Beginners Guide to Building Stone Retaining Walls

By Ken Lain, the mountain gardener

This is the time to turn your garden soils, plan crop rotation, and dream while turning the pages of that new seed catalog.  The soil is so easy to work right now that adding compost, manure, and plant food into your soil is almost fun for the winter gardener pent up indoors.

The next few weeks is the ideal time to create new raised beds, or put up a new retaining wall.  Keep these new garden beds, or retaining walls less than three feet high and they are ideal winter garden projects.


This tutorial is designed for beginners interested in building stone retaining walls using a wall-01“dry-stack” method, but it also works for retaining block and flagstone walls.  Other materials that could be used for such a project include landscape timbers, railroad ties, and cinder blocks.  These step-by-step instructions are meant specifically for walls built of stone.

The dry-stack method is not appropriate for walls that are to be higher than 3 feet tall. For taller structures, use mortared walls. After reading this column beginners can expect to spend two days to construct ten feet of wall.

In the planning stages, you will be working out all the logistics, taking measurements, gathering materials, etc.  If your slope is too large for a 3-foot-high structure, consider terracing the slope by building separate retaining walls in two or more places, rather than trying to do the whole job with just a single wall.

The greatest advantage for beginners is that a shorter wall doesn’t require engineered footers beneath the frost line.  A shorter length is far easier to build.

How to Build a Stone Retaining Wall

Head to your favorite rock yard and choose stones that have at least two sides that are flat, which become the “top” and the “bottom” once in place. The heavier the stones, the more stability you have, but also the harder the work will be. As a general rule, bigger is better especially at the foundation.

In addition to stones, assemble the following supplies ahead of time:

  • Line level and string or garden hose
  • Shovel
  • Mason’s hammer
  • Stakes
  • Carpenter’s level
  1. Dig a trench about 8 -10 inches deep, so that the first course of stone will be fully or mostly submerged. This will help your retaining wall withstand the pressure exerted by the garden soil it is holding.
  2. Plot where the retaining wall will sit at the bottom of the slope, using stakes andwall-02 string for a straight terrace; a garden hose is also good for visual placement. You will want the first course of stone to be level and a line level is the best tool for the job.
  3. To calculate the necessary width of the trench, just remember the base of the structure should be half the wall’s height. Angle the trench so that it inclines back slightly into the slope. A good rule of thumb is 2 inches back into the slope for every 1 foot of height. This provides the stability needed.
  4. Terraces of natural stone are laid one horizontal row at a time. The top row of stone consists of your largest, widest, longest, flattest stones, so hold some of these in reserve for the final row, or use capstones. The bottom row should be your most stable stones. Take the time to fit this row as closely together and as level as possible. Building terraces with natural stone is like fitting together pieces of a puzzle!
  5. Check to ensure that the stones run level left to right. But because you have built a slightly backward slope into the trench’s base, your stones will slope slightly from front to back. After completing this first course, or foundation, backfill with some of your excavated soil and any stones too small to use for building the retaining wall, and tamp down the backfill.
  6. When laying the next courses of stones, backfill and tamp down after completing each row. Tuck soil in between gaps in the terrace. When the wall is complete, you can root plants into the larger gaps of the wall that bring life to the structure. Cascading plants, such as creeping thyme, alyssum, ivy, creeping rosemary, and vinca minor are very attractive spilling down the sides of stone retaining walls.
  7. Make sure there is as little wobble as possible between each stone. To counteract wobbling stones use small flat rocks as shims for stabilization. Use a mason’s hammer to knick off stone fragments so as to achieve a better fit where needed.
  8. Continue in the same manner with succeeding courses. By the time your terrace is half its planned height, incorporate what are known as “deadmen.” In the case of stone retaining walls, the term refers to long stones laid perpendicularly across the wall, rather than parallel to all the other stones. The idea behind deadmen stones is to tie the structure into the slope in back of it for greater stability. These longer stones reach back into the slope so the weight of your garden soil helps stabilize the wall. The longer the stones you can find to serve as your deadmen, the better.  A good rule of thumb is to provide at least one deadman per 16 square feet of exposed wall face.
  9. As you reach the desired height of the wall, place the capstones on top. Capstones are similar to the stones used in your top row, in that they should be flat and have significant mass. They serve both to hold the stones under them in place and to provide a finished look, thus the importance of their being flat.

wall-03A Planting Tip

Garden plants help retain and solidify your new wall in place, and bring it alive.  Plants anchor and prevent erosion.  We have a lot of plant choices at the garden center right now, but three that come to mind for sunny locations are blue rug juniper, native creeping mahonia, and coral beauty cotoneaster.

Until next week, I’ll see you at the garden center.

