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Lythrum salicaria

Purple Loosestrife · Spiked Loosestrife

Family LythraceaeGenus Lythrum

A tall magenta flower spike on a red stem above narrow paired leaves, in summer meadow grass
FlowerIvar LeidusCC BY-SA 3.0

About the plant

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

The plant

Habit
Herbaceous Perennial, PerennialExtension Gardener Plant Toolbox
Habit
perennial or helophytePlants of the World Online
Height
2-6 ft0.6-1.8 mExtension Gardener Plant Toolbox
Spread
2-4 ft0.6-1.2 mExtension Gardener Plant Toolbox
Flower
Pink, Purple/LavenderExtension Gardener Plant Toolbox
Blooms
SummerExtension Gardener Plant Toolbox
Hardiness zones
3-9Extension Gardener Plant Toolbox

Growing conditions

Sun
Full sunExtension Gardener Plant Toolbox
Moisture
Good Drainage, Occasionally WetExtension 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.

Worth knowing

  • A single plant may make up to 2.7 million tiny seeds a year, carried by wind and water. It is invasive in New Zealand and North America. Wikipedia: Lythrum salicaria
  • Lythrum comes from the Greek lythron, blood, for the flower color of some species. William Turner coined the English name loosestrife in his 1548 herbal. Wikipedia: Lythrum salicaria

This source reports 10 treatments. All are shown.

Protocol 1

DerivedN. C. Deno, 1993

Difficulty Low Rated by us, not by the source.

Start around April 3, 2027 for a May 3 last frost.

  1. Sow and cover

    Temperature: 70°F 21°C Light: light

No stated waiting before sowing. Then 2 days to germinate.

100% germination in 1–2 days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Lythrum p. 175Public domain
Show the original text
Lythrum (Lythraceae). L. salicaria germ.70L(100% in 1-2 d), 70D(39%), 40- 70L(4%), 40-70D(none), and 73% in February through April in outdoor treatment using fresh seed. Seed DS 6 m at 70 germ. 70L(100% in 1-2 d), 70D(12%), 40(29%)- 70L(71% in 1-2 d), and 40(29%)-70D(none). Seeds DS 12 m at 70 germ. 70L(90% in 1-5 d), 70D(none), and 40-70D(90% in 3-4 d). Note the remarkably rapid germination, the germination in dark outdoors, and that the continuing DS ultimately eliminates the light requirement in the 40-70 treatment but intensifies the light requirement at 70. All of the above detail is of little horticultural interest for a plant that is often regarded as an invasive weed, but it does show some remarkable effects of DS.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Lythrum p. 175. 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 Low Rated by us, not by the source.

Start around October 6, 2027 for a May 3 last frost. Too late for spring 2027 — that needed starting on October 5, 2026.

  1. Dry storage

    Duration: 180 daysTemperature: 70°F 21°C

  2. Sow and cover

    Temperature: 70°F 21°C Light: light

about 6 months from start to sowing. Then 2 days to germinate.

100% germination in 1–2 days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Lythrum p. 175Public domain
Show the original text
Lythrum (Lythraceae). L. salicaria germ.70L(100% in 1-2 d), 70D(39%), 40- 70L(4%), 40-70D(none), and 73% in February through April in outdoor treatment using fresh seed. Seed DS 6 m at 70 germ. 70L(100% in 1-2 d), 70D(12%), 40(29%)- 70L(71% in 1-2 d), and 40(29%)-70D(none). Seeds DS 12 m at 70 germ. 70L(90% in 1-5 d), 70D(none), and 40-70D(90% in 3-4 d). Note the remarkably rapid germination, the germination in dark outdoors, and that the continuing DS ultimately eliminates the light requirement in the 40-70 treatment but intensifies the light requirement at 70. All of the above detail is of little horticultural interest for a plant that is often regarded as an invasive weed, but it does show some remarkable effects of DS.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Lythrum p. 175. 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 Low Rated by us, not by the source.

Start around April 6, 2027 for a May 3 last frost. Too late for spring 2027 — that needed starting on April 5, 2026.

  1. Dry storage

    Duration: 360 daysTemperature: 70°F 21°C

  2. Sow and cover

    Temperature: 70°F 21°C Light: light

about 12 months from start to sowing. Then 5 days to germinate.

