In a previous article, general information about soil compaction was presented.  This article aims to offer suggestions to remedy compacted soils and ways to prevent compaction in the future.

The purpose of reducing the level of compaction is to increase the amount of pore space in the soil structure.  An increased amount of pore space elevates the amount of water and oxygen available to the plant and other beneficial microorganisms.

Mediterranean Mounds:  In many instances, the cost and effort of amending a severely compacted soil (especially true clay-like soils) may be too great.  In these situations, consider importing well draining soils to be placed on top of the existing soil.  These soil mounds, commonly referred to as Mediterranean mounds, should be a minimum of 18” tall.  Before installing, break up the existing soil to the extent possible, then place the new layer of soil.  By breaking up the existing soil, you increase the opportunities for plants and microorganisms to reach beyond the new soil down into the existing, compacted soil.  Over time, the roots and microorganisms will likely reduce overall levels of compaction.
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Think of the word “soil” and what image first pops into your head?  If you’re like most people, you visualize a dark, fluffy, rich, nutrient-dense, compost-laden material.  But the reality landscapers and gardeners face is often a much different picture.  Arguably the most significant limiting factor in the success of a garden, soil compaction is a concept that few  understand.

What is Soil Compaction?

Simply put, soil compaction refers to the deterioration of structure through the loss of open voids, also known as pore space, between soil particles.  These pores are critical to the health of a plant because they store and transport water and air to plant roots and other soil microorganisms.  Without proper pore space, water and air movement through the soil is restricted.  As a result, you have plants with a reduced capacity to thrive and increased quantities of stormwater run-off.

What Causes Soil Compaction?

As one might suspect, soil compaction often occurs under the weight of heavy equipment, intense foot traffic, over-saturation of soils, and light foot traffic on moist soils. In addition, soil may compact because of improper landscape maintenance.  Two common places this occurs is on lawns and planter beds.  Lawns will easily compact when mowed when still moist, are not cored/aerated at regular intervals, or if organic material isn’t allowed to decompose naturally over the lawn.  Similarly, if planter beds are left un-mulched for long, chemical and natural processes will slowly harden and compact the soil (especially when watered with overhead spray irrigation) to the point of compaction.

Do I have Compacted Soils?

For you to ask this question, you likely have some plants that look like they are struggling but you can’t seem to nail down the problem.  Here are a few easy tests to help you identify if soil compaction is the issue:

-Visual Test:  Do you dread digging holes in the garden?  Do you require an adze and way too much sweat?  Do you see lingering puddles or water run-off from the bare soil surface?  Do your plants look down-trodden and no amount of water (little to lots) solves the problem?  If so, odds are good that you have a compacted soil.  If you aren’t convinced or want to know how serious of a problem it is, conduct the following Dig Test.

-Dig Test:  Excavate a 12” x 12” x 12” hole and fill with water.  Wait for water to infiltrate through the soil.  Wait 1-2 hours, then fill again.  Take note of the time at filling and record how long it takes the water to infiltrate.  Results:  If your second infiltration takes over 45 minutes (and you don’t have a very clayey soil to begin with), you likely have a soil compaction problem.

-Contact a Landscaper:  Most experienced landscapers carry around a soil compaction tester in their trucks.  These probes measure soil compaction quite easily and really only require your body weight.

Turns out I have Compacted Soils!  Now What?

Article:  Soil Compaction Remedies.

For many novice gardeners in California, the first step in the landscape design process is often well intentioned but misguided.

This misstep is usually a shopping spree at the local retail nursery where a flurry of impulsive purchases are based on what is blooming or looks good in a small pot.  The excitement that has brought them to the nursery is wonderful and should be applauded, but the lack of research and forethought prior to a landscape-shopping spree often results in long-term garden discouragement as the plants chosen die, grow too big, or don’t grow big enough for their needs.

So a great place for any novice gardener with few California landscape ideas to begin is to browse landscaping photos online, read landscape design guides on mediterranean landscaping, and visit landscape photo sharing sites.  There, a plethora of design examples and plant combinations exist that will get your creative juices flowing.  Save inspirational images or create lists with online tools such as Landscape Resource’s innovative Palette Builder. Read the rest of this entry »

Considering the history of California, it’s surprising our landscapes have taken on more of a northern European feel when the first massive and lasting influx of “settlers” hailed from a mediterranean climate:  Spain.

For over 350 years, the Spanish and summer dry influence defined the landscape.  Even today, the California mission gardens are some of the best indicators of the role the landscape played for generations.

With water always the limiting factor, plants were chosen very specifically to fulfill important roles such as providing shade, food, or other resources.

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