Sweet, plump, juicy watermelon is a favorite fruit any time of year, but can you compost the flesh and rind?
Luckily, you can safely compost watermelon. However, in the summer, you may have so many watermelon scraps it can overwhelm your composting system and cause problems.
To help you understand each pro and con of composting watermelon, how long it takes to decompose, and the steps to turn the material into rich fertilizer for your garden, I put all the details in this guide.
Don’t let the vitamins and minerals inside watermelon go to waste. Instead, use them to help your garden grow!
Can You Compost Watermelon Rinds?
Watermelon is an ideal fruit to compost as it contains a lot of water and decomposes quickly. The fruit’s moisture easily balances out dry compost ingredients such as leaves, grass clippings, straw, or cardboard.
Watermelon will contribute these essential nutrients to your compost:
- Vitamin A
- Vitamin C
- Amino acids
Can You Compost Watermelon Seeds?
Watermelon seeds are also a great addition to your composter, adding fatty acids, protein, magnesium, potassium, zinc, and copper to your finished material.
But, with the seed being very woody, you do need to give them extra time to decompose versus the flesh and rind.
If you have a vermicompost (worm) system, I recommend avoiding adding whole seeds to the trays, as worms can’t process the material. Instead, finely chop the seeds before placing them in the tray if you prefer to compost all your kitchen waste.
Pros And Cons Of Composting Watermelon
Completing any variety of very wet fruit or vegetables can cause problems in your compost, so you need to consider the benefits versus the disadvantages of composting watermelon to see if you’re up for the task.
- It is an excellent green or nitrogen compost material
- The rind, flesh, and seeds hold beneficial trace elements that contribute to healthy plant growth
- Adds moisture
- Adds potassium to the compost and simple sugars to feed soil microorganisms
- Recycles a bulky amount of kitchen scraps
- Seeds and rinds need extra prep for faster decomposition
- Can make compost slimy and stinky
- The sweet smell and sugars attract pests like rodents, birds, and gnats
- Requires a watchful eye and extra brown ingredients to keep the compost in balance during processing
Reducing kitchen waste heading to the landfill is an excellent reason to compost watermelon, as we all know how messy watermelon scraps are when you add them to your trash.
Avoiding fruit flies and leaks around your trash can is great. Still, some people may find composting watermelon bothersome as it tends to make the material smelly or slimy.
How Long Does It Take For Watermelon To Decompose?
The amount of time it takes for watermelon to decompose depends on where it’s left to break down.
Inside a composter, it can take as little as five to seven days for watermelon to become unrecognizable.
In a landfill, watermelon decomposition can take anywhere from a couple of weeks to years, especially if the fruit gets buried and the environment becomes anaerobic.
Without oxygen, the watermelon rinds and flesh won’t have enough microorganisms feeding on the material for it to biodegrade. A study known as The Garbage Project has shown that grapes and other similar watery fruit have been found perfectly recognizable inside a landfill after 25 years.
Lastly, watermelon left out on top of the ground can take several weeks up to several months to decompose fully.
Where the watermelon sits plays a significant role in how many pests and microbes feed on the material. Exposure to different weather conditions also plays a role in how quickly the watermelon will break down.
Composting watermelon is the fastest way to reduce the material into a reusable soil amendment by providing the perfect balance of moisture, heat, microbes, fungi, oxygen, nitrogen, and carbon.
How To Compost Watermelon
For fast processing of watermelon seeds, flesh, and rinds, take the time to do it correctly and avoid problems by following these steps:
Step 1: Chop Up Watermelon Scraps
It’s most helpful to chop up watermelon rinds and scraps of flesh into small chunks so that they can break down faster inside your composter.
You can put watermelon seeds into a food processor to break them apart easily, use a large knife to cut them up, or even pound them with a mallet or hammer to crack the casing open.
Whole seeds will take many months to decompose and will often germinate inside your compost if you don’t cut up or smash them first.
Step 2: Discard As Much Juice As Possible
To reduce the amount of moisture going into your composter, drain your watermelon pieces to eliminate all the excess fluid.
Toss the scraps into a strainer and let the juices drip out into your sink for fifteen minutes before bringing them to your compost pile.
You can also spread out the watermelon chunks onto a flat tray and leave it in the sun for a couple of hours to dry up the juice.
Placing the scraps outside will attract insects, animals, and birds, so use a netting material over the top to keep them away.
Step 3: Balance The Watermelon With Carbon Ingredients
Before you toss in your watermelon scraps to your compost, use a moisture meter to see how dry the material is so you can add the correct amount of carbon (brown) material to prevent it from getting too wet.
In general, you’ll want to up your ratio to 3:1 of brown material to watermelon scraps to keep the moisture levels in balance.
If you’re starting a new compost pile and using watermelon as a major ingredient, make sure you work in lots of dry leaves, straw, or cardboard to soak up excess juice to stop the pile from immediately getting slimy and attracting pests.
Mix in some compost starter to provide the beneficial organisms that will process your compost ingredients faster.
Top off the pile with a few inches of dry leaves to hold in moisture and any heat that begins to generate.
Step 4: Turn the Compost Often
To process all your compost ingredients, including watermelon, you need to refresh the energy within the pile by turning the material inside a tumbler or bin every four or five days.
Don’t go more than a week without turning an outdoor compost pile.
For an outdoor pile, dig down with your garden fork to the center of the bank and lift the material to the surface while pushing outward. Take material from the outer edges of the pile and dump it into the middle.
The goal is to bring in more oxygen, mix the green and brown materials, and distribute any liquid.
For a compost tumbler, give the drum several spins to mix up the contents.
For a compost bin, use a compost turning tool that will move the material without making a mess.
Instead of big, bulky watermelon scraps filling up your trash cans and heading to the landfill, you can compost and recycle them into free soil amendment for your yard.
Composting watermelon is straightforward, and with a bit of care, you can avoid common issues and instead reap the reward of nutrient-rich compost for your garden in a few short months!