Hi Leo, thanks for the input!
I have noticed that temps seem to be really important in germination...night temps more so than day temps. I'm trying to get 2 of each species started from seed. I've been doing 2 seeds of one species at a time. I've managed 6 species so far. I can't get Grandidier and Suarezensis to sprout. They swell but I can't get them to throw a root
Now it's much cooler than when I first started 2 months ago. I needed a second of some of the species I already sprouted so went back to try to sprout them. Gregori which took less than a week to open the first leaves back in September is now approaching 2 weeks and has just barely poked above the soil line. It's raising out of the pot, but slowly. The obvious difference now from then is that the house temperatures have cooled...especially the nighttime temps.
When I started, the house temps at night would be mid/upper 70F. Now nights are closer to 65F. Days are still getting to upper 70F due to the heat from the lights and that they are in a bright southern window. Still cooler than in September though, but not as much as the night temps. I'm going to give up trying to start more seed until spring when the night temps in the house start to rise again.
I'm hoping to keep the plants that have sprouted from dropping leaves until next fall since I don't know how old they need to be to survive dormancy. They're getting plenty of light right now...too much actually. Some have some slight leaf curling and one has some spots that look like leaf burn. Night temps might be too cool (mid 60F) but they are in the ballpark of what the botanical gardens claim the Climatron is kept at so...maybe??
It's interesting the variety of the 6 species I have so far. They range from 2-3" tall to almost a foot. Surprisingly, the first species that sprouted (gregorii) is the smallest and perrieri is the tallest by far even though the gregori is twice as old! The picture is of 2 perrieri (back two) and 2 fony (front two). They are the tallest 2 species so far.
You got it! Night time temperatures are the key. You must keep the nights warm to keep the trees growing, and the day time must be warmer than night. Do that, and you can keep them growing all year round. In the wild, the rainy season has clouds that trap heat and keep the nights warm, the sun makes the day hot, even if it is raining. In the dry season, there are few or no clouds, this allows radiant cooling cooling at night. Cool nights tell the Baobab that the dry season is here. It is the trigger that starts the dormant cycle. They don't wake up until the clouds return and keep the nights warm. They do not have winter and summer, it is only dry season and wet season.
Once the tree is chilled, it will start its dormant cycle. Leaves will start dropping. If the leaves turn yellow and drop, stop watering. Don't start watering until you see new leaf buds opening. Once the dormant cycle starts, the tree must be allowed to go through it. If you keep watering, you risk rotting the tree away. Water alone will not ''reverse'' the tree's dormancy cycle. It needs to run once started.
I have a trick that will help you with windowsill growing. I learned it growing orchids. A fan, or fans if your collection gets large enough. Get a cheap 12 cm or 9 inch diameter fan. Set it so that it blows either directly or indirectly at your plants on the windowsill. You want enough of a breeze that leaves wave a little bit. Trees in the wild can take WIND, so if one or two of your trees have leaves that move a bit more than a gentle wave don't worry. Leave the fan on 24 hours a day, 7 days a week. It doesn't mater if the fan is blowing low humidity household air at the trees. Just keep the air moving. If you have a ceiling fan in the room, this may be enough, leave the ceiling fan on 24 hours a day, 7 days a week. Fans are the trick that will vastly improve just about any plant you grow on the windowsill. Or under lights for that matter.
What does the fan do? First, the glass of the window tends to get cold from the cold outside. In winter, especially on a cold night you can feel the cold air falling off the glass. This can seriously chill any plants growing on the windowsill. A fan will help keep the plants on the windowsill at ambient room temperature. This will help keep the plants warm enough to not start the dormant cycle.
Second a fan will help keep leaf temperatures at room temperature. You know how a plastic pot heats up on a windowsill in still air? Well moving air will allow you to give direct sun to the leaf without risk of the leaf sun scorching. In raising orchids, there are some orchids that are noted for being cool growers. The problem has been giving them enough sun to grow well while still keeping them ''cool''. The answer is FANS, a breeze keeps the leaves cool and yet allows you to expose the orchid to full sun. No sunburn.
Third, a fan will keep roots healthy. Air moving across the surface of the soil will to some degree mix down into the soil. You will get significantly better root growth, with fewer issues with root rot if the air is moving.
Fourth, fewer insect issues. A fan will help keep down spider mite infestations. I have had fewer issues with spider mites, mealy bug, and aphids if all the plants have good air movement. It is not a guarantee, but it definitely helps.
Note all 4 benefits would help just about any houseplant. I learned this trick growing orchids, but you can see, it applies to virtually any plant.
So do your baobabs a favor, and put fans in or near your collection, and get the air moving.
At one point, we lived just a few blocks from Hausermann's in Villa Park Illinois. My orchid habit/addiction has tended to fluctuate with the children. I get a few dozen plants and get everything just about situated on windowsill, under lights, etc...then we have another child and they plants slowly decline as I prioritize child health over plant health. Child ages and I get some time back...and my collection grows again only to repeat the cycle! And so it was for 4 children...The last one leaves for college in a few years. I currently have only 4 orchids...we'll see where that is in 3 years...
