Root proof raised redwood garden beds

Redwood planter boxes with root protection

Last summer Stephan and I were tasked with designing and constructing some raised garden beds in Los Gatos. There were existing beds on the property that had become overrun with roots from a large oak tree in the back yard, rendering them useless and causing the old beds to break apart. Tree roots have a way of working their way into pretty much everything and can certainly become an issue in the garden as well, especially when they can find an area that is irrigated during the summer months.

2x6 frames before final assembly

Keeping this in mind, we had to come up with a design that would prevent root intrusion into the raised beds, which is impossible if the bed has any openings in the bottom. The standard procedure of covering the bottom with gopher wire wasn't going to work for this application.

In order to alleviate these concerns and to ensure the beds will last for many years to come, we enclosed to bottom of the beds with redwood 2x6 decking, turning them into large planter boxes, leaving a small space for expansion between each board, which is a must for any outdoor construction project using wood.

Assembled frames on pickup

There was concern over having adequate drainage into the existing soil with the bottoms in place as well so we opted to elevate each box using pressure-treated lumber. To prevent the boxes from sinking into the mud the weight was distributed onto 5/8" pressure treated plywood below. The use of pressure treated material normally isn't acceptable for use in vegetable beds (see linked post) but is fine here because it does not come in contact with the soil inside the boxes. The end result was four extremely durable large redwood planter boxes on bases that will last for decades.

These boxes are made entirely from construction-heart grade redwood 2x6 decking, which gives them a lot of flair. The top rails provide a working surface or a seat for those tending the garden and also add some strength to the boxes. Making all of the cuts and assembling all of the pieces takes a lot more time and skill, but the end result is well worth the extra labor. If you want to turn heads with your new raised beds or planter boxes, this is the way to go.

Robert carefully screws the bottom boards on

Inside view of the box

Instructional video- raised redwood beds

Here's a great video on how to construct a very basic redwood garden bed, produced by Bruce Bauer Lumber and Supply in Mountain View, CA. I like the simple design and ease of construction:

This type of bed utilizes 2x12s, has only a few pieces, and will last a very long time. 

The GRK screws used are expensive and probably overkill for this little project, but I find they are a huge time-saver for larger projects or if you are building multiple beds. I'll talk about fasteners at a later time

These guys use galvanized wire for the bottom of the bed. This is perfectly acceptable to keep out rodents, but stainless steel gopher wire is a better choice as it will last longer in the ground. You can order online here or if you're in the Santa Cruz area Mountain Feed in Ben Lomond carries it as well.

It's also a good idea to use some 1/4"  redwood lath strips screwed along the bottom perimeter to ensure critters can't push their way in through the gaps left between staples. Plus, working with those fencing staples can be a pain in the ass for those who don't have a steady hand with a hammer.

I will post my own instructional video and make a page the next time I build some beds.

Possible topics and things to look forward to

I'm working on getting some content pages up and running for this blog. The first is going to be on basic redwood bed construction. I figure it is going to be best to have a page with a link on the sidebar that discusses actual construction, and I'm working on putting together more photos from my projects, etc.

Upcoming blog topics may include the following:

A raised bed. Photo by Jinx McCombs. Creative Common License.

-gophers

-hanging boxes

-styles and design

-alternatives to redwood

-fasteners

As the blog evolves, I might change the focus a bit to include more general advice for garden layout and design to keep things fresh on here.

Also, I'll probably feature the blogs and designs of others, maybe in a design of the week format! Feel free to contact me if you have any photos, design submissions or ideas! Stay tuned.

Choosing the right lumber yard

When looking for a place to buy your lumber and fasteners, it is important to find the right product for the right price. The price of redwood fluctuates constantly and varies by region as well. Here are some factors to take into consideration before making your purchase:

Redwood garden box under construction at a nearby farm

Price: Lumber yards set their own prices, and you can save a lot of money by first calling around and asking for a price per foot for whatever material you want to purchase. I usually use standard 2x6 con-heart redwood which is common and typically used for decking. The price per foot is about $1.60 here in Santa Cruz but that will vary depending on your location. It is probably higher elsewhere as we have a lot of redwood available locally.

Quality: Be sure that the yard has quality lumber. Check to see if it is straight by sighting down each piece with your eye while you are at the yard. You don't want to see very much bowing or crowning in the material. If placing an order for delivery, tell them you want only the best possible lumber that they have. Many yards will try to pawn off all of their sub-par materials on homeowners who are unlikely to return lumber after delivery. Don't let them get away with it.

Delivery?: Ask each yard you call if you can have your building materials delivered to your address. This can be a big time saver, and time is money, at least for most of us. See if the yard will offer you a deal on a delivery. I like to pick up my materials in person, however.

