Adding coffee grounds directly to the soil as a fertiliser can be a good option. Coffee grounds are rich in nutrients, especially nitrogen. They also have some amount of other nutrients like potassium and phosphorous. Overall, this means that adding coffee grounds to your garden can work fairly well as a fertiliser.
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.
Brown Gold for the Garden
ground facts: Coffee grounds contain approxi- mately 2 percent nitrogen, 0.06 percent phosphorus, and 0.6 per- cent potassium by volume. They also contain many micronutrients including calcium, magnesium, boron, copper, iron, and zinc.
I've visited a site where a raised bed was ruined by too much coffee grounds. Like most kitchen waste, it is a fine amendment for the garden, but like anything else, coffee grounds can be overdone.” Contrary to popular belief, it's a myth that coffee grounds are acidic and will lower the pH of the soil.
To use coffee grounds as a fertilizer sprinkle them thinly onto your soil, or add them to your compost heap. Despite their color, for the purposes of composting they're a 'green', or nitrogen-rich organic material.
Egg Shells
Eggshells contain calcium, which plays a role in the strength and thickness of plant cell walls. Broken down egg shells on average contain 39.15 percent calcium, 0.4 percent nitrogen and 0.38 percent magnesium.
Compost coffee grounds for a vegetable garden instead of using them directly. Remember, coffee grounds are not good for tomatoes or seedlings. Get a soil test, especially if your plants are not thriving or you want to change the acidity of the soil.
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.
Plants that like coffee grounds also respond well to watering with coffee liquid. However, it is a fairly strong fertilizer, so this watering should not be done more than once a week.
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.
Banana peels are good fertilizer because of what they do not contain. They contain absolutely no nitrogen. While plants need nitrogen (remember the NPK on fertilizers), too much nitrogen will create lots of green leaves but few berries or fruits.
Coffee grounds contain around 2% nitrogen as well as varying amounts of phosphorus and potassium which are all very important for the growth of tomato plants.
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.
Squirrels aren't the only wildlife that are likely to be repelled by coffee grounds. You can also count on coffee grounds to keep deer, chipmunks, and snails or slugs at bay.
The shells also contain other minerals that help plants grow, including potassium, phosphorus, and magnesium. Eggshells are, therefore, an effective and inexpensive fertilizer for outdoor garden soil and houseplants.
Coffee grounds (and brewed coffee) are a source of nitrogen for plants, producing healthy green growth and strong stems. Coffee also contains calcium and magnesium — both of which are beneficial to plant health. To use coffee as a plant fertilizer, you'll need to dilute it. It should look like weak tea.
"It's fine to use coffee as a fertilizer," our senior lab testing technician, Jonathan Chan, says. "However, you should be careful because coffee can raise the acidity of the soil. Caffeine also is known to have a negative effect on plant growth."
Yes, coffee contains nitrogen, but in small amounts that are unlikely to make much of a difference to either your best indoor plants or your garden borders. If you do decide to occasionally use coffee to water your plants, make sure it's black, without any sugar or milk added.
The reality: coffee grounds can do more harm than good
Not a strong start. Then there's the fact that your soil might not even need more nitrogen, and an overload could restrict growth. So that's no good.
Leaching out of the grounds, the highly soluble caffeine percolates through the soil and has been repeatedly shown to severely stunt the growth of small, neighbouring plants' roots and slash the rate of seed germination, even at relatively tiny concentrations.
Sarah says the key is composting them first. "Give it six months to a year. The compost will break down the phytotoxins, and you'll still get the great benefit to the soil from using them."
One study published in the Journal of Agricultural and Food Chemistry found that coffee grounds were more effective at repelling rodents than commercially available products. Coffee's bitter compounds are responsible for its repelling effects. These compounds make the coffee unpalatable to rats and mice.
Which plants shouldn't you try this with? Don't add eggshell fertilizer to plants that prefer acidic soil, like blueberries. Ericaceous plants such as mountain laurel, pieris and azaleas also fall into that category. In extreme cases, low acidity for plants could impact their overall health and/or the resulting crop.