Excessive acidic soil can kill or hamper the growth of plants like asparagus fern, Chinese mustard, Italian ryegrass, lavender, orchids, rosemary, tomatoes, and geranium. The roots of these plants are also not potent to absorb the nutrients added by the coffee grounds in the soil.
In most cases, the grounds are too acidic to be used directly on soil, even for acid-loving plants like blueberries, azaleas and hollies. Coffee grounds inhibit the growth of some plants, including geranium, asparagus fern, Chinese mustard and Italian ryegrass.
Coffee grounds are highly acidic, they note, so they should be reserved for acid-loving plants like azaleas and blueberries. And if your soil is already high in nitrogen, the extra boost from coffee grounds could stunt the growth of fruits and flowers.
It's best to avoid using coffee grounds with plants that don't like acidic soil or high nitrogen levels in the soil. Some prominent examples of these plants include; tomatoes, rosemary, lavender, and asparagus. You need to think about your plant's needs when deciding what type of fertilizers you will use.
Coffee grounds don't work on potted plants, but if you have some succulents planted outside in your garden, you can place used coffee grounds directly onto the soil. As the used coffee grounds break down, they'll add nitrogen to the soil, a vital succulent nutrient.
There are a select few plants that can benefit from fresh grounds—including acidity-loving Hydrangeas, Rhododendrons, Azaleas, Lily of the Valley, blueberries, carrots, and radishes—but generally, most common houseplants will prefer low to no acidity.
Coffee's bitter compounds are responsible for its repelling effects. These compounds make the coffee unpalatable to rats and mice. They will avoid areas where there is the use of coffee grounds.
You may wonder if any animals are attracted to coffee grounds. Mice and rats pay little attention to the smell of coffee and rarely eat coffee grounds. However, there are smells these, and other pests hate. So, if you want to keep pests away, then here are some smells most of them hate.
Insect Repellent
Most bugs have a very strong sense of smell. Since coffee grounds are very potent, it's a perfect repellent to fight off those pests. According to the EPA, coffee grounds are most potent when they are burned.
'Your roses, azaleas, lilies, and hollies because they are acid-loving plants that will thrive best in the acidic characteristic of coffee grounds,' he adds.
WHAT PLANTS DO NOT LIKE COFFEE GROUNDS? Since coffee grounds retain moisture, avoid using on plants that prefer drier soil such as cacti and succulents. Avoid using grounds on plants that prefer alkaline soil such as asparagus, beets, geranium, lavender, rosemary, and spiderwort.
Coffee grounds are an excellent fertilizer, especially for orchids and African violets.
By adding coffee grounds to your roses, you create a barrier that will keep pests away and allow your rose bushes to thrive. So if you're wondering whether coffee grounds are good for roses, the answer is a resounding yes! Coffee grounds are an inexpensive and readily available organic fertilizer for your roses.
Roses do like coffee grounds, but too much too close can give them a nasty nitrogen burn and can kill your roses. Never sprinkle coffee grounds right next to the plant. There's a great way to…
ANSWER: To put it bluntly, no—coffee grounds are not good for herbs, and they should be used with care around the plants that do benefit from them.
Other Natural Repellents
Mothballs — place them around the perimeter, and their pungent smell will repel snakes. Vinegar — mix it with water and spray often. Caffeine — sprinkle coffee grounds or instant coffee granules. Spices — chili powder and cayenne pepper work the best.
Why coffee grounds? Since the bears have a strong sense of smell, such a pungent treat is extremely attractive and stimulating to them. The bears roll around in coffee grounds like a cat in catnip!
Asian Palm Civet
These are likely the most well-known animals that process coffee by eating the cherries and pooping out the beans. Known better as the kopi luwak, this coffee was once (and still may be) some of the most expensive coffee beans available.
But what exactly do mice and rats hate to smell? Mice can be kept away by using the smells of peppermint oil, cinnamon, vinegar, citronella, ammonia, bleach, and mothballs.
Since coffee grounds have such a pungent and intense smell, mosquitoes do not like to come near it. Mosquitoes are repulsed by all types of coffee, whether it is fresh, used, or burnt. The most effective way to use coffee grounds for mosquito control is by burning them, as it creates a stronger aroma.
Boost potted plants
When potting plants, place a few used tea bags on top of the drainage layer at the bottom of the planter before adding soil. The tea bags will help to retain water and will also leach some nutrients into the potting medium.
Spider Plant
Popular for thin, variegated, spider-like foliage, this air-purifying houseplant does well in mild-acidic soil. Take one part coffee to three parts of water to promote growth.
The fern will not thank you for adding coffee grounds. Coffee will put too much nitrogen in the soil for the fern, stopping the plant's development. More importantly, coffee has an antibacterial effect and kills the germs necessary for the fern. Therefore, it is best to keep your fern away from coffee.