Adding Nutrients and Stability with Cover Crops and Green Manures
A cover crop is a general term for any plant grown to prevent erosion, improve soil structure, and maintain soil fertility. Sometimes, you'll hear cover crops referred to as green manures. Green manures are cover crops that are used primarily to add nutrients to the soil and are tilled into the soil when they're still green. Green manures are the most useful cover crop for vegetable gardeners.
The advantages of using cover crops are impressive:
They add organic matter to the soil. By adding this matter to the soil, you improve water retention, aeration, and drainage.
They prevent erosion. Cover crops prevent erosion by holding soil in place in windy or wet areas.
They loosen compacted soils. Certain cover crops, such as oilseed radish and bell beans, have aggressive taproots (roots that grow deeply into the soil), sometimes reaching 3 feet deep, that help break up compacted soils.
They add nutrients to the soil. Legume cover crops, such as hairy vetch and crimson clover, through a symbiotic relationship (I scratch your back, you scratch mine) with rhizobium bacteria on their roots, convert atmospheric nitrogen into a type that they can use to grow. The process is called nitrogen fixing (see Chapter 7 for more on this relationship). When the cover crop is tilled into the soil, the nitrogen is released for the next crop. Also, taprooted cover crops bring minerals to the surface from deep below the soil.
They help control weeds. Cover crops control weeds by shading the weed seeds so they can't grow or by just being more aggressive than the weeds. Some crops, such as buckwheat, actually exude chemicals that inhibit weed growth.
They attract beneficial insects. Many cover crops attract good bugs that prey on garden pests, reducing insect problems on your vegetables.
If you want a healthier, more productive garden, and you have room, include cover crops each year in different parts of your veggie garden. In the following sections, I explain how to select and plant the best cover crops for your garden.
Choosing cover crops
Cover crops can be annual (they die after flowering or overwinter) or perennial (they regrow each year). For home gardeners, the best crops to sow are annual cover crops. These are easy to maintain and won't turn your vegetable garden into a cover crop garden.
The most useful annual cover crops for home gardeners are listed here. All but the grasses and buckwheat are nitrogen fixing:
Annual ryegrass, Lolium multiflorum, is a fast-growing, easy-to-establish grass that grows 2 to 3 feet high. It's hardy to -20 degrees Fahrenheit but can become weedy. Sow 1/2 to 2 pounds of seed per 1,000 square feet.
Berseem clover, Trifolium alexandrinum, grows 1 to 2 feet high and is easy to mow and till under. It's hardy to 20 degrees. Sow 2 pounds of seed per 1,000 square feet. Crimson clover, T. incarnatum, is closely related, grows 18 inches high, and is hardy to 10 degrees. It has pretty red flowers that attract bees.
Buckwheat, Fagopyrum esculentum, is fast growing, reaching 3 to 4 feet tall in about 40 days from seeding. It provides lots of organic matter, smothers weeds with its large leaves by shading them out, and exudes chemicals to prevent weeds from germinating. It breaks down quickly in the soil after tilling. Sow 3 pounds of seed per 1,000 square feet. Buckwheat doesn't fix nitrogen and is frost sensitive, so grow it in summer when the temperatures are warm.
Fava beans, Vicia faba, grow 3 to 8 feet high and are hardy to 15 degrees. Bell beans are a shorter (3 feet) relative. Edible varieties include ‘Sweet Loraine' and ‘Windsor'. Sow 2 to 5 pounds of seed per 1,000 square feet.
Field peas, Pisum arvense or P. sativus, come in several varieties that range in height from 6 inches to 5 feet high. They're hardy to 10 to 20 degrees. Sow 2 to 4 pounds of seed per 1,000 square feet.
Hairy vetch, Vicia villosa, is the hardiest annual legume (-15 degrees) and grows about 2 feet high. Sow 1 to 2 pounds of seed per 1,000 square feet.
