Method number one is good for colder zones like zones 4, 5, 6 and probably zone 7. Not sure what cold hardiness zone you’re in? Just do a Google search for “cold hardiness zone map”.
Method#1
1. Immediately after you collect your seeds dump them out on a work table. One by one pick the seeds up and break the wing off. Discard the wing and keep the part that contains the seed. How do you know for sure which part is which? The wing looks very much like the wing of a large insect. It has veins and it’s quite brittle. The part that contains the seed obviously has a bulge and is not at all fragile. Don’t be overly concerned about whether or not you broke off enough wing. What’s really important is that you keep the part that contains the seed. If there’s still a little wing attached that’s not a problem.
2. Put the seeds in a container that will hold hot water. Run the water from your faucet until it’s quite warm, but not so hot that you can’t put your hand under it. But close to that hot. Pour the warm to hot water over the seeds and just let them soak in the water for 24 hours. At first the seeds will float, but eventually they’ll almost all sink to the bottom. The ones that never sink are probably not viable, but it won’t hurt to sow them with the rest. Maybe they just didn’t get wet enough to sink.
3. Once the seeds have soaked in the water for 24 hours pour off the water and spread the seeds out on a paper towel. You can allow them to dry overnight to make them easier to work with. Next fill a flat with a good seed starting mix that drains well. I suggest mixing some additional Perlite into the mix to make sure it will drain well.
If you don’t have a flat just go to the dollar store and buy a plastic dish pan, and drill many 1/2″ holes in the bottom so any water that drains to the bottom can escape from the dish pan. The holes you drill should be no farther apart than one inch.
4. Sow the seeds on top of the seed starting mix and press them down lightly so they are embedded in the growing medium. Then lightly sprinkle a covering of seed starting mix over top of the seeds. The light covering of mix should be no more than 1/4″ deep. 3/16″ deep would be ideal.
5. Next cut a piece of hardware cloth (heavy screen) so it fits tightly inside the dish pan. The purpose of the hardware cloth is to keep mice, chipmunks or other critters from digging in the dish pan and eating your seeds. The openings in the hardware cloth can be anywhere from 1/4″ to 1/2″. Consider using light wire, twist ties, or zip ties to fasten the hardware cloth to the top of the dish pan so the critters can’t pull it up to get to the seeds. The hardware cloth does not have to be suspended above the soil in the dish pan, because come spring you will remove the hardware cloth long before your seeds have a chance to germinate. So just lay the hardware cloth on the growing medium. The fasteners are only to keep the hardware cloth from being blown out or removed.
6. Now it’s time to set the dish pan and Japanese Maple seeds outside in the elements. Weren’t expecting that were you? It’s important to understand that Japanese Maple seeds require a lengthy treatment of cold before they will germinate. It’s part of the natural process. So what we are doing here in method #1 is trying to closely mimic the natural process, but we are better controlling some of the environmental conditions so the results are more predictable.
When deciding where to place your dish pan of seeds in your yard, select a place that is out of the wind and hopefully in a spot where dogs, skunks or raccoons won’t disturb it or tip it over. The goal is not to keep it from freezing. It can and will freeze, and that’s fine. It might stay frozen all winter. That’s not a problem. Snow cover is also fine. Snow is actually an excellent insulator and would be really good for your seeds. Freezing won’t hurt them, but it does slow down the stratification process. So, if they were naturally covered with snow for long periods of time during the winter chances are the growing medium would not freeze, or would not stay frozen. That would be perfect. Just set the flat or dish pan out in your selected location and forget about it.
7. As spring starts to arrive check on your container to make sure nothing is sprouting yet. As soon as the seeds start to sprout you need to remove the hardware cloth, but you don’t want to remove it too soon. In the early spring, just about the time the leaves start to come out, remove the hardware cloth from your growing container. At this time make sure the container is in a shaded location. About 40% to 50% filtered sunlight would be ideal. Water the growing medium as necessary, but don’t keep it soaking wet. It’s important the growing medium be allowed to dry and warm up before you water again. The seeds need some water, but should not be soaking wet. But more importantly the seeds need to be warm come spring so they start germinating. That’s why you should water only when needed so the growing medium stays warm.
8. You’ve done all you can. Now it’s up to Mother Nature. Be patient. Growing Japanese Maples from seed is a slow but highly rewarding process. In two to three weeks if the weather is warm, you should see seedlings start to pop up. The first set of leaves they produce are called cotyledons. The cotyledons will not look at all like Japanese Maple leaves. Cotyledons are actually part of the embryo from within the seeds and help to nourish the little seedling until the true leaves appear and take over. Once the true leaves appear the cotyledons wither and disappear. At that point photosynthesis begins and your little seedlings are well on their way to becoming beautiful little trees, each with their own unique characteristics.
