Q. I’d love to have a landscape with herbs and other edible plants, but I’m frustrated by the quality of my soil. It’s hard, heavy clay and the plants aren’t thriving. How can I improve it?
A. Soil is the soul of a garden. Building healthy soil is satisfying because, over time, you’ll see a real difference—not only in the texture of the soil, but also in the beauty and productivity of your garden.
The secret is to work in as much compost and organic matter as possible when you first dig your garden, and every year thereafter. In addition, feed soil and plants with a variety of soil amendments, and blanket the soil with a layer of mulch.
Whether you have heavy, compacted clay that drains poorly or sandy soil that won’t hold onto nutrients and moisture, you can improve the soil by adding lots of organic matter. Organic matter improves soil texture, making it loose and crumbly so air, water and roots can move through it. Soil that contains plenty of organic matter also will absorb and store the nutrients it needs, while providing the good drainage needed by most plants, including herbs. Organic matter will balance pH problems, too, successfully mitigating the effects of soil that is either too alkaline or too acidic.
What’s more, organic matter feeds the earthworms, bacteria, fungi, enzymes and other beneficial microbes that allow plants to thrive, while boosting their resistance to disease and pests. Healthy soil is alive, teeming with microbial activity, so take care always to garden organically. Feeding your soil also feeds plants, so don’t be tempted by quick-fix, chemical-based fertilizers at the expense of the life in your garden.
Organic matter includes leaves, grass clippings, manure, pine needles, kitchen scraps (no meat or oils), garden trimmings and wood ashes. And while you could add these materials directly to your garden soil, it’s better to combine them into a compost pile, which will allow their thorough decomposition. The result will be rich, crumbly humus that is like the dark, earthy material you find on a forest floor. This is the best soil and plant food of all
I start my compost pile with leaves—not just my own, but also my neighbors’. I’m probably known as the crazy leaf lady on the block; I started by collecting bags set out on garbage day. Now some neighbors deliver their leaves to me. To this pile of leaves I add aged manure from a nearby horse farm, coffee grounds, eggshells, veggie scraps, dryer lint, the contents of my vacuum cleaner bag, and even hair trimmings. All of this will become humus as it decays. Harvesting rich, black compost from this pile is supremely satisfying, for me and for my soil.
Diet for a Healthy Soil
Plants need nitrogen, phosphorous, potassium and trace minerals for healthy growth, which can be provided through compost and organic soil amendments.
Nitrogen, which fuels green growth, is provided by grass clippings; green vegetable matter in the compost; and purchased amendments, such as cottonseed meal, alfalfa meal, fish emulsion, fishmeal and bloodmeal. Phosphorous, which boosts roots, fruits and seeds, is found in bone meal and rock phosphate. Potassium, provided by greensand, potash and wood ashes, promotes vitality and disease resistance. (See "Organic Soil Amendments" below.)
Calcium, magnesium, iron, boron, copper and zinc are essential to the soil in small amounts. Additions of seaweed, kelp meal, gypsum, magnesium sulfate, dolomitic lime, guano or horticultural molasses will help provide these trace minerals.
Don’t feel you have to buy all the soil amendments at once. I occasionally buy in bulk or large sizes, especially when I find them on sale.
Simple Soil Measures
Here’s how to make the most of compost and other organic soil amendments. After you create a new garden bed, spread the compost across the soil surface, then turn over the soil to mix it into the top foot or so, where most plant roots will be. If you’re preparing a bed in the fall to be planted in spring, you can use leaves, straw, sawdust or compost that is not completely decomposed because it will break down over the winter.
After the soil has warmed completely in spring, apply a layer of mulch—straw, shredded leaves, bark, pine needles or other materials you have in supply—over the soil surface. If you like, you can mix them together so they look like the forest floor. Mulch holds in moisture, keeps down weeds, prevents the soil surface from getting crusty, and eventually breaks down to further feed the soil.
In subsequent seasons, pull back the mulch and add an inch or two of finished compost; simply spread it over the soil, rake it in lightly and let the earthworms do their job. A one- to two-inch layer of compost can even prevent plant disease.
During the growing season, I add soil amendments every few weeks, usually by mixing up a brew in a 5-gallon bucket of water: a dollop of liquid seaweed, fish emulsion and horticultural molasses, as well as small quantities of a seed meal (such as cottonseed meal) and whatever else I have on hand or haven’t used recently. I use this liquid to drench the soil at the base of plants, or I spray it on leaves. Remember, soil building is a process. You can’t just do it one time and be done with it. If you do, your soil will quickly revert to its former state. But keep at it: From one year to the next, your soil—and your garden—will grow better and better. How good is that?
