Have you ever tried to grow lavender from seeds with little success and lots of frustration? Hopefully, I am not the only one. Before I learned about cold stratification, I had no idea that these seeds require a period of cold weather to initiate the germination process. Still, it makes sense, considering the temperature shifts in their native environment.
Lavender isn’t the only plant that requires cold stratification before planting. There are actually quite a lot of plants that have this requirement. Some of them are easier to grow from cuttings or divisions, but if you truly want to grow your plants from seed, cold stratification is something you want to be armed with the knowledge of first.
What is Cold Stratification
Cold stratification expedites germination or permits the growth of cold-dependent plants in warmer environments.
Many plants native to cooler climates require a period of cold weather to break their dormancy and initiate the germination process. Cold stratification is a way of mimicking that process so that germination can be expedited, or plants that require this cold weather to germinate can also be grown in warmer climates.
Not all seeds need the same conditions to encourage germination. Some need warm, moist weather, while others need a cold period. Some have more complicated needs, requiring a combination of different factors to break their dormancy.
Stratification happens naturally over the winter. The fluctuations in the weather trigger both the dormancy and the emergence from that dormancy, so the seeds know when the season is right to grow. Some seed packets will indicate if varieties require stratification, but others may not.
How To Do It
Initiate the stratification process early to give ample time for exposure to required cold temperatures.
The easiest way to cold-stratify your seeds in a moderate to cool climate is to plant your seeds in the fall. By planting in the fall, they will experience natural cold stratification without the gardener having to do much work. If you live in a warm climate, you’ll need to carry out the process artificially.
If the species you are sowing are native or you have a similar climate to their native range, the process is simple. All you need to do is know which seeds require stratification, and you can simply plant them at the right time, usually in the fall. This mimics the natural self-seeding process of these plants.
Flowers tend to drop seed in the fall before entering dormancy or dying off for the winter. The objective is to create a similar environment to the one they would naturally experience.
It can take one to three months to cold-stratify seeds, so consider that timeline when you choose a time to begin. If you intend to plant in the spring, you’ll want to time it so they are adequately exposed to cold temperatures.
Artificial cold-stratification is typically done using a refrigerator at a temperature between 33°-40°F. It is done wet or dry, depending on the type of seed. In general, if the seed grows naturally in an arid climate, it must be kept dry for this process, and vice versa.
Seeds that Need Cold Stratification
Without further ado, I’d like to share some information on common seeds that require cold stratification. Details on how to have the greatest success with these plants through the germination process are included.
Arnica
Remember that arnica relies on light for germination.
 | botanical name Arnica montana |
|---|---|
 | sun requirements Full sun |
 | height 1’-2’ |
 | hardiness zones 4-9 |
Arnica seeds should be soaked for four hours before stratification. They need cool, moist stratification for about eight weeks before they are ready to germinate.
They also need light to germinate, so do not cover them with soil. Just gently press them into the seed starting mix or potting soil.
Artichokes
Be cautious not to expose these seeds to freezing temperatures.
| | botanical name Cynara cardunculus var. scolymus |
|---|---|
| | sun requirements Full sun |
| | height 3’-4’ |
| | hardiness zones 7-11 |
If you are planning to grow your own artichokes this season, they will need a bit of assistance. Artichoke seeds need just a brief period of cold stratification to germinate. They can go in the fridge for about two weeks.
Don’t let these seeds freeze, as they are frost-sensitive. Start your artichokes indoors in seed trays, and keep them around 60°-70°F for best germination results.
Balloon Flower
For optimal growth, perform cold stratification and scarification before planting balloon flower seeds.
| | botanical name Platycodon grandiflorus |
|---|---|
| | sun requirements Full sun to partial shade |
| | height 1’-2’ |
| | hardiness zones 3-8 |
Balloon flower grows best if cold stratification and scarification take place before planting. These seeds like to be exposed to the sun for germination and can take a while to sprout.
They don’t handle transplanting well, so direct sowing is best. Expect your balloon flowers to germinate when the soil temperature reaches about 60°F.
Black-eyed Susan
Rudbeckia is a beloved choice due to its robust nature and constant blooming.
| | botanical name Rudbeckia |
|---|---|
| | sun requirements Full sun |
| | height 4’-5’ |
| | hardiness zones 4-9 |
Rudbeckia are a favorite in my garden. They are sturdy, consistent bloomers, and the bees adore them. Cold stratify your black-eyed Susan seeds for about one to three months and start six to eight weeks before your last expected frost. Transplant your seedlings once the average temperature reaches 65°F.
