Lewis and Clark Conservation District, 790 Colleen Street, Helena MT 59601  406-389-3895

Gardens, Rain Gardens and Xeriscaping


In the greater Lewis & Clark County area, precipitation amounts are variable and unpredictable.  Adopting sustainable gardening practices in outdoor landscaping allows for one of the largest opportunities for water savings.  This topic includes information on Xeriscaping, Rain Gardens, and Rainwater Harvesting.  If you have any questions please contact the Lewis & Clark Conservation District.

The average rainfall in Helena, Montana is about 9-12 inches a year and landscaping accounts for half of all residential water consumption.


Gardening in Lewis & Clark County will depend a lot on where you live.  The Helena Valley doesn’t get a lot of precipitation typically, and the growing season in the entire county is quite short.

Elevation difference, and location of buildings etc. can create microclimates.

The Conservation District is not the county’s foremost authority on gardening, irrigation for gardening and pests that we encounter in the county.

We recommend that you contact the Lewis & Clark County MSU Extension Office.

Rain Gardens

A rain garden is a plot of land that has been lowered–a hole or depression–and planted to capture water from impervious runoff such as roofs, sidewalks, and other urban structures that do not allow rain water to penetrate into the ground.

Rain gardens are important because as urban areas increase in size there is an increase of impervious surfaces which can lead to flooding which, in turn, can destroy homes and property.  This flood water also carries pollutants from parking lots, streets, and lawns into your streams and lakes. An increase of impervious surfaces also threatens our groundwater by not allowing a relatively even groundwater recharge, which can directly lead to the reduction of the quality of our water.

Creating a rain garden is simple. It is similar to a perennial garden with a few exceptions.  Besides being placed strategically to collect rainwater runoff from your home or sidewalk, or other impervious surface, they need to be placed somewhere with good soils where adequate drainage rates exist.  You will also want to keep your rain garden away from septic systems, water wells, utilities, and foundations.  Your rain garden should also be around 5-10 percent of the size of the impervious area that will be distributing runoff into the garden.

For example:

(3,000-square-foot roof) x (7% = 0.07) = 210 square ft

So your garden should be 21 feet long by 10 feet wide!

Read more about rain gardens at this link. Have a look at a Rain Garden Publication from the Natural Resources Conservation Service.


Rainwater Harvesting

How to build your own system.

Rain water collection can be used to supplement your main supply of water.  Harvesting rainwater can help reduce the severity of flooding, can provide water if there is a drought, and can reduce the demand on your well.  Harvesting rainwater helps reduce the amount of water that flows into stormwater sewer systems and stormwater runoff which usually carry pollutants into freshwater bodies.

Collecting rainwater is a fairly easy task and there are many different types of systems.   You can create your own system by hand or you can buy systems, you can store them outside, underground, or you can build an enclosed system that your drains directly lead to. You can use harvested rainwater to water your plants both inside and outside.



The term xeriscaping stems from the Greek word xeros meaning “dry.”  This technique is important to us here in Helena, Montana due to our high elevation semi-arid climate (basically a mountain desert).  Xeriscaping is important because this term represents a water conscious, water efficient landscaping method.

Xeriscaping reduces water and maintenance costs, enhances real estate values, increases plant survival, and allows for edible and/or decorative products.

Environmentally, xeriscaping improves water and soil conservation, reduces use of petroleum products, improves air quality, enhances urban wildlife habitat, and reduces water contamination.

The NRCS, DNRC, and the Montana Association of Conservation Districts have compiled an excellent file on Creating Native Landscapes in the Northern Great Plains and Rocky Mountains which goes into further detail, with planning steps, pitfalls to avoid, and plant options.  If you have any further questions please contact the Lewis & Clark Conservation District.

Soils-Formation and Characteristics

The following is a presentation made by CD Admin Chris Evans, for the Lewis and Clark County Library on March 23, 2022.  It’s about soil formation and how to work with the soil you have.

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