Q. Dr Myers: I purchased some clear plastic domes to root some native azaleas from htgsuppy this past spring. I am having trouble with the cuttings getting a fungus and rotting before many of them can root. The clear domes keep the humidity high but many of the leaves and cuttings rot before they root. Can you suggest anything I can do to keep them from rotting before they have time to root?
Hello,
It sounds like you may have too much humidity. You need to lower the humidity a bit to where the plants won’t wilt but the fungus won’t dominate. Taking the dome off more often should help. The domes you bought should have closable slits on the top that can allow moisture to escape. I keep the dome slits OPEN all the time.
Some things I do that may help: When taking cuttings I have a T5 light with high blue light bulbs within an inch of the top of the plastic dome. I keep the plants light regime 18 hour light on 6 hours off. You need to be able to move the light since even without fungal problems you should take the dome off the plants each day. I use a hand mister and gently mist the plants when I take off the lid. Before putting the dome back on again, I wipe all the moisture off the dome. You want to keep the plants wet, but not have everything else wet so that mold spores can thrive. The first few days after taking the cuttings I put the dome back on after I wipe it down. After 2-4 days I increase the time the dome is off the plants each day by 15 min. or so. For most plant at the end of the first week you should keep the dome off for long periods (hour or more) Once you see well developed roots, you should not put the dome back on. Another way to help keep fungus down is to leave some space between the cuttings/plants. Maybe use everyother row for cuttings. This allows some airflow which will help keep fungal growth down. The space may make it easier to spot and remove infected plants before the fungus spreads to other plants too. Every plant species will propagate differently, I have taken cuttings that have large white roots in a week, and other plants take a month to get enough roots to be called a plant.
Another thing to keep in mind is to try cleaning off the leaves/ stems with mild dish soap the day before you take the cutting to reduce the amount of fungal spores on them. If your mother plant has some fungus on the leaves you can bet there are billions of fungal spores all over the rest of the leaves. (If the mother plant has fungus you should try to increase airflow and get the mother plant fungal free first) You should also wash well/sterilize the tray dome and medium before putting cuttings in. You can use a 10-25% peroxide mix to sterilize the tray and dome. You will always have some fungal spores in the air but if you start with everything as spore free as possible, you may have more success. You could also try different mediums to increase rooting speed and/ or cut back on fungal growth, my favorite cutting medium was Rockwool, but I use the coir based rooting starter plugs from HTGSupply.com now. You can also try to use vermiculite, perlite, dirt and different mixtures of each and a few other mediums to take cuttings. You can sterilize these mediums in a microwave if you put them on high for a few minutes. Use small batches if you put too much medium in your microwave some parts might not get hot enough to kill fungal spores.
Good Growing,
Dr. E.R. Myers
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