Butterfly Bush
To germinate, the seeds of the butterfly bush need a brief period of cool, damp conditions.
| | botanical name Buddleja |
|---|---|
| | sun requirements Full sun |
| | height 5’-8’ |
| | hardiness zones 5-10 |
Butterfly bush is happy to grow in warm climates, but the seeds do need a brief period of cool, moist temperatures to germinate. Give them about four weeks of cold stratification and then sow indoors eight to 10 weeks before your last expected frost. They need light to germinate, so don’t cover them with soil. Just press them in lightly.
Note: Butterfly bush is invasive in some regions. Please check with your local extension office before planting and deadhead blooms before they set seed.
Catmint
A little cold stratification goes a long way for catmint seeds.
| | botanical name Nepeta |
|---|---|
| | sun requirements Full sun to partial shade |
| | height 6”-12” |
| | hardiness zones 3-8 |
Catmint doesn’t need very much cold stratification, but a little goes a long way. Pop these seeds in the freezer for a day, then soak them in water for 12-24 hours before planting. Seeds can be started indoors six weeks before the last expected frost or direct sown once temperatures rise to 50°F.
Chamomile
A mix of cold and warm stratification is necessary to germinate chamomile seeds successfully.
| | botanical name Matricaria chamomilla |
|---|---|
| | sun requirements Full sun to partial shade |
| | height 2’ |
| | hardiness zones 3-9 |
Chamomile seeds need a combination of cold and warm stratification to germinate. Keep them warm and moist for two weeks before cold stratifying for about four to six weeks.
The ideal temperature for chamomile seeds to stratify is between 33°-35°F. Start seeds indoors three to four weeks before your last expected frost, or direct sow when the soil reaches 45°F.
Chinese Lantern
Cold stratification, though not mandatory, enhances the germination rate of Chinese lantern seeds.
| | botanical name Physalis alkekengi |
|---|---|
| | sun requirements Full sun to partial shade |
| | height 1’-2’ |
| | hardiness zones 3-9 |
While it is not required, cold stratifying your Chinese lantern seeds will improve their germination rate. Give them two weeks of cold temperatures, and then soak your seeds overnight before planting. You can directly sow these seeds or transplant seedlings after the threat of frost has passed.
Coneflower
For optimal coneflower seed germination, provide a brief cold spell.
| | botanical name Echinacea |
|---|---|
| | sun requirements Full sun |
| | height 2’-4’ |
| | hardiness zones 4-9 |
Coneflower seeds germinate best when given a brief period of cool weather. Without this, you may only get a germination rate of about 30%.
Plant your seeds in a moist potting mix and cover. Then, place them in the fridge for about four weeks. Keep the soil moist during this period.
Evening Primrose
Remember to sow evening primrose seeds on the soil’s surface since they require light to germinate.
| | botanical name Oenothera biennis |
|---|---|
| | sun requirements Full sun |
| | height 3’-5’ |
| | hardiness zones 4-9 |
Evening primrose seeds need a brief period of cold stratification to improve germination. Give these seeds moist stratification for three to four days for best results.
You can stratify these seeds in their potting mix. Sow your seeds on top of the soil, as these seeds need light to germinate.
False Sunflower
Stratification is essential for false sunflowers, necessitating a month of cold and moist storage.
| | botanical name Heliopsis helianthoides |
|---|---|
| | sun requirements Full sun |
| | height 3’-6’ |
| | hardiness zones 4-9 |
For false sunflowers, stratification is required. These seeds should be kept cold and moist for about one month.
The seeds germinate at 65°-70°F, so they should be planted indoors or outdoors when the weather warms up. They take 21-28 days to germinate, so these require a bit of patience, as well.
Fuchsia
Fuchsia seeds may display variable germination times, averaging 30 days.
| | botanical name Fuschia |
|---|---|
| | sun requirements Partial shade |
| | height 1’-3’ |
| | hardiness zones 9-11 |
Even though they are warm climate plants, fuchsias need some cold stratification. It is important to not keep them at or below freezing, as they are not frost tolerant. These seeds need about one month of cold stratification before planting.
Fuchsia seeds can be unpredictable and take 30 days to germinate on average. Soaking them for 24 hours before planting will speed up the germination time.
Goldenrod
The low-maintenance goldenrod plant thrives in a wide range of climates.
| | botanical name Solidago |
|---|---|
| | sun requirements Full sun |
| | height 2’-5’ |
| | hardiness zones 2-8 |
Goldenrod is easy to grow and naturalizes well in most climates. Cold stratification is necessary for these seeds and should be carried out for 60 days.
