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Germinating seeds in baggies

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The concept

My standard method of germinating seed is what I call "the baggy method". It's my particular variation of an approach often used to check viability of seed, described by Norman Deno as the method used in his germination research, and employed by avid seedstarters the world over. An additional reference is a FAQ by the seed-starting community at GardenWeb. It's quite simple, really: enclose seeds within a folded dampened filter paper or other moist medium, place this in a zip-lock baggy, and wait for it to germinate. Well, there are some twists and turns, tips and techniques - I'll describe those on this page.

Filters and baggies

I use small (3" long by 2" wide) zip-lock baggies for most of my seed purposes - both storage and germination. They come in two basic variations: with and without a white writing strip in front. The former can be marked with a regular ballpoint pen, the latter require a fine-tip permanent marker. Either works for me. I discuss sources for baggies and other requirements on my supplies page.

As for the filters - I've settled on plain basket-type coffee filters, the kind that unfolds into a flat circle. The cheapest ones you can find work just fine. I cut these in half, and fold them as shown in the photos above: three times in half upon itself, and finally the tip folds up and over the wider part. This fits easily in the baggies, and has just the right moisture-holding capacity for germinating most seeds.

Getting things started

To start the seeds, I undo the last two folds of the filter paper, and spritz both sides with tap water using a general-purpose spray bottle. The goal is to get the paper evenly moist but not sopping wet. When I go overboard and saturate the filter, I simply lay it flat on the table and squeeze out the excess water.

For most varieties, I now place the seeds on one quadrant of the unfolded paper - say, the top left portion of the middle photo above. Because I keep careful records of my germination efforts, I either count out the seeds as I place them, or (for smaller seeds) I count them after I sprinkle them on the filter. I try to distribute them fairly evenly across the target area, that makes it easier to deal with them as they germinate. Then, I remake the last two folds, apply a little pressure to ensure good contact between seeds and paper, and slide the contraption into the ziplock baggy. I leave just a portion of the zip strip undone - enough to allow some air exchange, but not so much that the paper dries out too quickly.

The procedure is slightly different for seeds that require light to germinate. In those cases, I refold the filter in such a way that the seeds are covered by just one layer of paper, with the rest of the paper underneath.

Make sure to mark the baggy with the name of the seed variety! I also mark the date I started the seed, which makes it easier to find things in my seed-starting logs.

Meeting all their needs

Now the seeds are exposed to moisture, which is a basic requirement for all the biochemical processes that will eventually result in germination. But many varieties have other requirements we need to meet, without which germination simply won't occur. Let's start with the easiest first:


Many varieties are perfectly happy to germinate at room temperature, without any further pickiness. Our basement is about 65°F in winter, and gets a little warmer, to about 70°F when things warm up outside. That's fine for lots of seeds. Warmer temperatures may actually inhibit germination in some varieties.

Some seeds, especially those of warm-weather plants, require somewhat warmer temperatures. Tomatoes, peppers, and eggplants are good examples. Temperatures in the range 75-80°F tend to work well. For these varieties, I place the baggies flat on top of one of my shoplights. You may have a different place that provides a slightly warmer microclimate of just the right temperature.

Many seeds, especially those of perennials, shrubs, and trees from areas with cold winters, require a cold stage before they will germinate. Some need some time at room temperature before the cold stage. Some even require repeated cold and warm cycles. In germination references, these requirements are often referred to as warm and cold conditioning or stratification. It's important to realize that these stages must be provided while the seeds are exposed to moisture: the requisite biochemical processes simply cannot take place without it. To seeds, cold usually means from just below freezing to just above. Very few seeds require freezing to germinate - the refrigerator, on the other hand, is a great place to provide the cold stage. I keep an upright Tupperware container in the fridge that holds all the baggies of seeds that are undergoing their cold stage. This stage can last as short as two weeks, and as long as four months.


Quite a number of seeds, especially tiny ones, require exposure to light to germinate. I described above how for these seeds I fold the filter paper such that only one layer of paper covers the seeds - that's thin enough for light to penetrate. I then lay the baggies close to my grow-light setup, seed facing upward, so that they are exposed to light for about 12 hours per day.


