A simplified explanation of the classical genetic terms dominant, recessive and additive.
I am going to use diploids in my examples because classical (Mendelian) genetics (that many of us learned) usually do not apply as well to tetraploids.
If one of the parents of a cross has/shows a particular characteristic and the seedlings also show the characteristic then generally that characteristic is described as the dominant characteristic in comparison to the alternative characteristic. For example, I cross 'Pardon Me' with 'Gentle Shepherd' and I find that all the seedlings have red flowers. If all the seedlings are the same red colour as their 'Pardon Me' parent then red flower colour is dominant to white flower colour. White flower colour would be recessive to red flower colour.
Now if I take two of the seedlings from the cross 'Pardon Me' x 'Gentle Shepherd' (and both have the same red flower colour as their 'Pardon Me' parent) and I cross them with each other [red flower x red flower] I will find that some of those seedlings are red-flowered and some are white-flowered and I would describe white flower as recessive to red flower colour. However, it is very important to know that I do not expect many of those seedlings to have white flowers, in fact only one in four, on average would be white-flowered. And I could easily grow as many as eleven seedlings to flowering and not find a white-flowered seedling. Genetics is a numbers game and to be reasonably certain of finding certain characteristics in crosses one needs to grow sufficient seedlings.
If both parents of a cross must show the same characteristic for the seedlings to show the characteristic then that characteristic would be described as recessive to its alternative. If I cross 'White Temptation' with 'Gentle Shepherd' and all the seedlings are white-flowered like their parents then white flower is recessive.
If both parents of a cross show the same characteristic, say gold edges, and the seedlings show the same characteristic but in a more extreme form then the characteristic would be described as additive. In this case perhaps the gold edges are more pigmented or they are wider or they cover more of the petal edges, etc. The catch with additive characteristics is that there may be so little that the characteristic is not visible to our naked eyes in either parent yet when combined in the seedlings there is then enough of an effect that it becomes visible to us.
Most characteristics in daylilies (even in diploids) are not inherited in simple classical Mendelian ratios. Dominant characteristics are rarely the same in offspring and parents. They are partially dominant or there are many genes that affect each characteristic so that they are better described as additive rather than dominant or recessive.
In tetraploids, even in very simple situations where a characteristic is simply inherited in the diploid, the situation may typically be additive. In a diploid, WW might be red-flowered, Ww might have the same red flower and ww might be white-flowered yet the tetraploid versions might be WWWW dark red, WWWw red, WWww medium red, Wwww light red and wwww white flowered - better described as additive or possibly partially dominant.