The seeds should be lightly pressed into the top of the soil, as they need light to germinate. Germination will take two to three weeks if the soil is kept at or near 70°F.
Hardy Hibiscus
Hardy hibiscus seeds need a minimum of 60-90 days of cold temperatures.
| | botanical name Hibiscus |
|---|---|
| | sun requirements Full sun |
| | height up to 25’ |
| | hardiness zones 4-9 |
Unlike their tropical cousins, hardy hibiscus seeds need cold stratification. Hibiscus seeds need at least 60-90 days of cold temperatures to germinate.
After cold stratification, lightly scarify the seeds and soak them in water overnight. The seeds and plants are moisture and humidity lovers, so keep them moist and covered. They only take about 3-5 days to germinate.
Heather
When planting, gently press heather seeds into the soil without covering them.
| | botanical name Calluna vulgaris |
|---|---|
| | sun requirements Full sun |
| | height 1’-2’ |
| | hardiness zones 5-8 |
Heather seeds need cold and moist stratification for maximum germination. Six weeks in the fridge will prep your heather seeds for germination, which takes 28-35 days.
These seeds need a soil temperature between 55°-70°F for germination and exposure to light, so lightly press them into the soil, but do not cover them.
Hens-and-chicks
Remember that hens and chicks are succulents that can’t handle excessive moisture.
| | botanical name Sempervivum |
|---|---|
| | sun requirements Partial shade |
| | height 4”-8” |
| | hardiness zones 3-8 |
Hens-and-chicks, as well as all other varieties of sempervivum, require cold stratification of their seeds. Two to three weeks in the fridge will do the trick.
These seeds need light to germinate and a soil temperature of 70°F. These plants don’t need much moisture as they are succulent, so avoid waterlogging your seedlings.
Hops
Be patient with hops since they take 30-40 days to sprout.
| | botanical name Humulus lupulus |
|---|---|
| | sun requirements Full sun |
| | height 15’-20’ |
| | hardiness zones 4-8 |
If you’re thinking about brewing your own beer, you’ll definitely need some hops. Hops seeds should be moist cold stratified as close to 41°F for three months before planting.
These seeds require some patience, as they take 30-40 days to germinate. However, once they sprout, they grow very quickly, up to an entire foot in one day!
Hollyhock
Hollyhocks share common germination and care requirements with hardy hibiscuses.
| | botanical name Alcea |
|---|---|
| | sun requirements Full sun |
| | height 6’-8’ |
| | hardiness zones 4-8 |
Hollyhocks are closely related to hardy hibiscuses, and they have similar needs in terms of germination and care. While they may germinate without stratification, your germination rate will be significantly better with it.
Plant these seeds when the soil temperature is between 59°-58°F. They should sprout within two weeks.
Anise Hyssop
You should subject anise hyssop seeds to one month of cold, moist stratification.
| | botanical name Agastache foeniculum |
|---|---|
| | sun requirements Full sun to partial shade |
| | height 3’ |
| | hardiness zones 4-8 |
Anise hyssop is a favorite in the pollinator garden and spreads prolifically in its native areas. If you are planting it from seed, the seeds will require a brief cold stratification to improve germination results. Cold, moist stratification for one month before planting will produce the best germination rate, which takes one to four weeks.
Ironweed
Cold stratification is a valuable method for the challenging task of growing Ironweed from seed.
| | botanical name Vernoia |
|---|---|
| | sun requirements Full sun |
| | height up to 8’ |
| | hardiness zones 4-9 |
Ironweed is another popular plant in the pollinator garden. It can be difficult to grow from seeds, but cold stratification drastically raises the germination rate.
Ironweed seeds need to stay moist through the winter and stratification process. Stratification should last for six to eight weeks. Seeds need a soil temperature of 50°F or higher to germinate.
Joe Pye Weed
Avoid planting Joe Pye weed seeds deeply, and place your trays in a sunny location.
| | botanical name Eutrochium purpureum |
|---|---|
| | sun requirements Full sun |
| | height 6’ |
| | hardiness zones 4-8 |
Joe Pye weed is a great pollinator feeder and easy to grow. These seeds need 30-60 days of cold stratification to germinate.
They also need plenty of light for germination, so don’t plant deeply, and set your trays in a sunny spot. It takes Joe Pye weed seeds about four weeks to germinate in the soil at 70°F.
Larkspur
These showy flower seeds can be started indoors or planted directly in the soil.
| | botanical name Delphinium |
|---|---|
| | sun requirements Full sun |
| | height 3’-4’ |
| | hardiness zones 4-8 |
Larkspur doesn’t need much in terms of cold stratification. However, two weeks in the fridge will significantly increase your germination rate. You can place them in a damp paper towel inside a plastic sandwich bag and put them right into the fridge.
