Enjoying a Morning Cup of Coffee with My Houseplants

by Jane Malec, EMGV

A morning cup of coffee is a necessity at my house. It is just a part of getting the day started and I love everything about it — making it the night before, turning the pot on in the morning, and the aroma when it’s brewing. Over the years our coffee habits have changed due to the ever-fluctuating studies on the healthiness of, optimum consumption levels, or brew strength of a cup of coffee. It’s mostly decaf and fewer cups for us now.  Still, it remains a force of habit to pour the same level of water and ground coffee beans into the brewer regardless if we are running out the door or having a leisurely morning. Even if I reheat a cup later in the day, there is always a little left over brew sitting in the pot.

So I often walk around the house pouring the remaining cold coffee onto thirsty house plants. Our current home has a private well and I am ever more conscious of water usage. I make sure to pat myself on the back over my dedication to water conservation with every cup of coffee that soaks into the potting soil. I even wander outside to share the wealth with my container plants. A win-win, right? Or, maybe not. If there is a debate on human coffee consumption, I suddenly wondered if there might be one on plant consumption.

Coffee comes to us through a complicated path. To begin with, there are several species of coffee plants or trees, the two most commonly grown are Coffea arabica and Coffea canephora which is also called Coffea robusta. Arabica coffee is considered superior and commands a higher price than the robusta. Coffee production is a labor intensive process. The berries are picked by hand, sorted and allowed to ferment which removes a gelatinous tissue layer. Then they are washed with large amounts of fresh water. The seed of each berry, which is the bean, is roasted and then ground before becoming the beverage we enjoy. The degree of roasting the beans will determine the flavor, but not the caffeine level. Interestingly, the lighter roasts contain more caffeine so watch out you breakfast blend drinkers!

Which leads back to my curious question — is liquid coffee good for plants? There is a good amount of anecdotal information (on the Internet) concerning the use of brewed coffee for watering plants. However, there is little research-based information on this nor on liquid coffee’s benefits to soil.

However, there are some basic guidelines to help us understand if my “coffee watering practice” is helping or harming to plants. While coffee grounds tend to have a pH around 6.5 to 6.8 which is nearly neutral on the scale (neutral is 7), brewed liquid coffee is reported to have a pH level ranging from 5.2 to 6.9 depending on the type of coffee and how it is prepared. The lower the pH the higher the acidity; A drop in one full pH equals a factor of 10. For example, if the brewed coffee is 5.5 pH and the grounds are 6.5 pH, the brewed coffee is 10 times more acidic than the grounds.

Understanding that most plants like a slightly acidic to neutral pH and factoring in that most municipal water is slightly alkaline (pH greater than 7), it is possible that the acidity of the coffee could benefit plants. Also there are small measurable amounts of magnesium and potassium which are plant nutrients. Keep in mind that this information can only serve as a guideline as there can be other factors in play, for instance, if you have a private or community well, and whether or not you use a water softener.

The best recommendation is to follow some simple rules. Make sure the coffee is cold and then water it down. Never water with coffee if you add milk, cream or sugar. Know your plants pH happiness levels and then watch the impact this is having on your plants over time.  Adjust your morning coffee routine.   

Remember too much of a good thing is, well, too much of a good thing. Resign yourself to pouring some of the leftovers down the drain or on your compost pile. 

Maybe I could starting singing to my plants instead?  Hmm. 


Coffee as Fertilizer?

Yard and Garden

Clay soils


Best Practices for Container Gardening

by Andrea Laine, EMGV

Containers enable practically anyone to cultivate a garden. Containers can be placed inside or outdoors. Annuals or perennials, flowers or vegetables can be grown in containers. Herbs are especially well-suited for containers, and even trees and shrubs can be contained. Success lies in matching a plant’s growth requirements and growing conditions (Right Plant, Right Place) to the appropriate container and following good planting practices. Here is a primer on best practices for container gardening outdoors.

