Starting Seeds: Pre-germination

corn-germinating-on-towel-lah-1Vegetable seeds will germinate with or without soil. All they really need is an infusion of water to swell the seed coat, and sufficient warmth to signify spring. In fact, seeds for our most commonly grown food crops are among the easiest to start. They will begin their growth on a paper towel, a bed of agar, or even while still inside the fruit where they were formed! The home gardener can put this fertility to good use.

Germination may take several weeks in cold spring soils, but once a seed has broken its dormancy, it will continue to grow. Taking advantage of this, I usually sprout my pea seeds on damp paper towels. This requires careful monitoring, as I don’t want the emerging roots, which are extremely brittle, to break. As soon as the root emerges from each pea, I carefully sow the seeds outside. They go about two inches apart and two inches deep, covered with fluffy soil or vermiculite. It’s nice, but not essential, to point the roots downward into the earth. Since they have already started to develop, the baby seedlings break the soil in just a few days.

presprout-put-in-baggie-lahI treat corn in the same way, scattering some seeds across dampened paper towels. Rolling them up together, I seal them into a plastic bag, which I check daily. A little warmth helps… corn will sprout faster at about 75 – 80º F.

With our extremely short and cool growing season, the jump start I get from pre-sprouting corn often makes the difference between watching undeveloped ears succumb to fall’s first frosts, and harvesting a crop.

gel-1-lahCarrots and parsley, with their tiny seeds and long germination times, make good candidates for pre-sprouting on a layer of gel. While commercial mixes are available, a simple cornstarch base works fine. Mix a cup of water with a tablespoon of cornstarch. Heat, stirring, until the mixture thickens. Pour into a flat pan such as a pie plate and let set. Then sprinkle the seeds on top. Make sure there’s a bit of space around each seed. Cover with a piece of plastic wrap or a pane of glass to hold in moisture.

Within a few days, roots will begin to emerge from the seeds. Again, don’t let them get too long. If you break off the growing tip, the seedling will die. As soon as I can see the seeds are growing, I plant them. Take the pan outside and scoop each seed out with a small spoon, dropping it, along with its surrounding gel, into a hole about a half-inch deep. A covering of vermiculite makes it easier for the tiny leaves to break through the soil crust. Seedlings should appear within the week, as opposed to three weeks when planting seeds straight from the packet.

Our erratic spring weather can go from cool and damp to hot and windy in a matter of hours. Keeping seed beds damp for three weeks is challenging, to say the least. I have significantly higher germination rates when I plant pre-sprouted seeds, each encased in its own wet glob of gel.

Another advantage of pre-sprouting carrots is that it eliminates a lot of tedious thinning. You already know that the seeds you are planting are viable. Therefore, you can space them precisely where you want them. I usually plant carrots about four inches apart in all directions, across a four-foot wide bed.

Beans, on the other hand, are not a good candidate for pre-sprouting. Because of their huge cotyledons full of starch, germinating beans are extremely susceptible to cracking. It’s much safer to just plant them while they are hard and dry, and let them do their growing safely underground.

38 thoughts on “Starting Seeds: Pre-germination

  1. Thank you for sharing this information. Like you described the weather can be erratic and it’s near impossible to keep some seeds moist. I am definitely going to attempt pre-germination.

  2. Very interesting post. I have done the germination technique with the paper towels, but have never tried the gel process. I’m going to have to give that a shot this year. Thanks for posting. 🙂

  3. Leslie, I haven’t really tried many flowers… lobelia worked out really well, but that’s about it. But if I was going to grow many flowers this year, I’d probably give them a shot. (I won’t be gardening so much this year because I’ll be out of town most of April and most of June. Sniff.)

  4. I’m Dave in Newport. Last year I tried sowing carrots 4 times during the year and did not see one plant germinate. I followed all the advice on depth and temperature to negative results. I know the seeds are small, maybe if I tried to germinate them on strips of kitchen roll and then plant the whole strip I may get a few. Will try it and see. Glad I have seen this post.

    1. You probably had a hard time keeping the seeds moist for the 3 weeks it takes for them to germinate. Pregermination is a good idea. If the paper towels don’t give you results you expect, try germinating on a bed of water and cornstarch. Simply add a tablespoon of cornstarch to a cup of water and cook until thickened. Pour into a pie plate to cool. Then sprinkle the seeds on top, and cover with plastic wrap (leave an air space). Plant as soon as roots start to emerge, using a small spoon to scoop seed+goop.

