As a horticulturist, I’m a firm believer and advocate for sustainable gardening. During a discussion with a friend recently, over a cup of coffee, she asked me “Does lavender like coffee grounds”?
Now, I generate coffee grounds daily and know of the benefits that they can add to the garden. But, in the case of lavender, my first reaction to her question would have to be “No”. This is because I know that lavender does not like acidic soil. And, coffee grounds can be quite acidic.
Let me explain this a little further and give you some good examples of how best to use those nutrient-rich coffee grounds in your garden.
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Why You Shouldn’t Spread Coffee Grounds Around Your Lavender
Although coffee grounds can add quite a bit of nitrogen to the soil, they can also be highly acidic. Especially, if you like your coffee strong, like I do, and tend to use a finer grind.
Lavender prefers alkaline soil so it would not appreciate you adding something that might increase the soil’s acidity. In fact, gardeners who have naturally acidic soil, generally need to add some dolomite lime to raise the pH level if they want to grow lavender successfully.
Ideally, lavender should be provided with a soil pH of around 6.5 to 7.5. A pH of 7 is neutral, so you can see that lavender does like the soil to be slightly on the alkaline side.
Generally speaking, coffee grounds have a pH of around 6.0. This is definitely acidic and not the best option for your lavender.
Lavender also needs good drainage as the roots can be susceptible to root rot if they’re allowed to sit in water for any length of time. Coffee grounds can be a problem here too because they can become compacted if spread on the soil.
This means they might create a barrier or hard crust on top of the soil that will stop water from reaching the roots but also prevent it from evaporating.
Plus, coffee grounds also contain caffeine which can be harmful to plants in excessive amounts. While a small amount of coffee grinds won’t be a problem, you do have to be careful not to add too much around your plants.
Why Is The Correct pH Important For Your Lavender?
Different plants grow best in a range of pH levels. While there are many plants that like acidic soils, there are many others that don’t.
In the horticultural world, pH is measured in a range from 0 to 14. This means that soil with a pH of 7 is regarded as neutral. Soil that has a lower pH is regarded as acidic and soil with a pH over 7 is regarded as alkaline.
If you’re not sure of the pH level of the soil in your garden, you can easily purchase a pH test kit to find out.
So, what happens if your soil is too acidic for lavender? In general, highly acidic soils can stop your lavender plants from absorbing the necessary nutrients in the soil. As a result, your plants will not thrive and their growth will be stunted. You can find out how long it takes for lavender to grow by checking out this article I wrote on the topic.
On the other hand, if the soil is too alkaline (above 7.5), the same thing can happen. This is why it’s so important to ensure that you provide your plants with the correct soil pH.
Plants such as lavender, that are forced to grow in soils that are either too acidic or too alkaline, will not thrive and will eventually die if they’re unable to absorb the nutrients that they need.
How Can You Adjust The Soil’s pH Level?
Firstly, it’s important to understand that soil amendment or adjusting the pH of your soil will take time and should be done gradually so you don’t stress your plants too much.
To raise the pH level of acidic soil, you can add either lime or wood ash. I use wood ash around my garden a lot as it also contains a high level of potassium. This is perfect for flowering and fruiting plants.
But, once again, you want to only add small amounts at a time to ensure that you don’t end up adjusting the pH too much in the opposite direction.
On the other hand, if your soil is too alkaline, you can lower the pH and increase the soil acidity by adding sulfur or aged compost to it. This would be the only instance where I would recommend adding a very small quantity of coffee ground to the soil around your lavender.
How Can You Use Leftover Coffee Grounds In The Garden?
Now that you understand that coffee grounds aren’t really beneficial for your lavender, you might want to know how you can use them around your garden. Before I go into this, let’s explore the benefits of coffee grounds and how to get the best results.
Benefits Of Coffee Grounds
Coffee grounds are rich in nitrogen. They also contain other essential nutrients such as phosphorus, potassium and magnesium. These are all essential for healthy plant growth so you definitely want to utilize them in your garden.
Additionally, coffee grounds can help to improve the soil structure when they’re lightly raked in. Plus, they can help to retain moisture and are often used as a deterrent against slugs and snails.
Finally, coffee grounds can be a good food source for the worms that live in your garden. This means more nutrient-rich castings for your plants to enjoy.
So, how do you best incorporate coffee grounds into your gardening routine? Here are my top suggestions, plus a list of plants that do benefit from them.
Add Them To Your Compost
The main way that I prefer to use coffee grounds in my garden is to add them to my compost. I have a kitchen compost bucket that I empty the coffee grounds into daily along with other kitchen scraps.
This then goes out to one of my compost bins. I also ensure that I add plenty of brown materials such as dried leaves as well as other green materials like grass clippings. This is a great way to increase the green matter in your compost.
