This is a good winter project. At least it was for me.
These wooden plant propagation flats are really quite simple and easy to make. I used pressure treated wood so they would last and I’ve never had a problem with treated wood around my plants or rooting cuttings so don’t be concerned about that. Everything you read online is not true.
The boards that I used are all treated one by four material and there are only three dimensions to remember, or write down. Each flat has two end boards that are 12″ long and note that they are placed on the inside of the side boards.
Each flat has two side boards that are each 16″ in length.
Each flat has three bottom boards that are 13.5″ long, that way they can extend to the outside of the side boards. Any small nail is sufficient to nail the boards together. I just happen to have a brad nailer so I used that with 1.5″ brads. If I didn’t have the nailer I would have just purchased small nails and hammered them together by hand like in the old days!
Yes, there are rather large gaps in the bottom of flat and we often root cuttings in coarse sand. So will it fall out the bottom of the flat? Yes, if the sand is dry it will for sure fall out the bottom of the flat. What we do is line the bottom of the flat with a couple layers of newspaper, put the sand in, stick the cuttings and then move the flat to where it’s going to stay until the cuttings are rooted. By the time the newspaper rots the sand will be wet and packed and as the cuttings root the roots will bind the sand together pretty well.
You can also use something lighter like a light fluffy mix that contains peat and perlite.
The nice thing about these flats?
They are 3.5″ deep and that makes a nice, deep flat for rooting cuttings. They’ll last a long time and sun and cold won’t make them weak and brittle. With the bottom boards being positioned as they are these flats will also do a little root pruning for you.
Root pruning is good.
This is how it works. The cuttings start to root and as the roots grow toward the bottom of the flat they will eventually poke out the bottom of the flat. If the flat is sitting flat on the ground the roots will go out the bottom of the flat and root right into the soil making it difficult and stressful on the plants when you are ready to move the flats later. Breaking roots during the growing season is not a good thing. It can easily shock the plants causing them to wilt and possibly die.
Because these flats have 3/4″ of air space between the soil and the inside bottom of the flat the tiny roots hit that air pocket and the tips are killed. Believe it or not that’s a good thing. When the tip of the root is killed it can’t root into the ground, and once the tip of the root is dead the plant will go into survival mode and create lateral roots to replace the main root that was lost. This makes for a very dense root system and really healthy little plants.
It’s called air pruning and was developed many years ago.
The first record of air pruning that I know of, at least on a commercial basis was a grower who started growing tree seedlings in cardboard milk cartons with the bottoms cut out. The bottomless containers were placed on a bench that has a wire screen bottom. Once the roots reach the bottom of the container there’s no where for them to go, they hit the air, the tips are killed. The plant then produces a lot of lateral roots inside the container. Each time a root tries to escape out the bottom of the container the tip is killed and more lateral roots are produced.
Root pruning on tree seedlings is essential and it used to be done manually.
Tree seedlings typically want to grow one really long tap root to anchor the tree deep into the ground. That’s a good thing in the forest I guess, but in a nursery setting it is not good because nursery trees have to eventually be harvested to be sold. So growers used to transplant their tree seedlings two or three times just so the small trees would develop better root systems. When the art of air pruning tree seedlings was invented or developed, which ever applies, all of that changed.
Some growers who produce tree seedlings still do it the old way and there’s nothing wrong with that, but many are now using the art of air pruning to produce a stronger, healthier tree seedling.
So if you get the chance to buy some tree one year old tree seedlings, expect a high rate of loss because a one year old seedling that has never been transplanted is likely to have a struggle and a pretty low survival rate.
Here’s a little inside baseball for ya!
In the industry tree seedlings that are not grown in an air pruning system are sold as . . .
1-0. A seedling that is one year old and has been transplanted zero times.
2-1. A two year old seedling that has been transplanted once. That’s a much better plant than the 1-0.
3-2. A three year old seedling that has been transplanted twice. That little baby is going to have an awesome root system, and it’s rate of survival is going to be the highest of the three grades, and it’s got two full growing seasons on it’s little brothers. Therefore a faster finished tree for you.
And of course the price of each goes up with each season of growth and each effort to transplant the tree. The more you spend, the better the plant that you get.
Okay. That’s a little inside baseball. Don’t spread it around. You know how the Internet is. One person finds out and the whole world knows!
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Questions? Comments? Post them below and I’ll do my dangdest to get back here and reply to them for you.