Dahlia

Dahlia

Planting
It is recommended to plant tubers immediately upon arrival. If not possible, store tuberous roots at 45°-50°F (7°-10°C). When planting tubers it is important to place with the crown above soil and even with pot edge. If buried, number of shoots may be reduced and delayed. The first 5-6 weeks the
plants should be grown pot tight and then subsequently spaced. After planting, water the media well. It is necessary to keep soil moist (but not wet) until the shoots begin to grow rapidly (4-5 weeks).

Media
Plant into a well-drained, medium to coarse-textured growing mix. pH level should be app. 6.8-7. Be mindful if your medium contains bark to closely monitor the pH. It is advised to regularly test soil levels.

Temperature
Ideal average daily growing temperature 68°-72°F (20° – 22°C). Force at a minimum night temperature of 60°-64°F (15°-17°C). Higher day or night temperatures will accelerate flowering, but can also reduce plant quality if grown for prolonged periods warmer. Avoid temperatures above 80°F (27°C). It is possible to delay crop as selling period approached by lowering night temperature to 55°F (13°C).

Light
Dahlias require medium to high (<2500 foot candles) light intensity for optimal height control. Reduced light can produce taller plants even with use of PGR. It is suggested to light up to the end of April. Exception being if temperatures become too high than shading is recommended. Increased natural
day length of 12-14 hours promoted earlier flowering. Short days should be avoided as this will prevent or delay flowering and produce poor quality material.

Water and Feed
After planting, water the planting medium thoroughly. It is necessary to keep soil media moist (but not wet) until the shoot begins to grow rapidly (app 4-5 weeks). Please keep in mind on days of PGR application to ensure planing medium is uniformly moist. It is suggested to water plants late in the
evening and apply the PGR early the next morning. After shoots begin to grow from the crown, water should be applied directly to planting medium. A weekly leaching may be necessary to avoid salt buildup. Whenever possible, avoid wetting the foliage. Once the flower buds become visible, water
frequently as water requirements will increase. Dahlias require continuous feed after shoot growth becomes visible. A complete (NPK) fertilizer is required. A top-dressed slow release fertilizer (i.e.14-14-14) can be used or incorporated prior to planting. Also, 200ppm N of a 20-20-20 soluble can
be used 2-3 times a week. If needed, the liquid feed can be used as supplement to slow release fertilize.

Growth Regulators
PGR, such as A-Rest can be used as a spray to improve plant quality and height control. For height control, it is suggested to apply as a soil drench 10- 14 days after planting being careful that soil level is moist. For improved plant quality, PGR can be applied when the flowers buds become visible in the
foliage but have not elongated. Normally, 60-70ppm is very effective.

Flowering
Depending on the cultivar and forcing conditions, flower bud stage to opening of flowers is as follows:
1/2 inch (1.3cm) flower bud - 14 days
5/8 inch (1.6cm) flower bud - 10 days
3/4 inch (2.0cm) flower bud - 7 days
1 inch (2.5cm) flower bud - 4 days

Insects and Diseases
Thrips, aphids, beet army worm, red spider, white fly and root rot.

Common Problems and Causes
Old stem shoot removal - Occasionally, shoots will develop on nodes of old stem. When this occurs, remove as soon as possible to promote shoot growth from crown, these stem shoots will grow, but are very prone to breaking off old stem. Pinching - to develop high quality plants with maximum flowers, plants with a single strong shoot must be pinched. The best time to pinch out the terminal shoot is after the third or fourth pair of leaves have unfolded. The pinch should remove all terminal growth above the third or fourth pair of leaves. Normally, a pinch will produce 2-4 lateral shoots. There may be some double stemmed plants that need to be pinched. If one shoot grows much stronger than another, the strong shoot must be pinched. Do not pinch the weaker shoot. If shoots develop equally, they do not require pinching. Plants producing 3 shoots should not be pinched. In general, pinching will delay flowering 5-10 days and be slightly taller compared to unpinched plants.

Comments
Flowering potted dahlias should be shipped when the first flowers begin to open. These plants must not be cold stored. If they are developing too fast, you can disbud the terminal flower (s) and allow laterals to develop. This typically adds 5-7 days to period. You can also lower the greenhouse temp,to 50°-55F (10-13°C) to slow development. It is recommended to ship plants at 55°-60°F (13°-16°C). 

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