No room in a yard? Container gardens are a great way to grow vegetables with the proper precautions. Here are several considerations when planting in containers:  

Sun

Select plants based on sunlight exposure. Most vegetables require 6 to 8 hours of direct sun daily. Leafy vegetables like lettuce, onions, carrots, and beets can handle partial shade. Fruit-bearing plants such as tomatoes, eggplant, squash, and peppers need more than 8 hours of full sun.

Container  

Almost any container will do as long as it has adequate drainage. Smaller containers and those made of terra cotta or unglazed clay tend to dry out quickly during summer months. Smaller containers (those less than 8 to 12 inches in diameter and depth) may do in partially shaded areas. Porous containers (such as those constructed from clay, wood, or cement) should be thoroughly soaked in water prior to filling to prevent them from absorbing moisture from the soil.

A deeper container is better than one that is wider, as it allows more room for roots to grow downward in search of moisture and cooler temperatures. This promotes plant vitality during hot summers that require frequent watering. Containers should be at least 4 inches deeper than the anticipated mature root length. The roots in container plants are more susceptible to temperature fluctuations. Midsummer heat can damage delicate, hair-like feeder roots, leading to plant wilting even if the soil remains moist. Larger roots become highly susceptible to root rot fungus, which can ultimately destroy the plant. Overheated soil is a prevalent cause of failure in container planting. Thick wooden containers provide superior insulation; dark-colored containers absorb more heat, while light-colored containers reflect heat.
Drill drainage holes in containers, with larger pots requiring more holes. Prevent potting mix from washing out by placing a screen or broken pot chard over the holes. Disinfect reused containers with a 9-to-1 water-to-bleach solution before planting. Use saucers under pots to avoid staining surfaces. Do not allow containers to sit in water.  

For containers with saucers, use pebbles to elevate them above the drainage water level, to prevent root rot and increase humidity as necessary. Elevate smaller containers using clay risers, bricks, or wood to improve drainage. Large containers generally have sufficient drainage space.

What to Plant

Shallow-rooted crops like herbs, lettuce, green onions, radishes, and spinach are easy to grow. Carrots, potatoes, turnips, and other root crops need deeper containers. Tall vegetables such as eggplant, peppers, squash, and tomatoes require room for their extensive root systems. For optimal use of space, choose high-yielding dwarf and/or varieties, such as beans, beets, carrots, lettuce, peppers, radishes, and certain summer squash and tomatoes. Avoid "giant" varieties, and opt for short, bushy plants. Support vining or trailing crops from the start to avoid damaging roots later.

Seeds vs. Transplants 

Starting plants from seed can be more cost-effective. Transplants are typically sold as four to six young plants in a pack. Timing for starting seeds or transplanting into the garden is important due to temperature impacts. “Direct sow” indicates that it is safe to start seeds for a vegetable variety in the soil. “Transplant” means it is time to move transplants started indoors or purchased at a garden center into the container outside. Some plants are recommended to start from seed while others are recommended as transplants. Root vegetables such as carrots, turnips, and beets do not transplant well, so direct seeding is safest. Cole crops like broccoli, cauliflower, cabbage, and Brussels sprouts can successfully be transplanted into the container, with transplanting preferred to ensure maturity before heat slows production. Plant beans, beets, carrots, cucumbers, lettuce, peas, radishes, and squash from seed. Eggplant, peppers, and tomatoes are often purchased as transplants. Smaller size transplants (6 packs or 4” pots) develop better roots and grow more quickly than gallon-size plants.

Soil Preparation 

Avoid using garden soil as it may contain diseases, fungi, and is generally heavy and slow to drain. Purchase a high-quality, sterilized soil mix that can absorb moisture and drain efficiently. When planting in containers, using the appropriate medium is crucial for optimal results. The terms “potting soil” and “potting mix” are often used interchangeably, but there is a distinction between the two. Potting soil may include dirt, whereas potting mix does not. Due to its soilless nature, potting mix does not harbor any pathogens (fungi and other soil-borne diseases), making it safer for plants grown in containers.

