Another Experiment

moonwolf_gwMarch 31, 2011

Hi everyone,

OK, I'm trying something different with my hoyas. I've heard for awhile now about giving your plants leftover coffee and tea. Dad is a coffee drinker (I usually make it) and sometimes he has a little left over. Yesterday and today, (watering day for all plants, they need water about this time of week), I added the coffee to my watering can (it is diluted of course).

Dad did tell me that a co-worker of his at a previous job gave cold coffee to her spider plant and he said it grew like mad! Maybe my hoyas will enjoy the bath as well! Have any of you done this with any of your other plants?

Brad AKA Moonwolf

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Here in Brazil we use to put the coffee powder in our plants to prevent/avoid ants and I notice that most of the plants love it, but it is the powder (dregs), after the coffee is made, not the liquid.


    Bookmark   March 31, 2011 at 6:27PM
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Brad I guess it all depends on the plant and what conditions it likes. Coffee is naturally acidic so it could possibly acidify the potting mix but then again most mixes we use are naturally acidic and I am sure they have enough buffering capacity to prevent problems. I would not use coffee too often but just every once and a while. Plants normally grow in a fairly narrow range of pH so wild swings will not be good for root health.

One thing you could do that would be great for your other plants is to compost the coffee grounds and filters and use this to top dress or work into the soil.


    Bookmark   March 31, 2011 at 6:33PM
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I did a lot of reading a while back on the use of coffee grounds as a pesticide, as Mitzi refers to, and it's very interesting.

You can spray your plants with coffee to deter insects. It is considered a lethal natural insecticide, paralyzing or causing death. I did read one piece that said that combining coffee with other pesticides increases their potency up to 10x, and you should use it with caution for this reason.

You can use leftover coffee (diluted 1:4) to water your plants, as you are doing. I've read no more than once every other week.

You can spread the grounds 1/4" to deter ants and enrich the soil.

There's a nice discussion of this topic at the link below.

Personally, I cut caffeine out of my diet, but I'd try it if I hadn't.

Here is a link that might be useful: Coffee Grounds & Plants

    Bookmark   March 31, 2011 at 7:34PM
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Thanks, everyone for the information! Hmm, coffee as an insecticide? I wonder if it'll fight off mealies (still finding the little beasts!)

I wasn't going to use the coffee very often and I do wish I had a compost pile. I'd use it on both houseplants and the garden. I just made up a batch of spray (water and coffee) and I'll start spraying them tommorrow.

Brad AKA Moonwolf

    Bookmark   March 31, 2011 at 11:06PM
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If you're still struggling with mealy bugs, this guide does suggest that coffee grounds help.

Since you're into concocting homemade remedies, this page recommends an orange peel spray. It also says that the coffee spray is good for soft bodied bugs, although it doesn't mention mealy bugs specifically there.

And this site describes a garlic pepper concoction that's good for mealy bugs.

Also, you can work to build up the beneficial microbes living on the surface of the leaves and stems, which make the plant healthier discouraging attacks. There are a lot of organic solutions for this, such as using the bottom of a gallon of milk (the last 3oz), mixing in water, and spraying your plant with it. Coffee grounds on the soil also help in this role, at the rate of a handful once a month.

Keep in mind that organic treatments break down quickly, so if you want to have success, you need to really be consistent in your application, over a long period, until you see no more outbreaks. It is possible to avoid using chemicals, but you reallllly have to be serious and intense abut your program! :)

We're all routing for you!

    Bookmark   April 1, 2011 at 12:26AM
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I had one plant in the farm that was constantly atacked by ants. The ants ate all the plants, researching I found that the powder of coffee would be a solution.

So I tried to do that, for several months, I use to put a lot of coffee powder (after making the coffee) the result is that the plants looks great now.

I don't know if they would be the way they are without the coffee, but the ants desappear, they'are gone...

    Bookmark   April 1, 2011 at 9:22AM
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penfold2(4b, MN)

You might want to take a look at this:

Coffee and plants

Some people get good results with coffee grounds, so the negative effects may be tolerable in many situations. But most people seem to use them in the ground where there is much more room for error. Personally, I wouldn't use them in the ground, let alone in pots. There are plenty of other fertilizers without known plant toxins.

    Bookmark   April 1, 2011 at 10:33AM
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That's a good point, Pen, about many of the success stories coming from people using these treatments in outdoor scenarios.

