(Amman, Jordan )
I was advised to propagate hydrangea from
Stem cutting , and put it in a watered and
Drained soil in a small pot then put it in a
Zip lock plastic bag for 4-6 weeks,
My question is , what about ventilation
In this type of plastic "green house" ?
Without roots, there doesn't need to be any ventilation, and you want the humidity to stay high.
Using this system, it's absolutely crucial that you use sterilized potting soil, and make sure to keep an eye on things in there; if the condensation is too high on the sides of the bag, this will drip back onto the cuttings and cause them to rot.
Tiny droplets, as in, mist only accumulating on the sides of the bag is what you want.
If the droplets are any bigger, you have to open the bag and let some dryer air in.
I also blow into the bag, which does two things; it keeps the bag expanded and away from any chance of touching the leaves, and it also adds carbon dioxide, which helps them root faster.
I've had great success using this system for lots of different shrubs and plants, so I know it works.
Best of luck with it!