How to Prepare Winter Sow-Bags
Spanish Version
What are sow-bags?
Sow-bags are small, reusable bags that are used to make germinating seeds much easier during the cold winter - like a mini greenhouse! Sow-bags are easy to prepare, and can be a fun, quick activity to give back to the planet (and you can give them as gifts)!
Purpose of this activity: First and foremost - Giving back to our Great Mother. Secondly, gardening on a shoestring budget!
A special thank you to Jennifer Frazier for generously teaching me the time-honored technique of making winter Sow-bags.
She in-turn learned of this process form Trudi Davidoff, who has made many YouTube videos on the subject. The biggest difference is that we are using Native Perennial Seeds and we are doing this out West where it is dry and windy.
In this activity, you will create little outdoor reusable “greenhouses'' to germinate or sprout seeds outside, utilizing only our natural weather cycles and some water! The seedlings can eventually be planted into the ground (or maybe pots first for a short time – which is discussed later).
You may germinate Native perennials and annuals as well as Cool and Warm season veggies. You may also winter sow annuals. They are thought not to be as advantageous to the Native Bees, but you may grow them nonetheless. We will be focusing only on Native flowers and grasses for this activity. But the exact same principles apply for your veggies. The only caveat is don’t start the warm season veggies until late March – until after the spring solstice. Cold season ones can go in in January and February but neither go in with the Native seed bags.
Warm season veggies need warm temperatures to grow and mature. They won't fruit until night temps are in the 50 deg fahrenheit range. Once the fruit begins to form, it needs up to two months of frost-free weather.
Beans, corn, cucumbers, eggplant, melons, peppers, zucchini and summer squash, pumpkin and winter squash, sweet potatoes, tomato and watermelon are all warm season veggies.
Cool Season veggies are uniquely adapted to CO climate because they are able to withstand light to moderate frosts, adding a month or more of gardening time at the beginning and end of our growing season. At higher elevations, the are the only veggies that grow successfully.
The Perennial cool season veggies are asparagus, chives, horseradish, rhubarb and shallots and once established will grow for many years.
Annual cold season veggies are broccoli, cauliflower, onions, kohlrabi, potatoes and peas–leaf and root crops like cabbage, swiss chard and kale. Carrots, leek, lettuce, onion, parsnips, peas, radishes, spinach and turnips are also annual cool season veggies.
Facts about this type of sowing:
You can prepare the bags anytime between the winter solstice and the spring equinox. Start anytime from late fall to mid march (as long as you’re still needing a light jacket at night). You don’t have to do them all at once, either. Do a few every week or every few days.
You must use only potting mix (and I prefer soil that does not have added fertilizers, pesticides or other chemicals).
Don’t use seed starting soil mix as the growing medium in the sow-bag, because it does not hold water well enough and it is not nutritious enough to support the growth of the seedling once it sprouts. Also, avoid soil directly from the garden as it is very heavy and typically contains the wrong amount clay and/or sand for sow-bag germination.
You will have to use gallon-sized plastic bags in order to maintain enough moisture and soil to support the seedling roots. Smaller plastic bags won’t work.
You can expect somewhere between 70-80% germination rate. In other words, not all seeds want to germinate every year. In nature it has an even lower rate of germination.
So, not every seed in every bag will sprout. Some bags may not sprout at all this year. It is usually not because you did something wrong, but because that species just did not want to germinate under these conditions, this year.
Once the bag is set up you will have to keep an eye on it to keep it moist or the seeds won’t germinate. Moist does not mean swamped with water. Too much water and the seeds will rot. Good drainage is important - so if the bags are draining slowly, cut the holes bigger.
Materials needed:
Gallon-sized zipper-lock plastic bags (the kind that have the little sliders work the best).
Wooden clothespins with the little spring in them; One per sow-bag.
Thin, wooden food skewers or kabobs (the cheap ones you get from the grocery store) One per sow-bag.
Masking or painters tape, and a ‘sharpie’ to label the tape on the bag.
Watering can with a narrow spout or a tap that can be adjusted to slow flow.
Use a tray in the sink as you don’t want to clog up your drain with mud.
Native seeds; either from a seed envelope or wild gathered seeds.
All-purpose potting mix (you will be filling each gallon-sized bag about one-third full).
*Notes*:
A way to get your winter sowing home without soaking your car:
Plastic boxes or trays or some other impermeable container would be best, as the bags will be dripping wet.
You can start making winter sow-bags after the solstice in December, and all the way up to the equinox.
Bags started later in the winter and very early spring will still germinate, but the challenge is that you need to get them in the ground before it gets too hot.
Instructions:
Decide which seeds will be going into your bag and make a label that contains both the common and latin name. If you are going to use a seed mix with many flower seeds, you can label and save the envelope; for example “A”. In that case just write “A” on the tape. I don’t recommend combining flower and grass seeds in the same bag. Place the label near but not directly on the bottom of the sow bag. (If you put it on the side of the bag the sun will fade the label).
Place the tape on the bottom of the plastic ziplock bag.
Cut the corners off the bottom of the bag and cut a triangular notch in the middle of the bottom of the bag – this is so the bag will drain and not drown the seeds. The holes should be about ½ to one inch long. (Too small and the water won’t drain fast enough).
Fill the bag 1/2 way full with your Potting Mix. Again: 1/2 soil to 1/2 air.
Untreated soil and untreated seeds - seed starting mix is expensive and unnecessary. And no heavy soil from the garden.
Thoroughly wet the soil by running a gentle stream of water over the entire amount of soil either under a running tap or by using a watering can that has a small spout opening. You want the soil wet and to see water draining out of the bottom of the bag. You don't want a lake of water in the bottom. If there is a puddle of water in the bag, cut the holes a little bigger so the bag drains more quickly. There should be 1/3rd soil and 2/3rds air. Note that adding water to the soil will make it look more compact.
