Strawberries are popular and simple to grow, and raised beds can suit them quite well. It doesn’t take a lot of skill. There are just a few things to get right.
The best raised bed for strawberries is probably a 3×10-foot bed made with untreated 2×12 lumber. It’s sturdy, roomy for the plants, and easy to reach across. The lumber will last up to 10 years and won’t leach chemicals into the soil. It will also work on top of concrete or other barriers.
There are a lot of different beds of varying sizes using many materials. Some of them have a lot of potential problems. I’ll share my concerns, and explain why I have them.
The Perfect Raised Bed for Strawberries
Strawberries have a shallow root system. That’s good for raised beds. A lot of plants don’t always do good in raised beds because the roots can go several feet deep. For most plants, three feet is about right. Strawberries can handle a fairly shallow bed because the roots don’t go deep.
Strawberries come in two types. There are everbearing varieties, which flower and fruit throughout the year, and short-season varieties, also called June-bearing varieties. The everbearing types grow bigger and have deeper root systems to feed the higher growth and fruiting.
Those ones like 10 to 12-inches of root depth. The June-bearing types often have roots down to 6-inches. a 12-inch deep bed will work with all varieties of strawberries. Higher beds wouldn’t pose any issue other than being more expensive to build and fill.
I asked in a gardening group what people’s favorite bed dimensions were for strawberries. Most gardeners agree that a bed depth of 10-12 inch bed shows better results than a shallower one. And, a lot of people said to not go over 3 feet wide, otherwise, it’s hard to reach across.
The most popular size was 10-12 inches high, 3-feet wide, and about 10-feet long. It’s small enough to manage, large enough to spread out growing plants, and deep enough to work over any soil. Untreated wood beds are the most popular choice among master gardeners.
The reason is that the Untreated wood becomes a home for much of the soil life. It’s a more natural normal part of healthy functioning soil life. It also holds a bit of moisture, further benefiting creatures like worms and frogs who burrow into the soil. Untreated 2-inch thick woods usually lasts 5-10 years.
Treated wood can last 20-40 years, but will leach harch chemicals into the soil and on your food. The leaching chemicals have a bad effect on healthy soil life. After all, the way it works, the chemicals kill microbes that would try and break down the wood. My advice; don’t use treated wood.
Don’t Use a Barrier Under a Raised Bed
My first concern about a raised bed is putting them on a barrier. A lot of people like to put a barrier of some kind, often bricks or landscaping fabric, under the bed to keep the soil in and keep weeds out. That can kind of make sense, but there are two downsides to a barrier under a raised bed.
First off, you are limiting the downward root growth. Something like concrete, bricks, and even gravel will definitely inhibit plant roots from reaching a healthy, natural depth. We try hard to keep healthy, strong plants so they will happily do their plant thing, but by limiting their roots, you might as well have forgotten to ever water them.
Even a landscaping fabric will inhibit downward root growth and stunt your plants. It’s designed to be had to get through. It’s an honest fact. Roots can work through it, but plants will expend excess energy trying to put their roots where they need to be if you have a shallow landscaping fabric.
I’ll add a third one in there, free of charge. Barriers inhibit and obstruct natural soil life. In gardening, soil life is everything. (I highly recommend the book Soil Science for Gardeners, it changed my perspective on things.)
The biggest issue with barriers, even fabrics, is that larger creatures of the soil web can’t get through it. Worms, grubs, beetles, all the good little creepy crawlies are kept out. They play a huge role in soil health and in jumpstarting soil in the spring. Do you really want them inhibited?
Barriers can also encourage poor drainage, That’s four things I guess. A solid barrier under your bed can cause the soil to hold too much water. With a solid barrier, one wet spring, a week of rain, or accidentally leaving the sprinkler on over the weekend would cause plant roots to start dying off.
All that said, I don’t recommend barriers under raised beds. Let the soil in your bed contact the soil beneath and become part of the larger soil system of life.
a simple DIY option that anyone can build and costs about $100 in materials.
Soil Mix for Raised Bed Strawberries
My favorite soil mix for shallow rooting plants like strawberries is 25 percent composted manure, 75 percent native soil. To fill a raised bed, calculate the depth times width times height. Get 1/4 of that in compost, and just toss it together somewhat evenly.
For a 3 by 10-foot, 12-inch tall bed, that’s about 7 cubic feet or about 10 five-gallon buckets. Now, that’s a lot. you can easily do half that and still be alright. Filling a raised bed takes a lot of work. Go easy and don’t hurt yourself.
How Often to Fertilize Strawberries in a Raised Bed
Strawberries are generally fertilized 2 or 3 times a year. test your soil to determine soil fertility, and add the recommended amounts in the instruction booklet. The Lusterleaf 1602 soil test kit is my favorite. You’ll want it to show nutrients around the middle, or a bit higher.
If you have 15 percent of higher organic content in the soil, like the mix I recommended, you are able to cut back 50-75 percent on fertilizing. The higher organic soil prevents nutrient loss so it needs a lot less fertilizer. I would start with 50 percent less and see how it goes.
If you have a shortage of fertilizer during the growing season, by all means, correct it, but simply sprinkling fertilizer won’t do much for a while. Granular fertilizer can take a month or more to really work well. So, we do a quick-acting method too.
You can mix a water fertilizer solution and use it as a foliar spray (spray it onto leaves). That’s how to quickly correct a shortage of fertilizer. 10-10-10 or similar strength fertilizer can be used at 1/2 cup per gallon of water, then lightly sprayed on plants.
You can do this twice a week or so for 3-4 weeks as the granular fertilizer begins to work into the soil. Don’t overdo it. Don’t mix it too strong, and mist it lightly but evenly. I use an old window spray bottle. Strawberries don’t use a ton of nitrogen so a 10-10-10, or other even fertilizer will do fine.