Ken Lain can be found throughout the week at Watters Garden Center, 1815 W. Iron Springs Rd in Prescott, or contacted through his web site at or .


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All Purpose Plant Food & Flower Power the Dynamic Duo of Mountain Soil

Our rocky mountain soil makes gardening a real challenge and we can all use every edge we can get to successfully grow vegetables, flowers and shrubs in this unforgiving climate.

Enter the dynamic duo to the rescue. Available exclusively at Watters Garden Center.

Available exclusively at Watters Garden Center, Prescott AZ

Available exclusively at Watters Garden Center, Prescott AZ

All Purpose Plant Food offers the meat and potatoes of the plant’s diet. Use at planting and then four times a year to provide sustainable feeding for lawns, plants, vegetables, shrubs & trees. In fact just about everything you plant will benefit All Purpose Plant Food.

Available exclusively at Watters Garden Center, Prescott AZ

Available exclusively at Watters Garden Center, Prescott AZ

Flower Power was described by the “Mountain Gardener” Ken Lain as the “Snickers bar for plants.” Use to give flowers and vegetables a boost that will perk up their blooms before a garden party and elsewhere around the garden. As always, follow the directions on the label.

To listen to the entire response to a question about when to use which product at one of our recent Garden Classes Click Here



Free Design Fridays with Rich Olson

Landscape DesignDesigner Rich Olson has been such a huge hit during our Design and Raised Bed Gardening classes, that I’ve invited him back for more.  We’re offering Free Design Fridays, each Friday from 10 AM to 3 PM starting April 19, 2013 in front of the greenhouse.

Rich Olson

Just bring in your photo and dimensions of the area to be designed – no appointment necessary.  You will receive a free personal 30 minute professional design session with Rich Olson, using 3D design software.

Successfully Planting Technique this Spring

Planting- shrub complete.jpgPlanting success in spring comes down to the right food. If you followed this column’s advice earlier in the month and put your plant foods down before the last moisture, your timing couldn’t have been better. Deep moisture also will make garden soils easy to work. Your shovel will slip easily into the soil making this the perfect time to plant the larger items in the yard.

If you are a DIY kind of gardener the next month is the time to plant large sizes of pine, spruce, shade trees, and privacy screens. Moist soil makes it easier to dig the hole and new roots will spread easily into the surrounding soil. Even if you have the garden center plant a large plant for you, to avoid stress on your back, deeper-rooted plants still will root out more easily.

This week marked the official start of spring and the planting season. Here are a few planting techniques that ensure plant success in the yard. A few of these steps will be familiar, but others have been adjusted for more successful planting in mountain clay soils. Local landscapes can be a challenge, but these easy to follow planting steps will ensure your plants of a happy, successful start in your garden.

A planting hole correctly dug and properly amended will result in a healthy, vigorous plant. Below is my 6-step planting technique that consistently works for local gardens.

Step 1The bowl-shaped hole should be the same depth as the plant’s root ball but three wider. Plants don’t need a deep hole; they thrive when able to stretch out just under the soil’s surface in search of food and water. That is why a bowl-shaped hole promotes the best root development. Be sure to rid the hole of rocks that are larger than a golf ball.

Step 2 – Check for good drainage by filling the newly-dug hole with water. If after 12 hours the water has not completely drained away, dig a chimney-like hole into the bowl-shaped hole until you reach the next soil band and check the drainage again. All plants need drainage, drainage, drainage.

Step 3 – Improve the planting soil by amending it with composted mulch. NO manure needed; it is too strong for new plants. There are two types of soil in mountain gardens. One is hard clay which does not drain well; the other is loose granite that water flows through as it flows through sand. Good mulch will keep clay soil loose and aerated, and retain water up around the root ball in loose granite.

Watters MulchThe amount of mulch per plant should be equal to the size of the root ball. That is the quantity of mulch you will need to blend with native soil to fill in around each plant. Spread a layer of mulch as top dressing to insulate the plant and retain water around the newly forming roots. If you are working with granite soil you should add a 3-inch deep layer of additional mulch on top of the root ball.

If your planting area has so many rocks that once you have removed them there isn’t any native soil left, use a good potting soil instead of mulch. Planting only in mulch is too heavy for most plants, but potting soil will add drainage and encourage healthy roots.

Step 4 – Don’t bury the plant; keep the trunk out of the soil. The top of the root ball you see exposed at the garden center should remain exposed when transplanted into your garden.

