How to Grow American Arborvitae from Seed (Germination Guide)
The American Arborvitae (Thuja occidentalis), also called Northern White Cedar, is a cold-hardy evergreen native to parts of Canada and the Great Lakes region of the United States. It is valued for dense evergreen foliage, screening, wildlife cover, and adaptability to moist soils.
Growing American Arborvitae from seed begins with a 24-hour pre-soak followed by 60 days of cold, moist stratification. After stratification, sow the seeds 1/8 inch deep, tamp the soil, keep the seed bed moist, mulch lightly, and provide some shade. The seeds require light for germination.
Quick American Arborvitae Germination Guide
Pre-soak: Soak seeds in water for 24 hours
Stratification: Cold stratify for 60 days
Planting depth: Sow 1/8 inch deep
After planting: Tamp the soil, keep moist, and mulch the seed bed
Shade: Cover the seed bed with some shade
Light: Required for germination
Step 1: Soak American Arborvitae Seeds for 24 Hours
Soak American Arborvitae seeds in room-temperature water for 24 hours before beginning cold stratification.
After soaking, move the seeds directly into a damp stratification medium.
Step 2: Cold Stratify American Arborvitae Seeds for 60 Days
Place the soaked seeds in a lightly damp medium such as vermiculite, peat moss, or another moisture-retaining seed-starting medium.
Place the seeds and medium inside a sealed plastic bag or lidded container and refrigerate for 60 days.
Duration: 60 days
Temperature: Approximately 33–40°F (1–4°C)
Medium: Damp, but not saturated
Location: Household refrigerator
Check the seeds periodically and keep the stratification medium consistently damp throughout the cold period.
Step 3: Sow American Arborvitae Seeds 1/8 Inch Deep
After completing 60 days of cold stratification, the seeds are ready to plant.
- Fill a container or prepared seed bed with a fine, well-draining growing medium.
- Sow each American Arborvitae seed 1/8 inch deep.
- Lightly tamp the soil after planting.
- Keep the seed bed consistently moist.
- Mulch the seed bed lightly.
- Provide some shade while still allowing light to reach the seed bed.
Step 4: Provide Light and Some Shade
American Arborvitae seeds require light for germination.
The seeds should still be planted 1/8 inch deep as directed, but avoid heavy mulch or dense coverings that block light completely. Provide some shade to protect the moist seed bed from excessive drying while maintaining bright conditions.
Why Do American Arborvitae Seeds Need Cold Stratification?
American Arborvitae seeds benefit from a period of cold, moist conditions before planting.
The recommended treatment is 60 days of cold stratification, which provides the winter-like conditions needed before germination.
Is Soaking American Arborvitae Seed the Same as Scarification?
No. The recommended preparation is a 24-hour water pre-soak.
Physical scarification such as nicking, filing, or sanding is not required by this germination protocol.
Do American Arborvitae Seeds Need Light to Germinate?
Yes. Light is required for germination.
Sow the seeds 1/8 inch deep as directed and avoid burying them more deeply. If mulching the seed bed, use only a light covering so light can still reach the germination zone.
Why Should the Seed Bed Have Some Shade?
Some shade helps protect the shallow seed bed from excessive heat and rapid moisture loss.
The goal is bright but protected conditions, not darkness. Because the seeds require light, avoid dense shade or heavy coverings that block light completely.
How Should American Arborvitae Seeds Be Watered?
Keep the seed bed consistently moist throughout germination.
Because the seeds are small and planted only 1/8 inch deep, use gentle watering. Fine misting or bottom watering can help prevent the seeds from being displaced.
What Soil Is Best for American Arborvitae Seeds?
Use a fine, moisture-retentive but well-draining growing medium.
American Arborvitae tolerates moist soils once established, but young roots still benefit from good drainage and airflow.
American Arborvitae Seedling Care
Once seedlings emerge:
- Provide bright light with protection from intense heat
- Keep the growing medium consistently moist
- Avoid stagnant, waterlogged soil
- Maintain gentle airflow
- Handle small seedlings carefully during transplanting
Hardening Off American Arborvitae Seedlings
Seedlings started indoors should be gradually acclimated to outdoor conditions before permanent planting.
- Begin with short periods outdoors in bright shade.
