2/5 in 3rd w). A second sample germ. 70-40(10/20 in 3-11 w) and 40(3/18 in 3-11 w)-70(5/18 in 1-12 w).
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Phlox p. 191. 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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