90% germination in 1–5 days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Lythrum p. 175Public domain
Show the original text
Lythrum (Lythraceae). L. salicaria germ.70L(100% in 1-2 d), 70D(39%), 40- 70L(4%), 40-70D(none), and 73% in February through April in outdoor treatment using fresh seed. Seed DS 6 m at 70 germ. 70L(100% in 1-2 d), 70D(12%), 40(29%)- 70L(71% in 1-2 d), and 40(29%)-70D(none). Seeds DS 12 m at 70 germ. 70L(90% in 1-5 d), 70D(none), and 40-70D(90% in 3-4 d). Note the remarkably rapid germination, the germination in dark outdoors, and that the continuing DS ultimately eliminates the light requirement in the 40-70 treatment but intensifies the light requirement at 70. All of the above detail is of little horticultural interest for a plant that is often regarded as an invasive weed, but it does show some remarkable effects of DS.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Lythrum p. 175. 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 January 7, 2027 for a May 3 last frost. Too late for spring 2027 — that needed starting on January 6, 2026.

  1. Dry storage

    Duration: 360 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: dark

about 15 months from start to step 3. Germination happens during step 3, in 4 days.

90% germination in 3–4 days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Lythrum p. 175Public domain
Show the original text
Lythrum (Lythraceae). L. salicaria germ.70L(100% in 1-2 d), 70D(39%), 40- 70L(4%), 40-70D(none), and 73% in February through April in outdoor treatment using fresh seed. Seed DS 6 m at 70 germ. 70L(100% in 1-2 d), 70D(12%), 40(29%)- 70L(71% in 1-2 d), and 40(29%)-70D(none). Seeds DS 12 m at 70 germ. 70L(90% in 1-5 d), 70D(none), and 40-70D(90% in 3-4 d). Note the remarkably rapid germination, the germination in dark outdoors, and that the continuing DS ultimately eliminates the light requirement in the 40-70 treatment but intensifies the light requirement at 70. All of the above detail is of little horticultural interest for a plant that is often regarded as an invasive weed, but it does show some remarkable effects of DS.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Lythrum p. 175. 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 Low Rated by us, not by the source.

  1. Sow outdoors and leave it

    Up in February through April.

No stated waiting before sowing.

73% germination.

This source doesn't state how long step 1 lasts.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Lythrum p. 175Public domain
Show the original text
Lythrum (Lythraceae). L. salicaria germ.70L(100% in 1-2 d), 70D(39%), 40- 70L(4%), 40-70D(none), and 73% in February through April in outdoor treatment using fresh seed. Seed DS 6 m at 70 germ. 70L(100% in 1-2 d), 70D(12%), 40(29%)- 70L(71% in 1-2 d), and 40(29%)-70D(none). Seeds DS 12 m at 70 germ. 70L(90% in 1-5 d), 70D(none), and 40-70D(90% in 3-4 d). Note the remarkably rapid germination, the germination in dark outdoors, and that the continuing DS ultimately eliminates the light requirement in the 40-70 treatment but intensifies the light requirement at 70. All of the above detail is of little horticultural interest for a plant that is often regarded as an invasive weed, but it does show some remarkable effects of DS.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Lythrum p. 175. 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 July 8, 2027 for a May 3 last frost. Too late for spring 2027 — that needed starting on July 7, 2026.

  1. Dry storage

    Duration: 180 daysTemperature: 70°F 21°C

  2. Cold moist stratification

    Duration: 90 daysTemperature: 40°F 4°C

    29 germinated in this phase.

  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 2 days.

71% germination in 1–2 days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Lythrum p. 175Public domain
Show the original text
Lythrum (Lythraceae). L. salicaria germ.70L(100% in 1-2 d), 70D(39%), 40- 70L(4%), 40-70D(none), and 73% in February through April in outdoor treatment using fresh seed. Seed DS 6 m at 70 germ. 70L(100% in 1-2 d), 70D(12%), 40(29%)- 70L(71% in 1-2 d), and 40(29%)-70D(none). Seeds DS 12 m at 70 germ. 70L(90% in 1-5 d), 70D(none), and 40-70D(90% in 3-4 d). Note the remarkably rapid germination, the germination in dark outdoors, and that the continuing DS ultimately eliminates the light requirement in the 40-70 treatment but intensifies the light requirement at 70. All of the above detail is of little horticultural interest for a plant that is often regarded as an invasive weed, but it does show some remarkable effects of DS.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Lythrum p. 175. 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 March 15, 2027 for a May 3 last frost.