- Increase outdoor exposure gradually over 7–14 days.
- Introduce gentle morning sun before stronger exposure.
- Protect young plants from drying wind during the transition.
- Keep the root zone evenly moist.
- Transplant once seedlings are acclimated.
Where Is American Arborvitae Native?
American Arborvitae is native to parts of Canada and the Great Lakes region.
Its native range includes Maine, Michigan, Minnesota, New Hampshire, New York, Ontario, Vermont, and Wisconsin.
Where Should American Arborvitae Be Planted?
American Arborvitae grows well in full sun to partial shade and prefers reliable moisture.
Good growing conditions include:
- Light: Full sun to partial shade
- Soil: Moist, well-drained soil
- Moisture: Reliable moisture, especially while young
- Climate: Very cold hardy
- Space: Allow room for mature height and width
Is American Arborvitae the Same as Northern White Cedar?
Yes. Northern White Cedar is another common name for Thuja occidentalis.
Despite the common name, it is a member of the cypress family rather than a true cedar of the genus Cedrus.
Will Seed-Grown American Arborvitae Look Identical?
No. Seed-grown American Arborvitae are genetically unique.
Seedlings may vary naturally in:
- Growth rate
- Foliage density
- Mature width
- Overall form
- Branching habit
If an exact named arborvitae cultivar is desired, vegetatively propagated nursery stock is more predictable than seedlings.
How Can Young Arborvitae Be Protected in Winter?
Young plants can lose moisture through their evergreen foliage during cold, dry, windy weather.
Keeping plants watered before the ground freezes, maintaining mulch over the root zone, and providing wind protection in exposed locations can help reduce winter drying.
Common American Arborvitae Germination Problems
Skipping the Pre-Soak
Soak American Arborvitae seeds in water for the full 24 hours before cold stratification.
Cold Stratification Was Too Short
Cold stratify the seeds for the full 60 days.
Planting Too Deep
Sow American Arborvitae seeds approximately 1/8 inch deep.
Blocking Too Much Light
American Arborvitae seeds require light for germination. Avoid deep planting, heavy mulch, or coverings that create darkness.
Letting the Surface Dry Out
Shallowly planted seeds can dry quickly. Keep the seed bed consistently moist.
Washing the Seeds Away
Use gentle watering, fine misting, or bottom watering so the tiny seeds remain in place.
Keeping the Soil Waterlogged
Maintain reliable moisture while still allowing good drainage and airflow around developing roots.
Exposing the Seed Bed to Harsh Sun
Provide some shade to protect the shallow seed bed from excessive drying while still allowing enough light for germination.
Expecting an Exact Cultivar Form
Seed-grown American Arborvitae are genetically variable and may not reproduce the growth habit of a named cultivar.
American Arborvitae Seed Germination FAQ
Do American Arborvitae seeds need to be soaked?
Yes. Soak American Arborvitae seeds in water for 24 hours before cold stratification.
How long should American Arborvitae seeds be cold stratified?
Cold stratify American Arborvitae seeds for 60 days.
How deep should American Arborvitae seeds be planted?
Sow the seeds approximately 1/8 inch deep, lightly tamp the soil, keep moist, and mulch the seed bed lightly.
Do American Arborvitae seeds need light to germinate?
Yes. Light is required for germination.
Should American Arborvitae seed beds be shaded?
Yes. Provide some shade to reduce drying and heat stress, but do not block the light required for germination.
Can American Arborvitae seeds be stratified in the refrigerator?
Yes. Keep the seeds in a damp medium in the refrigerator for the full 60-day cold stratification period.
Is American Arborvitae native to North America?
Yes. Thuja occidentalis is native to Canada and parts of the northeastern and Great Lakes regions of the United States.
Grow American Arborvitae from Seed
Soak 24 hours → Cold stratify 60 days → Sow 1/8 inch deep → Tamp soil → Keep moist → Mulch lightly → Provide some shade while maintaining light for germination
American Arborvitae seeds live in a narrow little Goldilocks zone: shallow but not exposed, moist but not swampy, shaded but not dark. Give them their 24-hour soak and 60-day winter, then keep that 1/8-inch-deep seed bed bright, protected, and consistently moist.