Crop Culture Report: Dahlia Balloon Series
The Balloon series consists of medium-height dahlias with very large balloon-like flowers. Bred by Kieft Seeds, the Balloon series is available in four bright colors. The dahlias may be grown in containers ranging in size from 4_ to 10-inches. Balloons also can be used as part of combination plantings. The large flowers should make a very colorful display and readily sell in any garden center or big box store.
The four colors in the Balloon series are: Deep Red, Scarlet, Apricot and Yellow. The plant habit is upright with medium to large vigor. The flowers are very large and round when they mature.
It is critical to root dahlias under long days to prevent premature flower induction. A night interruption of at least 4 hours or a day extension of at least 16 hours must be applied from the first day of sticking to keep the plant vegetative. The light intensity must be at least 10 foot-candles, but more light is acceptable. A common mistake is to not light or to only extend the day to 14 hours. This will not keep the plant vegetative, and finished plants may flower too small. It is important to keep the light on the plant at all times because a dahlia can initiate in as fast as five days.
Growers should use a well-drained, clean media with a pH ranging from 5.5 to 6.0. When sticking the cutting, be sure to stick the stem deep, even up to the first set of leaves. If the first set of leaves is under the soil, it will work fine. Do this to keep the finished plant from appearing floppy.
Root cuttings at a media temperature of 70-73¡ F. Try to remove mist as soon as possible (about 6-10 days). Cuttings benefit from low amounts of nutrients in the mist solution although it is not essential for rooting. Use of 50 ppm from 17-5-17 works very well for this purpose. Rooting adequately to transplant in a 105 should take 4-5 weeks maximum depending on temperatures. If a cutting is not rooting and has a large callous, it is likely that the cuttings are reproductive. This could be caused by not properly following the lighting guidelines during propagation. Lighting and pinching the bud out can help such cuttings to root.
Be sure to plant the liner as deep as the first set of leaves when transplanting. Deep planting helps keep the plant from drooping as it matures. Discontinue lighting of plants at the time of transplanting. Failure to discontinue the lighting will delay flowering. Growers should plant one plant per 4_- to 5-inch pot and 3-5 plants per 10-inch pot. Grow on at 65-68¡ F and fertilize at 100- to 150-ppm nitrogen with every irrigation. Keep soil pH at 5.8-6.2 and EC at 0.8-1.0 using a 2-to-1 soil test. No pinch is necessary for producing dahlias.
Applying B-Nine (daminozide) at 500-1000 ppm can be used to control the growth on dahlias. Powdery mildew can be a problem on dahlias, but it can be controlled easily by using a preventative spray labeled for powdery mildew. Spider mites, aphids and thrips can also be an issue but are easily controlled as well with a good spray program.
From transplanting, 4_- to 5-inch crops should finish in approximately 6-8 weeks. Ten-inch crops may take a little longer. Dahlias are best sold with a tight- to half-open bud to maximize the time flowering in the garden center. End users can plant these in beds and containers as well. They should also plant deep to keep the plant from being floppy.