By Steve Jones, Master Rosarian

No, this is not an article about some far away island with virgin sacrifices to appease the gods of fertility. Rather this concerns what makes a soil adequate to grow rose plants. 

Soil fertility is the capability of a soil to produce a crop or to grow plants. We have all heard of the great fertile lands of the Mesopotamia region between the Tigris and Euphrates Rivers. This land could grow anything in great abundance. The alluvium or fine slit from the rivers carried the nutrients necessary for good growth. Add to that good drainage and the soil was perfect for growing plants. But not all soils are adequate for growing plants, or they will eventually "fade" out. Soil is a constant evolving mass, where materials are always undergoing change, such as decomposition, erosion, dissolution, etc. This is why replenishment is very important.

Ancient man discovered that animal manures applied to the land will help aid in crop production. It is not known when this practice started but in Homer's The Odyssey (circa 700 BC) he mentioned the manuring of grape fields. They also found that human, plant, and animal remains added to the soil's fertility. Omar Kayyam once wrote:

          "I sometime think that never blows so red
          The rose as where some buried Caesar bled;"

Ancients also found that mixing different soils and mineral deposits together helped with fertility. Marl (calcium carbonate) was one of the earliest minerals mentioned that was added to the land. In recent years, the study of soil fertility has been studied intensively. We are always trying to increase the yield per acre for crops. This of course helps the rosarian who wants to have good soils in their gardens. 

Water Drainage and Availability of Nutrients
Soil fertility strongly depends on water drainage and availability of the nutrients necessary to promote good rose plants. Availability is the main key here. More often than not, we have to add nutrients to the soil in our rose garden. There are many factors that affect nutrients being available for uptake and plant growth, including: soil pH, form of the nutrient, water drainage, amount of microorganisms in the soil, temperature, etc. The first consideration for all garden soils is the pH. pH is critical for fertilizer availability to the plant. The ideal soil pH for a rose is a very narrow range (6.0-6.5) and soils should be tested from time to time. It doesn't take much to throw off the soil pH. 

Organic Material
The best soils for roses have about five percent organic material. Organic materials help hold water and fertilizers, providing good soil structure, and provides food for the soil bacteria which in turns provides nutrients to the rose. Most soils tend to be low in nitrogen, so organic materials will provide a steady, low concentration of nitrogen. Organic materials will also help improve the workability of the soil, often referred to as tilth. Dr. Nicholas in his book, The Rose Manual, stated, "To be fertile, a soil needs humus first of all. Without a liberal supply of humus, the other fertilizing elements would remain inactive." However, organic materials themselves, especially compost, will not provide all the nutrients needed by the plant.

Sandy Loam is the Best for Roses
Soil makeup is also important. Ideal soils for roses should be a sandy loam. This allows proper drainage and yet, retains nutrients. This equates to 60% sand, 20% clay, and 20% silt. You can do a simple test by collecting a soil sample, placing it into a glass jar with a lid, shaking it up, and let it settle out. The heavier particles like sand will settle out first, then silt, then clay. Organic matter will often float to the top. Measure the different distinct layers and take a percent of the total. This should give you a good idea of your soil makeup.

To grow the best roses, we need the best soil. Apply fertilizers in the appropriate amounts, keep your pH within the ideal range, add plenty of organic materials, keep the right soil makeup, and your roses will perform.

© Copyright Steve Jones. All rights reserved. Published with permission. 1/99 RE

For questions about Pacific Rose Society, contact: 
Chris Greenwood

Updated January 4, 2016

'Newport Fairy' Hybrid Wichurana
(Climbing Rose)