Kitchen Scrap Fertilizers: Waste of Time?

Kitchen Scrap Fertilizers from Farmhouse38.comWe’ve been composting for awhile here at the Farmhouse (see my composting set up here). I love being able to hang onto kitchen waste for a higher purpose. Some scraps go as treats to the chickens and parrot, while others go into a special compartment in our freezer (so they don’t attract flies) before being taken outside to the compost bins. But I was unaware until recently that certain scraps, mainly eggshells, used coffee grounds, and banana peels, can allegedly go straight into the ground as fertilizers.

There are a ton (okay, slight exaggeration) of these three things going into our compost bins, and so when I realized that they could possibly skip the bin and be applied straight, I got real excited. Because these are the things I get excited about. What.

So I broke out good ol’ Google, and I started doing some research. And just like anything that you hear going around the internet, I came up with really mixed messages. Allegedly, coffee grounds add nitrogen to the soil, and as such, are great as fertilizer for any acid-loving plants. But you’ll find people out there also warning you that they can make the ground too acidic. And you’ll find people saying they do absolutely nothing. Great. Banana peels, buried in the soil near the roots of the plant (or dried and processed into a fine powder), are thought to be a slow-release dose of potassium and phosphorus, as well as magnesium, calcium, nitrogen, and sulfur, and are especially perfect as a rose fertilizer. In fact, banana peels have been used as such since the Victorian era. And yet, you’ll also find people saying they do absolutely nothing. And that the garden rodents dig ’em real quick-like. Super. Finally, ground eggshells mixed into the soil around a tomato plant are supposed to prevent the dreaded blossom end-rot. But there are a lot of people who say this doesn’t even begin to work (that the calcium carbonate in egg shells takes so long to break down and be released into the soil, it’s just not worth it). Fantastic. Furthermore, it’s nearly impossible to find anyone committing to how much of any of these ingredients you should add to your soil. Which is frustrating, and also a bit suspicious. Is this all just wives’-tale-ery?

So what do I do? Test it for myself, that’s what.

Let’s start with adding eggshells to the tomato planting process. Tomatoes need calcium in order to resist blossom end-rot, and there are many conventional products on the market that can be added to combat this. But I don’t want conventional. I want to use my garbage. I’ve got a lot. The Ladybirds make sure of that. And you need a lot of eggshells for this (depending on how many tomato plants you’ve got or plan to have). As you use the eggs, rinse and then store the shells in a bowl in the fridge. I saved up about two dozen for this first trial run.

Kitchen Scrap Fertilizers from

The eggshells pass general inspection; ready for processing. Transfer them to a baking dish or cookie sheet.

Kitchen Scrap Fertilizers from Farmhouse38.comWhen you’re ready to process them, heat your oven to 200-250 degrees F and bake them in a baking pan for around 30 minutes (or until all the moisture is cooked off of them. If they start to brown a little, that’s ok). When the time is up, pull them from the oven and let cool. Now pop them in a food processor (or coffee grinder) and pulverize them into as fine of a powder as you can get them. The finer the powder, the quicker the calcium will break down in the soil. Apparently.

Kitchen Scrap Fertilizers from

This batch of two dozen eggs generated a half pint of egg dust.

Your (hopefully) magic egg dust is ready to use! Allegedly, the most ideal time to use it is when you transplant your seedlings; you place it in the bottom of the hole. But here’s where I could find no information on just how muchΒ you are supposed to use. So I am going out on a limb and trying several different quantities to see if there is any variation in results. In a few of my plants, I will use 1/4 of a cup sprinkled in to the bottom of the transplant hole, for a 4-inch pot sized seedling, in a few I will do 1/2 cup, and in a few more I will try 3/4 cup . I will report back on how this works; in previous years, I have always had a few plants suffering from blossom end rot–so we shall see how things go this season.

Kitchen Scrap Fertilizers from

1/4 cup of egg dust sprinkled in the bottom of the transplant hole.

Kitchen Scrap Fertilizers from

Another application method would be to sprinkle the egg dust around the soil at the base of an existing plant, and work it in.