Larkspur seeds can be planted as soon as the soil is workable and can be started indoors ahead of time. These seeds need darkness for germination, so plant them ¼” deep, and your larkspurs should pop their heads up in two to three weeks.
Lavender
The ideal chill time for lavender seeds is three to four weeks in the refrigerator.
| | botanical name Lavandula |
|---|---|
| | sun requirements Full sun |
| | height up to 4’ |
| | hardiness zones 5-9 |
If you love lavender like I do but have difficulty getting your seeds to sprout, there is good news ahead! Lavender seeds require cold stratification. Three to four weeks in the fridge is the right amount of time to prep these seeds for germination.
After cold stratifying your lavender seeds, you can start them indoors about 10-12 weeks before your last frost date or wait until the ground thaws and sow them directly.
Lobelia
Due to their minuscule size, initiating lobelia growth indoors is advisable.
| | botanical name Lobelia |
|---|---|
| | sun requirements Full sun to partial shade |
| | height 4”-18” |
| | hardiness zones 9-11 |
Lobelia doesn’t technically have to be cold-stratified. They are warm-climate plants that grow as perennials in zones 9 to 11. However, your germination rate will increase if you give your lobelia seeds three to four weeks of cold temperatures.
Don’t allow these seeds to freeze; after stratification, bring them to 70°F to germinate. These seeds are very tiny, so it’s best to start them indoors.
Lupine
Expect lupine seeds to sprout within two to three weeks once they warm up.
| | botanical name Lupinus |
|---|---|
| | sun requirements Full sun |
| | height 1’-4’ |
| | hardiness zones 4-9 |
Lupine seeds have a hard outer coating that needs special treatment. Soak your lupine seeds in water overnight before you begin your cold stratification.
Scarify your seeds with fine grit sandpaper, and then cold stratify for about one week. Germinate your lupine seeds in soil with a temperature between 65°-75°F; they should sprout in two to three weeks.
Marsh Marigold
These lovely marsh marigolds need a period of cold weather to stimulate them.
| | botanical name Caltha palustris |
|---|---|
| | sun requirements Full sun to partial shade |
| | height 8”-24” |
| | hardiness zones 3-7 |
Marsh marigolds are so bright and pretty in the garden. These pretty plants have seeds that require some cold weather to wake them up, as well.
In fact, this is one seed you can leave in the fridge all winter or for three months anyway. To germinate, sprinkle the seeds on top of moist potting soil and give them five to 10 days to sprout.
Milkweed
Typically, most milkweed varieties will sprout within 10-15 days once properly stratified.
| | botanical name Botanical Name: Asclepias |
|---|---|
| | sun requirements Full sun |
| | height up to 6’ |
| | hardiness zones 4-9 |
You probably know milkweed for its use by monarch butterflies as a larval food, as well as a nectar plant. These butterflies lay their eggs exclusively on this genus of plants, and more than 70 species are native to the United States.
Cold-stratify your milkweed seeds for three to six weeks with some moisture before planting them. Most types of milkweed have a germination time of 10-15 days.
Penstemon
Penstemons boast impressive flower power, making them delightful plants.
| | botanical name Penstemon |
|---|---|
| | sun requirements Full sun |
| | height 12”-24” |
| | hardiness zones 4-9 |
Penstemons, or beardtongues, are wonderful plants with tons of flower power. Their seeds need cold stratification for about five weeks just before planting.
Keep them moist and at just above-freezing temperatures. Penstemon requires patience, as the seeds can take six to eight weeks to germinate after they are planted.
Perennial Sweet Pea
Keep sweet pea seeds moist and refrigerate for approximately five weeks.
| | botanical name Lathyrus latifolius |
|---|---|
| | sun requirements Full sun to partial shade |
| | height 6’-9’ |
| | hardiness zones 4-8 |
Perennial sweet pea seeds need to be cold stratified at cold, but not freezing temperatures. They should be kept moist and can be refrigerated for about five weeks.
The seeds will germinate in soil that ranges between 55°-65°F, so as soon as your soil warms, pop these seeds in the ground and give them plenty of water. They should germinate in as few as ten or as many as 28 days.
This plant can become invasive, as it spreads rapidly via seeds and rhizomes. Keep it in a container and remove spent blooms to prevent spread.
Pincushion Flower
Scabiosa’s stunning appearance in floral arrangements and long vase life make these flowers ideal for cut flower gardens.
| | botanical name Scabiosa |
|---|---|
| | sun requirements Full sun |
| | height 8”-12” |
| | hardiness zones 3-8 |
These flowers look wonderful in a floral arrangement and have a long vase life, so they work very well in a cut flower garden. They will germinate without cold stratification, but your germination rate will be increased with just a little time spent in the fridge.
