Many different combinations of components can be used in a growing medium or substrate for producing garden mums. However, the media should be coarse, loose, and well-drained with high moisture holding and cation exchange capacities. The first decision about a growing medium is whether to purchase a commercially prepared medium or to mix your own. Commercially prepared media are generally excellent quality but may cost more than mix your own if needed in large volumes.
Mix your own substrates are generally composed of an organic, water and nutrient holding component(s) and an inert drainage promoting component(s) in close to equal proportions. The most common organic component is coarse sphagnum peat moss, though composted bark or other by-products may replace at least part of the peat. The drainage promoting component may be perlite, sand, calcined clay, vermiculite or polystyrene beads. An example of a growing medium for garden mums is indicated in Table 2.
The pH of the medium should be adjusted to 5.7 to 6.2 using dolomitic limestone which also supplies calcium and magnesium. The amount of dolomitic limestone to add depends on the pH of the initial components that should be determined by soil testing. However, a good starting point is 5 to 10 pounds per cubic yard. Phosphorus is often supplied in the mix using superphosphate at 4.5 pounds per cubic yard and a micronutrient fertilizer is also added according to the manufacturers directions. Many growers add an initial macronutrient charge to the medium at the time of mixing. This often consists of 1 pound per cubic yard each of calcium nitrate and potassium nitrate.
Rooted cuttings should be graded by size so that individual pots receive the same size cuttings. Unequal cutting size in the same pot inevitably results in an uneven, poor quality product. This can be compensated for only to a limited extent by pinching. Cuttings of each cultivar may be graded into:
Cuttings should be planted shallow with roots just covered by substrate. They should be planted in a moist substrate and watered twice soon after planting. The first watering should be clear water followed by a complete N-P-K fertilizer solution at a rate of 200 to 250 ppm nitrogen. The cutting may require mist or syringing four to five times per day in the first few days after potting. Do not allow the cuttings to wilt or plant quality may be adversely affected. Planting rooted cuttings generally occurs around the end of May in the Southeast (Table 3).
Many growers produce fall garden mums in prepared outdoor growing areas, though many are produced in greenhouses. An outdoor growing area should be in full sun and have easy access for production work and shipping. The area should be as level as possible and be covered with black plastic or gravel to control weeds. Garden mums require a lot of water, therefore an abundant, dependable, high quality water supply should be close by. Avoid an area with night lighting from street lights, security lights, or a busy street with frequent automobile lights. Artificial lighting during the night period can delay flowering.
Pots should be spaced in straight rows that allow ample room for growth. The amount of space is determined by the pot size as follows: space 6-inch pots 12 to 15 inches apart, space 8-inch pots 18 to 24 inches apart, or space 10-inch pots 24 to 30 inches apart. Rows of plants grouped together should not exceed 10 to 12 feet across with a 3 to 4-foot aisle on either side. This provide enough room to drag hoses and water without needing to reach more than 5 or 6 feet to reach the furthest pot.