When I decided to write about one of the largest and showiest spring flowers in Utah, I didn't count on record-breaking hot temperatures.
These flowers traditionally bloom for Memorial Day, so you might find that those in warmer areas have already finished their show.
Peonies are relatively carefree, cold-hardy perennials that grow well throughout the state. The large, showy blossoms are excellent cut flowers, and the leaves create an excellent background for smaller plants.
Once the plants are established, they need little care. They can grow in the same area for many years. They bloom reliably each spring (usually in May or early June).
There are three types of peonies.
The garden or herbaceous varieties have full, bushy stems that grow 2 to 4 feet tall and are covered in this column.
Tree peonies grow 5 to 6 feet high on woody stems. They are more expensive and are not as commonly grown in Utah. They produce many flowers on a shrub-like plant. The stems of tree peonies do not die back during the winter.
The newest group is the Itoh — or intersectional — hybrids that are crosses between herbaceous and tree peonies. They grow to 31/2 feet tall and bloom for a longer time than standard herbaceous types, and the stronger stems hold up the flowers better.
Garden peonies are grouped according to the shape of the petals into five types.
These are single, semi-double, double, Japanese and anemone. Each type includes many cultivars. The American Peony Society lists some 8,000 named cultivars of peonies. Flower colors are yellow, cream, pink, rose or deep red. Double peonies are the most common in Utah.
Peonies grow from tuberous roots or underground stems that store food. New growth develops from buds or eyes on the tuber. A single tuberous root may have many eyes, but there must be at least three buds for the plant to grow well.
Plant the tuberous roots with the uppermost eye one inch below the soil surface. Deeper planting is a frequent cause of the plants failing to produce blooms.
The immature spring shoots are bright red in color. They are easily damaged, so protect them from foot traffic and pets. Mature leaves are dark green and shiny.
Container-grown peonies can be planted anytime if given the proper care. Peonies need well-drained soil as the roots rot in wet soil. Chose the growing location carefully and prepare the beds because peonies can remain in place for many years without dividing or transplanting.
Grow peonies in full sun. They are not good competitors, so avoid growing them under trees or shrubs because the roots of these plants compete for water and nutrients. Plants need protection from strong winds to prevent the flower stems from breaking.
Weeds take water, nutrients, light and space from the plants. Remove weeds carefully without disturbing peony roots. Grass is very competitive, so keep turf grass away from the plants.
Peonies require regular irrigation. Keep the soil damp but not wet. Allow the soil to dry between waterings. Avoid sprinkling late in the day as that encourages fungal diseases.
Plants growing in fertile garden soil need little fertilizer. To increase flower size, apply fertilizer as needed during the growing season. They are sensitive to iron chlorosis in Utah's alkaline soils. The leaves turn yellow with green veins and do not grow or bloom well. Avoid overwatering the plants and treat with iron chelate when symptoms appear.
Because the plants get top heavy when the large blossoms form, staking the plants is sometimes needed. Stake plants only when needed and never place stakes in the center of the plant as this may damage the tuberous roots.
After the flowers drop the petals, remove them so that seeds do not develop. Leave the green foliage as this produces energy for the plant to bloom well next year.
When the foliage turns brown and dies in the fall, cut it back to the ground.
The most frequent complaint when growing peonies in Utah is that they do not bloom. They often fail to bloom even though the roots and tops are healthy. Peonies do not bloom when grown in too much shade. Poor drainage interferes with root growth and also prevents blooming.
Peonies do not bloom if eyes on tuberous roots are planted too deeply. The eyes or buds must be buried one inch or less below the soil surface.
Removing excessive amounts of foliage when cutting the blossoms or cutting the foliage back before it dies back in the fall interferes with blossom formation. And peonies may not bloom when other plants take the water, nutrients, light and space they need. Late frosts can also kill flower buds in the spring.
There are few peony diseases in Utah and most are controlled by careful watering and fungicides are needed only in rare instances.
Larry A. Sagers is a horticulture specialist for the Utah State University Extension Service at Thanksgiving Point.
Thanksgiving Point is offering a class on "The Art of Garden Photography," on Tuesday, June 5, 12 and 19 from 10 a.m.-12:30 p.m. Cost is $43.
In addition, Thanksgiving Point is offering a class titled "Passionate About Perennials," on Tuesday June 5, 12 and 19 from 2-4:30 p.m. and 6-8:30 p.m. Cost: $43.
To register for either class, log on to www.thanksgivingpoint.com or call 801-768-4971.