Ask your neighbors or grandma for gardening tips and tricks, and you’ll likely end up with a handful of garden hacks. Sprinkling dog hair to deter deer? Spraying hot sauce to keep away pests? And you can’t forget about burying food scraps in your garden to improve plant growth!
Kevin Espiritu went to work to find out how food scraps impact plant growth and health. He gathered five types of kitchen and garden scraps and designated a control group. He determined which method worked best by checking on the plants throughout their life and measuring the fruits they produced.
I’ll explain what Kevin learned and answer whether or not you should add food scraps to your garden.
The Short Answer
After burying five different types of food scraps and watching tomato plants grow, Kevin determined it’s not worth burying food and garden scraps under your plants. Composting the scraps and then adding the compost to your plants is a better alternative.
The Long Answer
Explore the growth disparities in experimental plants and their potential causes.
Hungry for more details? We’ve got them! Learn about how each experimental plant fared and discover possible explanations of why some plants exploded with green growth while others remained stunted.
The Experiment Setup
A controlled tomato plant experiment was conducted with uniform conditions and irrigation to compare growth outcomes.
As with any great experiment, Kevin sought to keep the conditions as stable as possible between the different test groups. To start, he planted six ‘Italian Roma’ tomato seedlings simultaneously so he would have a test group all of the same age and size. Once they were ready to transplant, he loosened the soil with a broad fork and kept the bed free of fertilizer.
Kevin spaced the tomato plants two feet apart to ensure the nutrients from one food item weren’t available to neighboring plants. He set up drip irrigation on a timer so each plant received the same amount of water.
Since gophers find food scraps delectable, Kevin set the scraps inside wire mesh to keep them from destroying the experiment. I’ve listed the six different experimental groups below, along with the names he gave to each plant so he could remember which group was which.
- Kitchen leftovers, named ‘Tahini’: sourdough starter, tahini pasta, and beans
- Garden scraps, named ‘Oxalis’: plant bits from weeding and pruning
- Fish heads, named ‘Noodle’: whole catfish heads
- Food scraps, named ‘Scrappy’ : bits and pieces of fruits and vegetables
- Fresh eggs, named ‘Eggbert’: whole eggs from Kevin’s chickens
- Control, named ‘Roma’: no material was added
Once each of the plots was prepared with the various scraps, he planted a seedling in each and filled the hole with soil. With the tomatoes in place, it was time to let them grow and take notes.
Kevin and Jacques conducted a tomato plant experiment, monitoring their growth and soil conditions.
Kevin kept track of the tomato plants and noted the plants’ conditions at two and a half weeks, one month, two months, and the end of the season. When the experiment came to a close, Kevin and Jacques examined the vegetation and fruit and dug up the soil to see what happened to the scraps.
One Month After Planting
Plant growth and health varied significantly after one month, with some thriving and others struggling.
A month after planting, the plants showed noticeable differences in growth and health. Some plants were green and bushy, with leaves ready to absorb solar energy and produce fruit.
Other plants were clear losers with stunted growth and yellowing leaves. You may be surprised to learn which plants were on top on this point—I know I was!
At the end of one month, here’s how the plants fared, with the winning plants first:
That’s right, the plant without any added material looked best! This plant had a bushy growth form with many healthy, green leaves.
The plant that received a few cracked eggs and one whole egg, aka Eggbert, was almost as big and healthy as the control plant.
The plant deemed Scrappy had a nice bushy and green form, but it was slightly smaller than the top two plants.
The garden scrap plant, Oxalis, was about the same size as Scrappy and was nice and green.
While the top four plants were green and bushy, the tomato plant with the leftover pasta and beans looked slightly yellow. It was also noticeably smaller than the other plants.
The catfish plant was clearly the worst-looking plant of the group. The plant was stunted and yellow.
Two Months After Planting
Tomato plants thrived and intermingled, showing noticeable differences after two months of growth.
After another month of water and sunlight, Kevin and Jacques checked back in on the plants. All of them were taller and had set fruit, and some plants had grown into each other to create a green jungle.
