New owner of this property with many overgrown shrubs. Gardenia plant (among others) about 5' tall and bigger across, bloomed great in spite of sick plant, but blossums didn't last for long either.
I'm thinking of severly pruning and spraying plants and ground with fungacide. What ya think?
What to use as home-made fungacide???
Without knowing what is wrong with your plant, it's not possible to treat it. Would you be able to show a pic of it? The blooms on the ones here don't last long either.
After blooming, when it starts to grow new leaves in the spring, would be the best time for pruning. Mature does not necessarily mean overgrown unless it does not fit in the space where it was planted. But even a mature shrub needs occasional guidance and maintenance. Simply opening up the plant to allow more air flow, removing weak or crossing branches, excessive twigs and suckers, and any dead parts, could be all your shrub needs to be more healthy and vigorous. Even when I'm pretty sure I'm going to whack a shrub drastically, I do that first to see what the good part(s) looks like, which is often a lot better and balanced than imagined, and not as much trimming is needed as initially suspected.
Does it have black mildew or stickiness from aphids? The mildew is kind of seasonal and trimming/increased airflow can help get rid of it. I didn't have any luck trying to wash it off but have seen it a few times and it doesn't stay long, even if I do nothing. I think you'll be pleasantly surprised how your shrub responds to trimming. You can thwart the aphids by knocking them off with water. These things seem to bother people more than the Gardenias, as long as there's plenty of light for it to be healthy and vigorous. You may want to fertilize when it's actively growing in the spring. The abandoned house next door has beautiful Gardenias that haven't been touched in years, Gardenias don't seem to need care unless you feel like giving it.
If it is sooty mold from honey dew you do not spray fungicide to control the sooty mold.
You want to control the aphids, scale and other sucking insects that are creating the honeydew that the sooty mold feeds on.
Do you know what scale looks like? These are pests that do not move around much, and often look like bumps or discolored spots on the branches.