Seed Needs, Mountain Phlox (Linanthus grandiflorus) 1,000 Seeds Quality Phlox seeds packaged by Seed Needs. This packet measures 3.25" wide by 4.50" tall and come with a full colored illustration on the front side, as well as detailed sowing instructions on the reverse. Annual Flower that blooms until the Fall & then dies with the first frost Mountain Phlox will grow to a mature height of 12 to 24 inches tall. These plants will prefer an area of full sun to light shade. Quality Phlox seeds packaged by Seed Needs. This packet measures 3.25" wide by 4.50" tall and come with a full colored illustration on the front side, as well as detailed sowing instructions on the reverse.