Coffee tends to have salts that may accumulate in the soil.
For that reason, I use coffee [grounds] in the yard and garden exclusively.

To acidify your soil, try one capful of white vinegar per gallon of water.
This will help counter the alkaline creep caused by most tap-waters.
If salts have been building in your soil, you might want to flush the soil
so that you don't end up with a glut of salts dissolved by the vinegar.

Josh

I would be afraid that the vinegar would kill the tree. I use vinegar on the weeds to kill them. How would vinegar not kill my tree?

How would it kill your tree?

You tell me. I've never killed a Conifer, Maple, or Citrus.

Are you saying that 1 capful of white vinegar per gallon of water actually kills your weeds?

Josh

The poison is in the dose. Many types of acid are used to acidify irrigation water. Nitric, citric, phosphoric, sulfuric are some of them. What else would you use to acidify the soil solution if not an acid? ;o)

Forum discussions frequently center on the question of adding dilute coffee/tea or grounds to plants as a 'tonic', but Arabica (coffee) and Camellia (tea) are known for their toxic alkaloid (caffeine) content and their allelopathic affect on plants as well as autotoxic (poison to their own seedlings) effects on future generations. Caffeine interferes with root development by impairing protein metabolism. This affects activity of an important bio-compound (PPO) and lignification (the process of becoming woody), crucial steps for root formation.

We also know that the tannins in both coffee and tea are known allelopaths (growth inhibitors). There are ongoing experiments to develop herbicides using extracts from both coffee and tea that cause me to want to say they might serve better as a nonselective herbicide than as a tonic. I would not use either on my plants; nor would I add tea bags/coffee grounds to my container soils.

Precisely why do you feel the need to acidify the soil (solution)?

Al

Oh - I forgot to mention that I use (and have been) vinegar on a regular basis. Using it to lower your irrigation water to a pH of around 6.0 is helpful, as it ensures better availability of nutrients (primarily the minor elements) and halts the normal upward creep in pH as soils age.

Al

garden guy,

I have used vinegar to kill weeds, and small amounts as they suggest on plants with no troubles.

As Al says. the poison is the dose. :) a tiny amount wont hurt your trees.

JoJo