Showy Milkweed Seeds - Asclepsia Speciosum - Help Save the Monarch Butterfly Showy Seeds. Milkweed, Speciosum, is appropriate for the Northern part of California primarily Perennial. Grows 3 feet tall, 1-2 feet wide. Fragrant pink flowers in summer. Monarch butterfly host plant. Spreads by seeds; large showy seed pods. Large Seeds .03 Oz. Marde Ross & Company has been a Licensed California Nursery since 1985.