What to consider before installing a raised garden bed

What to consider before installing a raised garden bed

If you're ready to install a raised bed garden or just thinking about the possibilities, there are a few things to consider before getting started. Like any construction project, your loft bed requires investment and planning. You want to get things right the first time to save unnecessary costs and hassles. After decades of working with elevated gardens, we suggest considering the following questions.

1. How do you decide where to put your loft bed?

Before deciding where to put your bed, think about what you want to plant. Most vegetables need at least 6 hours of sunlight per day, and the more the better. Leafy plants like Swiss chard, lettuce, and spinach will grow in less than six hours of sun, or some dappled shade throughout the day, but they will grow more slowly. Other crops need all the sunlight to thrive.

Once you've decided which plants to grow, choose your beds based on the amount of sunlight you want. You can calculate this using the Sunshine Calculator or a mobile phone app like Sunseeker or Lumos. In most cases, placing your bed from east to west -- and planting tall plants in the back -- means your crops won't be in the shade of anything next to them.

Related: 6 Beautiful Raised Bed Garden Layouts

2. What type of soil do you need?

Raised garden beds are lifted off the ground. For this reason, it's important to use a more absorbent soil mix to help retain water and nutrients. Absorbent materials can include anything from coconut coir (which can be expensive for large beds) to finished compost (more affordable and nutrient-dense).

Whatever you use, make sure the mixture comes from a source with a high percentage of organics. Topsoil mixed with compost and peat moss is a common mix. You can plant according to your plan to amend the soil with more specific minerals and nutrients. For more information, read 3 Soil Mixes for Raised Garden Beds.

3. What plants grow best in a highland garden?

You can grow just about anything in your raised bed as long as you have six hours of full sun. Root vegetables, leafy crops, peas and trellis-attached beans… these can all be grown in raised gardens. An important point to consider is soil depth, as different plants have different needs (see below).

4. How deep should you build your loft bed?

If the soil under your raised bed is rich enough to grow on its own, then you don't need to raise your garden more than 12 inches. That's because plant roots have access to nutrients a foot or so below the bed level.

If your soil is marginal, or you're installing your bed on concrete, you'll need to go higher—up to three feet in some cases. What you want to plant will affect the finished height of your bed, as different plants have different needs. Deep-rooted crops like tomatoes, sweet potatoes, squash, asparagus, and watermelon do best at a depth of 24 to 36 inches. See our guide for more details on soil depth requirements.

5. What size should a loft bed be?

Assuming we're talking about a rectangular raised bed, the length and width depend on several factors.

The easiest way to measure the width of a bed is to measure your arm from shoulder to fingertips. If your bed is accessible from both sides, you can double the arm length and subtract 6 to 8 inches. That's how far you can get comfortably. That means you end up with a 3 to 4 foot bed.

Length is another matter. Long beds with minimal paths make irrigation easier, but you'll need some less troublesome navigation. Popular lengths include 6, 8 and 10 feet.

6. Do you need cross bracing?

Cross bracing is useful for longer, wider beds because pressure from the soil can cause the bed to bow outward. This depends somewhat on the thickness of the board, but in general, beds six feet or longer will benefit from cross bracing.

You can stick a piece of wood on the bed above or below the soil level, or you can use stainless or galvanized steel.

7. What is the best way to fix the corners?

Corners are the weak point of raised garden beds. In winter, when the soil freezes and swells, the corners bear the brunt. There are many different ways to reinforce your corners and make your bed as long as possible.

The stakes driven into the ground at the four corners provide a convenient place to nail level boards on the DIY wood bed. They can extend about a foot into the ground.

Corner brackets provide a quick way to secure and strengthen the bed. They are great for DIY loft bed constructions. Some corner brackets have anchors that have pegs that can be hammered into the ground. Others are stacked together to stabilize multiple layers. The key to buying DIY bed corner brackets is to make sure they are designed to be the same thickness as your wood.

Adding exterior trim after your bed is built will strengthen corners and seams and add a complete look to your garden.

8. What are the best materials for raised bed gardening?

Popular materials for loft beds include wood, plastic, aluminum, and galvanized metal. Wood framing is easier to change shape in areas where freeze-thaw cycles occur, but corner reinforcement and cross bracing can often eliminate this problem. Plus, the wooden frame is easy to assemble yourself. You can easily accommodate tiered or sloping grounds with a wooden bed.

The best woods for raised garden beds include cedar, cypress, redwood or white oak. Availability varies by region, so be sure to determine if the wood at your local store is durable and rot-resistant. Avoid repurposing old treated wood, which may contain chemicals that have been banned from home use. Make sure any new treated wood is certified safe for growing food. With the rising cost of lumber, purchasing a loft bed kit has become more cost-effective.

Metal beds are another popular option, although some, like wood beds, will weather over time. Aluminum has a long lifespan, although the acid in the soil can corrode the zinc coating of the galvanized metal bed, causing the metal to rust. Thankfully, the process takes decades, whereas galvanized metal beds can last up to 25 years or more.

Composite raised beds are also available. They are made from a blend of eco-friendly, recyclable plastic and wood flour. Purchase complete kits or individual boards for DIY modular setups.

For the longest-lasting bed, consider one made from 100% recycled high-density polyethylene (HDPE). This is the same material used to make communal picnic tables, litter boxes and high-quality garden furniture. HDPE plastic can withstand a variety of temperatures. It won't seep any chemicals into your garden soil. Some varieties are so long-lived that they come with a 50-year warranty.

9. Does a loft bed need a bottom?

It all depends on the surface you plan to place your garden on. Most raised beds have no bottom. That's because a bed without a bottom allows your plants to grow deeper into the roots and drain better. However, if you're planting on a surface with invasive weeds or concrete, you can choose to install a base on your bed to block weeds or prevent staining.

If there are burrow pests in your area, adding a wire mesh bottom to your bed will help stop any damage from these unwanted visitors.

10. How should you irrigate?

Installing irrigation on a raised bed can save you time and money. Drip irrigation is the greenest and most cost-effective in the long run, especially if you have too many beds to water manually. It transports moisture slowly over time with very little evaporative loss. Drip irrigation is the answer if you plan to grow in the same location for many years.

If you're not sure how long your bed will last, or you're on a budget, a soaker hose can be a great solution. Choose a non-toxic and durable material (like this FDA-grade polyurethane soaked hose with lead-free fittings) or a double-walled variety to avoid kinks. Place it the length of the bed and away from mulch and soil that can clog pores. Use timers on soaker hoses and drip irrigation to save water and make life easier.

11. What is the best way to protect crops?

If you live in an area frequented by animals, fencing is the best way to protect your garden. Deer and rabbits chew, raccoons and cats dig, and even dogs dig beds for some types of fertilizer. Fences provide the best and most durable protection. Obviously, the fence needs to wrap around the perimeter of your garden, but the height will depend on the pests in your area. For more information, read How to Keep Deer Out of Your Garden.

12. What fertilizer should you use and when?

The finished compost is the best fix for your raised bed, hands down. This is because compost contains essential minerals and nutrients that plants need, as well as large amounts of organic matter used to improve soil structure. Add compost to each row or planting hole as you prepare your soil for the year, and again halfway through the season as a top dressing or mulch. Some crops, such as corn, squash, and tomatoes, could benefit from more frequent additions.

If you plan to grow Brassicas (broccoli, cauliflower, kale, cabbage, mustard greens, etc.), you may need to add lime to the soil before the growing season begins. To be sure, check your soil pH with a home tester. Avoid growing potatoes, peppers, and tomatoes in beds that have been recently limed.

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