So let’s move on to coffee grounds; acid-loving plants, such as hydrangeas, camelias, and azaleas can benefit from the application of coffee grounds. Even for plants that like it a little acidic, such as roses and tomatoes, they can be used sparingly. Supposedly, worms love them (and they’re great for adding to vermicompost). But…of course, when you start reading all the information out there about this, you undoubtedly run into the same cautionary tale: coffee grounds are great, but don’t use too much! Dear Zeus, no! Not that! And then, beyond that, there are plenty of accounts of how they do nothing at all. Great. Awesome. So how much is too much? Of course, no one wants to commit to this, and just like the eggshells, there are no quantity guidelines. Super. Thanks, The Internet.

So once again, I must go my own way. While I allow a good portion of our grinds to go out and into the compost bins, I reserve some in a bowl in the fridge. When I’ve filled the bowl (approx. 8 or so cups of used grounds), I place them in a baking dish and pop them in the oven (alongside the eggshells) for a half hour at 200-250 degrees F to dry them out. The reason for this is that damp grounds have a tendency to grow mold pretty quickly and this helps to prevent it.

Kitchen Scrap Fertilizers from

Bake them till they’re nice and dried out.

It seems as though there are several methods out there for applying the grinds. Many people will make a mulch of it around their acid-loving plants (and the thicker this is, the more likely it is to grow mold, so go thin with it). But if you’ve got chickens, this is not a good idea. Coffee grounds=sick chickens. So I prefer the idea of burying them pretty deep down by the roots of the plants–we’re talking several inches here. How much coffee grounds? Again, I have found no direction with this. For my rose bushes, I decided, at random, that I’d go with 1/4 cup to 1/2 cup, buried in a hole near the roots. My hydrangeas are all in the front yard, and therefore, out of the reach of chickens, so I’ve been applying coffee grounds as a mulch basically whenever I have them. I should also mention that I take any leftover coffee and, after it has cooled off, water my hydrangea bushes with it. So, they are pretty much coffee addicts at this point. In previous years, my hydrangeas have been pink, indicating the soil being neutral to basic–if the coffee grounds do their trick, the hydrangeas should become more purple to blue. They are leafing out now, so I’ll have my answer soon.

Kitchen Scrap Fertilizers from

My hydrangeas previously…pretty basic. πŸ™‚

Finally, we come to the banana peels.

Kitchen Scrap Fertilizers from

These were kicking it in the freezer with the rest of the kitchen compost waiting to be used, so they have a little extra debris stuck to them.

As I mentioned before, banana peels have been used as a rose fertilizer for a long, long time. Burying a single banana peel at the base of the plant is the simplest way to do this. As the peel decomposes, it releases nutrients into the soil; nutrients that roses, especially, are said to thrive upon. Some people suggest drying the peels and grinding them into a fine powder (to speed up the absorption process), but I feel like that’s a lot of extra work. So I went with the peel.

Kitchen Scrap Fertilizers from

I dug a hole several inches deep near the roots of each rose plant, and placed a banana peel and 1/4 cup of used coffee grinds in the bottom of it: a little nitrogen, potassium, and phosphorus cocktail.

Of course, truly the only way to be sure of what’s going on in your soil is to do a soil test. I really want to know if these methods work, so I tested my soil in each spot before application, and I will test again in a couple of weeks and see if there is any change, and then I’ll come back through and report my findings in this post.

Kitchen Scrap Fertilizers from Farmhouse38.comI should note that over-the-counter calcium tests are not super easy to come by, that I know of– so I’m probably just going to sit around and wait to see if I still get blossom end-rot. The tomatoes. Not me. In related news: does anyone know of an easy calcium test?

I’m curious to hear from anyone else who has tried these fertilizers; please comment and let me know your experience!

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30 thoughts on “Kitchen Scrap Fertilizers: Waste of Time?

  1. Julie @ Garden Delights March 12, 2014 at 1:12 am Reply

    I can’t wait to hear your results! I use the egg shells, but mine are coarser–supposedly the jagged edges of the shells also help prevent slugs? But then, of course, the shells don’t decompose as quickly to add the calcium. Huh. A conundrum. I love that you’re doing this research for us! πŸ™‚

    • farmhouseK8 March 12, 2014 at 1:21 am Reply

      LOL–thanks, Julie! Yeah, I’m definitely not going about this as scientifically as I’d like–but at least it’s something!!!

  2. cindyricksgers March 12, 2014 at 2:41 am Reply

    My compost is 90% coffee grounds and egg shells. When I generate a little banana peel/orange rind/carrot paring too, I feel like an absolute health nut! I’m a lazy composter, never turning my pile or concentrating too hard on getting it hot enough, so am anxious to hear your results. I too have read all of the mixed messages, but wasn’t keen enough to do my own tests. Thanks!