Winter rye, Secale cereale, is a very hardy grass (-30 degrees) that grows 4 to 5 feet high. It's the best grass for cold areas with poor, acidic soils and produces lots of organic matter. Sow 2 to 3 pounds of seed per 1,000 square feet.
If you want a wide selection of cover crops plus a lot of helpful information, check out the Peaceful Valley Farm Supply Web site at www.groworganic.com (see the appendix for address information).
Planting cover crops
The best time to plant cover crops is late summer to early fall. What happens next depends on the climate where you live:
In mild-winter areas, the plants will grow throughout winter and can be turned into the soil in spring.
In cold-winter climates, plant hardy types that will grow for a while in fall, go dormant, and then grow again in spring before eventually dying. Some less hardy types, such as annual ryegrass, will die back in winter and be easier to till under in spring. You can work them into the ground in late spring or early summer and plant vegetables soon after.
An early spring planting of cover crops also works in cold-winter climates, but you won't be able to work the plants in until later in the summer.
Because beds planted with cover crops won't be available for planting vegetables until you turn them under, you have to plan ahead to use your garden efficiently. If you're short on space, consider alternating vegetables and cover crops so that each bed gets a cover crop every 2 or 3 years instead of each year.
If you plant cover crops in fall after your vegetables are done, you won't miss a beat and can plant vegetables again in spring. If you plant cover crops during the spring or summer, you'll have to sacrifice some space in your veggie garden. I'd opt for this route only if your soil is very poor and you need to build it up while growing vegetables at the same time. Just rotate where you plant the cover crops in your garden, and after a few years, your whole garden will get a cover cropping.
Plant cover crops by broadcasting seed (Chapter 13 has more info about this technique). To make sure the proper bacteria are present for nitrogen fixing in legume cover crops, use an inoculate. Most suppliers sell an inoculate that you mix with the seed. Till the soil, sow the seeds, and lightly cover the seeds with soil. If the weather is dry, water the seedbed to get the plants off to an early start and then keep the soil moist until it rains.
If you grow cover crops up to planting time (spring or fall) in your garden, the best time to work the cover crops into the ground is just before they start to bloom. With taller types, you may have to cut or mow the plants down before turning or tilling them in. After you work them in, wait about 2 weeks before planting vegetables.
Giving Your Plants Some Friends: Companion Planting
A companion plant is one that provides some sort of benefit to other plants growing nearby. It's sort of like how a good friend makes life easier for you. Well, plants have good friends, too. For example, the cover crops that I talk about earlier in this chapter can be considered companion plants.
Some plants are grown together because they seem to increase each other's yields. But what I want to talk about here are companion plants that repel pests. Is that really possible? Well, I'm not so sure. No clear-cut evidence says companion planting works against pests. But some people swear by it. (Louise Riotte's Carrots Love Tomatoes published by Storey Publishing is devoted to the subject.) It is true, however, that a variety of plants, herbs, and flowers provides a diverse ecosystem so that predatory insects are more likely to hang around and take care of the bad guys. Besides, trying some of these combinations certainly won't hurt your garden.
These plants are thought to repel specific pests; plant them near crops where these pests are a common problem:
Anise planted among members of the cabbage family (cabbage, broccoli, cauliflower, kale, and so on) is said to repel imported cabbage worms.
Basil is said to repel whiteflies, aphids, and spider mites; it's a good companion to tomatoes because these are insects that feed on tomato plants.
Catnip is said to repel some ty
pes of aphids, flea beetles, squash bugs, and cucumber beetles.
Garlic may repel nematodes and other soil insects.
Leeks are thought to repel carrot flies.
Marigolds planted around vegetables are said to repel root nematodes, Mexican bean beetles, and Colorado potato beetles.
Mustard greens are supposed to repel aphids.
Nasturtiums are said to repel Colorado potato beetles.
Radishes may repel striped cucumber beetles.
Ryegrass may repel root-knot nematodes.
Southernwood may repel moths and flea beetles.