A premium potting mix will be lighter and prevent soil compaction. Soil compaction restricts a plant's access to water and nutrients, and inadequate aeration can suffocate its roots. Mineral components such as perlite, pumice, and vermiculite added to soil mixtures influence aeration, structure, and water retention. One or more of these components may be included in a potting mix. The other ingredients will either be organic or animal-based materials, or inorganic-natural materials, depending on the brand and type of mix. Organic/animal-based materials include aged composted bark, sphagnum moss, manure, worm castings, bat guano, or coconut coir (a sustainable material derived from coconuts that replaces sphagnum moss, which is not sustainable). Some mixes also contain synthetic or organic fertilizers, providing necessary nutrients. Choose nutrient-rich blends containing alfalfa meal, bone meal, or kelp meal.

Investing in quality potting mixes is essential. Generic or cheaper brands may include garden soil, which affects the soil’s texture and quality. Look for potting mixes that list their ingredients on the back of the package. If the mixture's ingredients are not specified, it is advisable not to purchase it.

Fertilizing Requirements

Plants confined to containers are unable to seek out nutrients or water. Consequently, restricted root systems require frequent yet light fertilization during their growth phase. Nutrients are depleted from the soil with each watering and must be replenished regularly. It is advisable to begin using a water-soluble fertilizer at one-quarter strength with each watering, starting two to four weeks after planting. Organic gardeners may use liquid fish emulsion, liquid kelp, or blood and bone meal for this purpose.
The three numbers on the fertilizer package, like 10-10-10, indicate its purpose:

• Nitrogen – green leaves
• Phosphorus – flowers and fruit
• Potassium – root growth

A higher number means more growth in that area. Do not overfeed; a little is good, but more is NOT better.

Water

All containers dry out quickly. Watering requirements will vary according to the season, type of container, soil mix, and sun exposure. Container-grown plants require more frequent watering than those growing in the soil.

Check containers daily. A soil meter can help determine if plants need water, but inserting a finger into the pot into the top inch of soil is an efficient and cost-effective method to assess moisture levels. If it feels damp, watering is not immediately necessary. If it feels dry, water until some drains out the bottom of the container. It is essential for water to reach the entire root system. If water contains salts that deposit on fixtures, thorough watering is important to allow water to drain from the bottom of the container. This leaches salts and prevents harmful levels from accumulating in the container.

In mid-summer and on windy days, daily watering may be required. In summer, use a saucer to catch excess water which can then be reabsorbed as needed. In winter, remove the saucer to prevent plants from sitting in stagnant water.

Water early in the morning to avoid wet leaves at night when temperatures drop, as mildew and disease organisms can thrive. Use a slow and even spray to avoid disturbing the soil. The lower soil volume and less insulation in a pot cause the soil to heat up and evaporate water more quickly. Plants, particularly edibles, prefer moist soil. Consistent watering will promote healthy container plants. Consider installing a drip system.

Mulch 

Mulch plants with straw or other non-woody material from June through the summer. This practice will reduce evaporation, conserve water, and enable plants to grow more effectively without unnecessary stress. Mulch forms a barrier that prevents weed seed germination and growth, thereby minimizing the need for weeding. It assists in retaining moisture within the soil, reducing the frequency of required watering. It also stabilizes soil temperature, protecting roots against extreme heat or cold. As mulch decomposes, it contributes organic matter and nutrients to the soil, enhancing its overall fertility. Finally, mulch provides a finished look to containers and can improve the overall appearance of the garden.
Several types of mulch available. Straw is an excellent choice, particularly when starting seeds due to its lightweight nature and ease of application. Caution should be exercised with hay as it may contain weed seeds. Compost is beneficial for nutrient provision and soil structure improvement. Shredded bark offers effective drainage and soil temperature regulation. Shredded leaves are a free and readily available option, although they may require composting or slight drying before use. Grass clippings can be utilized, provided they are free from herbicides and applied in thin layers to prevent mold development. Landscape fabric is effective for weed suppression but should be covered with mulch in other areas.
Apply a layer of mulch 2-3 inches deep around the plants with space around the stems for proper aeration. Avoid packing the mulch too tightly. This can restrict airflow and potentially lead to fungal diseases. Periodically replenish the mulch as it decomposes to maintain its beneficial effects. During extreme temperatures, an extra layer of mulch insulates the soil, preventing excessive heating and reducing water loss through evaporation. A thick layer of mulch will also safeguard plant roots. Use big enough pots to allow for a thick layer of mulch.