I have mint growing wild in the ground, I took a couple of cuttings, removed the bottom leaves and inserted them in Miracle Gro seed & cutting compost. The first time I placed them in a plastic bag to retain the moisture and placed them in my new plastic mini greenhouse. The next day the leaves had turned black and smelt awful, so I had to throw them away. Yesterday, I tried again, without the plastic bag - just placed them in the mini greenhouse. This morning they seem to have wilted. What am I doing wrong? Maybe they are getting too much sunshine? Any help will be greatly appreciated. Thanks.
With mint I'd just dig up a couple of stems with roots already on them. If your mint's are like mine they spread all over the place by themselves. When you say mini greenhouse, are you leaving it out in the sun? A plastic covered enclosure in the sun is basically a solar cooker.
With a cutting I'd remove all the leaves except the few at the growing tip. If they had much size to them I'd cut the outer half of them off to reduce the leaf area even more. I think that one of the nodes also has to be under the soil for it to grow roots.
My mini greenhouse is like the one in the picture. I put it in the balcony where it get about 5 hours of direct sunlight per day. We have a Mediterranean climate so I only intend using it in cool weather, otherwise I think the plastic will melt!! I've planted some speedy salad and lettuce seeds in it, as well as some small plants that I don't want to get blown away.
Regarding the mint cuttings, yes, I did cut off most of the leaves so that I would be able to push the stem deep down in the compost. I have now put these in a shaded part of my yard, and I also put a new cutting in a jar of water and placed that in the greenhouse. I saw a YouTube video that said it should root that way. Hopefully one of them will be successful!
Mint ought to root in a glass of water. Keep the water fresh by changing it daily or every other day.
If the stand is well established in the garden, then divide the clump, or at least dig up some from the edges that include some roots. Then pot that up in the right size container.
If it is not quite that mature then find a long branch of the mint and lay that over a pot of soil. Put a rock on the stem to hold it in contact with the soil in the pot. Keep it attached to the mother plant until the part in the pot has rooted,
The plastic cover is not tight fitting, so it hopefully gets some air from the bottom. When I plant seeds, should I still insert them into a clear plastic bag for moisture retention? Or is there no need if they are in the greenhouse?
That is going to depend on the air flow.
Too wet, and you are inviting soil diseases like damping off. Bagging them inside the greenhouse might do that.
Set up a test: Put a tray with some soil in a bag in the greenhouse, and another right next to it, not in a bag. Watch them both to see how fast the soil dries vs does it grow mold.
I had a very breezy 'greenhouse' and did not use extra bags for starting seeds. Just careful watering.
My seeds in the greenhouse have not yet germinated. They've been there for 2-1/2 weeks now. (speedy salad mix / lettuce / rucola). Tomorrow I'm going to try planting some cherry tomato seeds. I'll try putting a couple in the greenhouse, some outdoors in a shaded area, and some indoors next to the patio door. Hopefully something will eventually germinate!! I've had success with rucola where I just literally threw some seeds in a stone/soil patch on the ground (very shaded area).
My mint cuttings seem to have rooted. I placed one in a jar of water in the sunny greenhouse and it's got 2 long roots now. I also placed 2 cuttings, without any covering, in a shaded area, and they are resistant when I try pulling them gently. So now I should be able to transplant them all to one larger container.