Reversing Plant Aging

Why Plants Stop Growing—and How to Kickstart Them Again

As plants age, they stop producing new growth, stop flowering, and their leaves stop making protein and chlorophyll. Eventually, the leaves become yellow and drop off, and the plants become vulnerable to fungal infections (like rust) and insect attacks.

This aging process—called senescence—is biochemical and highly influenced by the environment. Thankfully, it can be delayed with plant hormones, either made by the plant itself or by soil microbes.

If your roses stop blooming after a couple of months, they’re likely either aging early or not getting enough light. But with the right knowledge, gardeners can slow this shutdown process and keep plants thriving.

Soil Health Is Everything

Plants can grow even in a bucket of rocks if you feed them water-soluble chemical fertilizers. But in regular soil, most minerals aren’t water-soluble. That’s where microorganisms come in—they break down organic matter into nutrients plants can actually absorb.

Although plants can make their own vitamins and amino acids, they’re also happy to absorb them from the soil if microbes process them first. You don’t need a degree in botany to be a great gardener, but it helps to understand some basics about plant nutrition and how they respond to their environment. Unfortunately, that kind of info is usually buried in scientific papers and hard to digest for most people.

A Garden Makeover with Fish Meal

Milly’s soil was about 50% clay—far from ideal for growing. After moving into her home, she planted roses and other plants, but they barely survived. Then, a friend gave her some high-grade fish meal (originally meant for soup stock). On a whim, we mixed two tablespoons of the meal into a gallon of water and fed it to her struggling roses.

The transformation was dramatic. Within weeks, the roses began to bud like crazy. Now they bloom for eight months out of the year, with lush green leaves and almost no rust—even though Milly lives near the foggy coast of Sonoma, California. Since starting the fish meal, aphids have also disappeared.

We tried it on the property’s sickly apple and pear trees, too. The leaves were yellow and rusted, the fruit was small and fungus-ridden, and Milly was ready to chop them down. Instead, we fed each tree four gallons of the fishmeal mix over the course of a year. The result? Lush foliage, heavy fruiting, zero rust, and completely worm-free apples and pears.

The plum tree we planted five years ago is now over 15 feet tall and so loaded with fruit that the branches sag under the weight.

Why Fish Meal Works So Well

We initially thought the fish meal’s protein was responsible—but it’s more complex than that.

This fish meal is a human-grade product made from fresh, whole fish that are either too small to be filleted or simply the wrong species. They’re processed within 8 hours of harvesting to retain freshness. The high heat from steam cooking halts decomposition and preserves the integrity of the plant growth factors and vitamins in the fish organs. These growth factors and vitamins are heat-stable, while the enzymes that normally break them down are not.

So, it’s not about protein—if it were, chicken manure would work just as well (spoiler: it doesn’t). These essential molecules are missing in manure because animals absorb them during digestion.

Eventually, we identified the magic compounds in the fish meal as precursors to auxins and cytokinins—two critical plant hormones.

• Auxins stimulate root growth and cell elongation.
• Cytokinins promote protein and chlorophyll production, cell division, budding, and flowering. They also trigger the creation of protective molecules that help plants fend off insects and fungi.

Together, auxins and cytokinins delay aging and promote continuous growth. Plants naturally produce them, but soil bacteria and fungi can also. When microbes release these hormones in the root zone, plant senescence is postponed—until harsh weather forces it.

The fish meal itself doesn’t contain these hormones, but it does contain the building blocks microbes use to make them. When we planted Milly’s roses, we packed the roots with fresh compost, which was rich in microbes. Once we added fish meal, those microbes got to work, creating growth hormones—and the rest is history.

Compost Alone Isn’t Enough

Plant-based compost doesn’t contain these hormone precursors. Why? Because plant hormones are unstable and break down soon after they’re made. Plus, high levels of auxins and cytokinins in the soil actually suppress a plant’s ability to make more. That’s nature’s way of keeping growth under control.

But we can bypass that block by getting bacteria and fungi to produce the hormones for the plant.

Bug Juice: Homebrewed Plant Fuel

After some experimentation, we discovered that baker’s yeast—when fed sugar and fish meal—also produces cytokinins. That’s the basis for our DIY “Bug Juice” fertilizer.

You can find the full recipe on this site. It’s simple to make and a great way to teach kids and adults about how plants grow. Some people make beer in the basement; now gardeners can make Bug Juice on the patio. Just don’t mix the two up.