The Quest for a Double-Flowered Yellow Clivia miniata at Longwood Gardens
by Jim Harbage, Alan Petravich, Robert Armstrong and Matt Taylor
In the mid 1970s, Longwood Gardens began a breeding program to develop improved forms of yellow-flowered Clivia miniata. At the time, yellow-flowered forms of Clivia were quite rare and were generally weak plants with small flowers and poor habits. The breeding project began by crossing a Clivia with small yellow flowers and poor plant habit with an orange-flowered plant that had exceptionally large flowers. The resulting F1 hybrids were all orange-flowered, suggesting the yellow-flower phenotype was recessive. Therefore seedlings of the F1 generation were intercrossed and some were also backcrossed with the yellow-flowered parent. Both of these crosses resulted in plants with large yellow flowers but they were floppy and the plant habits were not significantly better than the original yellow-flowered parent.
Then Longwood was given a yellow-flowered Clivia, that had a very upright formal habit with flowers held above the foliage. This cultivar has since been named 'Sir John Thouron' after the individual that donated the plants. Crosses were quickly made between the best yellow seedlings from the F2 and backcross populations mentioned above and C. 'Sir John Thouron'. Many of the progeny had outstanding flower size, number and form as well as excellent plant habit. These are currently being evaluated and some have been chosen for naming.
Three unusual seedlings emerged from the breeding program, which led to a new selection goal. These seedlings, one orange and two yellow-flowered, all had flower mutations affecting the petals referred to as “keeled” petals. The resulting effect produced flowers with a semi-double or ruffled appearance. The seedlings from crosses of plants with keeled petals varied with regard to keeling from individuals with no keeling to ones with much more pronounced keeling than even the parents. There were also individuals where the “keel” had actually separated from the petal to form an extra set of petals.
The next generation was intercrossed and selfed and the resulting seedlings are currently growing with first flowers expected shortly. A small proportion of this generation is expected to be yellow with significant keeling in the petals and possibly some with double flowers.
Anyone breeding Clivia knows that patience is a key requirement for success. Under typical container culture, Clivia require about 4–6 years from seed to flower and then will flower each successive year. The first flowers produced by a seedling are usually not representative of the plant's true genetic potential and proper evaluation of a seedling cannot be accomplished until the second or third flowering cycle. This means it can require a very long time to accomplish multiple generations of breeding.
We have been able to reduce the time to first flower of seedlings to less than three years by modifying our culture of the plants. Our approach is based on research showing that the time from seed sowing to first flower is strictly a function of the rate of leaf formation in the seedling. Once the seedling has produced about 13 leaves it will then flower. The time it takes to produce 13 leaves is dependent primarily on temperature, as well as moisture and fertility. Typical container culture of Clivia follows a cycle of warm temperatures, keeping soil moist, and medium to high fertility during the late spring through early fall followed by cooler temperatures, dry soil, and low fertility during late fall through early spring. The rate of leaf production can be increased significantly by keeping warm, moist, fertile growing conditions all year. The light intensity and day-length do not seem to affect leaf production rate under normal greenhouse conditions.