A number of years ago, I talked to a fellow who was a passionate geranium grower. He kept geranium "mother plants" in his solarium during winter. In February, he would snip-off close to a hundred cuttings and grow them into well-rooted transplants for his garden.
I could tell that he had a lot of experience with geraniums and that he knew what he was doing because he always had good success with his crop—well, almost always. The day that he talked to me he was exasperated because all of his cuttings were dying and he couldn’t figure why.
When I asked him if used the same growing protocol every year, he said yes—except for one thing. The one difference was that his son-in-law had given him some bags of “professional potting soil” that he had used to root the cuttings. In the past, he had blended his own mixture, but thought that the professional mixture should be just as good.
When I asked this fellow to provide me with a sample of his mixture for testing, the reasons why his cuttings were dying were very clear. The “professional potting soil” had an extremely low pH and an extremely high level of salt. The geraniums simply couldn’t survive in this toxic blend.
Once he got rid of the bad soil mixture, he was able to salvage quite a few cuttings although he had no where near his usual number of good cuttings.
The take home lesson with soils is this: with some experience, you can judge the physical quality of a mixture by looking at it, but you can’t judge the chemical quality visually. Only a soil test will reveal whether or not a soil’s chemistry is up to snuff.
In my "Soil: It's Not Dirt!" Workshop, I reveal all that you need to know about the physical and chemical properties of soils. Once you understand the basics you will know what to look for in a great quality soil.
- Jim Hole