Like all living things, plants need air, light, water, and nutrients to grow and thrive. The difference between a beginning gardener and a more advanced and productive gardener is understanding how these factors contribute and interact to produce a successful crop. This growers guide will explain these basic factors that can be referred to when reading the Seeds to Sow Crop Guides.
All vegetable and fruit crops require a minimum of 6 hours of direct sunlight. Plants make carbohydrates that are the building blocks of root, stem, leaf, and fruit development. The factory for that carbohydrate production is the process of photosynthesis in the plant’s leaves. The more hours the sun shines on the leaves, the faster the growth process goes. Less than 6 hours will mean slow growth. Shade will produce spindly, brittle plants that reach for the sun and produce smaller, fewer fruits. As the natural day length gets longer, moving from spring into summer, the number of days from seed to harvest will decrease. As the days begin to shorten, it will take longer to produce a crop. Light is also involved in fruiting. Some crops, like onions, respond according to day length. Some varieties are bred to produce onion bulbs during short days, and they will be the first onions to bulb and be harvested in the spring. Long-day onions will not bulb until well into the summer, taking up space that could be used for summer crops. Proper variety selection involves accounting for seasonality (planting at the proper time for a specific crop) and is an important part of gardening.
Temperature and Variety Selection
Temperature, along with day length, plays a major role in seasonality. Crops are classified as warm- or cool-season crops because of their ability to grow during either cool, short days, or warm, long days. They will not grow successfully if grown outside their proper season. Check the Seeds to Grow Planting Guide or Seeds to Sow Crop Guides for the best time to plant before ordering seeds or planting. Plants produce little growth during temperature extremes like freezing, or summer nights over 90 degrees F, but if planted at the right time they will survive and begin to grow again after the climate moderates. Planting too early may produce a tiny seedling that is killed by an untimely freeze. Planting too late may not allow enough time for the crop to mature or set fruit before temperatures become extreme or may leave the crop vulnerable to insect attack. Plant breeders have increased plant cold hardiness, the ability of many plants to set fruit at high temperatures, pest resistance, and the productivity of plants that produce in lowered light, like inside greenhouses or high tunnels. These are all things to consider when choosing varieties for your garden.
All vegetable plants need a minimum of 1 inch of water per week to grow well, though some crops may need more at certain times of development. Having a steady supply of moisture is critical during fruit formation. Uneven soil moisture can also affect the uptake of nutrients, such as calcium. Without soil moisture, calcium may be present but not dissolved in the soil for root uptake and the plant disorder called blossom end rot may damage fruits like tomatoes, squash, cucumbers, and watermelons. Too much water can cause problems, too, contributing to plant diseases and diluting the sweetness of fruits. Try to apply water early in the morning, so the sun can dry excess water off plant leaves, reducing the ability of some fungal diseases to get established. If using drip irrigation, the watering time of day is less important. Be sure drip tubing is placed near plants and makes direct contact with the soil, so that water goes directly to plant roots instead of soaking mulches or the empty space between rows.
For long-term, successful gardening, send a soil sample to the LSU AgCenter soils lab and, if needed, consult your county agent to help you interpret the results. Besides informing you about the current nutrient content of your soil and advising how to make up for any nutrients lacking, the lab will provide your soil texture. Soil texture is the proportion of the three soil particles — sand, silt, and clay — found in your garden soil. Sand is the largest particle. Pure sand is a poor growing medium, as its large pieces, fitted together, leave so many air spaces that water drains straight through and plant roots dry out quickly. Silt is much smaller and has been deposited by long-ago rivers. Clay is made of tiny particles, fitted tightly together. Because of its tight arrangement, clay is good at holding onto nutrients and water, but it does not have much room for air, which plant roots need. It may also hold onto too much water, waterlogging plant roots and leading to disease. The best soils are a mix of all three particles, called loam. If the mix is a little heavy on clay, it’s called clay loam; if more silt, it’s a silt loam; and so on. The soil texture can affect how well your soil holds onto nutrients and water and contributes to soil health. Soil test results will also provide your soil’s pH, the measure of how acid (0-7) or alkaline (7-14) your soil is. Ideal vegetable pH is around 6.5, though it differs a little by crop. Growing very far from the ideal pH (very alkaline or very acid) can affect whether needed nutrients in the soil will be in a form that your plant’s roots can take up and use. Sometimes altering the pH can be used as a tool to prevent some soil diseases from attacking the plant. In general, altering the pH is done by adding limestone to raise (make more alkaline) or sulfur to lower (make more acid) the pH. These are chemical reactions in the soil. They are not permanent and the soil will always revert to the original pH when the reaction has finished.
