To keep plants thriving, follow nature’s lead. Skip the chemicals—organic mulch, compost, and soybean meal provide all the nutrition your garden needs for steady, natural growth.
Coaxing Plants Further Along
For many plants, just about any mulch will suffice in keeping growth chugging along year after year; others need a bit more coaxing. Fertilizer, compost, and/or irrigation can lend a hand, when needed, in Weedless Gardening. As before, we will continue to follow Mother Nature’s lead and let millions of years of evolution take charge.
How do you know when plants will need some extra coaxing? First, it depends on what plants you’re growing. A 50-year-old maple tree with a well-established root system needs less help than a row of lettuce plants that are in and out of the garden in less than three months and during that time get their outer leaves picked off. Other considerations are soil, climate, and to a lesser extent, the kinds of mulches you use. Soils vary in their natural fertility and moisture-holding capabilities; poor or dry soils may need to be beefed up. The warmer the climate, the quicker plants grow and the faster mulches and nutrients disappear. An integral part of Weedless Gardening is keeping an eye on your plants—they often tell you what they need.
Look at fertilizers on display at any garden center, and the first thing you see are numbers. Lots of them: 5-10-5,10-10-10, 5-5-5, 30-10-10. You might also notice specific fertilizers for roses, tomatoes, bulbs—as if each kind of plant needs its own special pabulum. Look more closely and you might even find fertilizers for “spring feeding” or for “summer feeding.” It’s a wonder such plants can live together in a single garden.
Ignore all the fertilizer hype. It’s confusing and induces you to purchase more fertilizer than you need.
The Main Course
It would be wonderful if we never had to feed our plants. However, some nutrients are naturally lost when washed away by rainfall, a soil can be naturally deficient in some nutrient, and you do carry nutrients off-site when harvesting vegetables, fruits, and flowers. On the other hand, soils naturally enrich themselves to some extent, releasing nutrients locked up in minerals and even converting atmospheric nitrogen to plant food.
The kinship of Weedless Gardening methods with those of Mother Nature allows you, in many situations, to dispense with fertilization per se —in the sense of having to spread some powdered, concentrated, bagged material. Organic mulch that constantly blankets the ground is just as constantly decomposing. The resulting witches’ brew of compounds in the soil becomes food for plants, releases plant foods previously locked up in the rocky matrix of the soil, and facilitates plant uptake of some foods already dissolved in the soil water. Mulch alone usually provides enough food for the relatively minimal needs of wildflowers and established trees and shrubs.
Vegetables, flowers planted in a formal bed, and young trees, shrubs, and vines are generally hungrier plants. We demand a bit more oomph from a stalk of celery—it has to be extra succulent. Formal flowers are called on to provide an intense, nonstop show of blossoms. And young woody plants must quickly fill their allotted space. An organic mulch might still directly and indirectly supply all that’s needed by these plants in a naturally rich soil, depending on how intensely they’re grown. If the organic mulch is compost, which is relatively rich in food, so much the better.
If fertilizer is needed for naturally poor soil or for intensively planted vegetables, there’s no need to go back to the fertilizer display and wade through numbers, fertilizer types, and timing. More often than not, when Weedless Gardening from the top down, the only nutrient that might need to be deliberately added in the form of a concentrated, powdered, bagged material is nitrogen. Nitrogen is the first of three numbers prominently displayed on fertilizer packaging (the other two numbers represent phosphate and potash, two forms of phosphorus and potassium).
The Universal Pabulum
Among the best nitrogen sources—the one that I use almost exclusively —is soybean meal. It is a universal, “one size fits all” pabulum appropriate for all plants—as good for roses as it is for tomatoes, and equally effective for plants that need acid soils and those that need alkaline soils. Soybean meal is ground up, de-fatted soybeans whose protein is slowly broken down by soil microorganisms to become nitrogen that plants can use. It is “organic,” cheap, and available at feed stores. As a general recommendation, use 3 pounds of soybean meal per 100 square feet of planted area, and spread it once a year before laying down any kind of mulch. What could be simpler?
Sprinkle soybean meal, if needed, right on top of planting beds
Cottonseed meal is another nitrogen fertilizer, equivalent to soybean meal but more expensive. You could also use a ubiquitous 5-10-10 or 1010-10 fertilizer, the three numbers indicating the percentages of nitrogen, phosphorus, and potassium, respectively. For now, we’re interested in supplying nitrogen, so adjust the rate of any fertilizer according to how much nitrogen it contains.
