Speeding Up Acorn Germination

[Fishman]

My son has to do a high school science project. He is going to test and see if size matters by testing whether larger acorns from the same tree produce larger seedlings than smaller acorns. Unfortunately the project is due March 19. He has a little over 7 weeks. I have some sawtooth acorns that I pulled from the fridge yesterday. Some of the acorns in the bag have already started to sprout, but we don't have enough in a small and large size class to start the experiment with acorns that have already sprouted. I have put the acorns he will be using on a heating pad for several hours yesterday and today. We will measure and weigh the acorns tomorrow night and hope to get them planted in small grow bags tomorrow night and then place them inside under some grow lights. My question for the group is whether there is a way to speed up the germination process? The acorns will be at room temperature along with whatever heat the lights produce. I will place the acorns very close to the lights to start off. I had hoped to at least get the trees through their first flush with leaves before the project is due, but I am little worried that we will not have enough time to reach that stage. I know that once they send a stem up above ground that they grow pretty fast, but I am worried about them putting down too much root and not enough top growth. Anyone have any ideas on how I can speed up the germination process? Should I limit the amount of potting soil I put in the bags so they can start top growth? The grow bags are about 3" in diameter and 4" in height. Any thoughts or ideas are welcomed.

 

[Nebraskaz71]

I take a plastic "rubbermaid" food container, not sure what you'd call it but lock tight container for food, put my damp potting mix in a layer on the bottom, spread acorns over that, then put paper towels over them that I keep damp then seal the container shut put it in a warm place so that everything gets humid inside, works for me. Its essentially a sweat box.

 

[j-bird]

I was thinking along the same lines. Essentially a humid "green house" if you will. The warmth of the soil, without them drying out I think will be the key for germination.

I know that when I planted my sawtooths last year I thing ground temperature had a big part to do with germination and growth success. Those in containers did great, those direct seeded into plots did OK, those direct seeded in the woods didn't do worth a crap. The exposure to warmer soil/via sunlight (my containers where outside) made a big difference. Those that germinated sooner had more time to grow as well. I will have to go back thru my thread and see when I started seeing leaves.....I am not sure 7 weeks is going to be enough, but even if it's stem height that still tells you something.

 

[Nebraskaz71]

For reference sake, I am growing "heritage" acorns for the first time. Kept them in the fridge 2months or so, pulled them out, put them in my setup mentioned above and had taproots showing in 3 days on 50% of the acorns, the rest within 7 days. I put those into rootmaker 18s at room temp under lights and had stems within another 10 days on most, once a stem starts it took probably another 10 days before I had any leaves started. I wanna say i'm at about 6 weeks now since pulling them outta the fridge and most are 10" tall with 3-6 leaves that are roughly 5" in length.

 

[Cap'n]

Luckily your down south.You should have time. That's an awesome project.
Here is a link to some studies I found last year concerning acorn size.
http://deerhunterforum.com/index.php?threads/acorn-size-matters.1835/
I'd be interested to know the weight and measurements of your sawtooth acorns compared to the ones I have in the fridge.

 

[Fishman]

I think I have found a few things that may speed up the germination process. These two papers (Influence of Pericarp, Cotyledon and InhibitorySubstances on Sharp Tooth Oak Germination and Effects of different mechanical treatments on Quercus variabilis, Q. wutaishanica and Q. robur acorn germination) show that removing the seed coat (pericarp) will speed up the germination process. The first study found roots emerging 4 days after sowing and shoots sprouting up 2 weeks quicker than the control which was untreated acorns. The second study looked at three species and showed removing the seed coat improved germination and also speeded up shoot emergence over the controls. This makes sense since when the seed coat is removed the root radicle doesn't have to waste time or energy breaking through the seed coat. These papers and few others I don't list have some interesting stuff in them about removing part of the acorn where the acorn cup was to speed up germination, but I don't want to fool with that since it seems that it affects seedling height.

