Start with soil, not seeds
Before you put anything in the ground, fill your raised bed with the right soil mix. Most gardeners use a combination of topsoil, compost, and peat moss or coconut coir in roughly equal parts—this gives plants nutrients, drainage, and the ability to hold moisture without staying soggy. If you're starting with an empty bed frame, you'll need enough soil to fill it to within two inches of the top rim.
Measure your bed's length, width, and depth in feet, then multiply those three numbers together to get cubic feet. A 4-by-8-foot bed that's 12 inches deep needs 32 cubic feet of soil. Bags at garden centers usually hold 2 to 3 cubic feet, so you can calculate how many you'll need. Buying soil in bulk from a landscape supplier is cheaper if your bed is large.
Spread the soil evenly and water it thoroughly before planting. The soil will settle over the first week or two, so don't be alarmed if the level drops slightly. You can add a bit more soil later if needed.
Key Takeaways
- Fill your bed with a mix of topsoil, compost, and peat moss or coconut coir in roughly equal parts, leaving two inches of space at the top.
- Space plants according to their mature size, not their current size—crowding leads to poor air circulation and disease.
- Plant seedlings at the same depth they were growing in their containers, with the soil line at the base of the stem.
- Water when ready after planting and keep the soil consistently moist (not waterlogged) for the first two to three weeks while roots establish.
- Direct-sown seeds need to stay moist until they sprout, which usually takes 7 to 14 days depending on the plant.
Decide between seedlings and direct-sown seeds
You have two ways to get plants into the bed: buy seedlings (small plants already started in pots) or sow seeds directly into the soil. Seedlings give you a head start—they're ready to grow and produce faster—but cost more. Direct sowing is cheaper and works well for root vegetables, beans, peas, squash, and lettuce, but takes longer to reach harvest.
If you're new to gardening, seedlings are the easier route. They're more forgiving of mistakes and you'll see results sooner. Direct sowing works best if you're planting in spring or early summer when the soil is warm and you have time to wait for germination.
Space plants correctly for air and growth
Spacing is one of the most common mistakes home gardeners make. Plants that are too close together compete for water and nutrients, and poor air circulation invites disease and pests. Check the seed packet or the label on your seedling container—it will tell you the mature size of the plant and how far apart to space them.
A tomato plant that will grow three feet wide needs three feet of space in all directions from its neighbors. A lettuce plant that matures at six inches wide can be planted six inches apart. If the spacing seems wasteful when the plants are small, remember that you're spacing for their full size, not their current size. The bed will look full within four to six weeks.
Sketch out your layout on paper before you plant. This takes five minutes and prevents the frustration of realizing halfway through that you've run out of space.
Plant seedlings at the right depth
Remove a seedling from its container and gently loosen the roots with your fingers—this helps them spread into the surrounding soil instead of staying in a tight ball. Dig a hole just deep enough that the soil line on the seedling (the point where the stem meets the roots) sits at the same level as the soil in your bed. The exception is tomatoes: you can bury them deeper, up to the first set of true leaves, and they'll develop roots along the buried stem.
Backfill the hole with soil, press gently to remove air pockets, and water when ready. The soil will settle as it absorbs water, so don't worry if the plant sinks slightly.
Direct sow seeds at the correct depth
The seed packet tells you how deep to plant each type of seed—follow that instruction exactly. A general rule is to plant seeds at a depth equal to two or three times their width: tiny seeds like lettuce go barely under the soil surface, while larger seeds like beans go an inch or more down. Too shallow and they dry out; too deep and they can't push through to the surface.
Make a shallow furrow or hole with your finger or a stick, place the seed, cover it lightly with soil, and water gently so you don't wash the seed away. Keep the soil moist until the seedling emerges—this usually takes 7 to 14 days, though some seeds take longer. Once the seedling has its first true leaves (the second set to appear), you can water less frequently but more deeply.
Water consistently for the first three weeks
New plants—whether seedlings or sprouted seeds—need steady moisture while they're establishing roots. Check the soil with your finger each morning. It should feel like a wrung-out sponge: moist but not soggy. If the top inch is dry, water until the soil is moist two to three inches down.
Watering in the early morning is best because it gives foliage time to dry before evening, which reduces disease. Avoid watering the leaves themselves; water the soil around the base of each plant. After three weeks, most plants can handle drier periods between waterings, though you'll still need to water during hot spells or drought.
If your bed drains very quickly (sandy soil) or holds water too long (heavy clay), you may need to adjust. Sandy soil needs more frequent watering; clay soil needs less. You can improve both by mixing in more compost.
Add mulch to retain moisture and suppress weeds
Once your plants are established and about four inches tall, spread two to three inches of mulch around them—wood chips, straw, or shredded leaves all work well. Leave a two-inch gap around the stem of each plant so mulch doesn't trap moisture against the stem and cause rot.
Mulch keeps the soil cooler and moister, which means less frequent watering. It also prevents weeds from sprouting and makes the bed look finished. As the mulch breaks down over the season, it adds organic matter to the soil, which improves it for next year's planting.
Frequently Asked Questions
Can I plant everything at the same time?
No. Cool-season crops like lettuce, peas, and broccoli go in early spring or late summer. Warm-season crops like tomatoes, peppers, and squash go in after the last frost date in your area, when soil temperature reaches at least 60°F. Check your local frost date online or ask at a nearby garden center.
What if seedlings look leggy or pale before I plant them?
Leggy seedlings (tall and thin with few leaves) usually mean they didn't get enough light indoors. Plant them slightly deeper than normal—they can develop roots along the buried stem. Pale seedlings need more nutrients; mix a diluted fertilizer into the water you use for the first week after planting.
How do I know if I'm overwatering?
Overwatered plants often look wilted and yellow, which confuses people into watering more. Check the soil first: if it's soggy, stop watering and let it dry out. If it's dry, water. Soggy soil suffocates roots and invites fungal disease. Most raised beds drain well, so overwatering is less common than underwatering.
Should I fertilize when I plant?
If you mixed compost into your soil, you have enough nutrients for the first four to six weeks. After that, most plants benefit from a light feeding every two to three weeks during the growing season. Use a balanced fertilizer (equal parts nitrogen, phosphorus, and potassium) at half the strength listed on the package.
Can I replant the same bed next season?
Yes. Before planting, mix in two to three inches of fresh compost to replenish nutrients the previous crop used. If you grew tomatoes, peppers, or eggplants, plant something from a different family in that spot the next year to avoid soil-borne diseases. Rotating crops keeps soil healthy and productive for years.