Reasons why purple allium flowers in garden is such a popular idea is mainly because alliums are the easiest to grow and very hassle free. They are also the most versatile to add to a summer garden. An allium usually grows during the month of June. They are very less demanding and will grow in any kind of soil as long as it is well drained. They are completely disease resistant so no scare of pests ruining your beautiful allium garden. They are also drought resistant. The flowers of the purple alliums look like they are floating above the stem of the alliums because of the height at which it grows.