This is a problem that occurs with a few seedlings every year even when the soil or the air inside the humidity dome is moist. It seems to occur most frequently with hot peppers and occasionally with older tomato seed, which leads me to believe that it is related to a loss of vigor. [See the bottom of this post to learn more about seed vigor.] I suspect that in these cases the plant just isn’t strong enough to throw off its coat, so that outer shell just hangs on, eventually suffocating the little seedling.
The good news is that you can intervene with success. In some cases the seeds may be brand new and this issue could be down to a lack of humidity around the seedlings. In that case I would suggest keeping a closer eye on soil moisture over the long term. I check my seedlings everyday for just a few minutes to be sure the pots in the back of the tray aren’t drying out. If you don’t have one already, nothing beats a humidity dome for that first week or two, just until germination is achieved and the seed coats are off.
If humidity/moisture is not a problem and this is down to a couple of finicky seedlings, I suggest lightly spritzing* the seed coat with water. Leave it to soak in for a few minutes and spritz a few more times until it has softened up. Find the edge of the seed coat and gently pry it away with your fingernail. Work slowly because it is really easy to compromise the delicate stems of tiny, new seedlings. If it won’t budge, I’d suggest spraying again and come back later. I’ve lost a few seedlings in my time because I was impatient and pulled too roughly.
Quick Addition: The point has come up as to whether this situation is tantamount to butterflies that need the struggle in order to survive. This is a good question because I have had seedlings give up the ghost despite my intervention. They simply weren’t healthy enough to continue on. However, that has only been a small percentage of the time. The seeds were too old or not viable for whatever reason. For the most part removing the seed coat works and the seedling can go on to become a healthy transplant.
*Please note that spritzing seedlings is not something that I’d recommend as an everyday practice as I find that without proper air circulation it can lead to fungal disease and damping off. It is just a short term solution to this specific problem.
I once had a hot pepper that kept its seed coat for a week because at the time I didn’t know what to do. It just stayed like that and didn’t grow anymore. Eventually I decided to try to manually remove it. By pinching it on the wide side it opens it up enough to slip it off.
Since then I’ve started a lot more seeds and used the same method. Pinching it like you would to crack open a sunflower seed and gently pulling it off. Out of dozens of seeds like that I’ve only lost one from damage while trying to remove it. Risk you have to take but odds are better that it will survive and grow compared to leaving it as is.
I tried using tweezers but I find I can feel the edge better with my fingers. I don’t spray the seed coat before hand.
Good tip RE: pinching the sides. I don’t recommend tweezers because it is too easy to slip and kill the seedling. I spray because it softens the coat, making it easier to slip off.
LOL, this reminds me of the old Star Trek Prime Directive: to interfere or not to interfere?
Me, I interfere. I pry the seed cases off every time, unless the plant looks horrible, which is almost never. I’d rather do that than lose the plant, although a part of me thinks that eventually the plant will get its act together and shed.
The decision as to whether or not to use the seedling happens right before I transplant them into bigger pots. If they are weenie and I have way too many of them, they go into the compost bin. If they are teetering on the edge and I don’t have a lot of that variety, it gets some real estate in the glass greenhouse and lots of seaweed drinks. Right now I have a Tigerella, two Boxcar Willies, and a Gardener’s Delight in this very situation. Great topic for discussion – it’s not one I’ve seen before!
Ha! Yes!
I am the same as far as what makes it into the final planting spots. I always have double because I have a difficult time culling healthy seedlings. I’d rather grow them on and give them away.
You know, that happened to me just this year with one of my hot pepper seedlings. I tried the pinch the sides technique but unfortunately was a bit too rough, I suppose, as the top of the seedling ripped right off. Subsequently, I did a bit of googling on this (in hindsight, I guess it would have been better to do this beforehand!) and one odd suggestion that came to light was in the use of saliva to remove the seed coat. The thinking is that the enzymes in saliva will soften the coat and it will then come off easily. Well, at least now I have two methods to try the next time this happens.
Right now I have several seedlings of Mirabilis, 4:00’s, which are holding on to their black jackets way too long. Others nearby are quite tall and wide open with healthy leaves. The seeds were from last fall’s harvest.
I also favor misting to soften the seed coat. I use humidity domes, too.
Today was mild enough to place the entire tray outside for a bit of sun and a breeze, then it went into a coldframe for the overnight. I will have to check tomorrow to see if this helped the seed coats pop off.
I wonder if a low speed fan inside would stir up the stalks enough to make them pop at the top. I like using a fan to strengthen tomato seedlings when they are inching upward (but not yet allowed outside due to chilly temps.) I think this makes for a stouter stem (when used in conjunction with a close light source which prevents stretching.) Perhaps air movement to simulate the outdoors could trick the seedling into shedding its coat.
I’ve had the same problem occur with peppers. One thing that helped is I bought a seedling mat and put it underneath the pots. That warmed up the soil and I had great germination rate (pretty much 100%) and no seedlings had “shedding issues”. That heated mat really makes a big difference!
I have learned that planting watermelon or similarly shaped seeds pointy end up helps the plant emerge from the seed husk.