Have you ever wondered how to store seeds from your favorite native plants?
Every summer, I work on reforestation projects as a tree planter in the boreal forest. While on the job, I love to look at the native plants growing around me.
Year after year, I’ve been learning to identify each plant, and now I’m at the stage where I want to bring them home with me.
I’ve started a native plants nursery myself and have experimented to propagate many of those wild plants.
One of my favorite propagation methods is to grow directly from seed. It’s a tricky business, but finally figuring out a plant is a super rewarding process.
One of the important aspects of wild plant propagation is learning how to store seeds without damaging them.
In this article, we’ll be covering the best techniques I’ve found that works great for doing just that.
What you can expect to learn:
Let’s get started:
Seed Types: Orthodox vs. Recalcitrant
There’s no single sure way of storing every type of seed, your storing technique should differ according to what type of seed you’re working with.
There’s an important split in seeds that helps you determine how to store them, and it’s based on the moisture content they should have when dried and stored.
Up to 80% of all seeds are orthodox, they’re pretty much like the seeds we’re used to working with. In general, orthodox seeds are dried to a 5-10% moisture content and stored in the fridge, freezer, or even at room temperature.
Orthodox seeds can be stored for 5-10 years in home storage.
Recalcitrant seeds, on the other hand, need to maintain around 30% moisture content during storage to stay alive. They will also likely get damaged if stored in the freezer since ice crystals that form could kill the embryo.
Recalcitrant seeds should mostly only be stored at refrigerator temperatures. In general, they have a shorter lifespan than orthodox seeds.
Their lifespan can range from a couple of weeks to a couple of years.
Note: Most North American woodland plants produce recalcitrant seeds.
Orthodox and recalcitrant are a classification of seeds that focuses on moisture content. 5-10% for orthodox, and 30% for recalcitrant.
You should store your seeds according to their classification, and dry your seeds properly for successful storage.
When to Collect Seeds
Collecting seeds is usually more straightforward, but here again, techniques should vary according to the seed you’re collecting.
Seed maturity is a factor we don’t usually think about, but it is really important for some seeds.
When a fruit or seed pod looks mature for harvesting, it isn’t always the best time to harvest it.
Let’s get into the details:
You may be storing your seeds too early.
Why? The seed pod is brown and dry, it’s about to drop on the ground, that’s the prime time to harvest and store, right?
The fact is, many seeds still continue their maturing process after they’re released from the mother plant. Some seeds only complete the maturing process after being dropped and dried.
So you have to think of it like this, when you pick your seeds, you have to continue to give them the natural conditions they would naturally have. You shouldn’t just store them in the fridge or freezer right away.
For example, a seed in the forest drops in August then gradually dries through September, and only experiences true cold and freezing by the end of October.
Orthodox vs. Recalcitrant
Here’s a study from the Department of Agriculture in the UK where they compared maple vs sycamore (orthodox vs. recalcitrant).
- Maple seeds (orthodox) reached germinability 4 weeks prior to looking mature.
- Sycamore seeds (recalcitrant) reached germinability 10 weeks prior to looking mature.
Seeds shouldn’t be stored right away after harvest, they need to continue their maturing process.
Recalcitrant seeds benefit from being harvested in the green stage before they look brown and mature.
How to Store Seeds
When you place your seeds in the fridge directly after harvesting, you may be stunting the chemical process that is still going on inside the seed.
Storage prior to correct drying results in stored seeds that have not reached full maturity. Let them sit at room temperature until the time they would naturally hit cold temperatures outside.
We learned earlier that orthodox seeds should be dried to about 10% moisture while recalcitrant seeds to about 25% moisture.
What’s not to neglect here is how quickly this happens. Rapid desiccation is tolerated by orthodox seeds while not tolerated by recalcitrant seeds.
How can you reach that moisture content with drying methods at home?
A good way to dry seeds is to place them in a paper bag at room temperature. Alternatively, you can dry them on a hanging dryer rack.
- For orthodox species, seeds can usually be stored dry at −18°C for more than 5 years.
- For recalcitrant species, seeds should be stored moist at ≥10°C for less than 1 year.
Here again, the stratification period depends on what plant you’re working with.
There’s a concept called germination codes and it provides deeper detail on stratification and germination.
Here’s a generalized snippet that can help point you in the right direction.
Germination codes, simplified:
- A: Tropical & Annual Plants – Seed will germinate within 4 weeks if sown at 70°F/ 21°C. Place 1-3 months dry storage + ~60 days cold stratification.
- B: Temperate Wildflowers – Seed will germinate upon shifting to 70°F/ 21°C after 90 days of moist, cold stratification at 40°F/4°C – Sow outdoors in Fall.