Step 5 – Feed your new plantings with ‘All Purpose Plant Food 7-4-4”. This natural foodWatters Plant Food encourages strong root development, but is safe for pets, birds, and young family members. It works well, is easy to use, and has a large margin for error that other foods do not have. Just sprinkle the granules on top of the root ball and water well. This slow-release nutrient will feed newly forming roots a little each time you water. There is no easier way to nurture a strong root system.

root stimulatorStep 6 – Promote deeper roots with ‘Root & Grow’. Tired of cheap rooting substitutes and manufactured short cuts I developed this liquid rooting solution for our local gardens. A plant will push new roots into the surrounding soil when this liquid magic is added directly into the plant’s water source. Use a 2-gallon watering can and add the recommended amount of solution to the water; then generously soak each plant once it’s in the ground. Use this rooting tonic every two weeks until new foliage or flowers appear. This elixir works equally well on flowers, shrubs, or trees.

For exact planting details that include drawings and measurements ask for my ‘Guide to Mile High Planting’ the next time you visit the garden center. You also might like the useful companion piece ‘Mile High Watering Guide’.

Until next post, I’ll see you at the garden center.

Step-By-Step to Great Garden Soils

We kgarden soilnow that the better the soil the larger the harvest. Once you have tried digging your first planting hole in a mountain garden you learn that our native soils are HARD ! ! That’s why successful mountain gardening has always come down to soil quality. Skimp on spring soil preparation to “soften” the ground and a garden’s production can drop close to zero.

This week my raised beds are amended, turned, and ready for planting. Let me share a few secrets to mountain soil prep that return bushels of produce and a season full of flowers. Any backyard garden, whether in the ground or in raised beds, requires these easy steps. Container gardens have different requirements that I’ll write about later this month.

The more organic material any soil contains, the better the soil quality. Our mountain soils are hard because they lack organics such as compost, manures, and leaf molds. Because plants use up organic resources throughout the year, new organics must be added to keep the vitality of the soil.

A word of caution for those gardeners new to horse country. You are apt to see a sign in a front yard advertising “Free Manure”. But proceed with caution before you haul away this free organic additive for your garden. Horse manure is a great source of organic nitrogen, but not until it is aged. So, never introduce fresh manure into your garden. The salt and nitrogen damage is unpredictable.

We all know that whatever goes into a horse’s mouth comes out the other end. Watters barnyard ManureThat includes weeds as well as straw and hay. Also, grubs that we don’t want in a garden like and can find their way into the warmth of a huge pile of manure. The only way to get fresh manure suitable for gardening without the weeds and bugs is to age it, also known as composting it. You must compost it and check that there are no large white bugs eating at the middle of the pile. If this scenario isn’t for you, fear not. Read on and you’ll learn that you don’t have to deal with fresh manure to enjoy the pleasures of a successful garden.

For my smaller garden plots I use deodorized ‘Barnyard Manure’ that comes bagged and ready to add to the garden. This aged poop has a mixture of mature manure types, it doesn’t smell, and it isn’t slimy. This year my gardens received a generous dose of 50% Barnyard Manure and 50% Organic Mulch.

The mulch and manure additives ensure proper drainage, root growth, and water retention for your garden. But, certain mountain plants require calcium, magnesium, phosphorus, and some other minor elements, all of which should be added to garden soil., before turning the compost additives into the planting bed, add two sources of nutrition. The first is a layer of gypsum, also known as calcium sulfate, the most effective source of calcium for plants. The second is an organic plant food of your choice. I definitely recommend 100% organic “Tomato & Vegetable Food 4-4-6” for herb and vegetable gardens. It also works well in flowerbeds to produce amazing colors!

Soil pH creeps up during the growing season. This is a problem that results from poor water and one that must be corrected to keep plants in the ideal 6.5 – 8.0 pH range. In garden soil with more than an 8.0 pH production stops, fruit drops, the plants yellow, wilt, and finally drop their leaves. Granular “Soil Sulfur” turned into your garden soil to one shovel’s depth is the correction to bad garden pH, and every mountain garden needs it.

In summary, here is the formula of soil amendments and additives to use this spring: Begin with a 2-inch layer of 50% composted mulch and 50% deodorized manure. On top of this organic layer sprinkle the recommended rates of gypsum, organic Tomato & Vegetable Food, and Soil Sulfur. Turn these to one shovel’s depth into your garden soil and you are ready to plant.

Freshly turned soil is light and airy, so tread carefully on your amended garden soil so it retains this texture. Walk on predefined paths or use a wood plank to walk over the soil without compacting it unnecessarily. Deeply water the garden soil two times before planting. This will reduce damage if too much manure was added or if it congregated unevenly into the soil.

Exact additive amounts were not given in this column because those depend on the size of your garden plot. So visit me, or the staff at your favorite garden center, for exact quantities of each additive to purchase, remembering to bring along your garden measurements.

