Start with soil, not seeds

Fill your raised bed with soil before you plant anything. Most gardeners use a mix of topsoil, compost, and peat moss or coconut coir in roughly equal parts—this combination drains well while holding moisture and nutrients that vegetables need. A 4-by-8-foot bed that is 12 inches deep needs about 32 cubic feet of soil, which you can calculate for your own bed by multiplying length × width × depth in inches, then dividing by 1,728.

Do not use garden soil straight from your yard. It compacts in a raised bed and blocks water and roots. Bagged mixes sold as "raised bed soil" or "garden mix" at hardware stores are ready to use, though they cost more than buying components separately. If you are filling a large bed, buying in bulk from a landscape supply yard is cheaper than bags.

Fill the bed completely and water it thoroughly before planting. The soil will settle over the first week, and you may need to add more. Let it sit for a few days if you can—this helps it compress naturally and makes planting easier.

Key Takeaways

  • Fill your raised bed with a mix of topsoil, compost, and peat moss or coir rather than garden soil, which compacts and blocks drainage.
  • Space plants according to their mature size, not their current size, or they will crowd each other as they grow.
  • Plant cool-season crops like lettuce and spinach in spring and fall; plant warm-season crops like tomatoes and peppers after the last frost date in your area.
  • Water raised beds deeply and regularly because they drain faster than in-ground gardens, especially in hot weather.
  • Add 1 to 2 inches of compost to the top of your bed each spring to replace nutrients that plants used the year before.

Space plants by their full-grown size

The distance between plants matters more than most new gardeners expect. A tomato seedling looks tiny next to a lettuce seedling, but the tomato will be 4 feet tall and 2 feet wide by mid-summer. Plant it too close to other vegetables and it will shade them or compete for water and nutrients.

Check the seed packet or plant label for "spacing" or "distance apart." This is the distance from the center of one plant to the center of the next. Lettuce typically needs 6 to 8 inches; peppers need 18 to 24 inches; tomatoes need 24 to 36 inches. If the label says "thin seedlings to 12 inches," that means remove the weaker seedlings so the remaining ones are 12 inches apart.

Crowded plants are more likely to get fungal diseases because air cannot circulate around the leaves. They also produce smaller vegetables and fewer of them. If you are not sure about spacing, err on the side of more room—you can always fill gaps with fast-growing crops like radishes or lettuce later in the season.

Plant at the right time for your climate

Cool-season crops like lettuce, spinach, peas, and broccoli tolerate frost and actually taste better in cool weather. Plant them in early spring (as soon as soil can be worked) and again in late summer for a fall harvest. In mild climates, you can plant them in fall and harvest through winter.

Warm-season crops like tomatoes, peppers, squash, and beans need soil that is at least 60°F and air temperatures consistently above 50°F at night. Wait until after your area's last frost date—this varies by region and can be found by searching "[your city] last frost date." Planting too early kills seedlings or causes them to sit in cold soil and rot.

You can start cool-season seeds directly in the raised bed by sprinkling them where you want them to grow. Warm-season crops are usually easier to start from seedlings bought at a garden center, though you can start seeds indoors 6 to 8 weeks before your last frost date and transplant them outside when they are 3 to 4 inches tall.

Water deeply and often

Raised beds dry out faster than in-ground gardens because soil is exposed on all sides to air and sun. Check the soil by pushing your finger 2 inches down—if it feels dry, water. Most vegetables need about 1 inch of water per week, either from rain or from you.

Water in the early morning so leaves dry quickly and fungal diseases have less chance to take hold. Water at the soil level, not on the leaves. A soaker hose or drip line laid on top of the soil and covered with mulch delivers water directly to roots and wastes less to evaporation than overhead watering.

In hot weather (above 80°F), check soil moisture every day. Tomatoes, peppers, and squash especially need consistent water—letting them dry out and then soaking them causes fruit to crack or split. Mulch the top of your bed with 2 to 3 inches of wood chips or straw to slow evaporation and keep soil cooler.

Add compost each spring

Vegetables consume nutrients as they grow. After you harvest in fall, spread 1 to 2 inches of finished compost over the top of your bed and let it sit over winter. By spring, it will have mixed into the soil and replaced what was used. You do not need to dig it in—earthworms and microbes do that work for you.