    • farmhouseK8 March 12, 2014 at 5:38 am Reply

      Oh thank you for sharing! LOL, I am lazy with the compost, too–but it’s kind of flexible (at least mine seems that way!).

  3. yourlatherapist March 12, 2014 at 2:44 am Reply

    I so want to have my own little garden when I move πŸ™‚

    • farmhouseK8 March 12, 2014 at 3:27 am Reply

      It’s really such a rewarding thing in so many ways!! πŸ˜€

      • yourlatherapist March 13, 2014 at 12:39 am

        I can’t wait!! I’ll have to keep a close eye on my bunny so he doesn’t figure out a way in lol

  4. home, garden, life March 12, 2014 at 12:44 pm Reply

    Kate, I always save all eggshells from hard boiling, dry on the counter overnight, then grind in my spice grinder. Then 1/2 C goes in to my wild bird food: see recipe at This is especially great for wild bird during the nesting season, yet during the winter, even better.
    Your idea of baking raw shells is splendid, since the girls produce plenty of them. Kudos.

    I don’t drink coffee, yet when Whole Foods was giving away grounds from their barista counter, I brought 10# home and dumped them all into my composter.

    Soil tests are the only really way to know what our amendments are doing to our soil. Not sure if I trust the OTC kits. Your extension service is the best route, although pricy.

    Your efforts are commendable, Kate, and I will look forward to reading your FU reports.

    Right now I am experimenting with Moo Poo Tea from
    This is sun tea made with cow poo, served up in cute little muslin bags. I plan to use on all my peonies as they emerge and any seed starts. Check it out. Annie is another fine woman-owned business in CA.

    We are almost spring-like here in central VA. so I have a few weeks to enjoy the daffodils before the biting insects begin.

    Have a great growing season, oh talented one. Diane

    • farmhouseK8 March 12, 2014 at 2:52 pm Reply

      Thanks, Diane! I actually have been using Moo Poo Tea on some of my stuff for a couple of years! Love it! I actually just ordered more–and it’s gonna be part of my experimenting–I saved a whole part of my garden for that.
      I’ve been contemplating whether I should take the soil to be tested somewhere–but probably the best thing to do is test it with the OTC and then ALSO take it to a professional. Find out how accurate the OTC is, while I’m at it!! πŸ˜€
      Thanks for commenting, Diane!

      • home, garden, life March 12, 2014 at 8:00 pm

        Do let us know how accurate the OTC test is. Thanks! Diane

  5. Lilah March 12, 2014 at 1:14 pm Reply

    I had blossom end rot on my tomato last year. I used the calcium carbonate in pomonas canning box and it fixed the tomato.

  6. Bev March 12, 2014 at 3:03 pm Reply

    I am so jealous of your hydrangeas that are already leafing out! I am looking out my window at a lovely gentle snowfall. But enough already! I am soooo ready for plants to be leafing out around here. BTW, I love your writing style. I think it is how I would write if I had a blog, which I do not…yet . In the meantime, I will enjoy reading yours. Thanks!

    • farmhouseK8 March 12, 2014 at 5:30 pm Reply

      LOL–thank you, Bev!! Sending you warm wishes from SoCal–hopefully the snow will give it a rest soon!

      • Katie Gubbe March 28, 2014 at 11:59 pm

        I also love your writing style! This is my first time on your blog πŸ™‚
        It’s very relatable and easy to read, yet gives great information. Very friendly.

      • farmhouseK8 March 29, 2014 at 12:08 am

        Thanks, Katie!!! πŸ˜€

  7. Gail Saito March 13, 2014 at 3:59 am Reply

    Kate…I am so happy that you are conducting these tests. Now I don’t have to, as I will rely on your results! I also do the egg shell “thing”. This will be my first year. And as I have my coffee grinder out for the egg shells, I am grinding peanut shells for my compost pile, as it seems to take forever for the whole ones to break down. And by the way, my friend Bonnie has a web site with stuff for your bird And while you are at it, check out my web site for all of your seed ball needs
    Love your posts. You are a gifted writer!

