Forsythias (Forsythia spp.), with their brilliant yellow blooms and arching form are commonly used as specimen plants or as hedges in U.S. Department of Agriculture plant hardiness zones 4 through 9. The shrubs need plenty of room to grow and moist, but well-draining soil. If you lack these elements in your garden, try growing them in a container where you can adjust growing conditions to suit them.
Plant forsythias in containers from late spring to late summer. Plant them on a cool, overcast day for best results.
Choose a compact forsythia variety. Most forsythias have a free-flowing, almost wild form and can grow to 10 feet tall and wide, which is too large for a container plant. Try "Gold Tide" (Forsythia "Gold Tide") or "Fiesta" (Forsythia "Fiesta"), which both remain under 4 feet tall.
Select a large container that can hold at least 15 to 20 gallons of potting soil. Forsythias, like most shrubs, have a large underground root system and need plenty of room to support that growth. Plastic, terra cotta, wood or glazed pottery pots are all suitable, but make sure the pot has adequate drainage holes.
Place two or three pieces of broken pottery or styrofoam in the bottom of the pot. These pieces prevent soil from clogging the drainage holes and improve drainage, an important step to preventing root rot, a common problem in forsythias.
Fill the pot almost full with a lightweight potting mix made from compost, vermiculite or perlite. Avoid using garden soil, which is too heavy and might harbor disease.
Remove the forsythia gently from its container, if using a nursery transplant, and place it in the pot so the top of the root ball sits 2 to 3 inches beneath the edge of the pot.
Mix 1/4 cup granulated slow-release 10-10-10 fertilizer with the remaining potting soil. Add this mix to the pot and firm it down gently around the forsythia. Water the pot well to thoroughly wet the potting mix.
Water the newly planted forsythia every few days, or as needed to keep the soil moist, but not soggy. Forsythias grow best in slightly moist conditions and pots tend to dry out quickly. Newly transplanted forsythias are especially prone to drought stress until their roots become established.
Store your potted forsythia in a protected area in full sun. These tough shrubs can tolerate partial shade, but they bloom best in a location that gets six to eight hours of sunlight daily.