While some plants looked very similar, there were also noticeable differences. Here’s how the tomatoes looked two months after planting:
The garden scrap plant looked similar to many of the other plants in terms of size, leaf color, and fruit set. However, this plant was free from aphids even though the sap-sucking pests covered the other five plants.
The egg plant was right in line with the other healthy plants in terms of size and color. The plant had some aphids, but not nearly as many as some of the other plants.
The food scrap tomato plant looked pretty similar to the plant that received eggs. It was big and green but covered with a moderate amount of aphids.
Although the control group was still one of the larger plants, it was covered with tons of aphids. The leaves were still green and healthy, but it looked like there were enough aphids to cause some serious harm.
The fish head plant was still smaller than the four plants listed above, but it was covered with many flowers. Kevin suspected this may have been due to the large amount of phosphorus and potassium from the fish heads. And I agree! Fish fertilizer contains both phosphorus and potassium, which help support flowering.
At two months in, the leftover plant was clearly the loser since it was the smallest plant.
The End Result
The tomato plant experiment’s final results analyzed fruit production and food scrap decomposition.
Now’s the moment we’ve all been waiting for – the final results! After months of growing, it was time to harvest the tomatoes from each plant and take notes on fruit production and vegetative growth.
Kevin and Jacques harvested and separated the green and red tomatoes into individual piles. They considered anything more than 50% red as ripe. They then counted and weighed the ripe and unripe fruits to compare the plants’ fruit production.
Finally, they dug up the area underneath the plants to see what happened to the buried food scraps. Did the kitchen scraps fully decompose? What did the fish heads look like now? Well, you’re about to find out!
Tomato harvest data shows the egg-treated plant yielded the heaviest and largest tomatoes.
- Total tomato weight: 8 lb, 7.9 oz
- Average tomato weight: 1.13 oz
- Ripe tomatoes: 27
- Unripe tomatoes: 93
- Total tomatoes: 120
- Vegetation: 2
The plant that received chicken eggs produced the largest harvest and the largest tomatoes. However, it didn’t produce quite as many ripe tomatoes as the control group.
The control group had the most ripe tomatoes, likely due to balanced nutrient levels in the soil.
- Total tomato weight: 7 lb, 14.8 oz
- Average tomato weight: 0.94 oz
- Ripe tomatoes: 72
- Unripe tomatoes: 62
- Total tomatoes: 134
- Vegetation: 5
Although the control group didn’t win the prize of the biggest total tomato weight, it killed the competition when it came to ripe tomatoes. While all the other plants had far more unripe tomatoes than ripe tomatoes, the control group sported more red than green tomatoes.
As Jacques noted, the control group also had less vegetation than the other tomatoes with lots of fruit. This suggests that the tomatoes had enough nitrogen to produce a healthy plant but not so much that the plant prioritized vegetative growth over flower and fruit production.
While I can’t say for sure that this explanation is correct, other studies show that there’s a point at which increasing nitrogen fertilizer rates can decrease fruit production.
High nitrogen content in garden scraps promotes vigorous leaf and stem growth but not fruit development.
- Total tomato weight: 6 lb, 5.4 oz
- Average tomato weight: 0.96 oz
- Ripe tomatoes: 28
- Unripe tomatoes: 78
- Total tomatoes: 106
- Vegetation: 1
Although this plant had similar harvest numbers as the kitchen leftovers and kitchen scraps plants, it had the most vegetative growth of the three plants. Kevin and Jacques suspect this is due to the high amount of nitrogen from the garden scraps, and I agree.
Green materials like weeds and grass clippings are high in nitrogen and low in carbon. This means soil microbes can quickly and easily break them down.
When microbes act on the materials, they make the scraps’ nitrogen available for plant uptake. And since nitrogen is an essential nutrient for vegetative growth, it explains why this plant is larger than others.
The kitchen leftover plant initially struggled but later rebounded due to the breakdown of carbon-rich leftovers.
- Total tomato weight: 5lb, 12.7 oz
- Average tomato weight: 0.99 oz
- Ripe tomatoes: 23
- Unripe tomatoes: 71
- Total tomatoes: 94
- Vegetation: 4
The kitchen leftover plant is right in the middle of the pack in terms of total tomato weight and number of tomatoes. Although this plant was on the losing side at the beginning of the experiment, it bounced back to claim an average performance.
