Some seeds, like perennial Sweet Peas or Pansies, require special care in order to break dormancy and germinate. If you’ve ever questioned why certain seeds from brand-new plants never seem to germinate, cold stratification might be the answer.
Stratification sequences may differ, according to Master Gardener Susan Patterson: “Some seeds demand a warm and moist treatment, while others require a cool and wet treatment.” Other seeds, however, need a mix of warm and cool treatments, followed by a warm treatment, or a warm and cool moist combination, followed by a dry cycle and a warm phase. Before starting any seed stratification endeavor, it is essential to understand what seeds need to emerge from dormancy. In order to expose the seed to air and moisture, certain plants also require stratification from heat, such as from fires.
Cold and moisture are the two main conditions for cold stratification. It is better to plant when winter is expected to last, depending on where you reside. The seed coat can break down and there may not be much germination if you sow when it’s too warm.
However, if you are starting in the early season, soak your seeds for 12 to 24 hours before placing them in a plastic bag or other airtight container with sand, peat, or an equal mixture of the two. Label and date. See if they are sprouting frequently. Some seeds must be stored in the freezer for a longer time than others.
According to Pinetree Garden Seeds, “soaking them in cold water for 6 to 12 hours prior to beginning the process can help reduce the overall stratification time needed. Additionally, this aids the seed in absorbing some of the moisture it needs for the upcoming chemical processes.
1) If your plant reseeds, you can simply disperse your seed as soon as it seeds if it doesn’t matter where the new growth appears. Any unruly plants that sprout up against your garden plan can be moved to where you might decide you want them, given away as a last resort, or eaten if it is acceptable, or composted. For breadseed poppies, I employ the broadcast technique. However, occasionally you might change your garden layout to make room for what you hope will turn out to be a magnificent display of beauty!
If you have a seed packet, a more formal approach would be to choose the location, prepare the soil, and scatter your seeds there in the fall. Put a tag on the location, date, and information. Keep them moist; when they are ready, they will sprout.
Floods or drastically changing weather, such as cold, hot, and cold, could be risks of these two strategies. Just in case, keep some extra seeds on hand. Then you move on to way #2, or you can practice both method 1 and method 2 just in case.
2) You might apply the paper towel technique. Put the seeds on one side of the towel, moisten it, then fold it over to cover them. Place the towel inside a plastic bag and zip it up. Place it in the refrigerator and wait. Some advise checking every two to three days and getting rid of any mold. Others advise waiting 10 days. Some estimate that it could take a month or two. They should be thrown away if they develop brown spots around them or begin to smell musty. However, the key goal is to keep that towel damp!
If you already have a seed package, here is myseedneeds’ recommendation for poppies for the lazy gardener! We advise a brief cold stratification period of 6 to 12 weeks, but gardeners who don’t want to deal with damp paper towels and plastic baggies can just store their seed packets in their crisper drawer for a few months.
You could also soak your seeds first. Put equal amounts of sand and peat in a pot and add worm castings to aid with germination. Place your seeds in. Put the pot or container inside the refrigerator, on the ground in a protected area, or buried up to the pot’s top on the north side of your building, which is more exposed to the elements. Keep those seeds moist at all times.
Restoration Seeds published this thorough guide to How to Germinate Your Seeds on Permaculture News. It gives more alternative Cold Stratification methods and incorporates them! starting at the Cold Stratification section. Great advice! Read this!
Harold and the Cats of Alchemy make a crucial point about sustainability: “Seeds…won’t come up all at once, way the seeds of most cultivated plants are bred to do.” Because they are more like to the wild and hence have a solid motive to stagger their germination, seeds that use cold to germinate are more likely to survive and produce more genetic variation. This implies that there will be a higher possibility of receiving plants that will thrive in your environment.
On a seed packet, terms like “self-sowing,” “perennial,” “cold hardy,” or “cold stratification” are signs that your seeds might benefit from cold treatment.
Numerous Common Domestic Flowers are significant companion plants, including Sweet Peas, Zinnia, Johnny Jump Ups, BreadSeed Poppy, Cosmos, and Pansies.
Wildflowers! Here is a great MAP to help you choose local wildflowers that need to be cold-stratified before being planted in the spring in your area. United States Meadows Native wildflowers make excellent companion plants because they draw local bees. Make sure to start early enough to allow for planting time because they need to stay in your fridge for 4 to 5 weeks. Your seeds will grow nicely and germinate more quickly. For monarchs, don’t forget to plant native milkweed!
