Hello, I live in Northern VA have a Lakemont Seedless Grape in a 5 gal pot. This year vine produced a lot of little grape clusters which are getting bigger, but some of them are dying out. We've had hot weather these past few days ~100 degrees and there are two grapes side-by-side. The other vine is from this season and looks fine. I reviewed several pages in this post and I hope that what I am seeing is only stress from heat. I noticed some green branches have black dots on them and not sure if that is normal. Other vines from this season don't have them and there are no leaves on them. After reading some posts initially I came to the conclusion that its root system may be too big for a pot and it may be hot too, so I plan to put it in the soil. I also gave it some fertilizer because last time I did it was over a month ago. As you can see from the pictures it is only beginning, but watever it is I would like to take care of as soon as possible. Not sure if all the little grapes will dry out or fall off. I was so excited since it is my first year even seeing them. Thank you so much in advance for your advice. Thank you.
My first guess is Magnesium deficiency, less likely potassium. It's very hard to treat for a specific deficiency in a pot, so I suggest a soluble fertilizer with appropriate micronutrients and a light touch. If you have a local hydroponics store, you may be able to find a more specific foliar spray, again to be used with a light touch. For a definitive answer you would need a lab analysis that would far exceed the value of the vine. Deficiencies or general failure to thrive can be caused by root damage such as might occur from sun heating of the black plastic pot. Ralph
Ralph, thank you SO much. Narrowing this down to a deficiency is extremely helful. I've made some adjustments including transplanting vine into the ground. I'll make a follow-up post once there is a change in status. Hopefully there is an improvement.
