By Richard Jauron
Planting flowers to improve a home landscape is an excellent first step. But what happens when they don’t bloom properly – or at all? How can these problems be remedied?
Some flowers take special care, and ISU Extension and Outreach horticulturists can help decipher these issues. To have additional questions answered, contact the ISU Hortline at 515-294-3108 or hortline@iastate.edu.
My peonies bloom poorly. What could be wrong?
There are several factors which may cause peonies to bloom poorly. Peonies perform best in areas that receive at least six hours of direct sun each day. Peonies that receive less than four hours of direct sun will not bloom well. Plants growing in a shady location should be transplanted to a sunny site in September. Peonies planted too deeply often fail to bloom well. When planting peonies, position the peony buds 1 to 2 inches below the soil surface. Peonies that are planted too deeply produce lush foliage, but don’t bloom well.
Recently planted or divided peonies may not bloom well for two or three years. The new plants need to grow stronger before they are capable of blooming well. Also, premature removal of peony foliage in July or August weakens plants, resulting in few flowers the following spring.
My bearded irises are no longer blooming well. Why?
The bearded irises may need to be divided. Bearded irises should be divided every three to five years as the plants quickly become overcrowded and don’t bloom well. July or August is the best time to dig, divide and transplant bearded irises.
Lack of sunlight could be another possibility. Bearded irises bloom best in full sun. (Plants need at least six hours of direct sun per day for best flowering.) Plants in partial shade may not bloom well and should be transplanted to a sunny site.
My daffodils produce foliage in spring, but no longer bloom. Why?
If the daffodils aren’t blooming, the plants weren’t able to store enough food in their bulbs in the previous year. Daffodil foliage typically persists for four to six weeks after blooming. During this four to six week period, the daffodil foliage is manufacturing food. Much of the food is transported down to the bulbs. In order to bloom, daffodils must store adequate levels of food in their bulbs. Cutting off the foliage before it has died back naturally may prevent the plants from storing adequate food in the bulbs.
Allow the daffodil foliage to die completely before removing it. Plants in partial shade in May and June may not be able to store enough food in their bulbs because of insufficient sunlight. Dig up daffodils growing in partial shade when the foliage has died back and plant the bulbs in a location that receives at least six hours of direct sun per day. If given good care and favorable growing conditions, weak (non-blooming) daffodils can be encouraged to flower again.
My tulips are no longer blooming. Why?
Most modern tulip cultivars bloom well for three to five years. Tulip bulbs decline in vigor rather quickly. Weak bulbs produce large, floppy leaves, but no flowers.
To maximize the number of years tulips are in bloom, choose planting sites that receive at least six hours of direct sun per day and have well-drained soils. Promptly remove spent flowers after the tulips are done blooming. Seed pod formation deprives the bulbs of much of the food manufactured by the plant’s foliage. Lastly, allow the tulip foliage to die back naturally before removing it.
Dig up tulips that are no longer blooming and discard the bulbs. (Small, weak tulip bulbs will likely never bloom again.) Plant new tulip bulbs in the fall.