Article I wrote for the Portland Dahlia Society Bulletin:
Dahlia Talk
05-28-23
Headline:
Usual Well Organized Session Devolves into a Fertilizer Laden Melee
By Ted J. Kennedy
About 25-30 avid participants from the USA and one from Australia were in attendance. There was one person missing and that was Dan Baulig who organizes the session. He had the excuse of watching his grandchild play on a baseball team vying for a State Championship. He will gladly tell you how their team won and how his grandchild contributed to the victory.
We spent most the two hours on the most popular subject for dahlia growers, especially at this time of the year and that was FERTILIZER with some soil type discussion, herbicide warnings, macro nutrients and micro nutrients and numerous stories from the past on how someone used to do it. And lots of personal experience was shared. I will list numerous fertilizer suggestions and a sentence or two about it.
One quick comment. Over the years, there have always been organic growers and growers who use less than organic solutions to grow dahlias. 30 years ago when fertilizer was discussed at club meetings nearly all of the growers used chemical fertilizer with abandon. At this meeting, I do not believe there was a single person who only used chemical fertilizer and most were converts to organic solutions especially when they work so well.
Soil acidity was discussed and two areas in the USA were identified, one here in the PNW where most soils are acidic and the places in the USA where soil is alkaline. In a way, pH discussions are like true confessions, when people admit they could do more to correct their soil pH. Lime is used here in the PNW and sulfur is used in alkaline gardens. Dolomite lime was compared to regular lime.
Magnesium is related to the pH discussion and this micro nutrient is often somewhat deficient in soil tests. Dolomite lime is one of the recommended cures as it has the nutrient and corrects pH very well. We had a minor discussion on Epsom salts, magnesium sulfate and I believe it is an organic chemical that can be used.
Fertlilizer Rates: Soil tests were discussed and they frequently express their fertilizer recommendations in pounds per acre and pounds per 1,000- square feet. One person was confused as he wanted a recommendation for fertilizer per plant. We tried to express how we determine how much fertilizer to use and the frequency of the application. I am not going to try list the solutions but they were very enlightening.
Phosphorus was discussed in great depth. The main issue for most of the people is that when they get their soil test back it says their garden has too much phosphorus with a common comment: very high. The negatives of too much phosphorus were discussed. We also talked about the “low nitrogen “ fertilizer recommendations that have caused much of the problem. Some discussion was on how to lower the phosphorus levels. Number one is not to add more phosphorus to the soil and that includes bone meal. At least then the problem would not get worse. Several people related they have been unsuccessful in lowering the phosphorus levels even though they have not added any in several years. I could say you should have been there to get an answer to the issue but will say that one solution to lower phosphorus levels is to remove a crop from the garden and that crop would have phosphorus in it. Farmers harvest crops and remove them from the soil and this lowers phosphorus. Dahlia growers remove only flowers. Removing the dahlia stalks at harvest time may really help in this issue.
Types of fertilizers Discussed: Bat guano, types of compost, and one that was talked about more than others was chicken feather meal. The meal releases nitrogen slowly over several months. One chicken feather user user had the only soil test done in the spring that showed adequate nitrogen was still in the soil. Many of us have never seen a test with those results. He also uses some leaf mold and covers it to protect it from the rain and that too may be why he does not loose nitrogen. Many types of manure and manure tea were discussed. Worm tea was discussed in some detail. Sea weed of various types was discussed and it was noted that you cannot legally gather it from beaches. Of course, that was said after the person reported that it was the best fertilizer she had ever used. Fish fertilizers of the liquid type and pellet type were discussed. Warren Vigor's fertilizer was discussed in positive comments. Many more and you should have been there to hear the various fertilizer stories.
Compost and herbicide was discussed and the mushroom compost herbicide debacle was discussed.
Mulch was discussed and the risks and benefits ranged from total disaster and the loss of an entire dahlia garden to it was the best thing I ever did for the dahlias. In summary, mulch is not good when the ground is wet and cold in the spring and is good when it gets very hot and it cools the soil temps and preserves moisture. Lots of discussion and you must do it right if you do it.
No till Gardening was discussed in some detail.
Soil Types were discussed and sandy clay soil was discussed along with clay and more clay. Swan Island Dahlias wonderful soil was discussed.
Other miscellaneous subjects were talked about including getting tubers to show eyes. Teresa Bergman went though her successful process where she used damp vermiculite in plastic shoe boxes. Tuber rot was talked about a bit. One subject that was not discussed was leafy gall and I was glad as it has been talked to death. This summary of the session is woefully inadequate and I will always say you should been there and most of what was discussed has not been included here.
