This means you can set out transplants sooner and extend your growing season. Since raised beds are well drained and the soil is above ground level, the soil within the bed warms up earlier in the spring. This enables gardeners to set out transplants sooner which helps extend the growing season. A cold frame can be set on top of the bed during early spring to protect young seedlings and transplants from late frosts and strong winds.
The cold frame can be lifted off the bed once the crops become established, and moved to another bed to help protect successive plantings. If you are young, fit, and full of energy, then bending over or kneeling down to tend your garden may not be an issue. But if you are prone to back strain, or if you have any mobility issues, then a taller raised bed will make gardening easier. Photo by Filip Urban on Unsplash. Container gardening in elevated planters is another option for gardeners with limited mobility.
These gardens can be tended while sitting in a wheelchair. However, the same principles apply in container gardens with respect to soil depth requirements, top-dressing amendments such as compost, fertilizer, and mulch. And taller plants grown in container gardens usually require staking or tying to trellis. For more information, read our article about Wheelchair Gardening Tips. The taller you build your raised bed, the more volume it will hold.
As the soil is watered it becomes heavier and this exerts pressure, which may cause your bed to bow outward in mid-span, near the top. Manufacturers of raised beds often supply these supports, but if you are building your own beds, then you may want to include this feature. The cross-support can be made using wood, composite plastic or aluminum.
It is a simple job, and the aluminum stock is available at most hardware stores. Cedar raised beds come in six height options, from 5. Composite beds come in four height options, from 5.
This is because most root growth in vegetable gardens occurs in this relatively shallow depth. Nutrients such as compost and fertilizers are added to the bed from above and lightly tilled in. Taproots will travel deeper into the soil if nutrients and water are available, and this also brings more trace minerals to the plant.
Larger vegetable plants will send down deeper roots. When plants are able to send their roots deeper, they are less likely to fall over in windy conditions or if the ground becomes too wet. Large-leafed, shallow-rooted plants such as broccoli, Brussels sprouts and cauliflower will still require staking to ensure they stay upright as they grow to maturity.
Knowing the average root depth for your garden vegetables will help you decide where to plant each crop and how deeply to prepare your soil. When preparing a garden bed for planting, it is helpful to know the root depth of vegetable crops since this has a bearing on where you may decide to plant certain crops and how deeply the soil is prepared.
For example, in our garden we may plant shallow rooted crops like lettuce in beds where the subsoil has more clay and does not drain well. The deeper clay does not affect the shallow roots, and they benefit from the added moisture. Plants with deeper roots, such as tomatoes, would not do well in this soil depth. Some raised beds are set on cement patios or on gravel surfaces , which prevent roots from going deeper than the height of bed sides.
In these cases, it is especially helpful to know the soil depth requirements of different vegetable crops. Gardeners can compensate by building the raised beds higher to allow for more root space. These taller beds enable deeper rooted crops to be planted even if there is no soil beneath the bed, but drainage must be provided by blocking the bed up an inch or so, or drilling drain holes near the bottom of the bed sides.
For most vegetables, the bulk of the root mass is within the top six inches of soil. The soil should be light and well aerated to enable roots to access available nutrients. Deeper soil provides additional nutrients and trace minerals, which further facilitate plant growth. Plants will send some roots deeper if the soil conditions permit. So, what do I mean by well-aged? I shred the leaves, wet them down well and, in six months to a year, they are rotted and ready to be incorporated.
I guarantee friends and neighbors will be happy to share their supply. Years ago, I discovered the value of adding soil containing minerals. It made a noticeable difference to the success of everything growing in my garden.
Minerals are the most important ingredients that no one seems to talk much about. You can check out a lot more on mineralizing your soil in my podcast on the subject. Here in the Atlanta area, granite is everywhere, so most mineralized soil blends here are made of granite dust. Azomite is another common and great option.
If you can find this in bag or bulk, buy it. Fortunately, a little goes a long way. Worm castings are significantly higher in all the primary nutrients your plants need to thrive. In fact, worm castings add five times the nitrogen, seven times the phosphorus and ten times the potassium than ordinary topsoil.
Castings add one more layer of complexity to overall soil makeup. Suffice it to say; this medium is one of my secret weapons to creating highly-productive garden soil. Adding vermicompost composted worm manure to your raised bed gardens will provide another layer of organic richness.
Mushrooms are grown in mixtures of natural materials like hay, gypsum, corn cobs, cottonseed hulls, etc. Ground Bark: There are many varieties of ground bark from which to choose, but pine is the most commonly available.
Be sure to use aged bark for this application. Freshly-chipped wood will rob from rather than benefit your soil during initial decomposition.
Ground bark is a good carbon source. It will break down over time, and its coarse texture provides space for the movement of water and oxygen through your garden beds.
