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Trichostema dichotomum

Bastard Pennyroyal · Blue Curls · Forked Blue-curls · Forked Bluecurls

Family LamiaceaeGenus Trichostema

A blue-violet flower with four short upper lobes and a long white lower lip spotted purple, its stamens arching high above it.
FlowerBob Peterson from North Palm Beach, Florida, Planet Earth!CC BY-SA 2.0

About the plant

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

The plant

Habit
Herbaceous Perennial, WildflowerExtension Gardener Plant Toolbox
Habit
annualPlants of the World Online
Height
1-3 ft30-90 cmExtension Gardener Plant Toolbox
Spread
1-2 ft30-60 cmExtension Gardener Plant Toolbox
Flower
Blue, Purple/Lavender, WhiteExtension Gardener Plant Toolbox
Blooms
Fall, SummerExtension Gardener Plant Toolbox
Native range
Canada, lower 48 statesPLANTS Database
Hardiness zones
7-11Extension Gardener Plant Toolbox

Growing conditions

Sun
Full sunExtension Gardener Plant Toolbox
Soil
SandExtension Gardener Plant Toolbox
Soil pH
Neutral (6.0-8.0)Extension Gardener Plant Toolbox
Moisture
Good Drainage, Moist, Occasionally DryExtension Gardener Plant Toolbox

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

Sources: Extension Gardener Plant Toolbox — NC State Extension; Plants of the World Online — Royal Botanic Gardens, Kew; PLANTS Database — USDA NRCS.

Worth knowing

  • Forked bluecurls is an important nectar plant for bees. In northern Florida it has been recorded visited by many bees, among them Bombus impatiens. Wikipedia: Trichostema dichotomum

This source reports 4 treatments. All are shown.

Protocol 1

DerivedN. C. Deno, 1996

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 daysTemperature: 70°F 21°C

  2. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C Light: light

  3. Cold moist stratification

    Duration: 90 daysTemperature: 40°F 4°C

  4. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C Light: light

about 12 months from start to step 4. Germination happens during step 4, in 21 days.

66% germination in 21 days.

Seed Germination Theory and Practice, 1st Supplement — N. C. Deno, 1996 · 1st Supplement, Trichostema p. 82Public domain
Show the original text
Trichostema (Lamiaceae). T. dichotomum is best germ. in 70 GA-3, 88% in 5-15 d for fresh seed and 100% in 4-8 d for seed DS 6 m. However, significant germination is obtainable in 40-70L(31% in 4-13 d), 70L-40-70L(66% in 3rd w), 70D- 40-70D(4%), and 10% in OT. DS 6 m or 12 m had littie effect, but seeds DS 3 y were dead.
Seed Germination Theory and Practice, 1st Supplement, 1st Supplement, Trichostema p. 82. 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

Difficulty Moderate Rated by us, not by the source.

Start around June 27, 2027 for a May 3 last frost. Too late for spring 2027 — that needed starting on June 26, 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 Light: light

about 9 months from start to step 3. Germination happens during step 3, in 13 days.

31% germination in 4–13 days.

Seed Germination Theory and Practice, 1st Supplement — N. C. Deno, 1996 · 1st Supplement, Trichostema p. 82Public domain
Show the original text
Trichostema (Lamiaceae). T. dichotomum is best germ. in 70 GA-3, 88% in 5-15 d for fresh seed and 100% in 4-8 d for seed DS 6 m. However, significant germination is obtainable in 40-70L(31% in 4-13 d), 70L-40-70L(66% in 3rd w), 70D- 40-70D(4%), and 10% in OT. DS 6 m or 12 m had littie effect, but seeds DS 3 y were dead.
Seed Germination Theory and Practice, 1st Supplement, 1st Supplement, Trichostema p. 82. 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, 1996

Difficulty High Rated by us, not by the source.

  1. Dry storage

    Duration: 180 daysTemperature: 70°F 21°C

  2. Sow outdoors and leave it

about 6 months from start to sowing.

10% germination.

This source doesn't state how long step 2 lasts.

Seed Germination Theory and Practice, 1st Supplement — N. C. Deno, 1996 · 1st Supplement, Trichostema p. 82Public domain
Show the original text
Trichostema (Lamiaceae). T. dichotomum is best germ. in 70 GA-3, 88% in 5-15 d for fresh seed and 100% in 4-8 d for seed DS 6 m. However, significant germination is obtainable in 40-70L(31% in 4-13 d), 70L-40-70L(66% in 3rd w), 70D- 40-70D(4%), and 10% in OT. DS 6 m or 12 m had littie effect, but seeds DS 3 y were dead.
Seed Germination Theory and Practice, 1st Supplement, 1st Supplement, Trichostema p. 82. 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, 1996

Difficulty Very 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 daysTemperature: 70°F 21°C

  2. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C Light: dark

  3. Cold moist stratification

    Duration: 90 daysTemperature: 40°F 4°C

  4. Warm moist stratification

    Duration: 90 daysTemperature: 70°F 21°C Light: dark

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

4% germination.

Seed Germination Theory and Practice, 1st Supplement — N. C. Deno, 1996 · 1st Supplement, Trichostema p. 82Public domain
Show the original text
Trichostema (Lamiaceae). T. dichotomum is best germ. in 70 GA-3, 88% in 5-15 d for fresh seed and 100% in 4-8 d for seed DS 6 m. However, significant germination is obtainable in 40-70L(31% in 4-13 d), 70L-40-70L(66% in 3rd w), 70D- 40-70D(4%), and 10% in OT. DS 6 m or 12 m had littie effect, but seeds DS 3 y were dead.
Seed Germination Theory and Practice, 1st Supplement, 1st Supplement, Trichostema p. 82. 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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