In our country, there is a tradition to present only an odd number of flowers as a gift, and to lay an even number on the grave. For example, it is customary to bring two carnations to a funeral.
Since such a tradition is typical only for Russia and Bulgaria, perhaps its roots go back A. Agapkina, L. N. Vinogradova, V. Ya. Petrukhin, S. M. Tolstaya. Slavic Antiquities: An Ethnolinguistic Dictionary in 5 volumes in the beliefs of the Slavs. In many everyday and ritual situations, an odd number was assessed as positive for them, associated with luck and well-being.
For example, the wedding train was supposed to consist of 7 or 9 people. The peasants believed that odd stripes from the edge of the field would bring more harvest, and if an even number of eggs were placed under the chicken, the chickens would not hatch or would be weak.
Even numbers were generally perceived as negative, associated with death. For example, in some areas, a paired number of objects had to be placed on the grave, in others, an even number of washerwomen had to be invited.
Perhaps, over time, these beliefs transformed into the habit of paying attention to the number of flowers in a bouquet. And although a gift cannot harm a person in any way, it is definitely not worth breaking traditions and presenting two or four roses, especially if you are going to please a superstitious person.
At the same time, it makes no sense to count the number of buds in the finished composition. To accept an even number of flowers in a bouquet for a bad wish can only be a very suspicious and touchy person.
There are mentions on the Internet that the volume of the bouquet may indicate the attitude of the donor. As a rule, the number of flowers increases in proportion to the intensity of feelings — from one rose on the first date to 101 during a marriage proposal.
At the same time, there are no real traditions or generally accepted norms related to the volume of the bouquet. So, when choosing flowers, focus only on your taste and financial capabilities.
And you should also think about whether it will be convenient for the person who received the gift. For example, if you go for a walk, a large and heavy bouquet can cause a lot of inconvenience to both participants of the date.