5 Clever Ways to Use Coffee Grounds in Your Garden

01/12/2024 | Ken Davis Fertilizer, Garden Tips, In the Garden

by Ken Lain, the mountain gardener

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If you make a daily pot of coffee, you have a fabulous source of the organic matter right at your fingertips. Coffee grounds can make your garden happier in several ways, and not just that coffee gives you more energy for weeding and pruning. Don’t toss the grounds. You can put them to work.

On the Go Answer – Readers Digest-type Condensed Version of this Article
• Small amounts of coffee grounds have many benefits in the garden, just not around tomatoes.

• All plants enjoy brewed grounds and neutral in pH acidity.

• Worms are attracted to used coffee grounds.

• Acid loving plants like fresh unbrewed grounds.

• Large Starbuck quantities of grounds should be composted first or racked into our garden soil.

• Many gardeners say coffee ground repel slugs and snails.

#1 Coffee in Compost
Put coffee grounds in your compost bin. There are two types of compost material: brown and green. Your coffee grounds may be brown in color, but in compost jargon they are green material, meaning an item that is rich in nitrogen. Coffee grounds are approximately 1.45% percent nitrogen. They also contain magnesium, calcium, potassium, and other trace minerals. Other green compost materials include food scraps and grass clippings.

Adding coffee grounds and used paper coffee filters to your compost provides green compost material. This must also be balanced with brown compost material, which includes dry leaves and newspapers. This brown to green compost ratio should be a 4-to-1 ratio of brown compost material to green compost material. If you have too much green stuff, your compost starts to smell. If you don’t have enough, your compost won’t heat up enough. Compost for Better Gardens for more details.
#2 Fertilize With Coffee Grounds
Add coffee grounds directly to the soil in your garden. You can rake it into the top couple inches of soil, or just sprinkle the grounds on top and leave it alone. In smaller amounts, especially when mixed with dry materials, coffee grounds provides your gardens with nitrogen. Used coffee grounds are actually nearly neutral in pH, so they shouldn’t cause concerns about their acidity.

You can also make coffee ground “tea.” Add 2 cups of used coffee grounds to a 5-gallon bucket of water. Let the “tea” steep for a few hours or overnight. Use this concoction as a liquid fertilizer for garden and container plants. It also makes an excellent foliar feed spray directly on the leaves and stems of your plants.

#3 Feed the Worms
Add coffee grounds to your worm bin weekly; worms love coffee grounds. Just don’t add too many at once, because the acidity could bother your worms. A cup or so of grounds per week for a small worm bin is ideal. In addition to using coffee grounds in your worm bin, earthworms in your soil will also be vattracted to your garden when usine them mixed with the ground as fertilizer.

#4 Keep the Pests Away
Create a slug and snail barrier. Coffee grounds are abrasive, so a barrier of grounds placed near slug-prone plants may just save them from these garden pests. However, be warned that some researchers quibble with this advice and don’t think it useful. You may want to have a backup plan in mind if it doesn’t work. Many cats dislike the smell of coffee grounds and avoid using your garden as a litter box if you mix coffee grounds into the soil.

#5 Fresh Coffee Grounds for Acid-Loving Plants
While used coffee grounds are only slightly acidic, fresh (unbrewed) coffee grounds show much more acididy. Your acid-loving plants like hydrangeas, rhododendrons, azaleas, lily-of-the-valley, blueberries, carrots, and radishes get a boost from your fresh grounds. Caution, tomatoes do not like fresh coffee grounds; keep them away from this part of the garden.  This could be a good use for coffee that is getting old in your pantry or a type you bought for visiting friends but isn’t your usual Cup-of-Joe.

Fresh coffee grounds still have most of their caffeine content as well as the acid. Be cautious in using fresh grounds around pets or your Wire Terrier may become extremely wired.

Dissenting Research Into Coffee Grounds in the Garden
One research study found that using spent coffee grounds in growing broccoli, leek, radish, viola, and sunflower resulted in weaker growth in all soil types, with or without additional fertilizer. The good news is that the coffee grounds improved the water holding capacity of the soil and decreased weed growth. The researchers think the poorer growth was due to the plant-toxic compounds naturally present in the coffee grounds. If you aren’t getting the results, you hoped for, with coffee grounds, you may want to try your own experiments with and without them in your garden.

Secret Mountain Recipe for the perfect garden soil – for amendments that add vitality and richness to your garden soil go deeper with Preparing Garden Soils for Spring Planting

January Garden class stacy teaching

Spring Garden Classes begin in January.

The season ahead is exciting. We have a new series of Garden Classes free to fans of this column. Here’s the roster of exciting classes starting in January. We go deep into growing better. Check out this spring’s entire class selection offered every Saturday @ 9:30 am

January 13 – Happy Healthy Houseplants with Professional Style

January 20 – Top Local Landscapes with Flare

January 27 – Why January is the Month to Plant Wildflowers

Until the next issue, I’ll be helping gardeners here at Watters Garden Center.

Ken Lain can be found throughout the week at Watters Garden Center, 1815 W. Iron Springs Rd in Prescott, or contacted through his web site at WattersGardenCenter.com or  Top10Plants.com.