Do you use soil amendments in your MG containers?
I have been growing most of my morning glories in containers of various sizes over the past 8 or 9 years. I used to dump the soil out of each container each spring and refill with fresh bagged potting medium. I subscribe to Horticulture magazine and one year they published an article on beneficial soil fungi (mycorrhizal fungi). After reading this article and conducting research online, I changed my way of growing MGs to a system that is similar to the no-till farming methods growers of certain crops use. Instead of dumping the soil each spring, I have been leaving the soil intact and planting into the container each May after the last frost date. I also dip started seed roots into rooting medium that has the beneficial fungi before potting them on. The fungi form a symbiotic relationship with the plants by infecting the plant's roots; fungi pass along Phosphorus (P) to the plant and plant passes along carbon to the fungi, as I understand it, along with other nutrients. High P fertilizers have a negative effect on the fungi and so I have had to go with fertilizers with a P value of 1 or less in the NPK forumula.
Any kind of major tilling of the soil breaks up the fungal hyphae in the soil and has a negative effect on the beneficial fungi.
You can google for all sorts of articles on mycorrhizal fungi. I found an informative article that you can download as a pdf (see link below).
I also use compost tea or compost on top of the soil of the container. The beneficial microbes from the compost work in concert with the mycorrhizal fungi to make for a more robust plant, so the theory goes...haven't any quantitative data yet.
Do any of you use soil amendments other than high P bloom booster fertilizer in your growing of MGs? I would enjoy hearing about what worked or didn't for you.
Here is a link that might be useful: Mycorrhizal fungi article pdf download