If you don’t already know all the ins and outs of making your own good compost, you might want to read an article that I wrote on the topic titled “Make Your Own Compost In 3 Easy Steps”.
For me, this is the easiest and most beneficial way of using coffee grounds in the garden.
Compost is ideal for improving nutrient-poor soil and helps to provide your garden plants with all the goodness they need. Compost can also be useful for improving the moisture-holding capacity of sandy soil to keep your plants hydrated for longer.
However, there are also certain plants that love acidic soil and would benefit from some coffee grounds directly.
Here are just a few.
Tomatoes
Tomatoes do like slightly acidic soil and would benefit from the nutritional content in coffee grounds. However, you don’t want to add too much because of the high nitrogen content.
While nitrogen is essential for healthy plant growth, adding too much to plants like tomatoes can cause them to put on a lot of green growth rather than produce flowers and fruit.
Here’s an article I wrote about the benefits of coffee grounds for tomatoes and what you should and shouldn’t do.
Rhododendrons And Azaleas
Both azaleas and rhododendrons, who are in the same family, appreciate and thrive in acidic soil. This means that they would certainly benefit from the addition of coffee grounds.
However, make sure that you balance the nutrients with additional organic fertlizers to ensure that your plants are also getting a healthy dose of potassium if you want plenty of gorgeous blooms.
Blueberries
Who doesn’t love to munch on a delicious bowl of blueberries? If you want to grow these in your garden, you’ll be happy to know that they simply love acidic soil. In fact, the ideal pH level for blueberries is between 4.5 and 5.5.
This means that these plants will benefit from an application of coffee grounds every now and then. Once again though, you will need to balance the nutrients by giving your blueberries an organic plant fertilizer that’s high in potassium.
Cranberries
Cranberries are another fruiting plant that simply loves acidic soil. This means that you can safely sprinkle some coffee grounds around your cranberry plants and reap the benefits.
Hydrangeas
If you grow hydrangeas in your garden, you will be aware that you can change the color of the flowers simply by altering the pH of the soil.
Acidic soil will produce blue flowers while alkaline soil will produce pink ones. I’ve actually tried this on my own hydrangeas and the change in the flower colors is quite interesting to observe.
Gardenias
Gardenias are also fond of acidic soil and will benefit from a small amount of coffee grounds occasionally. They’ll also love the additional nitrogen but make sure you supplement this with an organic fertilizer that contains ample amounts of potassium.
African Violets
Popular indoor plants such as African violets can benefit from the addition of a small amount of coffee grounds to the potting soil. This will provide some additional nitrogen to keep your plants thriving.
Lily Of The Valley
The lily of the valley is another acid-loving plant that will benefit from a small amount of coffee grounds every now and then.
The Best Way To Use Coffee Ground Around Acid-Loving Plants
Now that you know about some acid-loving plants that will benefit from the use of coffee grounds, it’s important to understand how to best apply them.
You can use coffee grounds as a mulch around your acid-loving plants. However, don’t apply them too thickly because they can become compacted and prevent water from seeping down into the soil.
So, make sure that you only spread them in a relatively thin layer.
Alternatively, you can gently rake the coffee grounds into the soil around your acid-loving plants. Just be careful not to disturb the roots of the plants as you’re doing this. This will also prevent the grinds from clumping and creating an impervious layer on top of the soil surface.
Another good idea is to spread your coffee grounds around the perimeter of your vegetable beds as they’re said to deter snails and slugs. These pests don’t like crawling over the grinds and you’ll also find that the caffeine is toxic to them.
Frequently Asked Questions
While roses will benefit from the nitrogen content in coffee grounds, they should be used sparingly around your roses. Here’s an article I wrote on the subject.
Yes, you can, especially around acid-loving plants as they are a good source of nitrogen and can reduce the pH level of the soil. However, be sure to only place a thin layer on the soil so that they don’t form impervious clumps. Or, mix them with some other form of organic matter for a nutrient boost.
No, coffee grounds should only be used around acid-loving plants such as azaleas, hydrangeas, rhododendrons, blueberries and cranberries.
Coffee grounds can be used to deter slugs and snails. However, even a diluted solution of brewed coffee can have the same effect thanks to the caffeine content.
Final Thoughts
If you’ve ever wondered whether lavender likes coffee grounds, my answer would be “No”. This is because coffee grounds are fairly acidic and lavender prefers a more alkaline soil. The only time I would recommend adding a small amount of coffee grounds around your lavender is if the soil is highly alkaline.
However, coffee grounds are nutrient-rich organic materials and they can have a variety of uses around the garden. One excellent way to use them is to add them to your compost pile or throw them into your compost bin.
There are also quite a few acid-loving plants that you may be growing that will benefit from the use of coffee grounds. Just remember to use them in moderation only.
And finally, coffee grounds do help to deter slugs and snails. This means that they can be beneficial if you spread them lightly around your vegetable garden.
