Sun & Rise Over Run


May Apple: Sun - Full to Partial Shade, Soil Moisture-Dry to Medium

In the previous post, Tend the Soil , I focused on one of the three primary factors that affect plant growth in restoration projects, soil conditions. As previously noted, evaluation of all three factors is essential in the creation of a viable restoration plan; the other crucial influences on prairie plant growth are sunlight and site slope topography.

A critical factor to consider when selecting plants for a restoration area is the sunlight exposure. Six to 10 hours of sun a day are needed to sustain prairie plant growth. Some species require full sun to thrive whereas many woodland plants do best in the shade of a woodland tree canopy. Other native plants have the ability to grow in areas with a wide range of sunlight conditions.  According to the Prairie Nursery, sunlight conditions can be divided into four basic levels:

1) full sun: direct sun all day to at least one half day of full sun;
2) partial sun: direct sun for no more than one half day, shaded for at least one half day;
3) partial shade: little or no direct sun, with diffuse light from the edges or through a canopy of tree leaves creates partial shade conditions; and

4) full shade: no direct or diffuse light reaches the ground. A dense canopy of trees completely shades the forest floor. The forest also minimizes wind speeds, protecting woodland plants from excessive drying or physical damage from high winds. The shade of sugar maples, beech, basswood, and dense conifers typify full shade conditions. (Diboll 5)

Ox Eyed Sunflower: Sun- Full, Soil Moisture -Dry, Medium, or Moist

Prairie plant species that have adapted to conditions of high light intensities, heat, wind, and even hail grow in full sun. Native plants that have adapted to growing conditions with low light intensity, but require protection from temperature changes, high winds, and hail thrive in full shade. Plants that prefer the intermediate sunlight conditions between full sun and full shade or partial sun can often tolerate full sun growing conditions in a garden situation that provides some shade or protection for part of the day. Sun-loving plants on the other hand, do not thrive without sufficient sunlight, and therefore, cannot be planted in shady areas. Similarly, shade loving plants only grow in tree canopy protected areas and usually cannot tolerate full sun. Shady prairie areas should be planted with native savanna or woodland species. Both Prairie Nursery and Prairie Moon Nursery offer seed mixes and pre-designed gardens to fit a site’s sun and soil conditions.

Sunlight intensity and soil drainage are also affected by the land’s slope and aspect. Slope refers to the steepness of the land’s surface and aspect refers to the geographical direction the slope faces. No matter what soil type, hilltops and steep slopes tend to be drier than depressions and valleys. In general, slopes increase the rate of the soil’s water drainage affecting the overall soil moisture available to the vegetation.

It is important to note, the greater the slope, the faster the soil drainage, which results in drier the soil. South and west facing slopes will be hotter and drier due to exposure to direct sun and winds in spring and fall for at least part of the day. East facing slopes will generally have more moderate soil conditions, receiving only the cooler morning sun. Cooler and wetter conditions are seen on north facing slopes because they receive direct sun for only a short period of time in mid-summer.

Four unique groups of prairie plants have been created based upon the hydrology or soil moisture level in which the natives grow best: Dry, Medium, Moist, and Wet. These are defined below:

  • dry soils are soils extremely well-drained sandy or rocky in nature and do not hold water and tend to dry out rapidly;
  • medium soils are well drained, loamy and clay-based soils that do not experience standing water;
  • moist soils tend to be damp and may have standing water for a few days in spring or fall. However, the  soil’s surface usually dries out by late spring or early summer, while the subsoil remains moist; and
  • wet soils are damp almost all year round, even in mid-summer. Spring usually brings flooding to wet soils, with standing water remaining  for a week or longer in early spring, but for only a few days in the summer.

A list of prairie and savanna flora associated with soil moisture gradient in the adjacent diagram can be found in the Wisconsin Department of Natural Resources Technical Bulletin number cited below or here. Prairie Nursery also has assembled a list of plant species categorized by soil moisture requirements.

To determine the hydrology and moisture level of the soil, observe site and determine whether the natural state is dry, medium, or wet in nature. Observe the area after rainfall and note whether the site forms puddles, retains water, or  water drains quickly. Decide whether the site in a low-lying area or upland. Make note of any river, lake, or spring is located on the site and its proximity to your restoration site. Compare the sites characteristics to the moisture levels given above to determine the site’s moisture level. Performing a percolation test is an alternative to the previously suggested subjective, soil moisture evaluation.” Water drainage should be one-quarter inch per hour or faster for dry or mesic prairie plants to do well. Plant wet prairie species if your soil drains slower than that. If you have areas that are consistently wet, plan to plant wetland species in that area.” Finally, species moisture requirements differs greatly between dry prairie, mesic prairie, wet prairie, and wetland habitats; select species that will thrive on your site.

In these two consecutive posts, we’ve learned that three main factors determine the growing conditions for a plant; they are 1) soil, 2) sun, and 3) slope aspect. Soil, sun, and slope of the site must be evaluated when selecting plants, since all three of these essential factors determine whether plants will flourish in a certain location. Once a site’s growing conditions have been determined, site specific plants can be selected to match the site.

Related articles

Resources

Cochrane, Theodore and  Iltis, Hugh. Soil moisture gradient and the effect on species composition. Atlas of the Wisconsin Prairie and Savanna Flora, WDNR Technical Bulletin No. 191, 2000. Web. 15 Apr 2012.

Diboll, Neil. “Designing and Planting Your Prairie Garden.” Prairie Nursery, The Productivity Source, LLC., N.D. Web. 13 Apr. 2012.

Diaboll, Neil. “Step By Step Site Analysis Procedures for Developing a Native Landscape Plan.” Prairie Nursery, The Productivity Source, LLC., 2012 Web. 24 Mar 2012.

Kilde, Rebecca. “Going Native: a prairie restoration handbook for Minnesota land owners.” Minnesota Department of Natural Resources, Section of Ecological services Scientific and Natural areas Program, 2000. Web. 15 Apr. 2012.

“An introduction to using native plants in restoration projects.” National Park Service, N.D. Web. 14 Apr. 2012.

Smiley, Thomas E. and Martin, Thomas R. Soil Drainage Analysis and Treatment Considerations. Bartlett Tree Research Laboratories Technical Report. N.P. N.D. Web. 15 Apr. 2012.

 
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