Tansy is supposed to repel some aphids, squash bugs, and Colorado potato beetles as well as ants.
White clover may repel cabbage root flies.
Wormwood may repel flea beetles.
Many herbs, such as rosemary, oregano, and coriander, also are said to repel pests. Smaller companion plants, such as marigolds, can be interplanted with vegetables. Taller or more vigorous plants, such as ryegrass or wormwood, should be planted nearby — but not among — vegetables. You don't want them to overwhelm your veggie plants.
The research on companion planting may be thin, but hey, give it a try to see if it works!
Making Your Garden Work Double Time with Intercropping
Intercropping is a space-saving technique in which you grow fast-maturing, smaller crops among slower-growing, larger vegetables. By the time the bigger plants start to take over, you have already harvested the crops in between. Intercropping makes one bed as productive as two.
The best crops for intercropping include beets, carrots, lettuce, onions, radishes, spinach, and turnips. Use these examples to help you decide how to do it:
Plant lettuce, carrots, or radishes among young tomatoes and broccoli. For that matter, plant carrots and radishes wherever you have open space.
Plant turnips and other root crops among your cabbage.
Plant spinach or lettuce under your bean trellis. As the weather warms, the beans will shade the spinach and keep it cool.
Plant green onions between rows of corn.
Succession Planting for an Extended Harvest
Succession planting is a method of extending the harvest of vegetables, such as radishes and corn, that ripen all at once and lose quality if left in the garden instead of being harvested. Farmers use the technique to ensure a constant supply of vegetables to take to market; you can use it to produce a consistent supply of vegetables to take to your table. To succession plant, you simply make smaller plantings separated by 2 to 3 weeks instead of planting everything at once. Some great crops to succession plant are lettuce and greens, bush beans, beets, carrots, onions, radish, spinach, and sweet corn.
If you want to experiment with succession planting, use these steps:
1. Figure out how much of a certain vegetable your family needs for a 2- to 3-week period and how much room it will take to grow it.
Figure 16-1 shows a sample garden plan for succession planting. Check out Chapter 3 for additional information on how to plan your garden.
2. Break your planting beds into three or four appropriate-sized sections to grow your 2- to 3-week supply of the vegetable.
3. At the start of the planting season, plant the first bed; wait about 2 weeks and plant the second bed, and then plant the third bed about 2 weeks later.
Just about the time you finish harvesting the first bed, the second bed will be ready to harvest.
Figure 16-1: A sample plan of succession plantings.
The length of your planting season will determine how many successive plantings you can make and how successful the later plantings are. Depending on the weather, some of your later plantings may not yield well, but that's another reason to plant a number of plantings through the season: you're sure to get some of every type of veggie.
Another way to use succession planting is to replace a crop that's finished producing with a new one in the same place. With this method, you can grow more and a wider variety of vegetables in a small space. Just make sure you're planting a cool-season veggie for spring or fall and a warm-season veggie for summer. Table 16-1 lists some good succession planting combinations to try. (Chapter 3 has more information on cool-season and warm-season veggies.) You can choose one veggie from each column to plant in succession.
Yet another way to ensure a constant harvest of vegetables is to plant using the square foot method. This method is for the mathematically inclined (even though you don't need an A in calculus to use it). You select a 4-foot-by-4-foot section of your garden and divide it into 16 squares (each section is 1 square foot). Each square will have a different number of plants, depending on what you're growing:
1 plant per square: Tomatoes, peppers, broccoli, cabbage, cauliflower, eggplant, corn, melon, squash
4 plants per square: Lettuce, garlic, Swiss chard
8 plants per square: Pole beans, peas, spinach
16 plants per square: Beets, carrots, radishes, onions
By planting so few plants, you'll have many small harvests, and you can easily make more succession plantings and rotate plantings each year. (I talk about crop rotation later in this chapter.)
