This subject is probably one of the hardest to explain and to write about, but I will attempt to do so anyway. One of the reasons why the dahlia is one of my favorite flowers is because, to a certain extent, I can control when they come into bloom.
The biggest factor in timing blooms is the weather. Cold spells and hot spells can really throw off your timing. So I will explain what I do to combat this.
My biggest tool is a calendar. I get one every year and keep it on my desk. I like the kind that usually hangs on a wall and that has plenty of room to write in the spaces. The first thing I do is to find the dates for this years shows on it and write them down on it. I then start writing in the following dates:
70 days before show
65 days before show
60 days before show
7 weeks before show
6 weeks before show
5 weeks before show
4 weeks before show
32 days before show
30 days before show
28 days before show
26 days before show
24 days before show
22 days before show
20 days before show
10 days before show
What is this all about? It’s called Planning! The 70, 65, 60 days before the show is normal topping times for most AA, A and B size dahlias. The 7 weeks and 6 weeks before the show are pinching dates. The 5 week date signifies no more pinching. At 4 weeks before the show it is time to start selecting show buds. At this time I will show you the chart that I use religiously.
It takes 55-65 days for small, 1/4 inch long laterals to mature to a fully developed bloom. AA and A dahlias take about 8 weeks to bloom from pinch times. B dahlias take about 6 weeks. Now this is all dependent upon different factors; the weather, the variety, some are slower to grow, the forms, ID and FD are slower. Now the chart:
AA-A — Formal and Informal Decorative | 30-32 days
AA-A — Semi Cactus | 27-29 days
AA-A — Cactus | 26-28 days
B — Formal and Informal Decorative | 28-30 days
B — Semi Cactus | 25-27 days
B — Cactus | 22-25 days
BB — Formal and Informal Decorative | 26-28 days
BB — Semi Cactus | 23-25 days
BB — Cactus | 20-22 days
The size of the bud I’m usually looking for is a small pea size bud, which is normally about 3/16. It’s a good idea to vary the sizes you select, especially if you have more than one variety and multiple plants of one variety, especially if you are going for multiple bloom entries. At 10 days before the show, if your blooms are showing color, it is a good chance it could be a show bloom.
Another rule I follow is limiting the number of buds or laterals per plant. I cut out and have only 4 laterals or buds on AA & A varieties, 6 on B varieties, and 8-10 on BB varieties.
Now this is something else that is very important. You should have no blooms blooming on these plants before this. If you do, it cuts down on the size of the blooms and the strength of the stems – one or 2 blooms doesn’t do too much damage.
Also another important factor is to keep the laterals or buds spread around the plant. Example: 4 laterals or buds on AA or A – one to the east of the stake, one to the west, one to the north and one to the south of the stake. This prevents the blooms from coming in contact with each other, causing damage to the blooms or petals.
Now before I go any further, I should explain some terms to you, especially since this article is for beginners.
Topping or Stopping: Is the pinching out or cutting out of the center of the plant and is usually the terminal bud. This allows the other laterals to develop.
Pinching: Pinching out the center of a lateral to allow other laterals to develop.
Lateral: Is the growth from a full set of leaves on either side of a stem or branch.
Double Pinch, Double Cutback, & Double Topping: It is the pinching out of the center of growth of a lateral that is going to bloom too early.
There are 2 methods which can be used for timing of blooms; one method is to pinch out the center of the plant when it has developed 4 to 6 sets of leaves, or pinched out when you know the topping days to bloom days of that variety. I have some varieties that I let go to even more than 6 sets of leaves, and then select the best 4 to 6 laterals from that bunch for my show buds.
Another method is called double topping, double pinch or double cutback method. You top or pinch as normal when 4 to 6 sets of leaves have developed. You then pinch out all buds up until the 6th week before the show. Keep in mind it is better to cut back too early than too late. A plant cut back too late will not produce blooms in time for the show. This method works well for varieties that you are unfamiliar with or new varieties.
I have a listing of some AA, A and B varieties that I raise and the general range of topping to bloom time is:
All the rest of the varieties I raise are normally double topped.
I start all my dahlias in individual trays or flats using a good potting soil of black dirt, sand, perlite, etc. I usually start tubers toward the end of April, starting with miniatures, poms, ball, miniature balls, etc. Then I start the bigger varieties next. So all of my dahlias when planted are started tubers with 2″ and 1″ plants when set out. I then protect them a week to 10 days with milk cartons or old coffee cans with the bottom cut out.
I do hope this article was of some use to you, and that you aren’t totally confused by it. I even get myself confused sometimes. Please feel free to give me a call and ask questions.
Note: James Dahlin created a spreadsheet table to illustrate Randy’s instructions.