Monday, June 16, 2008
Love those raised garden beds
How do I love thee... let me count the ways:
You are always mellow.
You are twice as productive as my ex.
You are warm and mosit, but never wet.
I don't have to bend over ( forwards or backwards ) to work with you.
Yes, I am in love with my raised garden beds. And anyone I know who has started gardening in raised beds never goes back to "in-ground" growing. So, there has to be something to it. Let's take a closer look at what makes this such an easy and productive gardening style.
First, let's define raised bed. It is simply soil (or other growing media) raised above the natural grade of the soil. Farmers find that raising planting beds, even just a few inches, results in improved yields and quality. Check out those fields of melons, tomatoes and strawberries some time you're near a farm. You'll see what I mean. Home gardeners usually go a step farther... raising the beds eight, twelve or even twenty-four inches above ground level.
Why are raised beds so productive? Most of it has to do with the soil. Soil in a raised bed drains better (gravity at work). And poor drainage is a major reason for plant failure. Raised beds warm up more quickly in the spring, allowing for early planting and growth. Soil in raised beds is spared the compaction that occurs when we garden "in-ground". Think about how hard bare soil becomes when it is walked on repeatedly. Then you use a tiller to relive the compaction, which further destroys soil structure, and on and on....You won't be walking in the raised beds. And your tillage implements are likely to be your fingers. Very handy. They are always where you can find them.
You get to radically amend the soil that the beds contain. A good rule of thumb is to use about 1/3 to 1/2 of your native soil and mix it with good, finished compost. This results in a very mellow ( soft, loose crumbly) growing medium that plants love. Organic gardeners can boost soil fertility by choosing composts with high levels of plant nutrients (aged manures). Even lousy, clayey soils or uber-porous soils are improved in this way because of the magical properties of organic matter... it aerates heavy/clayey soils and improves moisture holding capacity of light/sandy soils.
OK, you've got a well-drained, aerated, moisture-holding, warm growing medium. If you're a plant, what's not to love? A little fertility (organic or otherwise) and you're going to grow to your full potential...at least until the rabbits, ground hogs, bugs and diseases appear. But that it another story.
What are raised beds structures made of and how big should they be? Here is where you can get creative. No one says they have to be square or rectangular. If that works for you, fine. A buddy of mine has serpentine raised beds made of rocks. Beautiful and functional. I've got beds made of black locust, dawn redwood and white oak. Make them any dimension you want but here are a few tips. Don't make them any wider than twice your reach or you won't get to the middle. Even this may be a stretch. So a maximum width of forty-eight inches makes sense and there is nothing wrong with beds as narrow as twelve inches. I think mine are thirty-six. If I stretch I can reach the other side. How about height? Eight to twelve inches seems to be common. Six is OK and you can stack beds and make the whole thing as high as you want. It is lovely to garden standing up.... or sitting in a chair. If you end up with the typical, low bed, get one of those cushioned pads to kneel on and you're in business.
What kind of wood should you use? I won't enter the pressure treated lumber controversy. Lumber treated with copper, chromium and arsenic (CCA) was popular for years. Certainly plants had no problem with it (unlike wood treated with creosote or pentachlorophenol). Yes, arsenic is a toxic substance but it is likely that your exposure to this was minimal. Now, other preservatives are available and CCA is not an option unless you inherited some. After many long conversations with gardeners about the relative hazard of CCA treated wood I came to this conclusion: anything that takes away from the potential for you to enjoy your garden (or is going to make you gag as you bite into your first born beet) ain't worth the benefits. So just find a material that you are comfortable with. There are lots of options. If you can find black locust and have the patience and strength to make beds out of it... your great grand children can use them. Put it in you will. Don't ask me where I got my twelve-inch dawn redwood boards. I ain't telling. It is light, apparently durable and a pleasure to nail and screw. Time will tell if it will compete with black locust for durability. I kind of doubt it. Saw mills are getting few and far between but they are still out there and can sell you rough cut lumber for beds. Hey, you can order pre-cut, rot resistant cedar boards for raised beds on-line if you have the money. You've got options. Cement blocks work.
A few final things that make raised beds fun. You can convert a raised bed to a cold frame easily by attaching something that will support light transmitting plastic. Beds become mini-greenhouses for pennies. Now you are extending your growing season dramatically. Floating row covers work nicely too but offer less heating potential.
Weeding, a chore even for garden fanatics, is so much easier in raised beds. Weeds still emerge but pulling them is child's play. And because your crop plant density is so much higher in raised beds, their competition reduces weed growth dramatically. By the way, this plant density accounts for much of that two-fold yield increase over in-ground gardening.
Tools get smaller. There are nifty cultivation and planting tools for raised beds. Nothing is motorized. And fingers can do most of the planting. Instead of a hoe you'll be making seed planting rows with your pinky.
I suppose I could go on and on but those are the high points.
Any downside to raised beds? Well, despite all of that nice organic matter, raised beds do dry out quickly. So watering becomes important. Maybe even critical. Since they have high organic matter content the contents of the beds "shrink" during the course of the year as the organic matter decomposes. So you have to refill beds annually. Do it in the fall after the harvest season and let Mother Nature get things setteld in over winter. Other than that, I can't think of a negative. And even watering is really just adding a level of garden management that pays off.
Ok I gotta go. I have a date with Romaine.