I realize that heat and humidity also play a role so hopefully we can keep the seeds warm and moist. I am going to remove the seed coat for his experiment to hopefully speed things up. Since I have extra acorns I am going to run my own little experiment and plant a few small and large acorns that I won't remove the seed coat from. I will then see how long it takes the untreated acorns to produce a radicle and roots verses the acorns we removed the seed coats from. These untreated acorns will also act as insurance if removing the seed coat somehow screws things up, although I think the teacher is more interested in the kids learning the scientific process than producing statistically valid results from the project.

I will report back to everyone in a couple of months. I am not sure if this will change the way anyone grows trees, but it is interesting.

 

[Fishman]

Those in containers did great, those direct seeded into plots did OK, those direct seeded in the woods didn't do worth a crap.

I think sawtooths don't tolerate shade very well. My parents' have about 10-15 around their place and even though they produce acorns you never see any seedlings. They are planted along the outer edges of the woods and while the trees do great, you just don't see any seedlings in the woods. Some seedlings will pop up in the open areas, but my dad mows those areas so the seedlings never develop.

 

[Fishman]

I wanna say I'm at about 6 weeks now since pulling them outta the fridge and most are 10" tall with 3-6 leaves that are roughly 5" in length.

That is some pretty good growth. I planted some swamp chestnut oaks outside in rootmakers last October. I had one shoot pop up before Christmas. It now has three leaves and is about 4 inches tall. My 11 trays have been outside except I move them in the garage when it is supposed to get below 30 degrees. It looks like most of the acorns (swamp chestnut, bur, and white oak) have all put down roots, but they seem to be waiting for warmer weather before they send up any shoots.

 

[Fishman]

Here is a link to some studies I found last year concerning acorn size.
http://deerhunterforum.com/index.php?threads/acorn-size-matters.1835/
I'd be interested to know the weight and measurements of your sawtooth acorns compared to the ones I have in the fridge.

It may have been your post that gave me the idea to test whether size does matter. I read about it somewhere on this forum. Some of the research I have seen shows that these initial size differences in the tree just due to acorn size can still be significantly different 10 years down the road. While the differences are statistically different, in the real world it may not be that big of a deal. Does it really matter if your tree is one foot taller after 10 years?

I will post the ranges of the lengths, widths, and weights of the acorns later this weekend. They came from my neighbor's tree across the street in a residential neighborhood. These sawtooths are the largest that I have seen. My parents have 10-15 trees while their neighbor has about 40. Most of these are a little over an inch while some will go 1.25 inches.

 

[Fishman]

Here is what we found on the large group of 12 sawtooth acorns. The lengths of the acorns averaged 1.21 inches with a range of 1.13 to 1.31 inches. The average width was 0.83 inches with a range of 0.76 to 0.87 inches. The average weight was 8,82 grams (0.31 ounces) with a range of 7.36 to 10.28 grams.

How do these compare to the ones in your fridge Cap'n? What really surprises me is the various size and shapes of sawtooth acorns that I have found this year. My dad has one gobbler size that is pretty small, but the local Walmart has two trees in the parking lot that if you only looked at the acorns you would not think they were the same species. One is about 0.75 inches long and skinny while the tree right next to it is less than 0.5 inches long but is wider than it is long. There is a large range in size and shape.

 

[Cap'n]

Here is what we found on the large group of 12 sawtooth acorns. The lengths of the acorns averaged 1.21 inches with a range of 1.13 to 1.31 inches. The average width was 0.83 inches with a range of 0.76 to 0.87 inches. The average weight was 8,82 grams (0.31 ounces) with a range of 7.36 to 10.28 grams.

How do these compare to the ones in your fridge Cap'n? What really surprises me is the various size and shapes of sawtooth acorns that I have found this year. My dad has one gobbler size that is pretty small, but the local Walmart has two trees in the parking lot that if you only looked at the acorns you would not think they were the same species. One is about 0.75 inches long and skinny while the tree right next to it is less than 0.5 inches long but is wider than it is long. There is a large range in size and shape.

