Ever since I started gardening, I’ve been improving and maintaining my soil to increase my yields of vigorous herb plants with large, abundant leaves and high levels of essential oils. Long before the term “recycling” became a catchword, I was returning plant nutrients to the soil in the form of homemade compost and cover crops that I tilled under. Over the years, I’ve developed an organic liquid fertilizer that not only makes herbs grow faster and stronger, but is actually made from herbs.
Something I learned from my parents and have always done is to lay fresh-cut leaves and stems that I’ve weeded or pruned around the base of my plants and wait for rain, microorganisms, and time to release their nutrients to the soil. One winter day, while sipping a restorative cup of herbal tea, the idea came to me that my plants might also prefer their tonic in liquid form, a sort of vegetarian manure tea based on a mixture of dried herbs.
I discovered that the practice of using herbs as fertilizer dates back hundreds of years: as far back as the ninth century in the case of comfrey, for example, and to the eleventh for raspberry and dandelion. That’s really not surprising. Like all other green plants, herbs surrender their nutrients to the soil when they decompose.
The fertilizer formula I came up with contains twelve herbs, listed below, which together contribute nitrogen, phosphorus, potassium, and the ten other mineral elements essential for plant growth along with numerous other beneficial substances. Many have traditionally been used as fertilizers. Two of these herbs, tansy and mint, have a reputation for attracting great numbers of earthworms, which themselves are prodigious fertilizer manufacturers. Most of these herbs are vigorous growers, so if you have them in your garden, you probably have plenty to spare for making fertilizer.
• Tansy (Tanacetum vulgare)
• Nettle (Urtica dioica)
• Mint (Mentha spp.)
• Hop (Humulus lupulus)
• Comfrey (Symphytum officinale)
• Leaves and fruit of raspberry (Rubus idaeus)
• Dandelion (Taraxacum spp.)
• Coltsfoot (Tussilago farfara)
• Purple coneflower (Echinacea purpurea)
• Soapwort (Saponaria officinalis)
• Sage (Salvia officinalis)
• Garlic (Allium sativum)
I’ve tested my herbal fertilizer for three years, giving one group of plants fertilizer, compost, and water while giving another group of similar plants just compost and water. Large- and small-scale growers also have used it, in greenhouses as well as outdoors. We’ve all been pleased with the results.
I’ve found that both perennial and annuals treated with the fertilizer look healthier. Seedlings have good color and don’t suffer transplant shock. Many of the plants fertilized this way have withstood the first frosts better than the controls. There also is no danger of burning the plants by using too much of this fertilizer, as there is with some conventional fertilizers.
The differences are subtle at first but become more noticeable during the seventh to eighth week of application. I harvested my herbs every three weeks and found that my treated plants put out vigorous new shoots within four days of cutting—usually considerably ahead of the control plants.
Preparing the fertilizer
My formula is based on dried herbs. You may purchase them or dry your own. Hang your harvested herbs or lay them on screens to dry in a cool, dry place until they are crisp.
To make about a pound of dried fertilizer blend, combine 21/2 ounces each of tansy, nettle, mint, and hop, 1 ounce each of comfrey, raspberry (leaves only; if using fruit, add it later when you brew the stock solution), dandelion, coltsfoot, purple coneflower, soapwort, and sage, and 1 clove of garlic. Store the mixture, tightly covered, in a cool, dark place.
If you’d rather substitute fresh herbs for dried, use the same proportions specified above, but in double or triple the amounts. Don’t be concerned if you don’t have all the herbs called for; just use more of the ones you have.
To mix your stock solution, place the herb blend in an old pillowcase or other cloth bag and tie the top shut. Place the bag in a 24-gallon trash can and fill the can with water. Put on the lid to keep out mosquitos, birds, and small children.
Let this stock solution steep for about five days, or until it begins to ferment. In cold weather, I add a teaspoon of fish emulsion fertilizer to the can of water to help fermentation along. Use the stock solution as outlined below, then spread the spent herbs on your compost pile to get every last bit of good out of them.
Fertilizing the garden
Good soil is a prerequisite to a successful garden. I recommend adding 6 inches of compost annually to any garden soil. My homemade compost consists of herbs, grass, and leaves that have been aged for eighteen months. You can also add kitchen waste (but no meat or fat).
I’ve worked out schedules for three types of garden soil. Choose the one that is appropriate for your soil.
For deep, rich, humusy loam:
In spring, water in your transplants with diluted fertilizer (mix one part stock solution to one part water). Thereafter, apply full-strength stock solution around the base of each plant every two weeks until a month before the expected date of first frost.
For sandy soil with some organic matter:
Apply stock solution over the garden in spring a week or so before sowing seeds or setting out transplants. Then follow the same procedure recommended above. Because liquids drain faster through sand than through loam, you will need to use more fertilizer.
To build up clay soil containing little organic matter:
This is a real soil makeover but well worth the time and effort it takes. Working in copious amounts of organic matter opens up the clay so that more oxygen can reach plant roots.
In spring, soak the garden area with stock solution (a 24-gallon batch will soak an area of about 3,000 square feet). Sow a cover crop of buckwheat, which is great for bees and crowding out weeds. When it blooms, till the buckwheat into the soil, reapply fertilizer, and sow another crop of buckwheat. Cut down the stalks in autumn and dress with lime if a soil test shows that it would be beneficial. Till the stalks under in the spring, reapply the herbal fertilizer, and plant some annuals. Follow the feeding schedule for loam and topdress with compost periodically. In autumn, till the soil, lime it again if necessary, and sow a crop of winter rye or another cover crop recommended by your extension agent. In spring when the green shoots are 1 to 2 inches tall, turn them under, reapply herbal fertilizer, and plant your perennials—at last!
Heidi Herzberger lives in Gilmanton Corners, New Hampshire. With her husband, Dan, she packages and sells her fertilizer formula under the name Earthminder.