It is a common belief that used coffee grounds are acidic and that they will acidify your soil. Lets see if it is true.
Do Coffee Grounds Acidify Soil?
Soil
Increasing Soil Acidity
There is a lot of advice on how to make make acidic soil both in print and on the net. You can use coffee grounds, pine needles, and sulfur to name a few. This advice has two problems. Firstly, the recommended product may not actually acidify soil. For example in Do Pine Needles Acidify Soil I show that pine needles do not make acidic soil. Coffee grounds don’t acidify soil either. The second problem is that before such advice is given it is important to know the soil types (ie soil texture) being treated. Let’s take a closer look at this.
How to Get Rid of Moss in Lawns
Lots of people want to know how to get rid of moss in the law, but a better question to ask is, “why does moss grow in lawns?”The most common response to this question is that the lawn receives too much shade and that the soil is acidic. The common advice is that grass will grow better if you limb up the trees and add lime to the soil to make it less acidic. Or you can spread a moss killer for lawns.
What about moss that is growing in a sunny area? What about moss growing in soil that is alkaline? There is much more to the moss story and the only way to really get rid of moss in a lawn is to understand why it is there in the first place.
Liming Acidic Soil – Adding Lime
Your soil is acidic and you would like to change the pH so that it is less acidic. The universal advice is to add lime to the soil ie liming your soil. Lime is alkaline and it will neutralize the acidity of the soil and make it more neutral. Adding lime certainly works – but there is a catch!
Do Pine Needles Acidify Soil
This is an old gardening myth that just won’t rot away!
This common, incorrect, advice goes as follows: if your soil is alkaline (ie has a pH above 7) and you want to make it more acidic, add pine needles to the soil. Since pine needles are acidic they will acidify your soil. This advice is very prevalent especially for growing acid loving plants such as azaleas and rhododendrons.
There are two important questions to ask. Firstly, are pine needles acidic? Secondly, do they acidify the soil? Let’s have a closer look at both questions.
Compost Tea
Compost Tea has become a very popular topic. The following is a quote from Fine Gardening (ref 2):
Gardeners all know compost is terrific stuff. But there’s something even better than plain old compost, and that’s compost tea. As the name implies, compost tea is made by steeping compost in water. It’s used as either a foliar spray or a soil drench, depending on where your plant has problems.
Why go to the extra trouble of brewing, straining, and spraying a tea rather than just working compost into the soil? There are several reasons. First, compost tea makes the benefits of compost go farther. What’s more, when sprayed on the leaves, compost tea helps suppress foliar diseases, increases the amount of nutrients available to the plant, and speeds the breakdown of toxins. Using compost tea has even been shown to increase the nutritional quality and improve the flavor of vegetables. If you’ve been applying compost to your soil only in the traditional way, you’re missing out on a whole host of benefits.
Let’s look at the facts.
Soil Amendments – Don’t Amend Before Planting
Almost every book, and most web site tells you that you should amend your soil before planting a new plant. This seems to make a lot of sense. Few of us have perfect soil and we don’t want to put our new expensive plant into poor soil. If we amend it, the plant should grow better? That’s a common garden myth.
