Building Raised Garden Beds, Part 2

‘Tis the season to garden and put in new garden beds.  In Part 1 of this article a couple days ago, we went over in detail the new and improved hugelkultur bed. Below are some more thoughts on the how and why of raised garden beds.

First a look at the two other new raised beds and the one wide row.  The onion bed below is a little wider than conventional, but I had a couple of long big pieces at 57 inches, and I hated to waste good wood by trimming it.   Including the eight inches of timber width, the total bed width ended up at more than 5 feet.

Progress on the 5'5" x 15'0" onion raised bed. Timbers are all staked down, and backfilling has begun. Over the tilled/spaded native clay soil, an intermediate layer of old cow manure dug up from the barn.

The raised bed’s footprint covers last season’s pole bean patch.  Legumes are plants considered to be a nitrogen “fixers” (probably the subject of a whole future post on green manures). They absorb nitrogen from the air, and concentrate it on root nodules.  After the plants die off, the nitrogen is released and available to future crops.  Together with the manure amendment, and the worm compost fertilizer I’ll be adding as the season goes on, hopefully will increase soil fertility.

Backfilling complete, side mulching operation under way

The backfill soil was “mined” from the old hay pile under the oak trees.  I don’t quite know how long those hay bales have sat there and rotted away.  The soil underneath the hay piles is a wonderful black loamy consistency.  Spading it and carrying it over is more than a few wheelbarrow loads and a good workout, but cheaper than a gym membership.

Mulching done, red, white and yellow onions planted, wide raised row at left for the strawberries also done, third 5' x 7' squash/zucchini bed started... I think it's time for a beer.

Why Raised Beds?

Several reasons, in no particular order:

(1) Lessens soil compaction.  Hard, compact soil is a no-no, while well-aerated, fluffy garden soil has good “tilth”, or structure (*). while  Plant roots and microbial soil life need oxygen for optimal growth.  Big stompy human feet smush the soil and drive out all the air.  For this reason, keep the width of raised beds no more than 4 or 5 feet (120 to 150 cms).  This allows arms-length reach-in from either side.

(*) from Wikipedia:  Soil in good tilth is loamy, nutrient-rich soil that can also be said to be friable because optimal soil has a mixture of sand, clay and organic matter that prevents severe compaction.

(2) Drainage.  Plants don’t like to get their feet wet. If they did, they’d live in a swamp.  Planting at ground level, especially in heavy and water-retaining clay soils, increases the chances that heavy periods of rain will literally drown young plants.  By raising the growing space above the ground, this ensures proper drainage and optimum moisture levels.

(3) Soil temperature.  The soil in raised beds warms up faster in springtime, giving young plants and seedlings an energy boost.   On the flip side, being raised off the ground with a higher wind load profile will also cause the whole bed to dry out faster in the hot winds of summer. This will require more irrigation, or more strategic water conservation techniques like ollas (*), rock borders, and drip irrigation.  Use of rock borders, as explained below, can help regulate temperature and moisture.

(4) Pest protection.  In some gardens, moles, voles and gophers run rampant  (moles are my own personal nemesis… I use the Nash Choker Loop Mole Trap to ensure their timely demise) Building wood-framed raised beds with bottoms armored with wire-mesh hardware cloth is a good tactic. The raised bed in the picture below was built with an armored bottom.

A soon-to-be-used terracotta Olla, a $1 find at a yard sale --- also in the picture, clockwise: Amish Deer Tongue (a type of green Lettuce), Red Romaine lettuce, Australian Ruffled Lettuce, Winterbor Green Kale (now flowering), "Bright Lights" Swiss Chard, and a newly planted "Bonny Bell" Green Pepper

(*) more from Wikipedia:  Because water seeps through the walls of an unglazed olla, these vessels can be used to irrigate plants. The olla is buried in the ground next to the roots of the plant to be irrigated, with the neck of the olla extending above the soil. The olla is filled with water, which gradually seeps into the soil to water the roots of the plant. It is an efficient method, since no water is lost to evaporation or run-off. [note by 101C:  this irrigation technique is particularly effective in arid climates]

Free Building Materials

Edging for flower beds need not cost a fortune, or anything at all.  Out at the hacienda, I was fortunate to find and recycle adequate fencing timber which was just laying about the property.