Generally, our aim is to apply 2/10 pound of actual nitrogen per 100 square feet, whether the nitrogen comes from 2 pounds of 10-10-10 (2 pounds fertilizer x 109%N = 0.2 pound nitrogen), 4 pounds of 5-10-10 (4 pounds fertilizer x 5Y%N = 0.2 pound nitrogen), or 3 pounds of soybean or cottonseed meal (3 pounds fertilizer x 7%N = 0.2 pound nitrogen).
Concentrated Organic Sources for Major Nutrients
- Nitrogen: soybean meal, cottonseed meal, alfalfa meal, blood meal, leather dust, poultry manure, fish emulsion, guano, hair, hoof and horn dust
- Phosphorus: colloidal phosphate, rock phosphate, guano, bonemeal
- Potassium: wood ash, granite dust, greensand (glauconite), Sul-Po-Mag (langbeinite)
Anything Else on the Menu?
Most of your plants probably won’t need any bagged, conventional fertilizer other than some soybean meal, if that, but still keep a vigilant eye on them for signs of starvation. Hungry plants won’t squeal like starving pigs, but they can tell you when they’re hungry, and for what (see the box at right). Low-level hunger might result in stunted growth that can go unrecognized unless it’s dramatic. More severe deficiencies result in misshapen or off-color leaves, fruits, or stems. Generally such problems Should not arise in Weedless Gardening, where the constant stream of Organic materials provides a smorgasbord of plant nutrients. Should symptoms present themselves, however, don’t be too quick to lay the blame on your soil’s lack of a particular nutrient. Off-color or misshapen leaves could also be traced to aphids, frost, virus diseases, or hail, among other things.
If lime or sulfur was needed initially, regular additions of either are likely to be needed to keep the soil acidity in a range to suit particular plants. A simple soil test provides this information. Sprinkle any needed lime or sulfur on top of the ground every year if needed, so it can work its way gradually down to the root zone.
Abundant organic matter goes a long way toward averting problems with maintaining correct soil acidity, just as it keeps plants well nourished. These materials buffer acidity, allowing for more slack in what plants feel is “just right.” So keep chanting the mantra “organic matter.”
Organic vs. Synthetic Fertilizers
“Organic” fertilizers are natural materials that supply plant nutrients in their raw state or after slight processing. Manures, ground-up rocks, and composted vegetable wastes are examples of organic fertilizers. These fertilizers generally provide plants with a long, slow feed of a nutrient smorgasbord, and their manufacture puts minimum demand on the planet’s natural resources.
In contrast, chemical fertilizers are relatively pure compounds, usually synthesized in factories. They are concentrated sources of nutrients that, in most cases, are quickly available to plants but can also quickly wash out of the soil or burn plant roots.
Despite the potential benefits of organic fertilizers, many gardeners make the mistake of using them in the same way as synthetic ones. For instance, a gardening “expert” on the radio was touting the benefits of guano, or bat droppings. He was right about guano’s being rich in nutrients—almost 20 percent nitrogen in a form that can be taken up quickly by plants. And guano is definitely natural—it’s scooped out of caves where bats hang out. The problem is that guano doesn’t differ much in its effects on plants and soil from 20-10-10 or any other quick acting synthetic fertilizer. The same could be said for blood meal, poultry manure, and other concentrated, quick-acting organic fertilizers.
What is missing from all synthetic fertilizers and from concentrated organic fertilizers is bulk, which comes from organic materials rich in carbon. Types of raw bulk are straw, autumn leaves, sawdust, hay, and manures. (Most of the bulk associated with manures comes from the sawdust, straw, or other material used for animal bedding.) Bulky materials such as compost, peat moss, and old manure become stabilized through decomposition. The benefits of bulk include getting soils to hold more air and water, making plant foodstuffs already in the soil more available, and helping plants fight off certain diseases.
The lesson is, don’t necessarily seek out the most concentrated or “richest” organic fertilizer. And if you do use a concentrated fertilizer, add plenty of bulky organic materials along with it.
Nutrient Deficiency Symptoms
- Nitrogen: stunted plants, yellowing leaves beginning with oldest ones, and early shedding of leaves.
- Phosphorus: stunted plants, purplish leaf coloration of seedling leaves
- Potassium: tips and edges of leaves turn yellow and finally die, beginning with oldest leaves.
- Calcium: malformation or stunting of growing tips or youngest leaves, blackened ends of pepper fruits
- Magnesium: discoloration of areas between veins of young leaves, any shade from red to purple to yellow depending on the plant
- Sulfur: stunted plants and yellowing of youngest leaves
- Iron: areas between veins on youngest leaves turn yellow, with veins remaining green
Nature knows best. By using organic fertilizers like soybean meal, you nourish both soil and plants gently and sustainably—creating a stronger, healthier, weedless garden.