Sustainability: Some retailers only sell products that are harvested in a sustainable manner. Proper stewardship of our forests is extremely important to ensure that they are preserved for future generations to utilize and enjoy. One such retailer here in Santa Cruz is Big Creek Lumber. This company is committed to environmental stewardship, the best redwood around, competitive pricing, and great customer service.

Ease of access: I really try to avoid shopping at places like Home Depot and Lowe's. Not only do they often have substandard material and awful customer service, but the indoor lumber yards prevent easy loading of your materials. It is much nicer to be able to drive into the lumber yard and get what you need without dealing with the awkward carts provided by these stores. If you must shop at these places, call ahead and get them to set you up with someone to help you load your lumber. Try not to get lost in the aisles.

Raised beds and drainage

One of the benefits of utilizing raised beds in your garden is that they allow for proper drainage in areas that do not have good natural soil percolation rates. Take the following into account when you build and place your beds:

Be sure water can pass through the bottom of the bed-- This is usually accomplished by having a box with an open bottom. If you must build a base for the box (if it's going to be placed on a concrete patio for example) you should be sure to either drill holes in it or leave 1/4" gaps between your boards in order to allow for water to drain underneath. Sometimes it is necessary to elevate the beds so there is a small space underneath for the passage of water. If you don't want water to flow out onto the ground then you'll have to install a drainage system in the bottom of the box, which can be complicated.

Use soil that will drain properly-- If you are amending your own soil, be sure to create a mix that will absorb water but still let the excess pass through. If you have a lot of clay in your soil, mix it with some sand, perlite, rice hulls, or another inert amendment to lighten it up.

Keep the area around beds dry-- Place gravel, mulch, wood chips, or pavers around your raised beds so that you don't end up with a muddy mess to stand in while tending the garden. Mulch is great for areas surrounding gardens as it is cheap, easy to transport and install, keeps your boots relatively dry, and blocks weeds to a certain extent.

Choosing a location for your new garden beds

There are several things to consider when you try to find an appropriate location for your garden beds. Picking the wrong spot can lead to disastrous results. You need to have the following:

Sunlight-- Find an area of your yard that will get lots of sunlight. It will be hard for you to grow anything if you don't get at least 4 hours of direct sunlight a day, and the more the better if you want your plants to grow optimally. Certain crops such as tomatoes and bell peppers require long periods of sunlight in order to properly develop. If you live in a dark area, such as a heavily forested, urban or coastal region, you may have to do some research before deciding what to grow in your raised beds.

Protection from Deer-- If you live in an area where deer are a problem, you'll have to have a tall fence surrounding your garden. Many a harvest has been spoiled by hungry deer; they can devour plants down to nothing in a very short period of time. In my experience most alternative methods to keep deer away (cougar piss, fishing line, and whatnot) are ineffective, so exclusion with a good welded wire or redwood fence is an absolute must to protect your investment.

Slope-- A level area to place the bed is necessary unless you modify the bed to fit the contour of a hillside. The top should be level so that the soil saturates evenly when you water. I recommend using terraces to place your beds on. More on this topic to come.

Visual appeal-- A garden will give new life to an old yard. Place it somewhere that will be pleasing to the eye, check the spacing between walkways, etc. and try to pick a spot where it will be centered between obstacles and landscape features. 

Farmer Stephan selects the perfect location for raised beds in this client's backyard

Accessibility-- Be sure that you can access your beds in order to work in them. I try to leave at least 18 inches (0.5m) of room around the sides of my beds so that I can easily work around them. This prevents having to climb up on the side of the bed in order to reach the back. Also consider who is going to be tending your garden. Some folks will require more space than others.

Is it ok to use pressure-treated lumber on raised garden beds?

Photo by Rusty Clark. Creative Common license.

Pressure-treated lumber is extremely popular for outdoor applications. It lasts for decades without rotting and can be placed directly in contact with the ground. A frequent question that arises is whether or not it is acceptable to construct raised vegetable garden beds out of this material.

Before 2003, most treated lumber contained high levels or arsenic, which was proven by the EPA to slowly diffuse into the surrounding soil making it toxic. Since then alternative compounds have been used and treated lumber is supposedly safer.

There is debate as to whether or not the chemicals in the "new" treated wood such as copper derivatives can leach into the soil and end up on the dinner table. Studies have been conducted with mixed results on this matter.

Personally, I would never use treated lumber to construct garden beds. Redwood looks much nicer and also has similar longevity. The cost is only slightly higher, and you don't have to worry about the risk of consuming the fungicides in treated lumber that may end up in the soil. It should be noted that in many regions the use of treated lumber is banned for those seeking organic certifications.

Why risk your health for a product that doesn't look as nice? There are viable alternatives to redwood which I will cover later, however using treated lumber on vegetable beds is a bad idea in my opinion.