Ground bark brings a diversity of particle size that can really amp up your plant health. Composted Cow or Poultry Manure: Well-composted animal manure has been a mainstay of organic soil fertility for thousands of years because of the nutrients, organic matter and variability of particulate matter that it adds to complement overall soil make—up. What has changed are farming practices and the resulting risk of manure. For that reason, I recommend you use cow or poultry manure but not horse manure.
Purchase composted cow or poultry manure by the bag and from a trusted source. Many people have poisoned their soil with killer compost including me , by inadvertently adding herbicide—tainted ingredients usually found in horse manure. I do not add horse manure — anymore — because horses are more likely to consume hay which may have come from fields sprayed or oversprayed with persistent herbicide.
The traces of herbicide no matter how minute they may be will kill or severely disrupt the normal growing habits of many garden edibles as effectively after being composted as the day they were manufactured. There may be a source of horse manure you would really like to use.
In that case, you can perform a bioassay test. Perform this simple test before you ever let the manure come into contact with your plants, soil or compost pile. This image demonstrates an important visual of how worms break down organic material to create a soil profile that helps bind soil particles in a moisture-rich environment.
Horse Manure: It bears repeating. If tempted to use horse manure, be sure to check out the link for the bioassay test. That little bit of time could save you years of grief. Peat Moss: This may come as a surprise. Peat moss is, however, not a sustainable material.
It takes hundreds of years for peat to develop in peat bogs. It can aid water retention, but once peat moss dries out, it is difficult to re-hydrate. Have you ever watered a dried out container, but the water just rolled off the surface? Artificial Fillers: Although it may be tempting to take up space with fillers as you first build those raised beds, I advise against them.
Although they might save you some initial cost, even organic fillers can be problematic. Over time, they will break down, and the surface of your garden bed will sink, requiring you to add more soil later. Most importantly, fillers can hinder drainage.
I performed my tests using containers so that you can see it for yourselves. Whether in a small space like containers or a large space like raised beds, the science remains the same. Fill Dirt: This, too, might be tempting as a cost savings, but it will hinder all your other efforts to build that healthy growing environment. What is fill dirt? Fill dirt is underneath the topsoil and includes none of the inherently good qualities of topsoil.
Biochar does have some nutrient value. Photo: Mark Highland. Fire Ash: I recommend against putting any fire ash directly into your garden beds. If your fire ash is all wood-based, it can be a good addition in a small quantity to your compost pile. Mycorrhizae: This fungus is very popular as a soil ingredient in bagged products. Adding mycorrhizae to your soil may provide a benefit.
Building that initial raised bed garden environment with quality ingredients will provide you good results the first season. However, those crops you grow will be making non-stop nutrient withdrawals from those beds. How do you do that? Amend your soil once or twice each year with organic nutrients like those I described above — not synthetic fertilizer. By amending your garden beds, you will see better soil in season two, great soil in season three, amazingly rich soil in season four, and so on.
Before you amend your soil for the first time and about every couple of seasons, I recommend that you get a soil test. A soil test will determine the pH levels and deficiencies of your soil to help guide your amendment choices. The nutrients you provide the soil will be most optimally taken up by your plants when the soil is at a neutral pH.
In early September — before I plant my winter, cool-weather crops — I topdress with an inch or two of compost. In late March — before I plant my summer crops — I do the same. Amend your soil once or twice each year with a topdressing of quality compost. An inch or so goes a long way to keeping your soil productive. Sometimes, I lightly scratch the compost into the bed surfaces, but I usually just lay the compost on top, cover with mulch and walk away. Remember that microbial party we got started when first building the bed soil?
So, they will naturally and quickly work all the compost back down into the party with the rest of them. I would be:. On the off-chance something undesirable has made its way into those mediums, compost works as a buffer to help neutralize any potential negative effect. Many of you asked if you should remove the existing soil and start all over.
To that I say — no. Replacing your existing bed soil is laborious, expensive, and time-consuming. You might be surprised at how quickly garden beds, even those that have been neglected for years, can be rejuvenated. If this is your situation, I still recommend against tilling the soil. Instead — using a pitchfork or a broadfork , stab the garden soil deeply and wobble the fork around to create a little space around the tines.
Then, fill those spaces with compost. A broad fork is a good tool to provide deep access for amendment penetration in existing raised beds and bring new life to tired and compacted beds. Are your beds too full to amend? If your bed surface is plumb up to the top of your sidewalls, remove any debris — if possible. You can use the raised garden bed soil calculator to calculate how many bags of soil you need for you raised garden bed.
The soil calculator will also calculate the total cubic feet of soil needed for your raised garden bed. Just fill in the dimensions of your raised garden bed to easily calculate the number of bags of soil needed for your raised garden bed.
Bags of soil are commonly sold in 0. This post is powered by Planting , a team of passionate gardeners sharing their knowledge of gardening with the world.
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