About those mums.
JustPutzinAround asked a question about mums on another thread. I thought it might be better to just start a posting dedicated to this topic. Mums are interesting but seem to create a lot of confusion and questions. The original question is copied below.
I am wondering if you have to pinch back mums sometime during the summer to get that absolutely full and gorgeous flush of blooms on them in the fall. What if they set buds too early in the year?
The rule of thumb for our area is to continue pinching back hardy mums until about the 4th of July. I will pass along my opinions (I stress MY opinions because I am sure others have different practices that work quite well for them.) First, I think we have to define what is a hardy mum and what isn't.
You can buy blooming mums at all times of the year. These are almost always a plant that will not endure Iowa winters and/or Iowa weather in general. They are most often simply called "florist mums" and are bred exclusively for a hot house environment. Most of these are what is called daylight neutral plants because they really don't care what time of the year they bloom. The cut-flower industry and florists prefer these because the grower can determine when they want these to bloom rather than depending upon natural, seasonal conditions. Hardy mums determine when to set bud dependent upon the number of available daylight hours (actually hours of darkness). This translates to blooming in the autumn.
Unfortunately, when purchasing "hardy" mums, you often are not sure that this particular variety is going to be hardy for you. Just because the tag says "hardy" it is no guarantee. I define hardy mums as those that will survive in MY garden. Most mums succumb to "winter kill" not from excessive cold temperatures but rather excessive winter wetness. Good drainage is imperative. Over the years, I have bought lots of so-called hardy mums. The ones that survive, I propagate and plant masses of them to great effect. The ones that don't survive winter, I consider a good riddance. I have a number of them that reliably bloom in the colors I like. These also reliably bloom in a predictable succession. The yellow ones start things off and two weeks later come the bronze ones followed in another two weeks by a red one with yellow centers. This order of bloom succession took a few years to dawn on me but now I use it to stage my plantings.
I offer this all as a round about way of answering JustPutzinAround's question. Each of my mums start setting buds at different times. Although the 4th of July is a pretty good rule of thumb, it really depends. I know of no place to gather this specific information other than through personal trial. The problem most people face is that they keep putting off pinching their mums until it is almost the 4th of July. All of a sudden, they realize they had better get it done pretty quick or it will be too late. Well, for that "absolutely full and gorgeous flush of blooms" you really need to have been pinching them several times long before Independence Day. The advice to stop pinching by the 4th of July unfortunately gets translated in practice to mean the mums (if lucky) got pinched back only one time on the 4th.
Invariably, when people ask if they can pinch back mums after they have set bud, they are admitting that they have procrastinated far too long. I do not pinch back after buds are set. However, there may be hope for us procrastinators yet. I recently attended a symposium where the director of the University of Minnesota's horticultural development program showed slides of some new mums they are growing that do not require pinching to get a full, rounded blooming habit. Promising things are happening in Gopher country.
I would like to hear about other people's mum experiences/practices as well.