  1. Sow and cover

    Temperature: 70°F 21°C Light: dark

No stated waiting before sowing. Germination time not stated; 21 days assumed.

39% germination.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Lythrum p. 175Public domain
Show the original text
Lythrum (Lythraceae). L. salicaria germ.70L(100% in 1-2 d), 70D(39%), 40- 70L(4%), 40-70D(none), and 73% in February through April in outdoor treatment using fresh seed. Seed DS 6 m at 70 germ. 70L(100% in 1-2 d), 70D(12%), 40(29%)- 70L(71% in 1-2 d), and 40(29%)-70D(none). Seeds DS 12 m at 70 germ. 70L(90% in 1-5 d), 70D(none), and 40-70D(90% in 3-4 d). Note the remarkably rapid germination, the germination in dark outdoors, and that the continuing DS ultimately eliminates the light requirement in the 40-70 treatment but intensifies the light requirement at 70. All of the above detail is of little horticultural interest for a plant that is often regarded as an invasive weed, but it does show some remarkable effects of DS.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Lythrum p. 175. 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 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 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: dark

Steps after step 2 run on after germination.

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

29% germination.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Lythrum p. 175Public domain
Show the original text
Lythrum (Lythraceae). L. salicaria germ.70L(100% in 1-2 d), 70D(39%), 40- 70L(4%), 40-70D(none), and 73% in February through April in outdoor treatment using fresh seed. Seed DS 6 m at 70 germ. 70L(100% in 1-2 d), 70D(12%), 40(29%)- 70L(71% in 1-2 d), and 40(29%)-70D(none). Seeds DS 12 m at 70 germ. 70L(90% in 1-5 d), 70D(none), and 40-70D(90% in 3-4 d). Note the remarkably rapid germination, the germination in dark outdoors, and that the continuing DS ultimately eliminates the light requirement in the 40-70 treatment but intensifies the light requirement at 70. All of the above detail is of little horticultural interest for a plant that is often regarded as an invasive weed, but it does show some remarkable effects of DS.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Lythrum p. 175. 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 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 daysTemperature: 70°F 21°C

  2. Sow and cover

    Temperature: 70°F 21°C Light: dark

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

12% germination.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Lythrum p. 175Public domain
Show the original text
Lythrum (Lythraceae). L. salicaria germ.70L(100% in 1-2 d), 70D(39%), 40- 70L(4%), 40-70D(none), and 73% in February through April in outdoor treatment using fresh seed. Seed DS 6 m at 70 germ. 70L(100% in 1-2 d), 70D(12%), 40(29%)- 70L(71% in 1-2 d), and 40(29%)-70D(none). Seeds DS 12 m at 70 germ. 70L(90% in 1-5 d), 70D(none), and 40-70D(90% in 3-4 d). Note the remarkably rapid germination, the germination in dark outdoors, and that the continuing DS ultimately eliminates the light requirement in the 40-70 treatment but intensifies the light requirement at 70. All of the above detail is of little horticultural interest for a plant that is often regarded as an invasive weed, but it does show some remarkable effects of DS.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Lythrum p. 175. 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 Very high 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 Light: light

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

4% germination.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Lythrum p. 175Public domain
Show the original text
Lythrum (Lythraceae). L. salicaria germ.70L(100% in 1-2 d), 70D(39%), 40- 70L(4%), 40-70D(none), and 73% in February through April in outdoor treatment using fresh seed. Seed DS 6 m at 70 germ. 70L(100% in 1-2 d), 70D(12%), 40(29%)- 70L(71% in 1-2 d), and 40(29%)-70D(none). Seeds DS 12 m at 70 germ. 70L(90% in 1-5 d), 70D(none), and 40-70D(90% in 3-4 d). Note the remarkably rapid germination, the germination in dark outdoors, and that the continuing DS ultimately eliminates the light requirement in the 40-70 treatment but intensifies the light requirement at 70. All of the above detail is of little horticultural interest for a plant that is often regarded as an invasive weed, but it does show some remarkable effects of DS.
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Lythrum p. 175. 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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