Can Coffee Boost Your Christmas Cactus Blooms? Here’s What an Expert Says

We recently heard from a Better Homes & Gardens reader who shared their Aunt Mabel’s secret to making a Christmas cactus bloom. “She gave it ½ cup of cold coffee once a month. It works on ours, also,” they wrote. Plenty of TikTok videos tout coffee as a bloom booster for Christmas cacti, too.

So, is coffee really a magic potion that will get your plant to flower? To find out if this recommendation holds up to the science or if it’s actually not helpful, we checked with a plant expert who left no doubt on the subject.

Is Coffee Good for Your Christmas Cactus?

Chelsea McKinley, plant health care specialist at the U.S. Botanic Garden in Washington, D.C., says coffee is not good for a Christmas cactus, or any other houseplant for that matter.

“My recommendation would be to stop doing weird things to your plants,” she says. “I get that people are trying to reduce their carbon footprint and use sustainable materials when they garden, but there’s not a lot of science or research behind it.”

Coffee is Not Fertilizer

“While coffee contains very small amounts of nutrients, like nitrogen, they are negligible,” McKinley says. The nutrient that plants need to make buds and blooms is phosphorus, yet coffee contains none.

To get your Christmas cactus to bloom, look for fertilizers with a high phosphorus content. That’s the middle number on a fertilizer label, so look for a 10-30-20 or a 5-10-5 ratio. Want to stay away from synthetic fertilizers? “There’s a lot of organic options out there nowadays that are proven to work,” McKinley says.

If you are determined to use coffee to feed plants, compost your used coffee grounds, then brew compost tea. Composting coffee grounds is the best way to get their full potential to feed plants, McKinley says.

Coffee is Not a Reliable Soil Amendment

Christmas cactus likes slightly acidic soil, and coffee can lower the pH in the soil, McKinley says. But she advises against using coffee as a soil amendment. The reason? It’s impossible to know the pH for that coffee you pour on a plant because there are so many variables. Coffee pH ranges from 3.7 to 5, McKinley explains. Light roast coffees are more acidic than dark roasts.

Where the coffee is grown also affects its pH, as does the variety of coffee and the strength that it’s brewed. So you’re dealing with imprecise pH levels and no guidelines for usage. That’s a problem because potted plants like Christmas cactus don’t have enough soil to protect against human error, unlike plants that are grown in the ground. Potted plants are much less forgiving of iffy gardening techniques, like pouring coffee on them. It doesn’t take much to overdo things and create unfavorable conditions for your plant.

But what about Aunt Mabel and her Christmas cactus? “Sure, coffee might work for this one person using this one coffee. But for you, it may be a completely different scenario,” McKinley says. “Unless you are willing to conduct an experiment where your plant could die, do not pour coffee on your potted plants,” she adds.

Stick with Labeled Products

Assuming you’d rather not risk a dead plant, coffee is clearly not your best bet to get your Christmas cactus to bloom. If you’re worried about providing nutrients to support flowering, “there are numerous regulated fertilizers and soil amendments that have been tested by scientists and proven to work to grow plants,” says McKinley.

The best way to get your Christmas cactus to bloom is to “use products that are reliable, consistent, and uniform,” says McKinley, along with providing the proper amounts of sunlight and water.