|What is the proper way to propagate Mandevilla plant - particularly a red one? Also one of the plants I have potted continues to get yellow leaves. Too wet? Thank you.|
There are a couple of ways to propagate your red Mandevilla. One is by collecting the seeds, the second is through tip cuttings and the third, which is probably the easiest process is through layering.
Stem cutting from mandevilla can be taken in the spring or summer. Choose side shoots 2-3 inches long and cut them from the plant. Dip the cut ends in powdered rooting hormone and insert them into sandy peat soil. Keep the cuttings moist(not too wet) and supply extra humidity by either draping a plastic bag over the pot or by inserting sticks around the inside rim of the pot and draping plastic wrap over the top to make a tent. Roots should form in 4-6 weeks and then you can transplant them each into 3" pots. Pinch back new growth to promote side shoots and bushier plants.
The method of propagation by layering is relatively simple. Choose a stem that will touch the ground (or set a pot filled with moistened potting soil near the parent plant and lay the stem over the pot so part of the stem is touching the potting soil. Anchor the stem down (I use bent paper clips) and then cover the top of that part of the stem with more potting soil. As long as the stem is making good contact with the moist potting soil it will develop roots. It takes several months but eventually the stem will root and you can cut your new plant away from the parent plant. The best part is that it is already all potted up.
I think yellowing leaves can be the result of too much water. Try allowing the top of the soil to dry out slightly before watering your plant.
Best wishes with your mandevillas!