Do orchids like coffee grounds? Here's why experts warn to be careful with this DIY fertilizer

Making your own fertilizer can involve using up household waste and getting creative - what's not to love? It's important to think carefully about what you're feeding your plants, however, so that they can reap the benefits and avoid adverse effects.

If you care for orchids in your home, you'll know that they can be tricky to keep happy. You might expect that because coffee grounds are good for plants, using them to fertilize your orchids is also a good idea. However, be cautious with this plant food solution.

Don't panic if you've already put coffee grounds on your orchids because it does offer some benefits. Find out below what plant experts told us when we asked if orchids like coffee grounds.

Do orchids like coffee grounds?

There are many reasons why you might want to use coffee grounds on plants. For the most part, it offers plenty of nutrients and can boost growth.

'It's a good source of nitrogen, potassium and other nutrients that can promote healthy growth and flowering,' says Jana McDaniel, garden expert and founder of First Saturday Lime. 'The grounds also help to acidify the potting mix slightly, which many orchids prefer,' she adds.

You'll often notice NPK plant fertilizer numbers on plant food bought from suppliers. This refers to the amount of nitrogen, phosphorus and potassium in the fertilizer - all of which help with growth.

For indoor flowering plants like orchids, phosphorus can be particularly important to encourage orchids to bloom for longer.

Phosphorus is present in coffee grounds, although not so much as other nutrients like nitrogen which boosts photosynthesis and growth.

Jana McDaniel

Jana is a garden expert and founder of First Saturday Lime, an eco-friendly pest control company. She has grown up tending to gardens and animals and now advises on gardening matters.

Risk of mold and root rot

But just because coffee grounds can offer nutrients for your orchids, doesn't mean you should rush to put them in your orchid's pot.

'Orchid roots need a very loose growing medium that drains well. That's why they're commonly grown in bark,' says Annette Hird, expert gardener at Easy Urban Gardens.

'Coffee grounds are usually very fine and so they would change the structure of the growing mix. Plus, when they dry, they can form a fairly hard crust which is not ideal for an orchid growing medium,' she adds.

In their natural environment, orchids grow on tree trunks as epiphytes. That's why they have orchid aerial roots that need repotting as they grow larger. Placing orchids in a heavy potting mix or soil will suffocate the roots and not allow them to drain properly, leading to houseplant root rot.

By placing coffee grounds in your orchid pot, you risk reducing its ability to drain - especially when you water your orchid and the grounds make a paste that hardens when dry.

'Coffee grounds will eventually develop mold that may do more harm than good for the plant,' notes Carmela de Castro, owner of Orchid Republic Floral Boutique.

A build-up of mold on your orchid's potting mix could risk common houseplant pests, as well as keeping the potting mix damp and unfavorable for your plant's health.

'Orchids have very specific needs and behaviors compared to the average houseplants, which is why some DIY fertilizers may not work as well to them,' Carmela adds.

Annette Hird

Annette Hird has an Associate Diploma in Horticulture and is an urban gardening expert. She has worked as a professional propagator and managed, maintained and improved many urban and rural gardens. She also enjoys growing her own fruit, vegetables, herbs and flowers as well as many different types of ornamental plants.

Carmela de Castro

Carmela is the owner of Orchid Republic Floral Boutique, a luxury florist with boutiques in Sherman Oak and Santa Monica, California. She specialises in bespoke flower arrangements, orchids and succulents.

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FAQs

How do you use coffee grounds on orchids?

Experts warn to be cautious when using coffee grounds on orchids, due to their ability to cause root rot and mold. However, coffee grounds do bring lots of nutrients to orchids and you can use them carefully to boost orchid growth.

'I recommend working them into the top inch or two of the potting mix when repotting your orchid,' says Jana McDaniel, garden expert and founder of First Saturday Lime. 'Use about one part coffee grounds to four parts potting mix. Be sure the grounds are dried out first before mixing them in,' she adds.

Always use coffee grounds on orchids sparingly and don't rely on it solely to provide your orchid with sufficient nutrients.

Coffee grounds can provide orchids with lots of nutrients, but their consistency can block the drainage of orchids and have adverse effects. If you choose to use coffee grounds on orchids, do so carefully and sparingly and ensure your orchid is still able to drain properly.

Discover other kitchen waste to use on your plants, including rice water on orchids, orange peels which are good for plants and banana peels which are good for plants.