Fertilizing gardens can be costly, especially if you are an organic grower. And even organic fertilizers can contain some unwanted chemicals. They are also wrapped in plastic, made in factories and shipped over long distances.
Finding truly sustainable, healthy and cost-effective solutions can sometimes be frustrating.
But what if I told you there was a way to make your own all-natural fertilizer at home using comfrey plants from your own garden?
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This hardy perennial grows quickly and easily, has beautiful blooms and best of all, it can be a completely free nutrient-rich source of fertilizer that can be used all season long.
See detailed information on growing and harvesting comfrey here.
Comfrey is a dynamic accumulator
It is worth noting that in permaculture terms, comfrey is called a “dynamic accumulator”, but there is some controversy among experts about the specific definition of this term.
All plants need three major macronutrients to grow and thrive; these are nitrogen, phosphorus and potassium, often referred to as NPK on fertilizer mixes.
Nitrogen is crucial for healthy growth and helps plants produce chlorophyll. Phosphorus promotes vigorous growth and helps protect plants against pests and diseases. Potassium promotes fruit and flower production in perennials and mature fruit-bearing annuals such as tomatoes and peppers.
See this guide to learn more about how your plants will benefit from these nutrients.
Comfrey is a rich source of all three of these macronutrients. It actually has more potassium than composted manure.
In addition, it contains high levels of many important micronutrients such as calcium and magnesium, which are also crucial for healthy plant growth.
Also referred to as a “dynamic” nutrient accumulator, this plant has deep taproots that draw both macro and micronutrients from deep in the soil to the leaves. These nutrients accumulate in the leaves where they are stored.
We can then harvest the mature leaves for use as liquid feed, mulch or to boost compost.
Although widely used in permaculture practices, it has not been scientifically proven that comfrey is actually any better than other plants for making fertilizer. Many gardeners, myself included, have had good results using comfrey tea, but your results may vary.
Natural pest control
In addition to its high nutrient content, some gardeners use a solution of comfrey tea as a foliar spray to prevent powdery mildew. Application to the leaves of plants can help prevent the spores from germinating.
The plant also attracts beneficial predatory insects such as wasps and spiders, so growing some in the garden can also help reduce pest problems.
How to make comfrey tea fertilizer
Comfrey tea liquid fertilizer is easy to make and use as a foliar spray, or add to the soil for annuals and perennials.
A word of warning though: it smells horrible! So be prepared to hold your nose.
Harvest comfrey leaves
To make the fertilizer tea, start by collecting a bucket full of the large, fuzzy leaves. I suggest you wear gloves when you harvest them, as the bristles can be a bit irritating to your skin.
When the leaves are at least 2 feet long, use a garden knife or scissors to trim them to a few inches above the ground. Harvest the outer leaves first so that the plant can continue to grow.
Trim the stems from the leaves you harvested – they are the vegetables you want.
Then place them in a container or bucket and press down firmly. I usually use a simple 5 gallon bucket. You can put some large rocks or rocks on top to weigh them down, then fill the bucket with water.
You can chop or shred the leaves to speed up the process.
Make sure you always cover the bucket. This keeps annoying insects away, prevents dilution by rainwater and, most importantly, prevents your whole garden from smelling bad!
Leave it to Steil
Place the bucket in a sheltered spot in the garden and let the fermentation begin.
To make a very strong tea, let the bucket steep for a long time. Recommendations are anywhere within a 3 to 6 week range. Once the leaves have broken down into a mush paste, you know the tea is ready.
In a pinch, any amount of time will yield you something useful. I’ve had good luck using comfrey tea that has only been steeped for a few days, especially if you put it in a warm area to steep.
Just sniff around for that telltale smelly aroma, which is a good sign that the leaves are breaking down and releasing the nutrients.
The final product will be a greenish-brown liquid and some very nasty, mushy leaves.
How to use comfrey tea fertilizer
Once you’re ready to use the liquid feed, scoop or strain the decomposing leaf gunk from the bottom of the bucket.
Toss this leafy goo into your compost pile, or use it to dress up other crops like potatoes and tomatoes.
Before use, you should dilute the tea with water, as it can be very strong and can burn the plants. How much you dilute it can vary greatly depending on how strong the brew is.
The darker the liquid, the more you need to dilute it. I’ve seen recommendations for dilution ranging from 1:2 to 1:15 parts tea to water.
If you’ve soaked it for a full 6 weeks and you have a full 5 gallon bucket of liquid, I’d recommend a 1:10 ratio, but if you’ve only soaked it for a few weeks, 1:4 is probably fine.
If you only let it sit for a day or two, you may not need to dilute it at all.
Once the concentration is diluted, you are ready to feed your garden!
Instead of using a watering can, I like to put the tea in a backpack sprayer and spray the solution on the soil and both the top and underside of the foliage, hitting annuals, shrubs and fruit trees.
Do not use comfrey tea fertilizer on seedlings or very young plants. If you are using it to feed younger crops, dilute the concentration significantly. Do not apply if heavy rain is expected so that the liquid has time to do its job before being washed away. For best results, apply just as the plants begin to flower and bear fruit.
You can also try a quick steep method, which is similar to how you brew tea to drink. Simply pour boiling water over comfrey leaves and let the concoction sit for up to 24 hours. Strain the foliage and dilute by half before use.
Or you can try continuous batch brewing, using a bucket with a nozzle on the bottom. In this method, water and leaves are continuously added to the bucket so that the fertilizer can be used as needed.
Each time you want to use some, simply lift the nozzle to pour out the desired amount, then top up with more water and leaves to let it marinate.
Another technique is to drill holes in the bottom of one bucket and place a second bucket underneath.
Pack the foliage into the inner bucket, weigh it down and cover. After a few weeks it will disintegrate into a black sticky mass. Collect the drops in the bucket below and dilute to about 1:15 parts of tea in water.
Other ways to fertilize with comfrey
One of the best things about this herb is how fast it grows. The robust foliage can be cut and used several times in one growing season.
So if brewing a stinky tea isn’t your thing, or if you want to try several approaches at once, here are some additional ways to use comfrey to boost soil nutrient levels:
1. Use the leaves as mulch. Just cut them down and dress them around the edges of plants, or toss heaps of foliage into fallow beds. Dig them into the ground or cover them with dried leaves or straw.
2. Leaves can also help get your compost pile started. The nitrogen boost helps activate the stack and acts as an accelerator to encourage rapid breakdown. For best results, crush them into a paste with a little water, pour into the compost pile and dig through. Be careful not to add too much, which will lose your ratio of brown to green materials.
3. Try putting a few shredded leaves in the bottom of planting holes before transplanting seedlings. They break down slowly and release nutrients into the soil, supporting healthy plant growth.
Closed loop gardening
Comfrey is truly one of my all-time favorite plants. I absolutely love the fact that I can make my own fertilizer while continuously recycling nutrients and organic matter back into my garden.
Next time your crops, fruits and flowers are looking a little sad, try giving them some comfrey tea and see the results for yourself.
Have you used comfrey as a fertilizer for your garden? Share your stories in the comments below!
For more organic gardening tips, try one of these guides:
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