My good friend, George asked me about the benefits of caffeine in gardening and I couldn’t resist answering it in a post as it’s such an interesting question. We all know caffeine as a great stimulant, but does that carry over to the plant world too?
Where Does Caffeine Come From?
Although it’s ubiquitously found in homes all across the country, caffeine is actually a toxic chemical produced by plants to help ward off predators. It’s shocking to find out that the very chemical we use to wake us up was made to put us to sleep. As insects suck away at the sap of the plants, they ingest fatal levels of caffeine which can lead to infertility, paralysis and death.
Spiders on different chemicals
As you can see from the image above, spiders exposed to caffeine have the most disjointed mental processes, and consequently, the web seems to follow no real set pattern. This is perfect from the plant’s point of view and an example of caffeine’s paralysing effects along with reducing co-ordination.
However, one of the biggest problems with a plant producing caffeine, is that it’s harmful to the plant itself and, if left unprotected, it would have more problems than a few flies. To counter this, the caffeine is stored in a vacuole (a sealed off compartment cell) so that it is only released when the cell walls are punctured. Nature really does feel like an endless war between magicians at times.
Most of the caffeine we consume comes from:
The kola nut
Coffee beans from the coffea genus
Leaves from the camellia sinensis (tea) plant
Using Caffeine As A Growth Aid
Humans get that lovable caffeine buzz (followed by a head pounding caffeine crash, of course) at around 30-40mg. Now, as with many drugs, this is subject to factors like tolerance, setting, method of administration and such, but for now we’ll go with 35mg to make things easier. Since the average plant weighs far less than you or I, this seems like a bit much to give your tomatoes. But, because they don’t metabolise caffeine in the same way we do, the exact figure needed is really up for discussion.
Before we start giving our plants anything though, we need to figure out a way to give it to them.
Brewed tea/coffee
Using coffee is a great idea and will definitely give your plants a boost, but this could be down to the potassium and not just the caffeine, so it’s very hard to get an idea of how effective it really is. The effects will be most prominent in popular crops such as: tomatoes, celery and potatoes, so even if they don’t respond to the caffeine content, you’ll definitely work on any potassium deficiencies.
Caffeine pills
While caffeine pills are a great source for caffeine in humans, the pills contain a number of harmful chemicals that can damage your plants. The ones on my desk right now contain: caffeine anhydrous, dicalcium phosphate (used as a filler to bulk out the tablet), cellulose (to help bind the tablet), magnesium stearate (another filler) and silica (stops tablets from sticking together).
The solution (no pun intended) here is to use a mixture of pure caffeine powder and water to eliminate the effects of any excipients (binders/fillers) and give a more accurate view of the effects on your average houseplants. If it’s going to work, this will be the chance, right? Well, maybe. Unfortunately, most tests I’ve found haven’t been too promising. In fact, quite the opposite as the researchers found at Dawson College.
Coffee grounds
This is another contentious one because again, it can’t really be proven that it’s not the nitrogen that helps plants grow. I’d still recommend that you add them to your compost as they’re a fantastic organic fertiliser. Starbucks are generous enough to give away free 5 pound bags at their stores as part of their recycling program and there is no limit on how much you can take.
If nothing else, they will definitely work for growing mushrooms and I’d recommend them above all soil types for that reason.
Conclusion
My theory is that plants just don’t metabolise caffeine in a similar way to humans and they store it in sealed containers for a reason. It’s very likely that caffeine will damage and possibly even kill your plants, so please be careful when using it around your prized plants. I’d recommend using a solution of 50% pure caffeine, 50% water on a patch of weeds first.
On the plus side however, we can put it to use as an insecticidal spray, which will help your plants to grow (though mainly through not letting them get eaten to death). Dilute about 1/2 of a cup of coffee with 500ml of water and spray it around (not on) your garden to keep those pesky pests at bay.
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{ 16 comments… read them below or add one }
Thanks man. A simple it’ll kill it or it’ll work would have done. But as always you get into the gardening zone and bam another great post.
I’ll be saving my spent coffee and tea for the compost heap. Plus my pipe ashes. Makes me feel more personally connected in some way.
I will keep you posted as to the effects of the new coffee enriched diet of my plant brood.
Thanks for the post! A lot of good information.
But I was wondering, have you tried it in your garden as an insecticide?
Hey Adam, I have indeed and although I’m only one set of results, they’re positive ones. I poured it around my pot set to stop the caterpillars from killing my basil again and it’s doing great so far.
From looking at your site though, I wouldn’t recommend using any of that, it looks far too good to pour on the floor.
With this information, I am surprised the coffee companies aren’t marketing their beans as useful for gardening :]
This would be a great news for companies that produce caffeine. It’s also great to know that this caffeine has lots of beneficial factor not only to mankind but also to plants. Great post by the way, a very interesting and informative post.
I use coffee grounds for my compost but was told recently that they are also a good way to keep snails and slugs away from delicate plants. Not sure if this is correct though. Very interesting blog.
Coffee grounds has worked in gardens for years. My parents use to do this when I was young in their garden. It sure made their garden soil more rich and they always had a great big garden and a lot of vegetables came out of it. You know I had forgot about it, but when I seen this post, it sure brought back lots of memories.
My parents are, and always have been, very keen gardeners and also have a vaste range of indoor plants. They have used tea (last drains in the kettle) to water their houseplants for as long as I can remember. I have never really known why, or even if, this was agood thing but I guess it must be. Maybe you are right about the potasium being the real benefit but mum will continue to water her plants with tea regadless.
This is the right way to do gardening – with stuff that nature gave us and not chemicals.
Would coffee that stays and you don’t want to drink anymore also work? Maybe if we put some water to it?
That’s a very interesting post – thanks a lot. We all know about the harmful side effects of pesticides for humans, animals and the environment…, Now I’m wondering if coffee grounds could act as a healthier, more natural replacement for pesticides?
You learn something new every day – I have got to say I have never heard of using coffee in the garden! That spiders web is crazy, but in an aesthetically pleasing way. Maybe you should have added in your conclusion that we would be better off consuming the coffee ourselves – that way we would have the energy to spend more time in the garden, which would lead to a better garden and healthy plants anyway!!!!
I remember my grandma always used to mix used coffee from the cafetiere and mix it with soil!
When I was growing up we had a compost pile, and always added the coffee grinds and paper filter to the pile. I will try the coffee “spray” and see if that keeps my plants from being eaten..since nothing seems to work. Great article.
Mike Perry, caffeine does keep snails away from the plants. This is what I’ve had in my experience.
Spent coffee is great for compost as the poster stated earlier. Don’t forget egg shells, and mix in a little peat moss. The pipe ashes sounds like one I never heard before however bonfire ashes do go into my compost.
I had no idea that coffee was so stimulating to plants. And that picture of what spider webs look like on different chemicals is really amazing. It makes me a little concerned about drinking coffee!!
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