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Experiments in Growing Seedling Mimosa Trees in the Greenhouse (Albizia julibrissin) – Part 1

I now have 8 miniature mimosa trees under lights in my greenhouse. I did go ahead and plant a couple more of the sprouted nicked seeds and 3 of the un-nicked seeds after reporting about my mimosa seed soaking that I began in January. What happened was that they all tried to grow, but the un-nicked seeds took at least a week longer. This put them at crucial growth points right after I returned from vacation, so that they did not quite get watered enough. So, only one of the un-nicked seed sprouts survived. (click on any photo to enlarge)

The nearly 6 week old mimosa tree seedlings in their original 3-4 inch pots, having an hour in the sun.

The nearly 6 week old mimosa tree seedlings in their original 3-4 inch pots, having an hour in the sun.

It is interesting to note how well all the seeds did after being soaked in water for so long. Visually, I cannot now tell the difference between the seedling trees. Some of the nicked seed mini trees are the same size as those from un-nicked seed. A couple of the trees from the nicked seed are larger, but I’m not sure why since one was in only a slightly larger pot terra cotta pot with a upper diameter of 4.5 inches, (the other seedling in the same size terra cotta pot was not so big) and the other was in the same standard 3 inch square pot as the other seedlings. I fertilized them all with a solution of fish emulsion once a couple weeks ago.

Since the above-soil growth of the little trees was taking up about as much volume as the pots, I decided to transplant them into gallon pots. It might have been best to do a more gradual step up, but I don’t have pots of that in between size on hand. Also, it is soon going to be time to do a lot more planting, so I wanted to avoid the step.

Mimosa tree seedling roots right before they are transplanted.

Mimosa tree seedling roots right before they are transplanted.

 

 

The root growth turned out to be strong, but only just beginning to curl up at the bottom. Not root bound at all. The roots were displaced easily when I touched them to make sure they would be stimulated to grow beyond their previous pot size. I don’t know if the “stems” can be can properly be called trunks yet, but they are already quite woody and stiff.

 

 

 

Two days after transplanting, there are still healthy looking nodes of new growth, so I guess the plants were not too stressed out by the process. I began exposing them to the outdoors for the first time the same day I transplanted them, but only an hour to begin with. It was a sunny day, around 60°F, so it was a good time to give them some fresh air. I am hoping to have them mostly hardened off before I need all of my greenhouse lights for other seedlings. The gallon pots take up a lot of room. I also gave them a bit more fertilizer. It’s about time to think seriously about where I might want to plant them.

The first 4 in their new pots take up a whole tray. I am trying to keep the leaves from touching so that they will grow outward as normally as possible.

The first 4 in their new pots take up a whole tray. I am trying to keep the leaves from touching so that they will grow outward as normally as possible.

The mini mimosa trees under greenhouse lights for at least part of the day until they are hardened off.

The mini mimosa trees under greenhouse lights for at least part of the day until they are hardened off.

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