Many plants can reproduce sexually and asexually because

a environmental conditions are not always right to produce flowers and seeds for sexual reproduction
b plants do not contain male and female parts
c plants can only produce female parts
d most plants need a wet environment to produce sexually

A. environmental conditions are not always right to produce flowers and seeds for sexual reproduction.

Explanation:

Plants reproduce by the means of both asexual and sexual reproduction. The asexual reproduction is simple and it does not requires the process of formation of gametes, pollination and fertilization. The plants in such cases reproduce by germination of asexual spores, vegetative propagation by using different parts of the plants like stems, roots and others. In sexual reproduction plants produce seeds by the fusion of the male and female gametes which are present in a typical flower. Sometimes plants due to deficiency of nutrients,growth factors, lack of proper sunlight and adverse climatic conditions are incapable of producing the flowers for sexual reproduction. In such conditions the plants would undergo asexual reproduction instead of sexual reproduction.