Dry your hands thoroughly or the seeds will stick to them.
Add seeds to the bag. Remember that when native seeds fall to the ground out in nature, they fall in large quantities and germinate very close to each other. So don’t try to do the one seed per square inch thing here like you would if you were planting indoors or in a formal seed bed. So layer a lot of seeds on the soil, and don’t push them deeply into the soil as most seeds will require some light to germinate. If the package or google instructions say to plant 1/8th of an inch deep just sprinkle some soil on top of the seeds. Don’t bury your seeds because the majority of them need some light exposure to germinate and if they are too deep they will rot.
Now prepare the stake and the clothes pin. You are doing this to protect the seeds from suffocation. You need a way to keep the bags propped open. You need gas exchange and a way for heat to escape. As the weather gets warmer you will need to gradually start opening the bag for heat exchange and for snow to get in. Take the upper corner of the bag where the sliding tab is NOT and make the corner of the bag as open and flat as possible and put a clothespin on there to keep it flat and open. That way, as you adjust the tab over the next few months, it can never completely close off. Again, air-gas exchange within the bag is crucial.
Next, place your long skewer stick in the soil near the corner where the clothes pin is so that the bag has enough structure to keep it from folding over when snow and winds affect the bag. The stick will keep the top from folding over on itself which would cause the temps to get too high in the bag.
Make sure the bag stays wet BEFORE the seeds germinate. 4 ways to keep the seeds wet:
Add in snow from a snow bank. (the most natural way)
Put bags in a shallow plastic box and put a small amount of water in the bottom and the soil will pull the moisture up into itself.
Use a watering can to gently slide water down the side of the bag. Don’t just dump water all over the top of the soil because it will disturb the soil too much.
Use a sprayer to wet the soil.
Place the bags outside on a shelf in the sun OUTSIDE. You can put bags close together, even touching but not packed in too much.
Keep your bags/seeds moist on the inside. You can tell if the bags have enough moisture because you will be able to see condensation on the insides. They should look like wet, little steamy green houses! If the bag is not heavy and without condensation, then put more water into the system.
Now leave them alone, in the sun, snow and wind and just make sure they are moist. Some folks rotate the bags now and again. I do not. (Too much work).
Come springtime, the seeds will sprout and grow. They may germinate sooner if we have really warm weather.
In the case of a very warm winter, you may want to give them some covering once in a while to remind them that it is still winter.
When it starts to get warm, start to gradually expose the seedling to the wind by folding the top of the bag back; in other words ‘cuff’ the bag like you would the bottom of pants. This will allow airflow to harden off the seeds. The little seedlings will have been acclimated to the cold and sun and temperature swings - but not to wind. Exposure to wind helps thicken the stems so you don’t grow spindly, weak stemmed plants.
The seeds will first sprout two immature ‘false leaves’ called cotyledons. They were formed from the nutrients inside the seeds. You must wait for the ‘true leaves’ to form. Should occur pretty quickly. Once you have two true leaves the plants are starting to grow in earnest.
The temps will be getting warmer and the seedlings will need to be watched for watering and too much heat. It is probably a good idea to move them to dappled shade under a tree without leaves. In nature these sprouted seeds would be protected by nearby plant growth. Cuffing the bag back will also allow the tiny plant to be exposed to some wind so the stems can thicken and become strong.
They’ll need water but be gentle so that you don’t flood the plants nor damage them by pouring water aggressively directly on them.
It will be time to put these beauties in the ground once the threat of the first frost has passed and that is typically Mother’s day in Colorado - but keep an eye on weather reports. By now, your plants will be several inches tall and ready to be gently removed from bag as though you were removing small ‘chunks’ of bread. Tease them apart and plant them either directly in the ground or if you have the space and patience, they could live for a couple of weeks max, in small planting pots.
Plant them amongst other plants if you have some already growing so that they have some protection. If you are starting a garden from scratch, you may need to find a way to create a bit of artificial shade - like with a light shade cloth supported by sticks or an upside down clothes basket.
Just don’t let them fry in the sun or alternatively freeze when we get an unusual frost. If that happens, I recommend covering the small plants with upside down plant pots to keep frost off their leaves and stems. You may uncover them once the risk of frost passes. Snow itself will not harm the plants, just freezing temps will.
Once they are planted, monitor them for sunburn. If it's gonna be a scorcher, cover it with, white, airy plant fabric. These newbies will need attention and watering at the base until they are will established, about 2 years. Some will bloom this year and others not until next year.
Follow basic care for newly planted Native Plants over the next couple of years!
Have fun!
Congratulations! You have successfully planted a biodiverse habitat that will serve the insects and song birds, as well as nesting sites. Good work!
Final Notes:
You will find that some of the Native plants, which are thought not to flower in the first year, do indeed flower during year one.
For example, several of us had great luck with Erigeron speciosus (Fleebane).
Some species’ seeds may require lots of prep before putting them in sow-bags. For example; heat stratification, scarification, or dark and cold temperatures. If you are experienced with these types of seed treatments or want to experiment with more challenging species, by all means do so and put them in the sow-bags after you have applied the treatments.
Note: these are physical treatments or adding simple things like a bit of natural soap, but I am not referring to chemical treatments like chemical fertilizers.
The USDA often has great instructions on treatment of difficult to germinate species.
I personally am going to do several species that require pretreatment before putting them out into the seed bags because I am hoping to introduce some difficult species that are difficult to find in nurseries because they are so hard to germinate. However, the treatment of these seeds is beyond the scope of this workshop.
Enjoy this fun, off-season gardening activity, and happy planting!
