Why does a flowering plant have so many leaves?
flowers require lots of energy, leaves produces energy for plants
The term that's synonymous with phylum, in the plant world, is division. So the phylum, or preferentially the division, of cactus plants is Magnoliophyta. It's the division for angiosperms, which also are called flowering plants. Flowering plants may develop from an embryo that has one or two leaves. A cactus is a dicotyledon, because it has two embryonic leaves.
Non seasonal flowering could mean two things: The plant is flowering outside of its normal flowering period. For example where Chrysanthemums are "forced" to flower outside of summer. Another meaning could be with respect to the term "seasonal"; annual plants are sometimes called seasonal, so non-seasonal plant could mean that its a perennial plant.