If you do not have compost, bagged compost from a garden center works the same way. Some gardeners add a thin layer of compost in mid-summer as well, especially if they are growing heavy feeders like tomatoes or squash. This is optional but helps if plants look pale or stop growing.

After 3 to 4 years, the original soil will have broken down significantly. At that point, remove the top 6 inches and replace it with fresh soil and compost, or empty the entire bed and refill it. This is a good time to rotate where you plant different crops—do not plant tomatoes in the same spot two years in a row, as this spreads soil-borne diseases.

Manage pests and diseases without chemicals

Raised beds have fewer soil-borne pests than in-ground gardens because you started with clean soil. The most common problems are insects like aphids, beetles, and caterpillars, and fungal diseases like powdery mildew.

Check plants twice a week for damage. If you see holes in leaves or insects on stems, remove them by hand or spray with water to knock them off. For larger infestations, insecticidal soap (made from potassium salts of fatty acids) works on soft-bodied insects like aphids and is safe for vegetables. Neem oil works on a wider range of pests but can damage some plants in heat, so use it in early morning or late evening.

For fungal diseases, improve air circulation by spacing plants correctly and removing lower leaves that touch soil. Water only at the base of plants, never on leaves. If powdery mildew appears, spray with a baking soda solution (1 tablespoon baking soda + 1 tablespoon horticultural oil + 1 gallon water) every 7 to 10 days until it clears.

Harvest regularly to encourage more growth

Pick vegetables as soon as they reach usable size. Lettuce and spinach can be harvested leaf by leaf when leaves are 4 to 6 inches long, or the whole plant can be cut at the base. Beans and peas should be picked when pods are tender and seeds inside are still small. Tomatoes taste best when fully colored but still slightly soft.

The more you harvest, the more the plant produces. A tomato plant that has fruit picked regularly will keep flowering and setting new fruit all season. A plant left unharvested will slow down or stop producing once it has made enough seeds. This is why a small raised bed can produce a surprising amount of food if you harvest often.

At the end of the season, pull out dead plants and add them to a compost pile (not diseased plants—throw those away). Leave the soil in place over winter; it will rest and be ready for spring planting.

Frequently Asked Questions

Can I plant vegetables directly in a raised bed without filling it with new soil?

Not recommended. If you place a raised bed on top of existing garden soil, roots will eventually grow down into it, and compacted soil will block drainage. Fill the bed with the soil mix described above. If cost is a concern, you can use a lasagna gardening method: layer cardboard, compost, grass clippings, and leaves in the bed, then top with 4 to 6 inches of soil. It takes a season to break down but works.

How deep does a raised bed need to be for vegetables?

Most vegetables do well in 12 inches of soil. Shallow-rooted crops like lettuce and radishes can grow in 8 inches. Deep-rooted crops like tomatoes, carrots, and parsnips need 18 inches or more. If your bed is only 12 inches deep, stick to shallow and medium-rooted vegetables, or grow tomatoes in containers instead.

What if my raised bed is in partial shade?

Most vegetables need 6 to 8 hours of direct sun per day. Leafy greens like lettuce, spinach, and kale tolerate 4 to 6 hours and actually prefer afternoon shade in hot climates. Tomatoes, peppers, and squash need full sun and will produce poorly in shade. If your bed gets less than 4 hours of sun, grow shade-tolerant crops or move the bed to a sunnier spot.

When should I stop planting for the season?

Stop planting warm-season crops 8 to 10 weeks before your first fall frost date—this gives them time to mature before cold kills them. You can plant cool-season crops up to 8 weeks before the first frost. Search "[your city] first frost date" to find yours. In mild climates, you can plant cool-season crops in fall and grow them through winter.

Do I need to add fertilizer to a raised bed?

If you fill the bed with compost-rich soil and add compost each spring, most vegetables will have enough nutrients. Heavy feeders like tomatoes, squash, and corn may benefit from a balanced fertilizer (like 10-10-10) applied mid-season. Follow package directions and water well after explore. Organic options include fish emulsion, seaweed extract, and compost tea.