Flower Garden - Tips on Growing Dahlia From Seeds

• Optimum conditions for seedling development that begins the day the crop is sown until cotyledon expansion.

• Expect radicle emergence in 2 days.

• Cover: Cover seeds with a thin layer of medium sized vermiculite to maintain moisture levels, as well as they do not need light for germination.

• Media: • pH: 5.5 – 5.8

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• Light: Provide long days starting at sow. Dahlias want      to form tubers under short days. Provide interrupted nights for a 12 – 14      hour day to suppress tuber formation.

• Temperature: 68° – 72°F (20° – 22°C) until radicle      emergence. Reduce to 65° – 68°F (18° – 20°C) until cotyledon expansion.

• Moisture: Saturated (5) until days 2 – 3 or radicle emergence.

• On days 4 – 7, reduce to moisture level (4)

• Humidity: 100% until radical emergence then reduce to      40 – 70%.

• Dehumidify: Provide horizontal airflow to aid in drying      down the media through evapotranspiration, allowing better penetration of      oxygen to the roots.

• Finish Bulking/Flower Initiation – Optimum conditions      during the vegetative period, beginning at transplant, needed for the root      to reach the edge of the container; AND to make the plant receptive to      flower initiation.

• Media: • pH: 5.5 – 5.8

• Light: Provide long days. Interrupted nights may be      needed to simulate long days. Flowering is inhibited by tuber formation,      which is only influenced by day length. Days shorter than 12 hours will      promote tuber formation instead of flowering.

• Temperature: For early spring flowering, optimal growth      is best obtained by growing plants at 65° – 70°F (18° – 20°C) nights.

• Temperature influences the speed of growth and the      overall quality of the habit. Temperatures cooler than 62°F (17°C) will      slow growth and produce more compact plants, but be sure that interrupted      nights or long days are provided to avoid tuber formation.

• Average Daily Temperature (ADT): 67° (19°C). ADT above      80°F (27°C) will inhibit or abort flower initiation.

• Time Frame when plants are receptive to flower      initiation: Days 28 – 35; 5 – 7 leaves present.

• Flowering Type: Obligate Long Day Plant – long days are      necessary for Flowering.

• Moisture: Alternate between moisture levels wet (4) and      medium (2). Allow media to approach level (2) before re-saturating to   level (4). Watering early in the day and providing good ventilation is      important to producing a strong, healthy crop. Do not let plants wilt.

• Too little water will produce small plants.

• Humidity: 50%. Dahlias prefer low humidity.

• Light: Full sun

• USDA Hardiness Zone: 11

• Garden Height: 7 – 9 inches (17 – 23 cm)

• Garden Width: 7 – 9 inches (17 – 23 cm).

To be sure about pH, test the soil with a pH meter. Apply fertilizer and lime using the results of the soil test as a guide.

• It is recommended that you use a relatively inexpensive, and follow the manufacturers instructions when testing the pH Level of your Gardens soil. To raise or lower the pH level in the soil either Limestone or Sulfur is utilized. Other materials will accomplish the same results; however the two that are listed are the most commonly used.

• Limestone is added to the soil to raise the pH level because limestone is essentially calcium and calcium reacts with water in the soil to yield hydroxyl ions .. a process known as, hydrolysis = thus the pH level in the soil is raised.

• Sulfur reacts with bacteria in the soil and produces sulfuric acid, which releases hydrogen ions thus causing the soil to become more acidic =the pH level is lowered. 

Application Of Lime (To Raise Soil pH)

To increase your pH by 1.0 point and make your soil more alkaline.

• Add 4 ounces of hydrated lime per square yard in sandy soils

• Add 8 ounces of hydrated lime per square yard in loamy soils

• Add 12 ounces of hydrated lime per square yard in clay soils

• Add 25 ounces of hydrated lime per square yard in peaty soils

• The addition of ash, bone meal, or crushed oyster shells will also help to raise soil pH levels.

Application of Sulfur (To Lower Soil pH)

If your soil needs to be more acidic, sulfur will lower the pH if it is available.

To reduce the soil pH by 1.0 point

• Mix in 1.2 oz of ground rock sulfur per square yard if the soil is sandy

• Mix in 3.6 oz per square yard for all other soils.

• Composted leaves, wood chips, sawdust, leaf mold and peat moss, will also help to lower the soil pH.