I've been thinking about the evolution of trees and other plants, and realized something I couldn't solve.
According to a video I saw online (I no longer have a link to this video), flowering plants evolved later than reptiles, birds and mammals. In general, that would mean that all flowering species of plants would be descended from one parent species.
I also saw in a natural history museum a cross-section of a tree from Hawaii. According to the museum plaque, because this "tree" lacked the characteristic rings, this suggested that it evolved from a much smaller soft bodied (or non-woody) plant.
This got me thinking. There are both flowering and non-flowering ringed trees (apple trees vs. conifers). There are also flowering vs. non-flowering non-trees (marigolds vs. grasses). If ringed trees suggest common ancestry, and flowers suggest common ancestry, how do we reconcile the fact that all combinations are found when looking at flowering vs. non-flowering and tree vs. non-tree?