Good evening, everyone, I'm new to the forum, but hoping that the local experts can shed some light on a disheartening situation. Two years ago when my grandmother passed away, we took a cutting of her immense grape vine and planted it in an EarthBox at our house. That summer and the following one it grew somewhat weakly and did not produce any grapes. However, this spring in seemed to flourish, and we were delighted to find three small clusters growing among the leaves. Unfortunately, in the past two weeks I noticed that a few of the leaves were starting to turn yellow, and then brown. The problem is now impacting more and more of the leaves, and I'm worried that the plant will wither away before the grapes can mature. (My hope had been to harvest the grapes to seed new vines.) I've read through many webpages on the yellowing of grape vine leaves. Either the symptoms don't seem to match, or they match more than one conflicting remedy (under/over watering). So, I'm at a loss as to how I can best intervene. If anyone in the community has any ideas, I'd be very grateful for your feedback. I've attached a couple of photos to help with the assessment.
From the photos I can't tell how large the entire vine is, but it appears to be sizable. The problem could be insufficient nutrients being delivered to the vine because the planter is too small for the size of the vine. I've never tried to grow them in a planter, but one Web site I checked said that the minimum planter size is 15 gallons. That was for a vine that is heavily pruned to keep it small. I assume that you are using well draining soil and the planter has holes in the bottom.
Thanks for your thoughts on this situation. I've received similar feedback from a "grapes and vines" group on Reddit. It may be that the vine has become somewhat rootbound. This surprised me, as it was just a cutting two years ago, and I didn't think roots grew that fast. But apparently they can. The EarthBox is actually two cubic feet in size, which is equal to 15 gallons. But I suppose the source you quoted only imagines keeping the vine in that planter for a limited time. I'm debating whether to try transplanting the vine now, in the middle of the season, or waiting until the winter. I suppose there's a good chance I'm going to lose the leaves and grapes either way, which would be unfortunate. But at least I have a possible diagnosis that I can act on now.
If the vine is not too rootbound, you could try pruning off parts of the vine to see if the soil can support a smaller vine. I would remove all branches that do not directly support the fruit clusters. I do that every year with vines that are planted in the ground.
Because this grape has so much sentimental value, I think it would be prudent to take a few cuttings to have plants on hand just in case you lose the main vine. I don't have a whole lot of experience with grape vines per se but I think that EarthBox is much too small. It doesn't have the capacity to provide the water or nutrients for a large vine and it likely gets too hot for the roots as well. In my opinion, you'd need at least a half-barrel to accomodate a grape vine capable of providing fruit. (When you do get to that stage, be sure to protect the ripening fruit against raccoons.)
Thanks for all the additional comments and suggestions. It sounds like cutting a few of the non-producing branches would have the benefit of both increasing the chances of the grapes maturing and provide an opportunity to propagate new plants. So, I think I'll attempt this over the weekend -- after reading everything I can find on how to give the cuttings the best chance of survival. I'm definitely not an expert there, and want to make sure I don't screw that up. As for the EarthBox vs larger planter or ground planting question, I can see how this container may no longer be suitable. However, I think we may wait until the winter to make the move. It seems like the plant may suffer the transition better in that season, and it gives me time to figure out the best choice among limited options (rental property).
Iron deficiency is the most common culprit that causes yellowing -- leaf tissues turn yellow, with only the veins remaining green. It is often the result of high soil pH in wet conditions. Nitrogen-deficient grapes will also show yellowing on mid-shoot leaves.
