Fill a Raised Bed

Before you fill your raised bed, consider what you will grow inside it. This will inform your choice of placement, type, and content.

Nutrient Needs: Heavy feeders (corn, cucumber, tomato, broccoli) will need plenty of nutrients. Consider adding a green layer, increasing compost, worm castings, or additional fertilizer. Light feeders (lettuce, peas, radish, sunflowers) won't be as demanding on the soil.

Soil pH: Acid-loving plants (blueberries, cranberries, raspberries, rhubarb) will need some adjustments in their soil blend. Adding peat moss, elemental sulfur, composted or aged manure, or pine needles as a mulch can do this.

Moisture Preferences: Some plants like well-drained soil (tomatoes, peppers, lavender, oregano). In this case, consider adding sand and/or perlite to the soil mix and using rocks for drainage. For those plants that like soil to stay moist (lettuce, kale, blueberries, watermelon), coco coir can retain water in the soil.

Depth: Shallow beds are good for greens, herbs, and root vegetables with short roots. Deep-rooted crops like carrots and tomatoes prefer a depth of at least 12-18 inches of soil.

Inevitably, the nutrients in the soil of a raised bed will diminish. However, there are a few practices to help ensure the health of your soil without adding harmful chemicals.

Plant Guilds
A plant guild is a group of plants that all contribute something beneficial to mix to create a more balanced ecosystem. In this method, you choose a set of plants to fill a different role:

• Main Crop: It's the central purpose of the guild, which has the largest yield or most valuable contribution, such as fruit trees, nut trees, or large vegetables like squash.
• Nitrogen Fixers: These plants improve soil fertility by converting atmospheric nitrogen into a form plants can use, such as legumes like clover, peas, beans, or lupines.
• Dynamic Accumulators: Deep-rooted plants, such as comfrey, dandelion, yarrow, and nettles, bring nutrients from subsoil layers, enriching the topsoil when their leaves decompose.
• Pollinator Attractors: These plants attract bees, butterflies, and other pollinators, ensuring the main crops, such as lavender, marigold, echinacea, and sunflowers, get pollinated.
• Pest Repellents: Certain plants, such as garlic, chives, nasturtium, and tansy, naturally deter harmful pests and protect the guild.
• Ground Covers: Low-growing plants, such as strawberries, creeping thyme, and clover, suppress weeds, retain moisture, and prevent soil erosion.

Rotate Crops
As you can see from the plant guild, different plants interact with the soil differently. If you want to separate planting between beds, try rotating them between beds each growing season. This will ensure that the heavy feeders don't run your soil dry in one bed.

Cover Crops
Soil should never be exposed to the elements. If you leave soil exposed, you ask for weeds to grow. Cover crops are a good solution for providing living mulch and helping the soil outside the growing season.

Timing: Cover crops can be grown any time of the year. Place them as ground cover during growing seasons or in between growth cycles. Here are some ways to use cover cropping in your garden schedule:

• Fall/Winter
  Protect against erosion, prevent weeds, and improve fertility over dormant months; plant 4-6 weeks before the first frost and terminate in early spring.
• Spring
  Add organic matter and prepare the soil for the growing season. Plant as soon as the soil is workable in the spring and terminate 2-4 weeks before planting the main crop.
• In-between seasons
  Fill gaps between growing seasons to protect the soil, plant after harvesting, and terminate 2-4 weeks before planting again.

Termination: Cover crops are chopped and dropped before they go to seed to prevent invasion. For nitrogen-fixing cover crops, work the cuttings into the top 2-3 inches of soil to decompose. Otherwise, leave the cut crop as a mulch layer.

Maintenance: As with anything you plant in the garden, ensure cover crops are watered, weeded, and generally healthy.

Cover crops can be planted for nitrogen fixation-ideal for improving fertility (clover, peas, vetch, alfalfa), weed suppression-good for fast-growing cover (rye, oats, or buckwheat), soil conditioners-helps break up compact soil (radishes, mustard)

Replenish Compost
Add 1-2 inches of compost or soil mix at the start of the growing season to replenish nutrients and improve soil structure. You can do this by raking the mulch to the side, layering on the compost, and then replacing and replenishing the mulch. If the soil requires it, this can also be done post-harvest. For heavy-feeding crops or struggling plants, layer compost around the base of the crops every 4-6 weeks.

Raised beds come in many shapes and sizes. Some can be purchased, and others are built. The type you choose has benefits and drawbacks. Here are some things to consider.

Material

• Wood: Affordable, easy to construct, and customizable in size and height. However, it may rot over time unless built with rot-resistant wood like cedar or redwood.
• Metal: Made from galvanized steel or corrugated metal panels. Durable, rust-resistant. It can accumulate heat in hot climates, potentially affecting plant roots.
• Stone or Brick: This type is built using stacked stone, bricks, or concrete blocks. It is long-lasting and sturdy, but it is heavy and labor-intensive to build and has a higher initial cost.
• Composite: Made from recycled materials like plastic and wood fibers, composite is rot-resistant, durable, and lightweight. It is more expensive than wood and may not be aesthetic for some.
• Straw Bales: These are made using straw bales as walls, which can decompose over time. They are inexpensive, biodegradable, and good for temporary setups. However, they have a limited lifespan and can attract pests or mold.
• Modular: Pre-made kits that can be assembled and expanded as needed. They are easy to set up and customizable. However, they are typically more expensive than DIY options.

Ground Access
Some beds are elevated off the ground with supported bottoms. These are good if you want your garden completely contained but can have issues with drainage. Other beds can be placed on the ground, and plant roots can have more depth in the ground below. This allows burrowing animals to find a way into your garden.