Your Petunias Will Thrive With The Help Of A Few Leftover Kitchen Scraps
Petunias can add elegance and whimsy to your garden. They're fairly easy to care for and don't need high-quality soil to thrive. However, they'll benefit from a dose of fertilizer every week or two, depending on the quality of their soil and where they're planted. If you end up fertilizing your petunias that often, you can reuse kitchen scraps to cut costs and be more efficient. If you like eggs and coffee at breakfast, save the leftovers to give your pretty petunias a boost of nutrients and ward off insects and diseases.
Coffee grounds and eggshells bring some benefits to the garden, but there are some misconceptions about these two ingredients that tend to spiral into misinformation on the internet. For starters, brewed coffee grounds won't change the pH of soil. They will improve the soil and add nutrients, but don't expect them to level out the pH value. As for eggshells, throwing whole shells in the ground won't do the plants any favors. They break down very slowly, so if you use them to add calcium to the soil, you'll need to grind them up into a powder so your petunias can use them. Add the eggshells to the soil before planting petunias to ensure it mixes well.
Coffee grounds help improve the soil
Using coffee grounds in the garden is a simple way to be resourceful, especially if you have to have your daily cup of joe. Though they aren't a great source of nutrients, they do provide small amounts of nitrogen, phosphorous, and potassium (NPK), the three nutrients that make up the NPK in fertilizer. They also provide low doses of iron, copper, calcium, zinc, and magnesium. When used with fertilizer, these nutrients will help your petunias stay fed, which is necessary if you want them to achieve their gorgeous colors. Grounds can also improve the soil by feeding microbes, which will help improve soil drainage over time. Too much caffeine can give you the jitters, but it can do the opposite for plants and slow down or even stunt their growth, so it's important not to overdo it. Only mix in ½ inch of grounds per 4 inches of soil. You can also add grounds to compost, but don't allow them to be more than 20% of the contents.
Coffee grounds will also repel and kill snails and slugs. Though they aren't typically an issue among petunias, they do like to congregate under groundcover plants. If you have large flowerbeds of petunias, you may find yourself with some slimy pests. Coffee grounds in the soil will help repel them, as will a coffee spray containing two parts brewed coffee and one part water to apply directly to the slugs and plant foliage.
Eggshells add calcium
Eggshells can boost your garden's growth by providing calcium. Petunias require calcium at the molecular level. Without it, their cell walls and membranes won't form correctly. Calcium deficiency often isn't a problem when the soil pH is neutral or alkaline, but it can become an issue in acidic soils. Petunias are happiest when the soil pH is 6.0-7.0, but if they're getting by in slightly more acidic soil, you can use eggshells to give them a boost of calcium. Since eggshells seem to take forever to break down, it's best to grind them up first. Rinse and dry the shells completely, then grind them up in a coffee grinder. The eggshell powder should be finely ground so no large chunks are left behind. Mix the powder into the soil around existing petunias or before you plant them. You can also boil eggshells in water and let them sit overnight. Remove the shells and water your petunias with the room temperature water.
Calcium sprays can be used to treat Botrytis blight on petunias. This is often used on commercial petunias since they can easily become infected with the disease during transit. If you boil eggshells and spray them on your petunias, it will behave similarly since it contains calcium from the eggshells. Be sure to test the spray on your plants first to ensure you don't harm them with the spray. Try a single leaf for a few days before spraying all of them.