      1. Ah, a tablespoon of cornstarch, not a teaspoon! That works much better. Could you correct that in your article above? (“Mix a cup of water with a teaspoon of cornstarch”)

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  6. Wow! No kidding, I put my radish seeds in that corn starch goop and they sprouted over night! I wasn’t expected it to go so quickly so now I have to run out and get my soil ready! Thanks so much for this post!

  7. I am soooo glad I found the carrot plus gel suggestion. I’ve had limited success with carrots–actually the best ever carrots were those seeds washed off their raised beds by torrential downpour, into crevice bstween bed and path, those were awesome (about 10 yrs ago). I’ve tried homemade seed tape (flour paste on TP), freezing them into ice cubes, spacing with a grid pattern, mixing with sand, mixing with radish, covering with sawdust, covering with cloth or cardboard……nothing has worked. Often wondered if i ciuld use Jell-o but i never eat that stuff.

    I think this gel idea will solve the spacing, moisture and germination issues all in one. It’s getting almost too late to try another 3-week germination (the old-fasioned way) so tomorrow, I’ll be mixing up some cornstarch gel! I already have great success with beets amd chard on paper towels, so I know how you really must check for signs of germination very frequently!

  8. Thank you so much for the gel recipe! I was having a really hard time with my tiny herbs and carrots! Mixing some up right now 🙂

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  10. This is a great idea. I would like to add that a corn starch like food product called Ultragel actually thickens when added to water without cooking. I will be trying it with my seeds today! I also thought that if you poured the gel and sprouted seed mixture into a Ziplock bag and cut off the tip just like frosting, you could squeeze a row of gel/seeds into your furrow saving time and creating a more even row.

  11. The Ultragel sounds perfect for this. I hadn’t heard of it, but I will be looking for it–thanks!
    You don’t need fertilizer. The sprouted seeds get planted long before they run out of stored food.

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  13. Had me a little confused for a while, but now realise you mean ‘Cornflower’ for the European side of the Atlantic. Will give it a try next year for carrots.

  14. Very interesting. I’ve been trying to germinate carrot and lettuce seeds for a week now and no success with the paper towel method. I will try this–this morning. Just wondering is it better to heat up in the microwave or on the stove?

    1. I don’t recommend germinating carrots or lettuce on paper towels. I certainly don’t recommend putting them in the microwave or oven! When I said they germinate faster with warmth, I was thinking of putting them on top of a mild heat source, such as a TV or insulated water heater.

      Paper towels work best for large seeds, such as corn. Beans will germinate on damp paper towels too, but they’re then too fragile to plant. It’s useful to see if your packet of seeds is still viable, though. If you want to pre-germinate carrots or lettuce, use the gel method. Carrots can take a while, but your lettuce seeds are probably dead. Did they dry out at any point? Once seeds take in water, they have to stay hydrated. Also, many lettuce cultivars need light to germinate.

      Hope that helps!

      1. I think Maria was asking if she should she heat up the mixture on the stove or in the microwave:)

  15. Old thread, but when you plant the carrot seeds from the gel do you put the seed at the bottom of the hole or try to put the root pointing downwards, thanks…

    1. The roots should be very short when you plant them, and they’ll figure out which way is down all by themselves. It’s best to be very gentle and just ease them into the hole.

  16. Just found this on Pinterest. Am in the process of starting off everything this weekend and was wondering about pre-sprouting some seeds. Have done it with flowers, but not veggies. So glad I did find this, now I know what to do with my carrots, radishes, corn and beets. Will keep you updated on how it works out.

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  19. Not sure if you’re still responding to comments given the date this was posted. Tried the gel method with a couple different varieties. It just seemed to ferment, and did not instill any confidence that the seeds would sprout instead of just rot. I’m not sure if the gel wasn’t thickened enough, the layer of gel was too thick, or what. Hoping you have some pointers before I blast pointlessly through all of my seeds. Thanks!

  20. Sorry you’re having problems. I never had trouble with the gel fermenting, or even getting moldy. It can get dried out if things take too long, which is why I cover it with plastic. Did you boil the cornstarch/water mix? That would sterilize it.
    The whole idea is to keep the seeds moist, and then protect the fragile roots as they germinate. My gel layers are about 1/4″ thick, and were pretty firm when thickened and cooled. I didn’t want the seeds sinking.
    Are you using new seeds? Are they germinating when sown normally? You may want to try damp paper towels instead, just to verify that the seeds are viable.
    Radishes only take a couple of days, at most, and lettuce germinates around day 3, if I keep things around 70 to 75 F.

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