Rainscaping Guide: What Do You Know About Your Site?

Identifying problem areas on your property helps determine your goals and indicates choices for specific landscape options to solve problems.

Topography and Flow
Observe the topography of your property and note how water flows during periods of heavy rainfall, as well as where offsite water enters the property. Other potential problem areas to record on your map include steep slopes, ponding in low wet areas, areas of recent construction and utility lines.

Utilities
Be sure to include overhead utilities on your map. In addition, call 1 (800) DIG-RITE to have all underground utilities identified and add them to your map as well.

Indicating where slopes exist and to which direction they drain will give a clear picture of those areas that contribute to rainwater runoff and may be prone to erosion. Be sure to assess whether your slopes are steep, moderate or gentle.

Note commonly traveled pathways and areas that are frequently used. Leave these sections of the landscape open using mowed turf, paths and/or patios to define those spaces. There are permeable products that are useful for creating patios and sitting areas as well as for pathways while still allowing rainwater to soak into the ground. Permeable pavement and brick or flagstone over a gravel base are commonly used. Other permeable options for pathways include mulch (wood or gravel) and stepping stones with low ground cover.

Note all desirable plants that will remain in your new design such as existing trees, shrubs and perennials. Determine and identify existing native plants to include in your plan. Existing plants are good indicators of soil and light preferences. Identify undesirable plants and invasive species that should be removed from the property.

Identify the north-south orientation of the property. Determine and note patterns of sun and shade and the time of day that it occurs. Shade-loving plants need shade from 11 a.m. to 4 p.m. in mid-summer (June–August) in St. Louis. Keep in mind that the sun/shade areas change with the seasons—in other words, where it is shady in the winter can often be hot and sunny in mid-summer.

Overfertilizing your soil can cause excess nutrients to run off during storms and pollute local streams. Most plants, especially native plants, need minimal fertilization to maintain healthy growth. An annual application of compost to the soil surface provides the nutrients, micro-organisms, and organic matter necessary for a healthy soil. If plants are not thriving in your soil, you may want to consider a soil test. Soil testing for nutrients and pH levels can identify if there is a problem—if a nutrient is missing or needs to be adjusted. Soil testing can also help prevent overfertilization. You may choose to have your soil professionally tested, use a homeowner soil test kit or run a simple visual inspection.

Visual Inspection
If your topsoil is dark brown, somewhat crumbly (friable), and has organic matter visible, soil amendments are unnecessary. A soil with adequate organic matter (compost) typically has sufficient nutrient levels to maintain healthy plant growth. Do a visual inspection of the plants as well to determine if they have healthy growth.

Test Your Own Soil
Do-it-yourself soil testing kits are available online and at your local garden centers or home improvement stores. These kits are not as accurate as a professional soil test, but will give an indication of whether there may be a soil or nutrient problem.

Professional Testing
A soil test gives the pH and the status of nutrient levels in the soil. It will also tell what type of soil it is, what the soil structure is, the percent of organic matter present and make recommendations for soil improvement. Multiple soil tests might be necessary if there are multiple types of landscaping (vegetables, perennials and shrubs, turf, etc.) in multiple locations for the landscaping (front yard, back of property, etc.). For more information on getting your soil tested and for a list of locations to drop off your samples, visit https://extension.missouri.edu/counties/st-louis/soil-testing.

Soil fertility – Nutrients that plants need in large quantities are called macronutrients and these are nitrogen (N), phosphorus (P) and potassium (K). Plants also need secondary nutrients calcium, magnesium and sulfur. Plants need micronutrients, in much smaller amounts, including boron, copper, iron, chloride, manganese, molybdenum and zinc. Compost, often referred to as organic matter (OM), is the best way to improve nutrient deficient soil.

pH – The pH scale measures how acid or basic a substance is. The scale ranges from 0–14. A test result of 0–6.9 is acid with 0 being the most acid. A pH of 7 is neutral. A test result of 7.1–14 is basic with 14 being the most basic. A wide assortment of plants grow well in soil with a pH of 6.5–7.5. Lime can be added if a soil is too acidic. Sulfur can be added if a soil is too alkaline.

Continue on to Is a Rain Garden Right For Your Site?