Hardy Perennial. This is one of the most popular penstemons for its spectacular and long lasting flowering season. Forms a bushy plant to 3ft. Penstemon can flower for up to six months of the year. They are best grown in a sunny or partially shady spot in the border, on a moister garden soil but will tolerate drought. Penstemon are resistant to slugs and other pests and attractive to bees. Sold in a 2 litre pot.