The timbers from the last 5′ x 7′ bed came from a rifle backstop that the last tenant had erected at the back of the pasture (**).  Lacking that, I would have turned to Craigslist.  A quick search turns out about a dozen postings on free rocks, free bricks, and free wood.

Treated 4″ x 4″ fence posts, which last longer than regular untreated construction grade SPF (spruce/pine/fir) lumber, can also be had by inquiring with fencing companies.  A couple that I called up offered that their yard dumpster, where old fence panels are dumped on a daily basis, is free for the picking through.  There is some concern by hard-core organic gardeners about leachate from the treated lumber, but to me it’s a very minimal issue.

Speaking of Craigslist, it’s also a great source for manure. Just plug in “free manure” in the search box.  Plenty of horse owners are looking to get rid of their piles of horse apples.  They may even load it for you.  Not for immediate application to flower and vegetable beds however, it should be composted for a season or two.

Sticks or Stones?

Backyard strawberry patch. Lots of warmth captured by the stone border and the brick wall

I’ve so far only used timbers at my remote garden to edge raised vegetable beds.

Stones and rocks and bricks can provide various benefits when used as border for a raised bed.

For one, their thermal mass absorbs heat from sunlight during the day, and releases it at night.  Although the use of stone pavers as in the picture at right take up a bigger footprint and increase the width of the bed (making a reach-in to the center of the bed a bit more difficult), we also seem to have less problems with invasive Bermuda grass.

The temperature differential of the rocks and the ambient air also causes condensation in the form of dew.  I suspect that if rocks were used for a tomato bed, the dew in the morning would create a more humid micro-climate around the bed as it evaporates, thereby lessening transpiration/moisture loss by the tomato plants. Just a thought.

Finally, using rocks and/or bricks will invite lizards to make their home among the border’s nooks and crannies.  Lizards eat bugs.  I suspect that lizards wouldn’t turn up their nose at blister beetles (hate them!) or leaf-footed bugs (hate them too) or squash bugs  (even more).

I think this will be my next vegetable raised bed project, using stones for the retaining border.

Square edged landscaping rocks used for our backyard flower beds. By decree of Mrs. 101, no vegetables allowed in these spaces (although I've snuck in a few herbs). The viburnum is flowering nicely, and the bud-laden peonies are up on deck. Note the morning glories sprouting up all over the lawn. I mistakenly planted one against the fence last year, and now they've re-seeded all over the backyard.

The landscaping rocks used in our backyard were anything but free of cost.  They were terribly expensive by frugal PF standards, but hey, they look nice.

(**) With regards to the last tenant and the rifle backstop, this guy was really a special kind of knucklehead.  He used the backstop to center his hunting rifle, but beyond it is our neighbor’s own pasture.  One of the four cardinal rules of firearm safety is “Know your target, and what’s beyond it”.  We’ve seen cattle and horses and even kids on ponies in this pasture!  Not planning on using it for the same disaster-inviting purpose, I dismantled the backstop and used the timbers for the altogether safer purpose of raised bed borders. This guy also was rumored to have raised special, um, herbs among the tomato patch.  The leaves of this herb looked a lot like tomato leaves, if you get my drift.  I’ve now spent several hours in the spring making sure no unwanted seedlings crop up.  Like I said, a total knucklehead.

Some readers have commented that I’m going through a crapload of work to put in some raised beds, but it ain’t nothing compared what needs to be done in a desert climate.  See what Mike (of Mike and Molly’s House fame) is doing with his own raised beds: “How to Build a Garden Bed in the High Desert“.  Also a nice write-up on the French Intensive method.

That’s it for this week.  This weekend, more planting and mulching at the home garden.  Readers, how’s your own gardening projects going. Send me pictures, promise I’ll post ‘em.

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Happy Easter, everyone!!