Numerous perennial common herbs serve as significant veggie companion plants, food for pollinators, and companion plants: Sage, Rosemary, Lavender, and Calendula
Make careful to look up each plant separately to learn about its unique requirements, such as length of time and temperature. An illustration of the perennial Oriental poppy (Papaver orientale) can be seen at SFGate. Some poppy varieties are easy to plant, whereas Oriental poppy varieties require special care!
- In a plastic bag, put 2 tablespoons of perlite or sand. It should be mildly dampened with water, but not made soggy.
- Mix 1 tablespoon of poppy seeds with the perlite or sand before adding them to the bag.
- For two weeks, store the sealed bag in the fridge. Check on it every so often, and if additional water is required, give it some, to keep it moist. Keep it from drying out.
- Take the bag out of the fridge, and keep it somewhere cool and dry for a week. Put the bag back in the fridge for an additional two weeks.
- For six weeks to three months, repeat this cold-thaw cycle. In the early spring, scatter the layered poppy seeds over moist soil. When the soil temperature is between 55 and 60 degrees Fahrenheit, they will begin to sprout in about two weeks. [Therefore, begin your procedure well in advance!]
Cold stratification is a straightforward method that, while it may need some commitment, definitely pays off!
Should sweet pea seeds be chilled?
One of the simplest flowering annuals to grow from seed is the sweet pea. In the garden, sweet peas are frequently direct-seeded. Give them a location with full to partial sun and rich, loamy soil that is deep, wet, and well-drained. To improve the soil and make it more friable, add lots of organic matter (compost, well-rotted manure, leaf mold, or humus).
When they are planted at times with colder temperatures, sweet peas thrive. The “season” for cultivating sweet peas is different depending on the location. To enhance winter and spring blossoming in western North America, sweet pea seeds should be sown from August forward. Although harsh freezes can cause sweet peas to die back, the plants can withstand frost without suffering too much damage. In the west, sweet pea blooms can be enjoyed well into the summer because of cooler nighttime temperatures.
Sweet peas can be started inside early for transplanting or planted right away once the worst of the weather has passed in the drier plains regions. Sweet peas have been successfully cultivated in Colorado’s hot summers by cut flower producers who mulch thickly as the plants mature and the temperature rises.
In the south, plant seeds in November or December for fresh cut flowers in early spring. In the non-coastal mid-west and northeast, start seeds indoors in February and transplant them outside after the ground thaws. In April, seeds can also be planted directly into prepared garden soil. The northeast’s coastline regions are also great places to raise sweet peas for the spring.
For sweet peas to bloom magnificently in your yard, you will need about 50 days of chilly temperatures (below 60 F). The seed coat of the sweet pea is tough and insoluble in water. There is no proof that sweet pea soaking will promote germination. A sweet pea seed’s outer layer can be punctured to allow for quick hydration, which speeds up and increases germination. The sweet pea seed coat can be easily nicked by scoring it with a nail cutter. When the soil is between 13 and 18 C or 55 to 65 F, sweet pea seeds will begin to sprout.
In holes that are about two inches (two knuckles) deep, plant seeds. Fill each hole with two to four seeds, and spacing them four to six inches apart. Till seeds have sprouted, thoroughly water and maintain soil moisture. Germination should occur within 10 to 21 days. Water the seedlings frequently once they start to grow to encourage robust, wholesome growth. Thin out the seedlings when they are three to four inches tall, spacing the strongest-looking plants four to six inches apart. You can enjoy your sweet peas for a longer period of time by sowing seeds once a week throughout a number of weeks.
Grow them in four-inch plastic or peat pots filled with a seed-starting mixture devoid of soil. Put two or three seeds into each container, each one being pushed an inch into the potting soil. Put the pots in a cool, dark location after covering with mix and water. Watch for new shoots to appear above the earth after about 10 days. Bring the plants outside into the sunlight at that stage. Keep them cool (below 55°F); if you keep them in a heated room, they won’t be hardy enough to move outside without a lot of time to harden off. Reduce the seedlings to one plant per pot until they have two sets of true leaves. As soon as the soil is workable, transplant into the garden about a month before the last date of frost because the shoots are hardy and won’t be affected by light frost. 12 inches should separate dwarf bushy forms, and 6 inches should separate climbing variety.
