I see what you are trying to do. It's not going to work. There are better ways to reserve rain water, without destroying the house and having the roof collapse. The problem will worsen with each time it rains without even mentioning black mold.

Here is a better way to harvest rainwater.
https://www.youtube.com/watch?v=NDFFkCFb-MA

As time goes on, Hank, the leak will only get worse, and worse, and worse etc etc; the wet will rot the woodwork within the roof so that it eventually all has to be replaced. I would suggest getting a builder to look at it and give you a quote for repair.

sorry Hank but I have to agree, that needs repairing and if you can't do it the you are going to have to pay to have it done.

I know you’re all perfectly correct but will have to pull the whole porch down to get at it. Thanks for the comments, Will give it some more thought.

Guess what Hank, the porch is going to have to be pulled down... otherwise water will get into the foundations etc. etc. - not something you want to have happen! are you sure a builder can't fix this?

That’s just what I told my son half an hour ago. I give in, will look into it tomorrow.

Is this your or your son's house... if your's don't wait for you son - get it sorted, at this time of year builders are scarcer than hens teeth!

Nice idea Hank , but not worth the subsequent probs it would bring . Have the work done , and then you could still grow something in the same place .

Hank - Are you moving to San Diego? :) This could be a sign!

Wonderful idea B, should have done it 20 years ago when we first visited my daughter there. Sadly it’s a bit late now.

It's never too late Hank, though the roof will still need fixing :)