What Should You Put at the Bottom of a Raised Garden Bed

Many people are interested in raised gardens because of the myriad of benefits that they offer. Some of those benefits include more control over soil type, improved drainage, and less weeds. Most importantly, if the native soil is not conducive to plant growth, you can fill raised beds with your own customized blend of soil.

A common question for new gardeners who have purchased raised garden beds is what they should put at the bottom. In an economy of soaring prices and inflation, it can become prohibitively expensive to fill raised garden beds. Therefore, many gardeners are seeking cheaper, more eco-friendly alternatives. This article explores how you can save time and money by using these tips to fill raised garden beds.

First Calculate the Amount of Soil Needed 

To start, to gain a general understanding of how much soil you will need, you will need to calculate the amount. While it does not need to be precise, it should be taken into account in order to eliminate waste associated with purchasing too much soil. This article lists out various configurations for Vego Garden products, allowing you to easily calculate the volume of soil needed. 

Try the Hugelkultur Method

To put it simply, you should put a layer of organic material at the bottom of your garden bed, which will break down and enrich the soil. This can include compost, or woody material such as logs, dry wood, branches, and leaves. Organic material is the best option, as it improves drainage as well as enriches the soil as it breaks down, and does not need to be removed from your raised beds later on. 

From our experience, the hugelkultur method is the easiest and most cost-efficient method to use. Originating from a German word that means “mound or hill culture,” the hugelkultur method incorporates organic matter such as rotted hay, plant waste, and compost, which are added to the soil in layers. For best results, use sticks instead of logs and wood that has already begun to decompose, making it easier for the components to break down. 

Useful tips:

Use the correct type of wood. Although hardwoods are recommended as they break down more slowly and hold water longer, softwoods are also acceptable. Woods that work best include birch, alder, maple, cottonwood, willow and oak.  Avoid allelopathic trees like black walnut, red oak, and sycamore, as they contain chemicals that inhibit plant growth, as well as rot resistant trees like black cherry and black locust. 

Enhance the soil with vermicomposting. Vermicomposting is a method of composting that utilizes worms to break down organic waste. Overtime, the worm castings produced by the worms can be harvested and used as organic fertilizer. This rich and fertile soil amendment is ideal for optimal root health and remedying depleted soils. Vego Garden’s in-ground worm composter eliminates the tedious process of harvesting worm castings by letting the worms do the work right in the ground, without the hassle or smell or traditional composting systems.  

 

Maintain moisture levels. As dryness is a commonly reported issue, maintaining moisture is an important aspect of hugel garden beds. Therefore, it is important to shift the soil into crevices to eliminate any dry pockets. One way to accomplish this is to continuously water the bed during construction to make sure there are no gaps. You should also use a good quality organic mix soil, which improves water retention.

What to Put at the Bottom

Some gardeners chose to implement a barrier at the bottom to keep out pests and weeds. 

Below are a few materials you can use:

• Cardboard or newspaper: Cardboard is a great option if you are on a budget. You can line the bottom of your raised garden bed with cardboard and newspaper to deter pests and weeds. In order to minimize the amount of chemical substances, choose cardboard that has no tape and minimal markings. 
• Stainless steel gopher net: For those that are seeking extra protection, garden coverings and nettings can be effective solutions in keeping critters from accessing your garden beds. Fortify your area with Vego Garden’s modularly designed cover system and stainless steel gopher net, created with functionality and quality at the forefront.

• Landscaping fabric: Landscaping fabric can be used on the bottom of raised beds for several reasons – preventing soil erosion, promoting water retention, and most importantly, keeping out invasive grasses. Unlike cardboard, which breaks down over time, landscaping fabric will not. A disadvantage is that it limits the growth of shallow-rooted plants, the movement of earthworms, and the mixing of soils. Unless you are experiencing a pervasive weed problem, deeper beds will generally not need it. 

What Not to Put at the Bottom

There are certain materials that you should avoid, as they can cause drainage issues or environmental problems.

Below are a few materials to avoid using:

Plastic or trash bags: As plastic is not a very permeable material, this will hinder drainage and lead to waterlogged roots. Over time, the plastic will break down and seep into the soil, contaminating it with plastic particles. 

Gravel: While some sites recommend using gravel to improve the drainage capabilities of the soil, that is a longstanding myth. There are other ways to increase drainage that are less troublesome than gravel. Eventually, the soil will mix with the grave and will prove to be very difficult to remove later on. The gravel also raises the water level, creating an insoluble barrier that can lead to problems with fungal diseases and root rot. 

Wood chips: Use wood chips sparingly, especially fresh wood chips. They can draw out the nitrogen from the soil, rendering it unfit for nitrogen heavy plants. You may choose to use wood chips as mulch at the top to suppress weeds, adding in about 2 – 3 inches.  

Frequently Asked Questions

Is it necessary to line my garden bed?

It’s not necessary to line the bottom of your raised beds, but you may choose to do so if you are experiencing pest or weed problems. If you are using a galvanized metal bed, then for the most part, lining is not necessary. The height of the metal raised beds will deter weeds, and draining conditions are usually sufficient.

Should I put rocks on the bottom of my garden bed?

You should avoid putting rocks in the bottom of your garden bed. A common myth is that this will improve drainage. Instead, this can actually increase water saturation levels as well as allow gravel to mix in with your soil, which can prove very difficult to remove later on.

How do I keep out invasive weeds like Bermuda grass from infiltrating my garden bed?

Cutting out the sod underneath your beds, then laying landscape fabric down underneath your beds work best. The fabric will allow water to pass through, but will help prevent weeds. If you cannot dig up the grass, you can also tarp it for a few weeks or months first, and that will effectively bake the grass.