    • farmhouseK8 March 13, 2014 at 2:11 pm Reply

      Thank you, Gail! I will check out both of those sites! πŸ˜€

  8. roberta March 13, 2014 at 10:32 am Reply

    I feel your pain, it seems most research on the internet leads to more questions than answers, we should be used to it, just like our government… I always have to add those sprays to my tomato plants for blossom end rot. Last year I didn’t buy any and it was my first year with chickens so… I just crushed them up by hand and sprinkled them around each plant, obviously not caring a wit about research! Could be coincidence but I did not have any blossom end rot!! This year I will crush them up and plant it with the roots as well as add them as a top dressing, maybe my water leaches the calcium out of it like it might be doing to my old bones!

    • farmhouseK8 March 13, 2014 at 2:10 pm Reply

      LOL! Interesting! Thanks for sharing, Roberta!!

  9. Charlotte Zweigoron March 14, 2014 at 4:21 am Reply

    Nothing scientific going on here… I heard that banana peels and coffee grounds were good for roses. My roses hadn’t fully recovered from being moved from a former home over 3 years ago. I kept a bowl in my kitchen sink and dumped our coffee grounds in it (we have a single cup coffee maker and made about 3 cups a day) as well as whatever banana peels were generated from banana munching and smoothies (1 or 2 a day); probably a week’s worth before the bowl got full, I dumped it around the base of the rose bushes and, for some unknown reason, decided not to let it actually touch the plant itself. I got the best roses we have had since uprooting the plants to move them to our newer home. They just perked right up! The difference in the plant was noticeable within several days. I will be looking forward to your test results.

    • farmhouseK8 March 14, 2014 at 3:59 pm Reply

      Thanks, Charlotte! So many people swear by this–I’m excited to see how it goes. The roses that I applied this stuff to are ones that have kind of bummed me out in recent years–so we shall see. I don’t know if I am just being overly optimistic here, but they already look pretty amazing (plus we had an incredible rain storm a couple of weekends back) and have their first buds on them. Anyhow–thanks for sharing!! πŸ™‚

      • Katie Gubbe March 29, 2014 at 12:03 am

        I think it’s good to be overly optimistic with your plants. Any plant well cared for and lived will be healthy and happy… Hippy dippy, right? But seriously, loved plants always do better than plants who are just maintained.

      • farmhouseK8 March 29, 2014 at 12:08 am

        I so agree, Katie!! πŸ˜€

  10. Shannon March 18, 2014 at 8:35 pm Reply

    I’ve tried each of those and have had *meh* results. Best growing in my garden by FAR is wherever the compost used to be. (When I flip it, I plant in the bottom portion of the old spot straight away. Healthy, heavy-producing, ginormous, HAPPY plants there. Always.) I give the coffee grounds to gardenia and hibiscus exclusively. All but the hardiest rose varieties hate me, bananas be damned. I’m curious how your experiment will go!

    • farmhouseK8 March 18, 2014 at 9:03 pm Reply

      Oh, thanks for sharing, Shannon!!! I’ve heard this same report many a time.
      Also–I just moved my compost bins and I’m super curious to see how well things grow where they used to be!! LOL

  11. Katie Gubbe March 28, 2014 at 11:53 pm Reply

    So excited to check this again in a few weeks! Members of the WA state chicken club told me to bake my egg shells the same way before I give them to my chickens so that they’re easier to peck at. That was the first time I’d hear that, so interesting that I’m seeing that technique again!
    I also use crushed eggshells in my garden for slug protection for my plants. It’s kind of gnarley, but when they crawl over them it cuts them open and kills them… Which makes me feel bad for them but youve gotta do what you’ve gotta do.
    I always fertilize my roses with coffee grounds, just dig some in every once in awhile, not really measuring.
    Like I said, so excited to see your results!

  12. Sourav April 25, 2015 at 4:22 pm Reply

    How are your plants doing after you applied the banana peels? Did it worked?

    • farmhouseK8 May 3, 2015 at 3:03 pm Reply

      There honestly wasn’t really any difference. I need to do this in a more controlled manner to really test it well.

      • Sourav May 3, 2015 at 3:07 pm

        Thank you FH for the response. In my case also no change. I made banana peel juice and poured it on the soil. No visual difference on plants health and no aid to blooming. I think the way this banana peel stuff is promoted in the internet … I mean its overrated.

        Please keep us informed and I will also let you know if anything works on my side.

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