For more information about square foot gardening techniques, look for the book All New Square Foot Gardening, by Mel Bartholomew (published by Cool Springs Press), his videos, or visit this Web site: www.squarefootgardening.com.
Rotating Crops to Preserve Soil Nutrients and Maintain a Pest-Free Bed
If you plant the same vegetables in the same spot year after year, you're going to cause a number of problems, including these:
Insects and diseases that spend part of their life cycle in the soil will build up there and be more difficult to control.
Specific nutrients that the vegetables need will consistently be depleted and will be harder to replace.
The way around these problems is to rotate your crops from season to season. In other words, plant them in different beds, as far away as possible from where they were planted before. Crop rotation is easy if you keep a journal and make note of what was planted where. And if you keep things out of the same beds for 3 years, you'll probably be in good shape.
It's important to do more than rotate individual crops. You should rotate families of crops as well. In Part II, I talk about vegetables such as tomatoes, peppers, eggplant, and potatoes being in the same family. A disease or insect that attacks one plant in a family is likely to attack others. Blight on tomatoes and potatoes is an example. When rotating crops, make sure you don't plant a family member in the same spot 3 years in a row. For example, in one bed, plant beans (legume family), the next year plant potatoes (tomato family), and the third year plant cucumbers (squash family). After that, you can start over with another legume-family vegetable or start another rotation series. Keep the families apart for 3 years, and you'll have fewer problems in the veggie patch.
If you only have one sunny spot to garden, consider using containers as a way to rotate crops. For example, plant your tomatoes in a container one year and in the garden the next.
Planting by the Phases of the Moon
Planting by the phases of the moon isn't just a New Age technique. It actually has been used for eons by many ancient farmers and gardeners. They noticed that certain vegetables perform better when planted during different moon phases. The planting seasons don't really change, but planting dates during those seasons become very important.
Here's how moon gardening works: If you divide the 28-day moon cycle (from the new moon to the full moon and back to the new moon) into quarters, as any calendar does, certain quarters are thought to be better than others for planting specific vegetables. The following list gives you an idea of what to plant when, according to the moon cycle:
The first quarter, when the moon goes from new moon (invisible) to a quarter visible, is thought to be best for planting asparagus, lettuce, broccoli, cabbage, cauliflower, and other vegetables that produce their seeds on parts of the plant that aren't eat
en.
The second quarter, when the moon goes from half to full, is best for planting vegetables in which the seeds are eaten, such as beans, tomatoes, peppers, and squash.
The third quarter, as the moon moves from full back to half again, is best for planting root crops such as beets, carrots, potatoes, radishes, and turnips.
The last quarter, when the moon goes from half to invisible, is not thought of as a good planting time. Instead, it's a time to prepare the soil and rid the garden of pests and weeds.
You can get even more complicated by factoring in astrological signs, planets, and how they influence plant growth, but I'll leave that up to you and your further research. I haven't tried factoring in these other elements, but I have a friend in India who swears by the results, as do many others. For more on moon gardening, check out this Web site: www.gardeningbythemoon.com.
Chapter 17: Keeping Your Plants Healthy
In This Chapter
Controlling insect pests
Preventing plant diseases
Keeping animals out of bounds
Considering how tasty homegrown vegetables are, you shouldn't be too surprised to find that other creatures want to share in your harvest. And, no, I'm not talking about your neighbors. I'm talking about garden pests, insects that want to munch on your tomatoes, and animals, like deer, raccoons, and rabbits, that are just plain hungry. In addition, your plants face the threat of diseases, such as blight, which turns your potatoes to mush. With diseases, prevention is the key; once they take hold, they're almost impossible to eliminate.
Does the thought of all these potential problems make you want to run for cover? Well, you don't need to. It's true that insects, diseases, weeds, and animal pests can be very frustrating, but it's only really bad when the damage gets out of hand. The secret is to nurture a healthy, naturally balanced garden. Every garden can withstand some damage, and you have many weapons in your arsenal to prevent pest problems from getting out of control.
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