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Kalmia angustifolia

Sheep Laurel · Lambkill · Dwarf Laurel · Wicky

Family EricaceaeGenus Kalmia

A cluster of deep pink cupped flowers among narrow leaves
FlowerA. BarraCC BY 3.0

About the plant

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

Safety

Toxicity
High severity. Flowers, Fruits, Leaves, Seeds, Stems. Andromedotoxin, a resinoid; arbutin, a glycoside, Grayanotoxin.Extension Gardener Plant Toolbox

The plant

Habit
ShrubExtension Gardener Plant Toolbox
Habit
subshrub or shrubPlants of the World Online
Height
1-3 ft30-90 cmExtension Gardener Plant Toolbox
Spread
4-6 ft1.2-1.8 mExtension Gardener Plant Toolbox
Flower
Pink, Purple/Lavender, Red/BurgundyExtension Gardener Plant Toolbox
Blooms
Spring, SummerExtension Gardener Plant Toolbox
Native range
Canada, lower 48 states, St. Pierre and MiquelonPLANTS Database
Hardiness zones
5-8Extension Gardener Plant Toolbox
Note
Deno warns his counts are rough: the seed is tiny and hard to separate from the crushed capsule.Seed Germination Theory and Practice, 2nd ed.

Growing conditions

Sun
Full sunExtension Gardener Plant Toolbox
Soil
High Organic MatterExtension Gardener Plant Toolbox
Soil pH
Acid (<6.0), Neutral (6.0-8.0)Extension Gardener Plant Toolbox
Moisture
Moist, Occasional Flooding, Occasionally Dry, 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; PLANTS Database — USDA NRCS; Seed Germination Theory and Practice, 2nd ed. — N. C. Deno.

Worth knowing

This source reports 4 treatments. All are shown.

Protocol 1

DerivedN. C. Deno, 1993

Difficulty Low Rated by us, not by the source.

Start around March 8, 2027 for a May 3 last frost.

  1. Separate the seed from its case

    Crush the hard capsule so light can reach the seed.

  2. Sow on the surface — do not cover

    Temperature: 70°F 21°C Light: light

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

50% germination in 14–28 days.

50-60%. Fresh seed or six months' dry storage; overwintering outdoors made no difference.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, KalmiaPublic domain
Show the original text
Kalmia (Ericaceae). Kalmia requires light as found by R. Jaynes for K. angustifolia, K. cuneata, K. hirsuta, K. latifolia, K. microphylla, and K. polifolia (ref. 41) and confirmed by myself for K. angustifolia and K. latifolia. In my studies it was found for K. angustifloia, and K. latifolia that a prior 3 m at 40 had no effect on percent germination, the induction time, the rate law, and the rate constant. The seed is contained in hard spherical capsules. These must be crushed to allow light to reach the seed. The seed is small and hard to separate from the hard capsules so that seed counts and percent germination are inaccurate. K. angustifolia germ. 70L (50-60% in 2-4 w) and 40-70L(35-60% in 2nd w). using either fresh seed or seed DS 6 m at 70 or 40. Overwintering outdoors or a prior 3 m at 40 had no effect. All dark treatments failed:
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Kalmia. 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 December 22, 2026 for a May 3 last frost.

  1. Separate the seed from its case

    Crush the hard capsule so light can reach the seed.

  2. Cold moist stratification

    Duration: 90 daysTemperature: 40°F 4°C

    Deno gives no length for this period; three months is his standard cycle.

  3. Sow on the surface — do not cover

    Temperature: 70°F 21°C Light: light

about 3 months from start to sowing. Then 14 days to germinate.

35% germination in 14 days.

35-60%. The cold does nothing for this plant -- Deno checked the rate constant too.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, KalmiaPublic domain
Show the original text
Kalmia (Ericaceae). Kalmia requires light as found by R. Jaynes for K. angustifolia, K. cuneata, K. hirsuta, K. latifolia, K. microphylla, and K. polifolia (ref. 41) and confirmed by myself for K. angustifolia and K. latifolia. In my studies it was found for K. angustifloia, and K. latifolia that a prior 3 m at 40 had no effect on percent germination, the induction time, the rate law, and the rate constant. The seed is contained in hard spherical capsules. These must be crushed to allow light to reach the seed. The seed is small and hard to separate from the hard capsules so that seed counts and percent germination are inaccurate. K. angustifolia germ. 70L (50-60% in 2-4 w) and 40-70L(35-60% in 2nd w). using either fresh seed or seed DS 6 m at 70 or 40. Overwintering outdoors or a prior 3 m at 40 had no effect. All dark treatments failed:
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Kalmia. 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 22, 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, in 14 days.

35% germination in 14 days.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, Kalmia p. 163Public domain
Show the original text
Kalmia (Ericaceae). Kalmia requires light as found by R. Jaynes for K. angustifolia germ. 70L (50-60% in 2-4 w) and 40-70L(35-60% in 2nd w). using either fresh seed or seed DS 6 m at 70 or 40. Overwintering outdoors or a prior 3 m at 40 had no effect. All dark treatments failed:
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Kalmia p. 163. 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

  1. Separate the seed from its case

    Crush the hard capsule so light can reach the seed.

  2. Sow and cover

    Temperature: 70°F 21°C Light: dark

    All dark treatments failed.

No stated waiting before sowing.

0% germination.

Light is the whole requirement. Every dark treatment failed.

Seed Germination Theory and Practice, 2nd ed. — N. C. Deno, 1993 · Ch. 20, KalmiaPublic domain
Show the original text
Kalmia (Ericaceae). Kalmia requires light as found by R. Jaynes for K. angustifolia, K. cuneata, K. hirsuta, K. latifolia, K. microphylla, and K. polifolia (ref. 41) and confirmed by myself for K. angustifolia and K. latifolia. In my studies it was found for K. angustifloia, and K. latifolia that a prior 3 m at 40 had no effect on percent germination, the induction time, the rate law, and the rate constant. The seed is contained in hard spherical capsules. These must be crushed to allow light to reach the seed. The seed is small and hard to separate from the hard capsules so that seed counts and percent germination are inaccurate. K. angustifolia germ. 70L (50-60% in 2-4 w) and 40-70L(35-60% in 2nd w). using either fresh seed or seed DS 6 m at 70 or 40. Overwintering outdoors or a prior 3 m at 40 had no effect. All dark treatments failed:
Seed Germination Theory and Practice, 2nd ed., Ch. 20, Kalmia. Quoted exactly. Every value on this card comes from this record; 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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