Will Pouring Tomato Juice On Hydrangeas Affect The Bloom Color?

Question

I have some out of date tomato soup that I could use to increase the acid content if that would have any effect.

Answer 1

I wouldn't do that, uncomposted. Besides, tomato juice sitting at, only, a pH of 4 will not acidify the soil enough to make a difference. It may also rot, which could be a death sentence to your plant, potentially.

Lemon juice sits at a pH of around 2 or 3, which is much more appropriate to acidify the soil. Just have care to test the pH of your water after adding, so that a gallon remains around 5, or 5.5 in pH. This will ensure that you don't over-do it, or chelate all of the nutrients out of your soil. That would be very counter-productive.

Here are some tips that will help you to achieve bloom color change:

https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/change-hydrangea-color.htm

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/raise-acid-level-soil.htm

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/adding-lime-to-soil.htm

https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/lower-acid-soil.htm