Bupleurum rotundifolium is an ideal filler and greenery, prized by floral designers for its abundant, ovoid foliage and small yellow flowers on long, elegant stems. A member of the Apiaceae family, it has several common names: Thoroughwax, Hound's Ear, Green Gold, and Hare's Ear. Bupleurum is a hardy annual that can tolerate some light frost, but it should be protected from heavy frosts in the field.

After unboxing and hardening off your plugs for a few days, transplant the plugs as soon as possible. Handle gently when you transplant, as young Bupleurum plants are sensitive to rootbinding, root disturbance, and stressful conditions like heat or drought that will cause premature flowering. The best time to plant is in the spring, after your last outdoor frost but before soil temperatures rise about 55F. Gardeners in zones 7 and warmer could opt for a fall planting, overwintering the plants for an early season bloom the following spring. Choose a place in your garden with loose, well-draining soil with a neutral pH and average fertility, though Bupleurum is fairly tolerant of most soils. This is a facultative long-day plant, meaning it can initiate flower buds at any day length, but generally it will put on vegetative growth during short days and elongate during the longer days of spring.

Transplant your plugs with 8 to 12 inches in between each plant. Do not pinch this plant or you will remove the growth tips. Though the time to bloom is entirely dependent on planting time and temperature, you can expect the first flowers in as little as 6-7 weeks after planting in the spring. For a longer blooming window in areas with cooler summers, plant multiple successions in the spring. It is normal for Bupleurum to die back in the heat of summer, as it prefers cooler temperatures. Bupleurum is quite robust and typically problem-free when it comes to diseases and insects, though you should watch out for self-seeding. If left to go to seed in the field, keep an eye out for new seedlings in the fall or spring following the initial planting.

As a cut flower, Bupleurum can last 7-10 days in the vase, and be stored for short periods in a cooler. Harvest the stems when the flowers are fully open, or the stems will wilt. Be sure to place your cuts in cool water right away to prevent wilting. To make harvesting easier, cut the entire plant all at once.