I think that the carbon-rich leftovers tied up nitrogen at the beginning of the experiment, leading to stunted growth. But as time went on, microbes were able to break down the food scraps. This gave the plants a dose of nutrients and allowed them to recover.
The kitchen scrap plant had average vegetation and fruit weight.
- Total tomato weight: 5 lb, 11.9 oz
- Average tomato weight: 0.94 oz
- Ripe tomatoes: 29
- Unripe tomatoes: 69
- Total tomatoes: 98
- Vegetation: 3
The food scrap plant was also middle of the pack in terms of vegetation and fruit weight. Since the scraps mainly contained bits of fruits and vegetables, these materials provided nutrients to plants. Their small size and low carbon content avoided nutrient tie-up during the first month.
Fish heads slowed tomato growth, likely due to slow decomposition and nutrient tie-up in the soil.
- Total tomato weight: 2 lb, 13.4 oz
- Average tomato weight: 0.57 oz
- Ripe tomatoes: 17
- Unripe tomatoes: 63
- Total tomatoes: 80
- Vegetation: 6
Although people often instruct others to bury fish heads or scraps under their plants, the catfish plant was the clear loser. It had the lightest tomato harvest, the smallest fruit, and the least vegetation.
So, why’s that? Kevin suggests it’s because the catfish heads are large pieces of material that take microbes a while to break down. Since they take so long to break down, the nutrients present in the fish aren’t available to the tomato plants. I agree with this, but I think there’s more to explore.
If the nutrients simply weren’t available to the plants, the catfish plant would resemble the control plant. However, the results showed the catfish plant was significantly smaller and also produced about a third of the tomatoes that the control group did.
My guess is that soil nutrients were tied up during the beginning stages as microbes worked to break down the fish meat. Once the material was broken down, the plants could take up the nutrients and rebound a bit. And as Jacques suggested, the soil might have turned anaerobic or acidic.
What Happened to the Buried Scraps?
Soil health relies on diverse microorganisms and decomposers breaking down organic matter.
When Kevin and Jacques dug into the soil under the tomatoes, they discovered that most of the kitchen and food scraps had vanished. Calcium-rich bones and eggshells remained, but all the other material had fully broken down.
And this makes sense. Healthy soil is teeming with life! You’ve probably seen decomposers like worms and pillbugs, but the soil is also home to microscopic life like bacteria, nematodes, and fungi that break down organic matter.
However, soil life varies tremendously between soils. Poor or damaged soils break down organic materials much more slowly than soils teeming with life. Leaving plant roots in the ground, applying compost, and growing cover crops can all improve soil health as they provide food as organic matter to the beneficial microbiology of the soil, ensuring that they continue to survive. In addition, some cover crops fix nitrogen in their root systems, which also improves the nutrient density of the soil for your plants.
Should You Add Food Scraps to Your Garden?
Composting organic materials enhances garden health by providing nutrients and beneficial microbes.
As Kevin explains, it’s probably not worth adding food scraps directly to your garden. In all but the case of the egg-fed tomato plant, the control plant produced more tomatoes. That means going through the work of adding food scraps to your garden isn’t only unnecessary but may also be harmful.
However, that doesn’t mean you should throw away your leftover pasta and garden weeds. Just compost them before adding them to your garden! When organic materials are composted, bacteria and fungi break down the larger particles into smaller forms. Adding compost to plants adds nutrients and a host of beneficial fungi that can help plants uptake those nutrients better. The compost can also feed beneficial fungi and bacteria strains that can assist your plants in combatting various plant diseases.
This experiment also explains why it’s important to add finished compost to your garden. If you can still detect plant stems and bits of food in your compost, decomposers like worms and bacteria haven’t finished breaking the material down. That means that the nutrients present aren’t yet plant-available.
Adding fully broken-down compost to your plants will add plant-available nutrients without tying up nitrogen or other nutrients. There are many different ways to compost, so chances are good you can find a method that works for you.
Even if people have told you to add food scraps to your garden, this action can actually stunt plants. Rather than adding the scraps directly to your soil, compost them and then add them.