Since there is a lot of division of opinion on this, perhaps it's something to be experimented with in moderation.

I meant to ask, Brad. How advanced is your mealy population at this point? Are you just seeing a bug every few weeks, or is it more intense?

    Bookmark   April 1, 2011 at 11:39AM
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I never used coffee to fertilize the plant, it was used to combat the ants, but the result was great, and I got really surprised. And I used around the stem in the ground.

    Bookmark   April 1, 2011 at 4:14PM
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GG, the mealies are on certain hoyas but not all of them. I can see them if I look closely. I find it odd they like certain hoyas over other ones. They killed my poor lacunosa but so far (luckily) nothing that damaging has happened to any other plant I have.

Brad AKA Moonwolf

    Bookmark   April 1, 2011 at 5:04PM
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pirate_girl(Zone7 NYC)


I hope you've heard that mealies are VERY contagious, especially in a Hoya collection. I'd put the plants still infected in another room from the healthy ones.

Yes, a lot of these home remedies are really for outdoor growing it seems.

Using spent coffee grounds indoors can bring bugs & gnats, I see you've said you'd dilute it in water, still, I'd be careful.

    Bookmark   April 1, 2011 at 5:14PM
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Hi Brad, are you smooshing or swabbing the ones you see with alcohol? Or are you just hoping your plants will persevere and survive?

What DO people do when they have mealy infestations on outdoor Hoyas? I guess I'd always thought about the issue from the perspective of a relatively closed system.

    Bookmark   April 1, 2011 at 5:26PM
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PG, yes I'm well aware of how contagious they can be (unfortunately). I really don't have a place to isolate them.

GG. yes, I'm attacking the ones I can get to (the ones in the leaf nodes are the hardest to get). Nothing bad has happened to them yet, like I said, but it just may be a matter of time. I still haven't sprayed them with my coffee/water mix but maybe tomorrow since it's getting dark and you're not supposed to spray plants in the evening.

Brad AKA Moonwolf

    Bookmark   April 1, 2011 at 6:43PM
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Yeah, you have pretty large plants, so it must be hard to get at them. Mine are all immature, so their nodes are all in clear site (well mostly).

Good luck! Let us know how the coffee works. I hate to be so bloodthirsty, but I just got the biggest rush out of imagining mealy bugs being snuffed out. I'll probably be reincarnated as a mealy bug. That'll serve me right!

    Bookmark   April 1, 2011 at 7:03PM
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Coffee grounds and egg shells are 2 excellent items to use in compost as Mike suggested. Also coffee grounds are excellent for African Violets in particular. About 15 years ago I performed a science experiment with AVs grown and watered w/ coffee vs AVs grown w/ straight water vs AVs grown w/ sugar water. The coffee grown plants looked the best and bloomed the best. The sugar water was second followed by regular watered plants. I received an A on that project but did not get picked to represent the school at the fair. I do not know what would of happened if I continued longer. The experiment lasted 3 months.

At this time I just use it in my compost but am not opposed to feeding a plant or two some coffee every now and again. I don't drink coffee though so I have to pick it up from the bin at Starbucks.


    Bookmark   April 1, 2011 at 9:08PM
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AndrewH(z8 Vanc. WA)

I once tried used coffee grounds and tea leaves as a mulch on a couple plants. It grew mold very quickly and then the fungus gnats were all over the place.

I'll never do that again.

    Bookmark   April 2, 2011 at 4:11AM
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Wait, so it's the caffeine that is bad for plants? (that's what the other thread says..) Can you use decaf coffee grounds then?

Also, for the mealies: swabbing with alcohol doesn't get them all. After researching advice here on the forum, I ended up attaching a spray head to a bottle of rubbing alcohol and just soaking my whole plant with it, (getting in aaaalllll the little cracks) and I have not seen a mealie since. (The plant didn't suffer at all either, but I read that you shouldn't do it while the sun is shining on the plant.)

    Bookmark   May 5, 2011 at 11:40PM
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I have a question about using compost. I have a large compost pile which I use for my veggie & flower gardens outdoors, but how would you bring the compost indoors? Compost has so many microbes...I can't imagine introducing those to my houseplants. Would you sterilize it first?
Hope someone can answer my question.

Beth "Lightning"

    Bookmark   May 6, 2011 at 2:34PM
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