Q. How can I know which plants are invasive before I buy?
A. Most beginning gardeners experience the occasional problem of enthusiastically planting something new, only to discover by the end of the season that it seems to want to eat up every inch of available garden space before it goes on to conquer the world. And sometimes a plant that is well-behaved in your climate might be Attila the Hun in another region of the United States. Oftentimes, you don’t know its growth habits until you grow it.
Many examples spring to mind. Take the dandelion: The leaves are nourishing greens for salads and the roots have a number of traditional medicinal uses, but it is widely regarded as a menace. Its puffballs toss so much seed to the winds that one plant can become a yard full if you let it.
Remember that vigor and fast, strong growth are assets in a plant—up to a point. That point can depend not only on the plant and the climate, but also on the amount of space you have in which to garden and your level of tolerance.
What can you do about the problem of invasiveness? Sometimes the very best approach is to know about a plant’s tendencies before you put it in your garden. Your best allies may be your neighbors and experienced gardening friends, your local garden center, the Cooperative Extension Office in your area, and the library.
If you want to grow a plant no matter how much trouble it is, here are some tips:
• Plant it and other equally tough plants in the same area of the garden and let them duke it out. Keep your eye on them to be sure that one doesn’t overwhelm the others.
• Put an aggressive plant in a pot on the patio instead of in the ground.
• Look in garden centers and mail-order catalogs for a cultivated variety of the same plant that doesn’t grow as tall or as fast. Sometimes, for example, a variegated plant (one whose leaves are splashed with white or yellow) is not as rambunctious as its all-green counterpart.
• Sink a plastic barrier into the ground to contain the roots (although many plants, given time, will hop over such a barrier with ease or burrow beneath it).
• If you have the room, plant it in an out-of-the-way spot where it can roam as it pleases.
• Plant it in a location where its roots are confined. Have you got a narrow strip of ground along a back alley or alongside a driveway or a sidewalk? You may be surprised at the niches you can find.
• Don’t provide the conditions it needs to thrive. Have you got a shady spot under a large tree where nothing else seems to grow? Try it there.
• Don’t unwittingly spread the unruly plant via your compost pile, where weed seeds will survive if the pile doesn’t heat up enough to kill them.
Watch the plant for a season to decide whether it’s worth the fight. Cultivate around it regularly, pulling out unwanted seedlings or taking a shovel to the edges of a spreading clump to keep it in its place. Remember that while you may admire and enjoy a vigorously spreading plant, your grumpy next-door neighbor might not.
Here are some plants that you may want to think twice about if you have a small garden (or at least keep your eye on them): fennel, wormwood and some other artemisias, evening primrose, some mints, comfrey, sorrel, common yarrow, horsetail, clary sage and bamboo.
Q. Now that I’ve grown herbs for a couple of years, I want to branch out a bit. Can you suggest any plants that will be good company and make my garden pretty?
A. When I began gardening years ago, the only plants I grew were herbs. I was intrigued by the idea of growing plants that were useful in some way, not merely beautiful, which had less appeal to me at the time. I was something of a purist about my herbs.
I don’t feel that way today. Growing herbs for my dinner table opened up the wider world of gardening to me. Now I don’t need an excuse to add any plant that intrigues me to my “herb” garden. I am always looking for companions for my favorite plants.
In early spring, when the chives start pushing their way up through the cold soil, the burst of happy, vibrant color from spring-blooming bulbs is most appreciated. Those early flowers are always a welcome surprise. Now is the time I’m grateful that I planted flowering bulbs in and among my perennials in the fall.
Hardy bulbs actually make quite good companions for most perennial gardens, as they add their brilliant color at the very time when the rest of the garden is still asleep, and the dry shade suits them in the hot summer, when they’re dormant. By the time the spring flowers are gone, when the bulb foliage dies back (and looks ugly as the bulb stores nutrients for the next season), the rest of the garden is ready to take over the job of providing beauty, color, form and fragrance. Mother Nature is efficient that way.
Bulbs also do well when mixed in with wildflowers in a meadow or a woodland setting. They can be planted in the shade around deciduous trees and shrubs, grabbing what sunlight they need to bloom before the bigger plants have even leafed out yet. They can be mixed in with carefree perennials such as calendula and violets. And they can be mixed in with groundcovers. Daffodils, tulips, grape hyacinth, crocuses, and snowdrops look lovely planted among creepers with interesting foliage—such as ‘Blackie’ sweet potato, lungworts, lamiums, ivy and prostrate rosemaries; the other plants fill in and disguise the bulbs’ dying foliage.
Organic Soil Amendments
Organic soil amendments are now widely available at many retail garden centers. Mail-order suppliers of organic soil products include: Garden-Ville, (888) 655-6115, Gardens Alive!, (513) 354-1482; Peaceful Valley Farm and Garden Supply, (888) 784-1722;
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