Caffeine appeared to have a negative effect on plant growth. Although caffeine is found naturally in many plant species and can be used on plants to manage pests such as slugs, snails, bacteria, and birds, this study concluded that caffeine stunts root development by reducing protein production (Batish et al., 2009).
Coffee contains a lot of nitrogen, which not only kills off weeds and bacteria but can also help certain types of plants (a.k.a those that prefer more acidic soil) flourish. Plus, your daily cuppa also contains significant amounts of magnesium and potassium, both of which are key factors in plant growth and health.
Can You Water Plants with Coffee? 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. To prepare the mixture, boil the coffee and pour one and a half times as much water.
Some plants seem to benefit and grow faster when caffeine is added to the soil, while others seem to become stunted or grow slower. There are also some plants that are not affected by the presence of caffeine 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.
The myth: coffee grounds are good for acid-loving plants
So it follows that they wouldn't mind the acidic nature of coffee (assuming that it is, of course). But not all plants like higher acid levels, and it's hard to compost/fertilise in a vacuum - risking damaging some of the others.
While many budding gardeners may be concerned that coffee grounds can attract pests, the reality is quite to the contrary. In fact, when implemented correctly, coffee grounds can be an effective way to repel certain pests such as wasps, snails, and mosquitoes.
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.
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. Coffee should be spread in a thin layer, rather than being clumped in one place.
Coffee works great on many types of flowering indoor plants but can be used outside as well. Diluted coffee adds just enough organic fertilizer to encourage bushier, healthier plants.
Coffee grounds add organic material to the soil, helping water retention, aeration, and drainage. 'Leftover diluted coffee can create a liquid plant fertilizer, too. Simply mix two cups of brewed coffee grounds with five gallons of water in a bucket overnight. '
'Coffee grounds are an excellent houseplant fertilizer due to their high nitrogen content (about 2 per cent) that releases slowly into the potting media as they decompose. However, coffee grounds have more to offer to plants than just nitrogen,' she says.
Chemically speaking, the stimulant is a pesticide. Caffeine is thought to ward off herbivores by helping make the plant dangerous to, and in some cases killing, the insects that feed on the caffeine-containing plant parts.
Like sulphur, cinnamon is a natural fungicide that helps most plants root, while inhibiting the spores that cause rot in stem cuttings. Dip prepared plant stems in cinnamon and push them into the soil. It's an effective rooting hormone that's easy to use and inexpensive.
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.
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."
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.
Yes, it's possible, but it should not be more than a thin sprinkling. If you add too much, the coffee grounds will form a dense layer on the surface of the potting soil that is impenetrable to water. On a regular basis, using leftover coffee to water your potted plants is a much better idea.
You know that last bit of coffee that always seems to be left in the carafe? Don't just pour it down the drain — you can use it to fertilize your plants, both indoor and outdoor. Coffee grounds (and brewed coffee) are a source of nitrogen for plants, producing healthy green growth and strong stems.
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.
Coffee grounds are commonly used to keep animals including slugs, snails, rabbits and fire ants from eating plants in the garden, and to keep cats from treating garden beds like litter boxes.
Because cockroaches eat just about anything, these uninvited houseguests may feed on coffee grounds. German cockroaches are attracted to the odor of ground coffee beans, although the food has no nutritional value to the insects.
Coffee Grounds
Not only do coffee grounds smell good, but they also work wonders when it comes to warding off unwelcome guests such as spiders.
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.