- C: Lilies or Woodland Forbs – Seeds germinate only after multiple cycles of warm and cold, typically 40-70-40-70 – Collect 3-4 weeks pre-maturity and sow immediately outdoors.
- D: Hydrophilic species – Seed needs a period of warm moist stratification followed by cold stratification and will germinate after shifting back to warm (70-40-70) – Sow in warm flats for 3 months, shift to cold for another 3 months, then warm in spring.
- G: Fleshy Fruit Seeds – Physical or Chemical inhibitors in the pulp and skin of fleshy fruits – Wash off all pulp to remove chemical inhibitors or physical barriers for water absorption before treatment.
- H: Micro Seeds – Seed requires light to germinate – Surface or near-surface sown, alternatively, moss-sow, but water with distilled or rainwater.
- I: Beans or Mallows – Seed requires scarification because of an impermeable seed coat – Physical abrasion helps the seed germinate faster, ie with sandpaper.
- *Hydrophilic seeds – Intolerant of dry storage – Sow immediately, or clean and store fresh seeds in a sealed plastic bag with or without vermiculite.
Note: Some native plants produce seeds that are combinations of germination codes. For example, a microseed could need the treatment of a C-type plant. Many woodland plants are hydrophilic.
How to Store Seeds: Mistakes to Avoid
Here are common mistakes to avoid if you want to successfully store your seeds.
- Figure out what type of seed you’re dealing with. Recalcitrant or orthodox? There are a few lists (1,2,3,4) out there to help.
- Do not store orthodox seeds in sealed plastic unless pre-dried. They will continue to lose moisture as they mature and you need to let it escape, or else they could get moldy. Use paper bags.
- Give time for your orthodox seeds to mature before long-term storage. Dry them properly and give them some months at room temperature before storing them in the fridge.
- Do not flash freeze recalcitrant seeds. They need to be stored with a high moisture content, which will turn into deadly ice crystals in the freezer.
- Store your recalcitrant seeds moist. Do not let them dry below 30% moisture, as this will kill them. Store them sealed in a plastic bag.
My Personal Lessons
I wrote about many of these plants and relayed information that was on the market. Although the information still has a lot of room for improvement, as these plants all have unique, little-known seed care.
I did succeed with some but failed with others. Here’s my report:
- Bunchberry: Fail
- Rock Harlequin: Success
- Wintergreen: Fail
- Birch: Success
- Cedar: Success
- Bluebead: Fail
- Mountain Ash: Fail
- Mooseberry: Fail
That’s a lot of failure, right? I put all these seeds through a similar cold stratification, that’s where I went wrong.
Where I found success is what I assume are the orthodox seeds, since I dried them all before storage.
Given I did store these in sealed bags, which is usually a no-no, they were stored only after thorough drying which I did right.
If you look closely, my failures all have one point in common, they’re all plants that produce their seeds from fruits. I’m thinking many of these must fit into germination codes D, G, and maybe C.
Here’s where I went wrong:
- Dried them in their fruit: I thought maybe the fruit would hold in the moisture, which isn’t a bad idea, but it also chemically inhibits the seed from germinating, maybe even stopping stratification.
- Didn’t let them mature: These were all berry seeds, they should have been stored in a moist environment to let them age and ferment.
- Didn’t clean them: I should have cleaned them and removed all pulp and coating before doing cold stratification.
- Threw them in the freezer: While I think it was a mistake, I think not entirely. These are seeds that thrive in environments that drop as low as -45 C during winter, I will give them the benefit of the doubt they could survive the freezer, but research says to store them in the refrigerator instead.
Additional notes: Wintergreen produces fruit that gives microseeds. I did try to surface sow with no success, but next time I will try to moss-sow since this is a common natural setting they thrive in.
I hope these little snippets from my experiments help you put things into perspective. Next year, I’ll be back to add my future results.
Until then, Cheers!
A: Yes, but be careful what seed you’re storing. Recalcitrant seeds can be stored in ziploc bags to maintain moisture, but orthodox seeds will benefit more from being stored in paper bags initially.
A: Yes, but be careful when you do, timing is important. Some seeds require a period of drying at room temperature, others require a period of warm-moist stratification.
A: Some orthodox seeds can be stored for 10 years and upward. Recalcitrant seeds, on the other hand, stay viable for a shorter amount of time, from a few weeks to a few years.
A: Mason jars are good for storing recalcitrant seeds at a certain moisture level, and orthodox seeds if they are already dried.
A: This depends on the type of seed, orthodox in paper, and recalcitrant in plastic.