Choose plants with a confined or compact growth habit. Most annuals fit this description as well as nearly all leafy green vegetables and some fruit trees – apples, peaches and figs. If perennials are your choice, look for ones labeled “bush,” “dwarf,” “miniature,” or “specifically bred for containers.”

Container Depth and Diameter
Match the size of the container to the plant’s growth requirements. You want to give the roots room to spread and take hold.

  • Annuals have shallow roots so a 6- to 8-inch depth container will do.
  • Perennials or plants with a taproot (carrots) require greater depth — 10 to 12 inches.
  • Herbs can thrive in 4- to 6-inch depth.
  • Shrubs and trees need a depth and diameter of 12 inches each.

The number of plants you intend to include in one container and their size at maturity are factors to consider when choosing the diameter of a container. In general, larger containers do not dry out as quickly and are less likely to restrict growth, flowering and fruiting.

Container Material
Be mindful of the porosity of the container you choose.

  • Nonporous: plastic, metal, fiberglass, glazed
  • Semi-porous: wood, pressed fiber
  • Porous: clay, unglazed ceramic, terracotta
semiporus container kathleen_moore ccby20
Containers made from wood are semi-porous. credit: Kathleen Moore cc by-2.0

Porous containers like terracotta lose moisture more readily. They are ideal for growing plants that prefer drier conditions like cacti or succulents. Nonporous materials will hold moisture in, thus require less frequent watering. Unglazed ceramic is not recommended for a winter garden it is capable of absorbing water which under freezing conditions may cause the pot to crack.

Container Drainage
Holes are necessary in ALL containers! This is a conundrum for those of us who are drawn to the many attractive containers on the market that do not offer drainage. Once upon a time, people would add stone or gravel to the bottom of the container to create drainage. The experts now recommend against doing that because it causes water to collect in the potting mix just above the gravel. Only when no air space is left in the potting mix will the water drain into the gravel below. In the meantime, plant roots are standing in water and developing root rot. Double-potting is the solution. Put the plant in a pot with drainage holes and place it inside the pot without holes. Remove the pot to water and drain.

Container Color
The color of the container also comes with consequences. Dark-colored containers will absorb heat. This is a plus in winter, but could be a drawback in summer as the potting mix will heat up and dry out. Avoid placing dark- colored containers in full sun. Metal containers also get very hot in the sun as do blacktop driveways. Containers placed on black-top surfaces may need extra care.

Potting Mix
Do not use soil from your yard! Purchase a quality potting mix or medium made especially for the type of gardening you will do. There are commercial mixes that are customized for indoor gardening, outdoor gardening, vegetables, cacti, African violets, orchids, etc. These mixes will have the right balance of fine and coarse textured components for what you want to grow. Plus there will be no weed seeds, disease or insects.

5-Steps to Planting Success
You’ve chosen a container, plant(s) and potting mix; Now it’s time to pull it all together and assemble your container garden. Aim for the soil line to be a quarter- to 3-inches from the top of the container. Plant the crown at the soil line.

  1. Fill container one-third with lightly damp potting mix.
  2. Remove plant(s) from its nursery container. Gently splay roots. Center plant in pot.
  3. Fill potting mix around the roots and up to the crown. Spread potting mix evenly. Do not tamp down the potting mix.
  4. Water well – until water drips from the container’s bottom. This initial watering will settle the potting mix. Add more potting mix if a water well forms.
  5. Top dress with mulch to reduce moisture loss. Be sure to keep mulch a few inches clear of the plant stem so air can circulate. Scatter pine cones or the spiky fruit of a sweetgum tree on top to discourage critters from digging.

Now sit back and watch your garden grow. Don’t forget to water regularly, fertilize periodically, and always site the container according to the plant’s light and temperature needs.

Photo Credit: Creative Commons BY-SA 3.0

Master Gardener Handbook: Plants Grown in Containers

Container Gardening Planting Calendar for Edibles