Many native North American plant seeds germinate after a period of cold and moist stratification. Cold moist stratification is not required; but is encouraged because it can increase germination especially if seeds have been dormant for a long period of time. We recommend that all of our seeds go through a 90-day period of cold and moist stratification. Please read all of the information below before planting your seeds.
Cold Moist Stratification Cold moist stratification is a common requirement for temperate species found throughout North America. In the wild these seeds would germinate in the spring following a cold winter. Typically, these seeds would disperse during the spring or summer and spend the winter months in the soil or leaf litter where they have some protection from the elements, but experience a cold and moist storage. Cold moist stratification can easily be replicated by sowing the seeds in pots and leaving them in a protected area (like a shed) outdoors to follow natural temperature variations or by storing seeds in the fridge in Ziploc bags with moist vermiculite or paper towel (for fine seeds). After the cold moist stratification seeds can be sown in the garden in the fall or early spring or left in pots in Ziploc bags and grown indoors under an appropriate grow light. Germination typically takes place in approximately 14 to 28 days when adequate moisture and temperatures (approximately 20⁰C/ 68⁰F) are provide.
Currently all the seeds we offer need to go through a cold moist stratification period. Some may also require a warm moist stratification, multiple cycles of warm and cold (double dormancy) or scarification. Please see read more about this below. Cold Moist Stratification Methods Cold moist stratification is best accomplished using one of two methods. Read the below instructions thoroughly before planting.
Natural Cold Moist Stratification: Planting the seeds in the fall or early winter will allow for seeds to grow through cold moist stratification naturally. Seeds can be sown in pots or on a level garden bed. Sow the seeds by lightly tamping them into the soil. Outdoors fall planting is best for most species, but if stored correctly seeds can also be sown in the early spring. Be patient, seeds can take a while to become established. Do not plant deeper than the thickness of the seed. Do not cover the with too much substrate as seeds need light to germinate, which will not take place until spring when the temperature and conditions are just right.
Natural cold moist stratification is also ideal for seeds that require warm moist stratification or a double dormancy as seeds will experience natural temperature variations. For seeds requiring a warm moist stratification or double dormancy they are best planted in the early summer or as soon as received. Seeds will need to be protected in your garden and watered throughout the warmer months.
Artificial Cold Moist Stratification: Mix seeds with vermiculite or a suitable seed starting substrate. Make sure you have roughly three times the amount of substrate, to the amount of seeds in the mixture. Place the mixture in a sealed plastic Ziploc bag in the refrigerator for 90 days. Make sure to write a label on the bag with the date for monitoring. Regularly check the bag to ensure the seeds are not drying out or sprouting, if sprouting occurs plant immediately. For smaller seeds storing on a moist paper towel is ideal. After 90 days the mixture is ready to come out. Remember that these seeds need to be kept moist and cool until planting.
Before taking it out of the refrigerator make sure to prepare some water 24 hours in advance. Fill a clean container with 2 litres of water and allow the water to stand for at least 24 hours without a lid. This will allow the chlorine and fluoride found in municipal water to dissipate.
After the water has been allowed to stand for at least 24 hours, take the mixture out of the refrigerator and spread on the top of a fill 4 to 6 inch (10 to 15 centimeter) plastic pots with a suitable seed starting substrate. No more than 5 to 10 seeds should be planted in a pot; so you may need 5 or more pots. Fill a plastic shoebox style container with at least 2 inches (5 centimeters) of the standing water. Place the pots with the seed substrate in the container of water, allowing them to soak up the water through holes in the bottom of the pot. Let the pots to soak in the water for as long as it takes to absorb water to the top of the substrate, approximately 1 to 3 hours. Do not pour water onto the top of the seed substrate. Finally place each pot inside of a sealed Ziploc bag labelled with the date and type of seeds.
Keep this pot indoors under a grow light for best results or near an east, west or south facing window with access to 3 to 4 hours of sunlight each day. Do not place in direct sunlight as this type of exposure may be too harsh for the seedlings. Most seeds should germinate and sprout within 14 to 28 days. Once the seedlings are 3 to 7 centimeters (1 to 3 inches) tall they will need to be potted into their own pots or planted into your garden with a suitable potting mix. When you open the Ziploc bag remember to do so gradually (only 1 centimeter or 1/3 inch per day) to avoid shocking the seedlings. Only plant seedlings in your garden if the conditions are correct for planting based on your hardiness zone and season. For most locations spring and fall planting is the most suitable.
