Here is my write up without the two nursery rhymes above.
Dahlia Talk 02-25-25
Ted Kennedy Hollyhill Dahlias
We set a new record and had 75 participants. I got onto the session early and there were only 7 people online before me. I like to chat with people before the meeting and here comes Steve Boley of Sandia(and other appellations) dahlias and we chatted.
I am in an awkward situation as I write this. I did a presentation on Dahlia Myths and focused mostly on fertilizer myths. I say this because the word âmythâ indicates that that there is something that is believed by a lot of people and lot of other people think it is not true. Am I taking the role of âmyth-busterâ and am ignoring the arguments that there is truth or some partial truth in the myth? I am going to report here not only what I consider myths but am going report the reaction of people in the session that had something to say one way or the other.
The big story is the myth that dahlias require low nitrogen fertilizer. This topic has been argued for time immemorial and the other euphemism is âSince Hector was a pupâ . I bet Hector was good dahlia grower. I am going to report this one as the last subject in this write-up.
Manure is good for your garden- Wow, I got lots of responses and the basis of the myth is that manure generally has too much what they call âmacro nutrientsâ meaning that the phosphorus and potassium are too high in relation to the nitrogen and can build up in the soil causing problems. This did spark a discussion about the various manures including cow, horse, alpaca, rabbit and especially chicken. My point of the myth was that you need to get a soil test to be sure that you are not accumulating âmacro nutrientsâ. So the myth should should say: â...if you get a soil test and make sure the manure is not adding excessive âmacro nutrientsâ and then manure can be a good thing for your garden.
Bonemeal is excellent for dahlias I am not going to back down on this one. Bonemeal is mostly phosphorus and does not break down for years to be available to the plants. Too much phosphorus is a problem.
Lawn fertilizer is bad for your dahlias This one was not disputed much and in many situations it may be just fine for dahlias.
There is no cheap time release dahlia fertilizer I extolled the virtues of Sultur Coated Urea that is very inexpensive but at least one person disliked the use of urea as fertilizer while another praised it profusely and buys it in bulk in 50 pound bags. Both people who spoke were very experienced, successful, best in show dahlia growers. I personally like urea and use the sulfur coated product.
Fish fertilizer has too much nitrogen for dahlias. There was lots of discussion in favor of fish fertilizer and I agreed with much of it. My issue is that it has too much phosphorous but in the small amounts used by it's proponents that is not an issue. No one seemed to mind that it has lots of nitrogen. There were names of legendary dahlia people who used fish fertilizer mentioned by some almost legendary people in the Zoom meeting. I like these âmy legendary mentor did thisâ comments.
You cannot add too much organic material to your garden I brought this up because the soil testing company that the local trial garden uses, does an organic material analysis and if you have too much organic material in the garden that is a negative. Two inches per year is generally recommended. I thought more people might dispute this one.
Epsom Salts is one of the best fertilizers. This was a tricky one as Epsom salts is not a âfertilizerâ and I could talk forever about it but it best used for magnesium deficiency. Not a lot of discussion.
Dolomite lime is always good for your garden I did a discussion of the use of it for magnesium deficiency and the recommendation by soil test people that you do not overuse it as too much magnesium is also bad.
And that covers the âDahlia Mythsâ except the âelephant in the roomâ myth Dahlias require a low-nitrogen fertilizer. We recommend using a fertilizer with a higher percentage of potassium and phosphorus.
I had always heard these low nitrogen recommendations and personally thought they are wrong but there has not been much scientific evidence. Somehow, I found a recent scientific paper on the subject done in Utah and it was a three year trial of nitrogen levels on dahlias. I read it and they determined that for the purposes of growing dahlia cut flowers, that a very high level of nitrogen was best both for the production of the flowers and they selected the amount that made the best economic sense also. Here is link to the paper: https://meridian.allenpress.com/jeh/article/42/1/14/499409/Nitrogen-Management-and-Virus-Incidence-on-
We discussed the results of the study and note that I did not have people read the study before the Dahlia Talk. Why did I do that? I wanted to get peoples opinions of the subject before they read the paper. We had a very interesting discussion on nitrogen and dahlias and I believe that at the next Dahlia Talk session we can discuss the study and decide how it applies to our dahlia gardens.
As usual, this summary of the Dahlia Talk Zoom Meeting does not cover but a very small amount of the content of the session. We also discussed dahlia breeding, growing and showing dahlias in Australia, the negatives of growing in sandy soil, how we can get someone from the UK to participate in Dahlia talk, the fairness of the criteria for the inclusion of varieties into the classification handbook based upon winning only two blue ribbons in shows. Lots of interesting talk on this subject. And lots more subjects.
