Have you considered simply top-dressing with used coffee grounds? They will break down slower and gradually acidify the soil quite efficiently. Lemon juice would probably give the plants a quick acid rush and then fade away into the soil.

(I use coffee grounds in all my hydrangea beds and they LOVE it!)

If I soak the soil of the miracle fruit with lemon juice next time ... you will probably kill the root hairs of the plant with the acid bath.

Try it and report back :)

I would not expect any significant change for any length of time using lemon juice.

Elemental Sulfur is generally used to acidify soils organically but don't expect it to work over night...it requires soil bacteria to turn it into sulfuric acid.

There are numerous potting soils made and sold for plants wiht particular soil pH needs and it would be much easier for you to buy on nad use that rather then try to adjust on your own.

Paperfinch, coffee grounds are actually not acidic. They're close to neutral.

Is this a containerized plant?

Yes. It's in a plastic pot. I guess working pine bark fines into the mix is the best way to go in terms of a long term solution.

Adding vegetative materials seldom does anything to lower a soils pH. The most common method to lower any soils pH is to mix in the appropriate amount of sulfur, or aluminum sulfate which is unnaceptable to an organic gardener/farmer.

Search the numerous threads on this board about pH and vinegar. Very same thing, very same answers.

Dan

insipid, you don't really need to worry about a long term solution for a container plant. You can easily add a bit of vinegar to your watering bucket and get the job done, which is what many container citrus growers do.

Ask about this over in the Citrus Forum.

I'm not growing citrus

Coffee grounds are full of minerals / vitamins, containing npk, and acidic pH levels ranging from 3.0 and about 5.0

Then they become between levels of 6.5 and 6.8 after brewing. The acid bean is mostly water-soluble, so it all goes into the drink itself.

hmm i am wondering if i added that coffee i don't like (but has been sitting in my cabinets for emergencies) to my starfruit tree if it would lower the soil ph to where they like it?