Warm Moist Stratification Warm moist stratification is a common requirement for temperate species that flower in the very early spring. In the wild these seeds are typically formed by the early summer and would germinate the following spring. Typically, these seeds would disperse during the early summer and spend the rest of the summer in warm and moist storage in the soil or leaf litter. They would then experience a cold moist stratification during the winter months. Typically, these seeds have the most success if sown while still fresh. If they cannot be sown fresh in the summer, they need to be kept moist at natural outdoor temperatures until the fall when they can be planted. While these conditions can be replicated by sowing the seeds in pots and leaving them in a protected area outdoors to follow natural temperature variations. We find the most successful way of growing these seeds is to plant them on a level garden bed during the early summer or early fall. This allow seeds to follow the natural temperature variations outdoors. We ship these types of seeds in a re-sealable plastic Ziploc bag with a small amount of vermiculite or moist paper towel (if the seeds are too small to distinguish from vermiculite) to keep them moist. Currently the species of native plants that we carry that require this include:
Bloodroot (Sanguinaria Canadensis)
Mayapple (Podophyllum peltatum)
Sharp-lobed Hepatica (Hepatica acutiloba)
Multiple Cycles of Warm and Cold (Double Dormancy) The seeds of some temperate species of plants require multiple cycles of warm and cold periods before they will germinate. This is typically referred to as a “double dormancy”. These seeds typically have hard seed coats and change in temperatures helps to break this coat and allow germination to take place. There are many resources for germinating these seeds including recommendations for fridge cycles. While the conditions can be replicated indoors we strongly recommend sowing these species as soon as they are received outdoors and allowing them to follow natural temperature variations. We find the most successful way of growing these seeds is to sow them on a level garden bed or in pots in a protected area in your garden as soon as they are received. You will need to regularly water the seeds throughout the warm season. Seeds that require multiple cycles of warm and cold require patience as they may not germinate until their second or third season. In addition, these plants are typically slower to grow and reach maturity. While they require a little bit of extra patience they are well worth the wait! Seeds that require double dormancy are best ordered by customers in temperate regions that can provide the proper natural temperature variations needed. Currently the species of native plants that we carry that require this include:
Red Trillium (Trillium erectum)
White Trillium (Trillium grandiflorum)
Scarification Scarification is the process by which a hard coat exterior of a seed is weakened, opened or altered to encourage germination. Some seed coats are so hard they do not allow water in which prohibits germination. In nature the seed coat would be broken down by passing through the digestive track of an animal where the seed would be exposed to digestive juices and/or rocks inside a crop, which would breakdown the seed coat.
There are several methods to scarify seeds including sandpaper, hot water soaks and soaking the seed in other substances. Physically rubbing the seed with sandpaper for a few seconds should be enough to break the coat. However, we like to follow this up with a hot-water soak. Pour boiling hot water over top of the seeds you scarified with the sandpaper and allow to sit overnight. If they sink in the water the seeds are viable, typically if they float they are not viable. If the seeds are small sandpaper may not be ideal, in which case we would only do the hot water soak. Soaking the seeds in substances like hydrogen peroxide, ethanol and citric acid can also work to soften the seed coat. In our experience however some sandpaper and/or a hot water soak works just fine.
After seeds have been scarified temperate species will then need to complete a cold moist stratification. Once scarified you will need to monitor the species during their cold moist stratification as they may be sensitive to decay.
Currently the only species of native plant seeds that we offer who require scarification are those plants in the Family Cactaceae, cacti. Tip for Planting Seeds Directly in the Garden When soil temperature, moisture and lighting conditions are ideal your seeds will germinate. If things are not right, native plant seeds will wait until conditions are suitable. So be patient, and do not disturb your soil for at two seasons (three seasons for some species)! Native plant seedlings are tiny when they first germinate, even though their roots are very long. The best way to control weeds is BEFORE you plant the native seeds. Trying to pull vigorous, fast-starting weeds will only disturb developing roots of your seedlings. To minimize losing native plant seedlings the first year, weeds can be cut off or back rather than pulled out. Preventing annual and biennial weeds from blooming and setting seed assures that they will not appear in your planting again. Perennial weeds will be stressed through cutting and will not compete successfully once your native wildflowers are established.
If planting in a garden bed sow seeds on a level surface where water will not pool and it will not be as difficult for seedlings to start. Sow the seeds by lightly tamping them into the soil. Outdoors fall planting is best for most species, but if stored correctly seeds can also be sown in the early spring. Do not plant deeper than the thickness of the seed and o not cover the with too much substrate as seeds need light to germinate.
It is not necessary to water a new planting, although moisture will help speed things along. Do not fertilize! The wildflowers are adapted to the garden conditions as they exist and fertilizer often makes them tall and gangly. Fertilizer can also stunt growth or even kill the plants over time. Native plants are adapted to a climate of cold winters, hot summers and regular rainfall. Such a climate favors deep-rooted, slow-growing, long-lasting perennials. Help preserve our native plant heritage and encourage more biodiversity in your yard! Planting Depth In our experience many of the plant species with small or fine seeds need to be sown superficially on a level surface. Many species with small seeds are stimulation by light to germinate. They are best planted in pots and simply pressed lightly into the substrate with the correct humidity.
We have also found that the majority of seeds need light to germinate and some are heavily dependent on light for germination. For the majority of species, we have found sowing superficially or with a small amount of medium on top is best. As a general rule of thumb do not plant deeper than the thickness of the seed. There are some exceptions to the rule but most seed appreciate adequate lighting.
Seed Lighting We generally prefer to start most seeds indoors with the use of a grow light so they get a good head start in the spring. We recommend using full spectrum lights when produce light with a colour temperature of 6400 Kelvin closely matching the wavelengths of natural sunlight. While we recommend starting seeds under appropriate grow lights, seeds can also be started indoors near an east, west or south facing window with access to 3 to 4 hours of sunlight each day. Do not place in direct sunlight as this type of exposure may be too harsh for the seedlings. Suitable Seed Starting Substance There are a wide variety of resources with a wide variety of recommendations and contradictions when it comes to a medium for starting seeds. A suitable seed starting substrate or medium will depend on the type of seeds you are planting. We recommend researching seed substrates and referring to your favourite gardening book and other resources recommendations. In our experience seed substrates from local garden centers mixed with a fine sand on top has worked well; however, many experts recommend mixing your own substrate with specific ingredients in specific quantities.