It's finally time to purchase your hydrangea (Hydrangea spp.). You've sorted through all the kinds and colors, researched hardiness -- depending on variety, they're hardy from U.S. Department of Agriculture plant hardiness zone 3 through 9 -- and then suddenly there's another piece to the puzzle. One retailer offers hydrangeas according to their age; another sells them by size. Understanding the differences can help you can make the best choice.
Hydrangea breeders develop new varieties from seeds produced by natural or controlled pollination of existing hydrangeas. As seedlings grow, a process of selection begins to identify those with outstanding qualities that might make worthwhile additions to the nursery trade. After a plant is selected, growers multiply the number of available plants by taking stem cuttings. Like people, a seed is a blend of the parents, and seedlings show qualities all their own. A cutting is like a clone; it duplicates the original plant in all respects. Cuttings are rooted in protected settings and are the beginnings of plants you eventually see for sale.
After cuttings root well, they move to the next phase of life. Depending on the grower and the plants' ultimate destination, they may be planted in a field or potted into containers to continue to grow. Although there are differences, the first step is often a 3- to 4-inch pot. A plant being offered as a 1-year hydrangea would normally have spent at least one growing season in that pot and be approximately 1 year old. Depending on the variety, the foliage would be just a few inches tall by that time. A 2-year-old plant would usually have spent at least one season in its 6-inch or 1-gallon container and be two years old. Depending on variety, those stems might be 18 inches or more.
Larger hydrangeas are grown in different ways depending on the retail outlet. Some garden centers purchase mature bare-root plants in spring, pot them into large containers and grow those plants over summer for fall sales. Other may buy immature plants, field grown or in small containers, and shift them into large containers to grow for future sales. Others buy mature container plants for immediate sale. Three-year hydrangeas may be 3-year-old, field-grown plants or 3-year-old plants grown in containers their entire life. Generally, only these more mature plants would be sold in larger containers, but that is not always the case.
Why Age Is Important
If you've ever had the disappointment of removing a plant's container only to have all the soil fall away and reveal tiny, immature roots, you understand container size can be misleading. If young plants are potted in large containers and sold before they've had time to develop properly, you may think you're getting a mature plant when you're not. Knowing the age of the plant tells you what you're buying, regardless of container size. Since many hydrangeas bloom only on stems grown in previous years, age also helps you understand when to expect flowers. Young plants need a season to become established, plus a season to grow wood capable of flowering. A 3-year-old hydrangea is mature enough to flower. However, growers may cut back the stems to encourage good branching and stronger roots. This can mean an additional year before the plant can bear blooms in your garden, but you'll have a healthier, more mature plant for your wait.