Another major contributor to soil health is organic matter. It’s not one of the three soil particles, but organic matter is anything that was once living plant (or animal) material. As this formerly living matter decomposes in the soil, it adds nutrients for both the plants growing in the soil and other organisms also living in the soil, like microbes, earthworms, insects, and other microorganisms. Many of these are beneficial to plants and all contribute to the natural balance of a good, living soil. When organic matter is added to the soil, it also acts a soil conditioner, slowing down the drainage of water from sandy soils and helping to break up tightly packed clay soils, making more air spaces for oxygen and improving poor drainage. It’s a good practice to dig several inches of organic matter into the soil every year. Most areas of the state have agricultural by-products like livestock manure, bagasse from sugar mills, ground bark from paper mills, gin trash, rotted hay, or municipal compost available free or at minimal cost.
Another way to add organic matter (and nutrients) to soil is to plant a cover crop, also called a green manure crop. Broadcast seed of a seasonally appropriate (warm- or cool-season) crop. Drag the ground with a rake to cover seed. Allow the cover crop to grow to the point of flowering (or until a few weeks before you plan to plant your garden); then, mow and turn under with a tiller or shovel. Freshly cut cover crops are much easier to turn in than those that have been allowed to dry. Good warm-season cover crops are Southern peas and buckwheat. Winter cover crops are Austrian peas, clovers, and annual ryegrass and other grains. Peas and clovers have the added benefit of fixing nitrogen in the soil, so you can fertilize less where a cover crop was recently grown.
Plants need nitrogen, phosphorous, and potassium for good growth, plus many other nutrients in smaller quantities. Even if your soil test results are excellent, you will still need to add nitrogen. By its nature, nitrogen is not held in place by soil and is often leached into surface and/or ground waters. It must be added at planting time (called preplant) for every crop you intend to grow. It’s available as a granular fertilizer, balanced with all three major nutrients like 13-13-13, or as a specialty fertilizer like 33-0-0 (33% nitrogen – 0% phosphorous – 0% potassium). Since nitrogen doesn’t stick around long, we add a little more as plants begin to produce, called a sidedressing (a little more on the side). Consult Seeds to Sow Crop Guides for specific quantities, apply to the soil, and rake in. Water when the garden is planted or after sidedressing to help the fertilizer dissolve. Granular chemical fertilizer is the most convenient form of fertilization, but it does little to improve soil health, like increasing organic matter or feeding beneficial microorganisms. Chemical fertilizers also negatively impact the microbial life of soil. An alternative choice is natural organic fertilizers. Most contain all three of the major nutrients, provide additional organic matter, and do not produce salts and acids that may build up with overuse of chemical fertilizers. Organic fertilizers also break down and release nutrients more slowly and evenly over the life of the crop. Good choices are manures, cottonseed meal, blood meal, compost, and worm castings.
Plants have an ideal spacing for each crop, usually just far enough apart that the foliage will touch and not interfere with the neighboring plant. The larger the plant, the greater the spacing. Plants may be grown at their ideal, size-determined spacing or they may be planted close together. If close together, individual plants will produce less, but many more plants together will make up for less production and may even produce more.
Your garden design can also play a role in plant spacing. In Square Foot Gardening, each plant is spaced at its ideal spacing within a 1 foot square. In traditional row gardening, plants are spaced, single file, at their ideal, size-determined spacing. Wide rows usually have 2-3 lines of plants within each row, staggered to allow closer spacing. In raised beds, plants can usually be spaced a little closer together. A planting method called French Intensive gardening calls for deeply dug, well-prepared, fertile soil with plants spaced quite closely together.
Seed or Transplants?
As a general rule, plants with large seeds (melons, corn, cucumbers, and squash) are planted directly in the ground. They can be grown as transplants, but they produce a large plant so quickly that it’s best to seed them indoors only a few weeks before planting outside. If grown too long in a seedling tray or pot, they do not transplant well. Greens are generally planted directly; so are onion sets and the seeds of other root crops. Many smaller-seeded plants like the cole crops (cauliflower, broccoli, and Brussels sprouts) and summer crops like tomatoes, peppers, and eggplant are best started inside 5-6 weeks before the expected planting date. Consult the individual Crop Guides before buying seeds and seeding transplants.