There are a few seed varieties that just don't like to germinate. Nature has built in complex mechanisms and requirements that aren't likely to be met in artificial conditions. Biologists have discovered various substances, such as plant hormones, that helps these "difficult" seeds germinate. The most popular is Gibberellic Acid GA-3. Although I've dabbled in trying this for seeds that won't otherwise germinate for me, I really don't have enough experience to know whether it works. The good news, though, is that the baggy method makes it easier to experiment, since it allows precise control over the amounts, concentrations and timing of any chemical applications. For more information, read Norman Deno's book or take a look at J.L. Hudson's gibberellic acid page.

Waiting for them sprouts

Now it's time to sit back and let Mother Nature take her course. But don't sit back too long, or Ma will get angry or impatient! I typically check the baggies once every 3-7 days, and spritz the filter paper with some water if it's about to dry out. The ones being kept warmer and those exposed to light get checked more frequently, since they dry out faster.

Without light and at cooler temperature, the filter paper stays good for several months (unless the seeds brought in their own mold with them - see below). But give them either light or heat, and mold/algae grow much more quickly, and the filter paper starts deteriorating in a few weeks. Even though this does not necessarily spell death for the seeds, inspecting the baggies becomes an unappetizing task. Transferring to clean filter paper will give things a fresh start. But for these reasons, I try to germinate without special treatment whenever possible. In my seed trials, you'll see instances where one year I germinated "with light", and the next year without. If germination was fine both ways, guess what I'll be doing from now on?

They germinate!

Gastrolychnis seeds germinating. Note how some have already freed their leaves from the seed itself, while for others only the root extends from the seed.

See how the roots of these newly sprouted navarretia seedlings all align the same way. This is the result of storing the baggy in the upright position, letting the roots seek the downward direction.

Seven little bins no longer hold potato chips. Instead, each holds the baggies that are due to be checked on the day of the week marked on the front of the bin.

The first sign of germination is usually little white radicles (first roots). For some seeds, these roots grow amazingly fast. The first time you notice they've germinated, the roots may already be an inch long! For this reason, I keep all of my baggies (except for the ones needing light or warmer temperatures) in upright position. This way, the roots grow down along the filter paper, instead of trying to grow through the paper.

What's that black/red/green/stringy/fuzzy stuff?

interesting color combinations...

Sometimes, you get a moldy mess. Often, when seeds mold it means that they weren't viable. But don't be too quick to discard baggies that grow some mold. Some seeds have symbiotic relationships with mold, which, even though it looks dreadful, actually helps it to germinate. Doing the seed check routine in the vicinity of a source of warm soap and water or disinfectant wipes, to wash your hands after handling particularly moldy baggies, can help limit the cross-contamination between baggies. Even so, I don't usually follow this advice myself, and don't have much trouble with mold affecting viable seeds.

Ah - soil at last!

I usually transfer the germinated seeds to cell-packs or pots as soon as they sprout radicles. Especially with small seeds, this is a delicate operation. I avoid touching them with my hands - I've found that the blade of a pocket knife, moistened by a quick lick to make 'm stick, makes for an excellent transfer tool, but you'll probably find that something else works best for you. After I've transferred as many seedlings as I think I'll need, I usually keep the baggy with extras around for a few days, just in case any of the ones in the cellpack succumb to damp-off or meet some other terrible fate.

Some species do just fine with this treatment, and happily live in the baggies for as long as two weeks after they germinate. Others don't appreciate this birth procedure at all, and go into decline shortly after germinating. Often, the tips of their radicles turn brown or black. Sometimes, they are still viable when this happens, sometimes not. It takes experience to know how quickly you need to take action after germination.

With some species, I've found (more recently: I'm still learning!) that it helps to leave the seeds in the baggy for a few days after they develop their root, in order for the seed coat to soften and leaves to develop. For example, many anemones have trouble shedding their seed coat if they are set in soil when their root first emerges: the seedlings just develop a stem, topped by unopened tough seed. Sometimes spritzing the seed with water helps, sometimes it doesn't. It works better to leave them in the baggy a few days, until green leaves make their appearance. I'm trying this for more and more species which germinate just fine but often fail to develop leaves in their pots. I'll try to make a point of mentioning this in my seed-starting details for individual species.

And then...

Once the seedlings are in a soil-holding container of some sort, the baggy method has officially come to an end - they are now just like any other seedlings, needing light, water, and nutrition in all the same ways. Read more about that on my general seed-starting page.

All of these are just my personal observations. Please let me know if you have questions or comments.

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