9. At some point your Japanese Maple seedlings will have to be transplanted so they have more room to grow and develop. You can do that as soon as they germinate by simply picking them out of the flat with tweezers and re-planting them in a flat where they’ll have more room, or you can transplant them into a cell pack. Cell packs are the flimsy, lightweight trays that annual flowers are grown in. Cell packs are nice because you can later remove the seedlings from the cell pack in nice little root balls. Cell packs are tapered so plants can be easily removed without disturbing the roots.
Or you can just leave the seedlings in the flat you started with, then at the end of the growing season when they are dormant remove and separate them. Even if they are really close together that’s usually not a problem for the first growing season. Throughout the first growing season make sure your seedlings only get about 50% sunlight, since direct sun will burn their leaves. After the first season I plant mine out in direct sun here in zone 5. They’d probably benefit from at least some sun and if you are in a warmer zone you should consider some shade. The older they get the more sun tolerant they are, but Japanese Maples in general take a bit of beating in the direct sun. Usually the damage isn’t serious, just some browning around the edges. All of the Japanese Maples in my yard and even the ones in the nursery are in full sun. Only the young ones get a little protection with me.
Method # 2
1. In this method you will collect the seeds in fall just as they start to turn brown. Collect the seeds simply by pulling them from the tree. They should come off the tree easily. Place the seeds in a paper bag and store them in a cool dry place. A basement or garage is fine. You are not going to do anything with those seeds for a few months, they’ll be fine in the paper bag as long as they are dry.
2. Establish the “target date” that you can safely plant your seedlings outside. Here in northern Ohio, zone 5 we are usually safe from frost after May 15th, so that is my target date. So I will count backwards from May 15th, counting back 100 days. That takes me back to February 5th. On February 5th I will retrieve my seeds from the paper bag, break off the wing as describe above and soak them in warm to hot water for 24 hours as described in method #1.
3. After soaking in water for 24 hours you need to mix the seeds with a combination of sand and peat moss, or a seed starting mix that contains some extra perlite. You will also need a large zip-lock type freezer bag, but of course that depends on how many seeds you have. Fill the plastic bag about 1/2 to 3/4 full with the growing medium to make sure have the right amount. Dump the growing medium out of the bag into a bowl. Pour the seeds into the bowl on top of the growing medium and mix them together with your hands. Next sprinkle some water on the mix and mix it some more. You want the growing medium damp, but not soaking wet. After mixing the seeds and the growing medium thoroughly pour the combination back into the zip bag.
4. Press down on the bag to force most of the air out, then poke about three holes near the top of the bag for just a little ventilation. Place the bag in your refrigerator. Don’t put it way to the back of the refrigerator because it’s usually colder back there and the medium might freeze. Although freezing won’t hurt the seeds, it will slow down the stratification process.
The Japanese Maple seeds need a 90 day cold treatment to initiate the germination process. Ideally they should between 38 degrees F. and 50 degrees F. In other words, about the same temperature as the main area of your refrigerator where you keep your milk. From time to time check on your seeds and make sure you do not have a mold problem. Some people add a little fungicide to the mix from the beginning to prevent mold, but I don’t think it’s necessary. Should some mold develop just add some fungicide at that time. Brand doesn’t matter, just a general fungicide from the garden store. Use only a small amount of fungicide.
5. After 90 days in the refrigerator remove the bag and inspect it for germinating seeds. If you see little sprouts pick those seeds out of the bag and plant them in a flat of seed starting medium. Just poke a little hole in the soil, press the seed into the hole and leave the sprout sticking out. If there are no sprouting seeds, or few sprouting seeds just leave the bag out on the counter at room temperature and within a week you should see more and more seeds sprouting in the bag. Remove the sprouted seeds and leave the bag at room temperature until no more seeds seem to be sprouting.
Do not discard the mix in the bag because there are probably seeds in there that are going to take longer to sprout, so just pour the mix into a flat and place it outside where it’s warm. Keep the flat watered but not soaking wet.
6. The sprouted seedlings that you planted in the flat are going to need some sunlight as they grow so you’ll either have to give them some artificial light for a few weeks or move them outside into a shaded area. They need a little sunlight, but direct sun will burn them up. From there just care for them as you would any seedling.