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Plant of the Weekis the “Mammoth Prescott Pansy”. This special variety was Pansy-Mammoth[1]found to deliver monstrous blooms that look you in the eye while beaming a smile from a huge monkey-like face! Within a few days after planting the ankle-high foliage is smothered with flowers that love our inclement spring weather. If you need a post–winter garden blossom fix this pretty plant is oh-so-easy to grow. It’s available in small and large ready-to-plant sizes that rarely exceed the $6 mark, so it’s easy on the wallet, too.

A contest reminder to my Facebook fans: I’ll be asking for photos of your best-looking container gardens later this spring. Post your photos, view all the postings, and vote on the photos you like most. Those with the most votes win garden prizes. So, go ahead, stack the deck by having your friends vote for your photo; the more gardeners involved the better! You could easily be the winner! Become a fan and subscribe to my page at

Until next post, I’ll see you in the garden center.


Finish Getting the Spring Garden Soils Ready

Plant Show Off Forsythia before they bloom for the best show this spring

Plant Show Off Forsythia before they bloom for the best show this spring

Soils thawed after the last few rains, it was time to prepare the gardens for the coming planting season. A fresh layer of manure and mulch, plant food and soil activator, with a blend of water holding polymers was turned to one shovels depth in my gardens this week. The soil was moist and very easy to work, you should do the same. Finish getting the spring garden soils ready.

Flower beds and the vegetable gardens now appear as a rich layers of chocolate made ready to absorb plants like a sponge. The first crop of lettuce, cabbage, arugula and broccoli will be planted in my gardens the end of this month. Pansies, daisy, stock, kale and primrose will follow as the first Forsythia celebrate the arrival of warm days. We are literally days away from the gardens awakening.

The rest of the pruning was completed this week, and under the perennial mums this springs foliage has started to emerge standing well over an inch tall. Daffodil, parsley, onions, herbal thyme all show sighs that spring arrives shortly.

Insiders tip – Red potatoes, sweet onion, Elephant garlic, rhubarb and asparagus have arrived at garden centers. We are a couple weeks from planting season, but buy your supply of bulbs, roots and divisions at your earliest convenience while stocks are fresh. The first of the vegetable supplies are very limited an become picked over as the season begins. Snap up the best of the supplies while they are fresh and store them in a cool garage until ready to plant. My garlic, parsley and onions plant last fall have already erupted from the soil as of this week. By they time your soil is turned these root crops can be plants. Bring on spring!

Feed plants before spring blooms

Feed plants before spring blooms

Next week my landscape gets a fresh meal of ‘All Purpose Plant Food’ 7-4-4. Putting organic foods on early is good for spring blooming lilac, forsythia, quince, fruit trees and the like. If it blooms in spring make sure to fertilize by the end of March for a better show. The buds on my cherries, apple and plum trees are huge right now and with a little extra nutrition your trees should really shine. Personally, I use the 7-4-4 blend of organic food on most plants in the landscape. The fruit trees, grapes and berries are hand delivered their own special meal tweaked just for them. For fruiting plants use the ‘Fruit & Berry Food’ 7.5-5-7.5 for a better harvest this spring. Go ahead, the landscape would appreciate some preliminary garden work done right now.

Finish cleaning up the landscape, cut back old perennials, pull the deal out of iris beds, shape grape vines and the rest. When the clean up is complete make sure to spray remaining plants with ‘All Season Spray Oil’. This is especially important for any plant that had bugs showing last year. This environmentally safe bug killer eliminate last years bugs wintering over in your yard, but more importantly it suffocates insect eggs laid last fall. This is especially important for fruit trees, roses and spring bloomers. I buy a couple quarts and shoot it through the hose end sprayer and spray liberally throughout the yard. This spray is much safer for pets, birds and people alike, but can only be used while temperatures are cool.

Show Off Forsythia is this weeks plant feature of the week. Loaded with huge buds it would be better to plant this showoff before it blooms. A definite upgrade to your grandmothers forsythia. This one remains tight and compact so no pruning is ever needed. An early spring blast of intense yellow flowers erupt from the ground. It is ‘fire wise’; with no pruning needed you can have that dream hedge without doing any of the pruning work. It keeps a smile on your face, because deer and javalina turn their nose up at the taste. This new variety shows off larger flowers that standout among the rest, but in limited availability because it is so new. Now is an ideal time to plant for a glowing spring show.

I specialize in bringing the migrating birds into local yards and my intention was to educate readers on the best feeder types filled with the right bird seed mixes to bring more birds into your yard this spring. As usually, much is going on in the gardens this week and I’m out column space this week. You are invited to this weeks free garden class taught by local birders Dawn Weir and Kelly Mattox.