I certainly don't have any that big. My average was 0.625 wide with the biggest being 0.875. The longest was 1.063 with an average of 0.875.
I figured yours would be larger but don't have anything to compare these to. I'd have to borrow my buddys broadhead scales to weight them. Really they are about the same size as a red oak acorn in this area. I do have some shumards that are much larger. In between a red oak and a bur oak. I have noticed a great deal of variance in the post oaks and blackjacks around here. All the trees look exactly the same but the acorns can range from skinny and long to short and fat. I'm going to go back to the same trees this years to see if they look the same this fall.

 

[Fishman]

Early results show that removing the seed coat will speed up germination. We looked last night at each individual acorn and my son recorded the observations. Five of the 24 acorns had a 0.25 inch root radicle while one of the five root radicles was around 3/8 inch long and had already started to point downward. That is pretty fast for 48 hours. Another 10 of the 24 had a little bump where the radicle will form.

Of the sawtooths acorns that I pulled out of the fridge last Wednesday, I picked another 12 for my own observations to see how quickly they would sprout with the pericarp left on them. So far, they haven't done anything. Sawtooths don't really crack the seed coat like the swamp chestnut and white oaks I planted last fall. The root radicle just breaks through the seed coat right at the end.

It looks like you can speed up your germination with removing the seed coat. I am not sure why you would want or need to, but it appears to be a viable option if time is of the essence. One thing I did note was that when removing the seed coat, one of the acorns that passed the float test was almost black while the other acorns were a bright yellow/off white color. It may have been viable, but I discarded it.

 

[Fishman]

The results of the science experiment are due tomorrow, so we took final measurements on Sunday afternoon. Three of the large acorns and two of the smaller acorns never germinated so we had 19 out of 24 (79%) produce seedlings. The large acorn seedlings ranged from 9.5-19.5 inches in height with an average of 14 inches. The small acorn seedlings ranged from 6-12 inches in height with an average of 9.4 inches. These height differences were significantly different. The seedlings were started from acorns on January 26 and the experiment ended March 18 so a little over 7 weeks.

This was an interesting learning experience for both of us. I knew that sawtooths grew fast, but I would have never thought you could have gone from an acorn to almost twenty inches in height in seven weeks. I was hoping to get 6-8 inch seedlings. They did that and then some. I kept having to rig the lights and move them up off the trees. I transplanted some of the trees Sunday and noticed that all of the seedlings had extremely small root development that may hurt them in the long run. I guess the trees were getting water and were too busy stretching for the light to waste energy developing their roots. I imagine they will put effort into root development now that they are in larger pots and are outside.

If anyone really wants to do it, you can definitely speed up germination by removing the seed coat. My unscientific estimate is that removing the seed coat speeds up germination by 10-14 days. I didn’t grow the other acorns that I didn’t remove the seed coat from, so I don’t know if removing the seed coat impacts seedling development.

 

[Cap'n]

Has anyone tried this with Chestnuts? I think I will start a flat of them with the coat off. I think it's interesting because if you look under a mast producing tree there are acorns that are half eaten, cracked open and in various forms of coat removal from deer feeding on them. I never would have imagined that the ones that were basically bit in half would produce a seedling faster than a whole acorn.

 

[Fishman]

Researchers have done studies that prove just what you observed Cap'n. Damaged acorns do germinate faster than undamaged acorns. These papers (link and link) show that cutting off the distal end (the end with the acorn cap) of the acorn speeds up acorn germination, but depending on how much of the acorn you cut off it can affect the size of the seedling. It seems that about 20% is the sweet spot for speeding up germination while not affecting seedling size. Other studies show that red oak acorns have germination inhibitors in the seed coat so removing the inhibitors is what allows for faster germination. I am not sure what would happen with chestnuts. I ruined most of mine this year so I don't have any to play with to see. Report back if you decide to test the chestnuts.