It seems such a waste—we use a tea bag to make a lovely cup of tea, and then toss it into the trash. It just screams to be repurposed—surely there’s some way to get some extra use from that depleted bag! So it’s no big surprise that the internet is suddenly full of lists with titles such as “7 Random Uses for Used Tea Bags.”
It’s fine with me if you want to soak your feet in exceedingly weak tea, or use it to clean your floor. I suppose the tiny bit of acid in the solution might possibly make a difference. But how about the garden-related suggestions? You might find advice such as:
Rose Bush Fertilizer: Sprinkle tea leaves around rose bushes to enrich the soil.
Nourish those hungry plants with used tea leaves. Break open a nutrient-rich tea bag and disperse the contents over the soil or add them to your compost. … You can also nurse your sickly plants back to health by watering them with twice-brewed tea.
Used Tea Leaves Make Great Soil: Using Your Tea Leaves to Feed Plants. Sprinkle your used tea leaves around the base of acid loving plants, including your tomatoes and roses. … [T]ea leaves contain all the big three nutrients, N-P-K, as well as some trace minerals. Sprinkle the used leaves on the soil and gently scratch them in. Of course, you can also add tea leaves to your compost pile.
Should I have been saving my (hundreds of) tea bags all winter to improve my garden this summer? Do tea bags (or tea leaves) truly enrich the soil, significantly lower the soil pH, and prevent or treat disease? Always curious about such claims, I decided to take a closer look.
First, I need to define “tea.” White, green, oolong, and black teas all come from the same plant, Camellia sinensis. To keep things simple, that’s the kind of tea I’m addressing here.
There are four ways that tea is supposedly beneficial: curing “sickly” plants, lowering the pH of the soil, adding nutrients, and adding humus. Let’s start with curing your ailing plants.
When we think of an sick plant, the question immediately rises—why is it sick? Did it receive too much water? Does it have a fungal or bacterial disease? How about too little (or too much) light? Is the soil compacted? Was it planted too deeply? Did the herbicide being sprayed next door drift over onto your property? It’s pretty obvious that pouring tea on any of these issues won’t help a bit, and might (in the case of overwatering) do serious harm. Watering with dilute tea might help if the plant is simply thirsty, but there are so many reasons a plant can be sick, how can one treatment cure everything? Claims of a panacea always make me suspicious.
What about lowering the soil’s pH? Since tea is brewed for varying lengths of time, at varying temperatures, and in varying amounts, it’s hard to say exactly what the pH of a cup of tea is. On average, however, black tea registers an acidic 4.9. That’s because tea leaves, like other brown leaves, contain tannic acids, which also give tea its brown color.
Remember, however, that the advice is for ways to reuse tea bags. I’ve tried trying to extract an extra cup of tea from my used tea bags. I end up with a pale, insipid liquid that isn’t much different from the hot water I started with. Maybe if you use your tea bags lightly, they’ll have more “oomph” left in them, but mine sure don’t. Then there’s the question of how much that extremely weak tea will lower soil pH. My soil is so full of alkaline limestone that even two or three tea bags aren’t going to have much of an effect.
It’s also important to ask if you even want to lower your soil’s pH. Colorado’s alkaline soils might benefit, but in much of the country gardeners add lime to raise their soil’s pH! And, of course, different plants prefer different types of soil.
Next is the fertilizer value of a used tea bag. Tea leaves do contain some nutrients, having an NPK ratio of 4.15-0.62-0.4. That’s a fair amount of nitrogen, the nutrient Colorado soils usually lack. The website where I found this information doesn’t explain whether these “tea grounds” were new or used. (I suspect they tested fresh leaves.) Still, tea leaves (in sufficient volume) could be a useful source of nitrogen.
Then there’s the humus claim. It’s totally true—tea leaves, just like any other leaves, will eventually rot and add humus to the soil. And many soils need more humus. I routinely add used tea bags to my kitchen compost bucket. Pretty much any non-salty plant matter is good for composting.
There was one more claim I came across—since tea bags absorb water, they might act as a reservoir in sandy soil or containers, keeping water available in the same way that hydrogel “water crystals” do. I suppose that could work, at least until the bag rots. To use them in this way, you’d have to make sure to dig down and bury your bags in the primary root zone, between 3 and 18 inches deep.
So what do we conclude? Adding tea bags to your garden isn’t a magic bullet, for roses or anything else, but they might be slightly helpful. Unless your soil is very acidic, they probably won’t hurt—unless the bag itself, which decays slowly, gets caught up in the tines of a tiller, causing it to jam. To get the most benefit for the least amount of effort, just toss them into the compost pile along with everything else.