Two weeks is all that is needed, and then they should be sown indoors about six to eight weeks before the average last frost date.
Prairie Coneflower
For optimal germination, prairie coneflowers prefer soil temperatures ranging from 68° to 80°F in a sunny spot.
| | botanical name Ratibida |
|---|---|
| | sun requirements Full sun |
| | height 1’-3’ |
| | hardiness zones 4-9 |
Prairie coneflower is different from most of our seeds in that it needs stratification that is cold and dry. Eight weeks is just about right regarding how long to cold stratify these seeds.
In terms of germination, these seeds germinate best in soil temperatures between 68°-80°F in a sunny location. Germination only takes two to three days for Prairie Coneflowers.
Prairie Violet
A soil temperature of 80°F is ideal for the germination of prairie violets.
| | botanical name Viola pedatifida |
|---|---|
| | sun requirements Full sun to partial shade |
| | height 3”-6” |
| | hardiness zones 3-8 |
Prairie violets are sun-loving and drought-tolerant, two characteristics uncommon to the genus. Their seeds need about 60 days of cold stratification in a moist environment. A minimum of 30 days is the least these seeds should be stratified for.
The seeds should be sown on top of the soil, as they need light to germinate. 80°F is a good soil temperature for prairie violets to germinate.
Sedum
Once the danger of frost has subsided, you can sow sedum seeds both indoors and outdoors.
| | botanical name Sedum |
|---|---|
| | sun requirements Full sun to partial shade |
| | height 1’-3’ |
| | hardiness zones 3-11 |
Many types of succulents need cold stratification to germinate, including plants in the Sedum genus. Sedum seeds should be cold-stratified for four to five weeks to increase the germination rate.
The seeds can be sown indoors or outdoors after the threat of frost has passed. They need exposure to light for germination, so don’t cover them with soil. Just sprinkle them on top.
Shooting Star
Place shooting star seeds on the soil surface and gently press them in for proper germination.
| | botanical name Primula sect. dodecatheon |
|---|---|
| | sun requirements Partial shade |
| | height 1’-2’ |
| | hardiness zones 4-8 |
This pretty wildflower blooms for a brief time in the spring. Their seeds prefer cold, moist stratification, which should be carried out for 30-60 days.
The seeds can be sown directly in the ground, but wait until the threat of frost has passed. They need light for germination, so lay them on top of the soil and press lightly. Don’t cover them with soil.
Soapwort
These seeds benefit from a month of cold stratification and thrive in a moist setting.
| | botanical name Saponaria |
|---|---|
| | sun requirements Full sun to partial shade |
| | height 6”-36” |
| | hardiness zones 3-9 |
Soapwort seeds need to be cold-stratified for about one month, but also like a moist environment. After cold stratification, place these seeds on top of the potting mix and in a sunny spot, as they need light for germination.
Germination should take place in 10-21 days. They germinate best with a soil temperature near 70°F.
St. Johns Wort
Typically, it takes about two weeks for St. John’s wort seeds to initiate their growth.
| | botanical name Hypericum perforatum |
|---|---|
| | sun requirements Full sun to partial shade |
| | height 2’-4’ |
| | hardiness zones 3-9 |
You may know this plant from its use as a homeopathic remedy, but it is also a very pretty plant with attractive yellow flowers. St. John’s wort seeds need to spend three or four weeks in moist, cold stratification to germinate.
They also need light to germinate and prefer a soil temperature around 70°F. It takes roughly two weeks for these seeds to germinate.
Wild Geranium
Cultivating this North American woodland native wildflower is a delightful choice.
| | botanical name Geranium maculatum |
|---|---|
| | sun requirements Partial shade to full shade |
| | height 12”-28” |
| | hardiness zones 3-8 |
This woodland native of North America is a great wildflower to cultivate. It is easy to propagate but not invasive and produces pretty pink flowers.
Wild geranium seeds need moist, cold stratification for 60 days for ideal germination success. Sow seeds in soil that is around 70°F, keeping the soil moist during germination. These seeds can take two to three months to germinate, so patience is required.
Final Thoughts
The simplest way to grow plants that require cold stratification is to plant them in the fall and allow nature to do what it does best. However, that is not always possible or convenient. Fortunately, the process of artificial cold stratification is a simple one. Armed with the knowledge of which seeds need it and for how long, we can grow many of the plants that may have eluded us in the past.
