By Seth Nagy
Cooperative Extension often receives gardening questions by email that may be of interest to many gardeners.
The question of interest this week is “I have read in several newspapers and magazines to save your coffee grounds and eggshells to add nitrogen and calcium to the soil. I have saved a rather large amount of both and don’t know what to do with them. Are there flowers, shrubs or vegetables that this would be good to put around?”
It is true, coffee grounds are a source of nitrogen and eggshells provide calcium. Go ahead and add the coffee grounds and eggshells along with other vegetable scraps from the kitchen to any compost pile. The eggshells should be pulverized before being added to the pile. It is also important to cover the eggshells after adding to the compost bin.
Although composting is suggested, coffee grounds should not cause a problem if used fresh from the coffee pot. Use the grounds the same way you would use compost. However, eggshells could attract the typical critters like rodents, stray dogs, skunks and our only native marsupial, the opossum. The residue left in the shell is enough to encourage scavenging by these critters.
Composting is suggested because it is the safest way to use any organic waste product in the garden or landscape. Good compost has an earthy smell and its initial ingredients become unrecognizable when fully composted. If the starting ingredients are still recognizable, just give it a little more time.
Some organic materials, such as manure, if used fresh can burn plants because of the ammonia release during initial break down. Also, fresh manure can potentially contaminate vegetable crops with pathogens. If manure is applied to the garden fresh, waiting 120 days before harvesting vegetables will eliminate the possibility of pathogen contamination. Putting fresh manure in the garden in the fall is an easy way to reduce potential contamination for next year’s growing season.
Other organic materials, such as fresh sawdust, will pull nutrients from the soil as it decomposes. This leaves plants looking like they are in need of fertilizer. Composting stabilizes fresh organic material, keeping it from leaking or pulling excessive nutrients from the soil.
Finished compost can be mixed in garden soil, put around plants like mulch, added to soil when planting ornamentals or mixed with potting soil. This helps soil hold water and nutrients. It also helps foster a healthy soil micro flora. Compost slowly adds nutrients to the soil.
Using fresh coffee grounds would be similar to using finished compost. When adding to soil, don’t add more than one third the volume in organic material. When adding to the soil surface as a mulch, spread it no more than 2 inches thick.
Seth Nagy is County Extension Director in Caldwell County. If you have questions, email firstname.lastname@example.org or contact the Caldwell Extension Center at 828-757-1290.