Rhubarb is a vegetable that is grown for its edible stalks, which are often used in pies and preserves. Though gardeners typically plant crowns, or established root systems, rhubarb seeds are used with some cultivars. The two main types of rhubarb seeds will produce mainly red or green stalks, which yield different levels of the tartness prized in cooking. Plants grown from hybrid rhubarb seeds will produce sterile seeds that cannot be replanted, but rhubarb plants are perennial and should last for several years.
The desired use of the edible stems determines which variety of rhubarb seeds to plant. Oxalic acid gives the stems their tartness, but the high concentration in the leaves is toxic. Usually grown in colder temperatures, rhubarb seeds take between two and three years to establish roots and produce edible stalks. Growers should be aware of the rhubarb seed stalk production of a particular cultivar, because in order to remain productive, seed stalks must be removed during the growing season. If open-pollinated rhubarb seeds are being used instead of hybrid seeds, then seeds can be saved from the parent plant and replanted, though the resulting rhubarb may differ from the original.
Cultivars that produce red stalks are generally thought to be sweeter in flavor than green stalks, but some argue that some varieties of green rhubarb seeds produce sweeter flavor. There is evidence to suggest that temperature plays more of a role in the color of the stalk. When the temperature is lower in winter and early spring, some plant stalks appear more red. Later in the season, the same stalks may appear more green as the temperatures heat up.
Pink or speckled stems can also appear in certain varieties. In several cases, the stalks of a rhubarb plant will be one color at the base and transition to another color further up the stem. Some cooks prefer a more uniform color stem for pies or preserves, while others may enjoy the visual interest of a speckled or gradient stem.
Crimson and cherry red rhubarb seeds produce long, thick stalks that are deep red and are thought to be good for cooking. The valentine variety also produces a dark red stem, but there are fewer seed stalks to deal with. Victoria rhubarb seeds tend to grow up to a year faster than other varieties. They produce a green stem. Other varieties like MacDonald, strawberry, and sunrise tend to produce a pinker stem, though color may vary even within a particular variety.