According to B. Rosie Lerner, Purdue University horticulturist and Master Gardener, raised-bed vegetable gardening offers advantages of soil conditioning and gardening ease. A raised bed, whether it is loosely piled or contained in a frame, lifts the garden above the original ground level. You can use the raised garden to create a planting area above compacted or poor soil. The added height makes planting and care easier for older or mobility-restricted gardeners.
Leaf crops such as lettuce, greens and spinach thrive in raised beds. Purdue University recommends commercial or home mixes of vermiculite or perlite mixed with organic matter as a quick-draining garden media. Salad greens prone to root rot and fungus need well-aerated soil. The sandy blend allows easy sowing for fast-sprouting salad veggie seeds. Rotate these short-season crops with radishes or parsley.
Tomatoes also grow well in raised vegetable beds. These plants like rich well-drained soil that warms in sunlight. Fungus infects tomatoes if they have wet foliage and water-logged roots. Raised beds allow the roots to drain and air to circulate more freely among the plants. According to David W. Sams, University of Tennessee Plant and Soil Science professor, these vegetables may require cages or stakes that do not overshadow low-growing vegetables.
According to The Green Line, gardening newsletter of the University of Illinois, carrots and other root crops including onions, beets and potatoes benefit from raised beds. Loose soil allows full root development and easy harvest compared to that from hard ground. These plants mature more slowly than leafy vegetables and are good background crops in raised gardens.
Plant beans and peas in raised vegetable beds as these shallow-rooted plants grow best in sunny, moderately rich soil. Beans and peas are heavy feeders for top production. Use a side-dressing of fertilizer. Scatter manure, compost and other organic matter over the seeds or in a band around the plant. Provide stakes or trellises to keep the plants off the ground.
Okra, corn and other full-sun warm-soil plants mature more quickly in raised beds. Master Gardener Lerner reports the ground warms early in spring so you can plant crops a few weeks ahead of regular ground gardens. With weeding in a raised bed, you won't have to walk between rows and damage fragile or wet foliage. Since corn and other stalk crops may develop disease that easily spreads among plants by contact weeding, raised beds will allow you to cultivate these crops more easily.