To avoid harming the roots, it is advisable to plant the stake or support with the seed or transplants when planting tall, long vine sweet peas. Although trellises are the most typical supports, there are various ways to climb. Sweet peas may climb on bird netting strung between two stakes, twine, string, or fishing line hung from the top of a split rail fence, a bamboo teepee, and brush stakes. If the support isn’t up against a wall, scatter seeds all around it to create a stunning display of blossoms that are visible from all angles. A four to six-inch layer of organic mulch will keep the roots cool and lengthen the growing season once the plants have been thinned out.
Avoid overfertilizing to avoid producing lots of very deep green foliage but few blooms. For the initial plant development, a 20-20-20 slow release fertilizer combination that is balanced works well. As an alternative, sweet peas benefit greatly from organic fertilizers. Composted manure mulching will help keep the soil moist and supply nutrients for healthy plant growth and blossoming.
When flowers start to fade, deadhead the plant if blooms are not frequently pruned. The plant will produce fewer flowers overall if seedpods are allowed to develop. More flowers will result from removing spent blooms.
Similar to other direct-sown seeds, the first difficulty for sweet peas is avoiding being devoured by rapacious birds, mice, squirrels, and other animals. Sweet pea seedlings are particularly susceptible to bird, slug, and snail damage if planted in the fall in a warm area.
Preventative actions frequently stop a problem in its tracks before it really has a chance to begin. For healthier plants, abide by these recommendations. Sweet peas should be planted in a region with sufficient airflow. Wet leaves are a magnet for fungus, so water early in the day so they are dry by dusk. Consider sweet peas as a type of food crop. Planting locations should be rotated so that sweet peas are only cultivated in one location every four years. Do not plant sweet peas where other legumes are flourishing or were previously planted. Garden peas, all varieties of beans, peanuts, and clover are examples of legumes.
In particular, certain specialized nurseries or garden centers may sell sweet pea plants. There might be sweet pea plantings in ready-made containers, creating an instant garden. When buying sweet peas, search for plants in individual peat or earth-friendly pots as they require special care when transferred. The better, the bigger the pot. Snip off any blooms or flower buds just before planting. Now is the moment to establish the roots thoroughly so they can support the needs of the developing plant. You will gain larger plants with a profusion of bigger flowers even though you give up early blossoms.
Plant in a pot or in garden soil that has been prepared. To protect the priceless roots from damage when transplanting, it is even more crucial to place the support first. Attempt to maintain the root ball’s unity. It should be planted at the same depth as when it was first emerging. Water it after gently firming the dirt around it. A week to 10 days should pass before mulching. Till the plants are well-established, make sure to maintain the mulch at least an inch away from the stem of the plant. Otherwise, you run the risk of suffocating the stem or potentially fostering bugs, illnesses, and insects.
Sweet peas entered the world of containers when “Cupid,” the first dwarf sweet pea, was introduced at the turn of the 19th century. Their small size makes them ideal for use in pots, urns, hanging baskets, window boxes, and other types of containers. Numerous varieties of dwarf sweet peas are offered in store-bought seed packets or through mail-order catalogs.
Sweet peas that climb are excellent container plants as well. Instead of placing one or two seeds in the center of the pot, place a circle of seeds an inch inside the rim of the pot, spaced a few inches apart. It is simplest to plant the support first, then scatter the seeds around it, in the constrained space of a container. Tomato cages make excellent supports for larger containers; the legs can be pressed into the potting soil. You can put a container of sweet peas in the garden in the early spring because sweet pea shoots aren’t affected by frost (at the same time youd plant seeds outside.)
Start trimming flowering stems for indoor bouquets when the first blooms show. You’re encouraging the plant to produce more flowers in addition to enhancing the lovely scent in the home. Every other day, during the morning hours when they are freshest, trim the stems. For climbing kinds, trimming lateral shoots that emerge from the base of the leaves will slow vegetative development, boost flower production, and improve airflow around the plant.
When you first arrange the stems, they will appear full. As the early blooms fade, the remaining buds will open. Make sure to get rid of any leaves in the vase that are submerged in water. If the base of each stem is trimmed off by 1/4 to 1/2 inch, a bouquet of sweet peas will easily last a week indoors. The water should also be changed every day.
The National Garden Bureau provided permission for this information to be republished. The person who wrote this fact sheet is Cathy Wilkinson Barash. Renee’s Garden provided the sweet pea image “Pastel Sunset,” while Bodger Seeds Ltd. provided the sweet pea images “Ocean Foam” and “Streamers Mix.”