Modern breeding has made dianthus hybrids easier to produce, offering multiple production methods to suit any business with a wide array of flower colors and forms. Cultivars from Whetman Pinks Ltd., whose breeding program focuses on fragrance and performance, have captured a lot of attention in the market. The finished pot size options range from a quart to 2-gallon.
Transplant liners into a well-draining perennial or nursery mix. For smaller sizes like 128s, a pinch is necessary about three weeks after transplant to maximize branching. While bulking and finishing, apply a well-balanced fertilizer targeting 150 ppm nitrogen constant liquid feed. Maintain pH of 6.0 to 6.5, and EC should not exceed 3 mS/cm. Bulk at 60° to 65°F night and day temperatures. Plant growth regulators are not required. Foliage does not need to completely cover the top of the pot prior to vernalization. Common pests and diseases include aphids, spider mites, fusarium and bacterial problems. Keep plants well-spaced and grow moderately moist, never wet.
There are different production methods that can be used for dianthus.
- The most popular method is to transplant liners into the final sales container in the fall and bulk prior to vernalization. Regardless of vernalization requirements, this will produce the best crop with the most uniform and fullest flower canopy. Plants can be overwintered outside in warmer zones, but covering with a frost blanket is recommended to avoid leaf burn from cold winter wind. Growing in a cold greenhouse or minimally heated hoop structure is also recommended if outdoor winter and spring conditions are very wet or if there is a lot of freeze and thaw. The best results are from plants held in a cold greenhouse, with the low temperature set at 35ºF. When outdoor temperatures exceed 38ºF, vent the greenhouse to keep it as cold as possible. Allow plants to flower naturally in spring. Supplemental light is not necessary.
- For a select group of dianthus varieties that do not require vernalization, such as the Early Bird and Scent First series, there is an opportunity to finish these inside a greenhouse for spring flowering sales. Transplant liners in late fall or winter and bulk at 60°-65ºF night and day temperatures. Then, move bulked plants to a greenhouse with night-interruption lighting from 10:00 p.m. to 2:00 a.m. and force at 55ºF night and 65ºF day temperatures. Flowering response is about 9 to 11 weeks depending upon variety.
- Because many of the newer genetics do not require vernalization, another option is to transplant liners into quarts or gallons in spring. Finish outdoors under naturally occurring daylength and temperature and sell in early summer. This is not recommended for Dianthus gratianopolitanus cultivars–these should be produced using option No. 1 only.
These tips were provided by Melanie Neff, technical support specialist for Green Leaf Plants®. Using data collected in the trial garden in Lancaster, Pa., she and the product support team develop authoritative technical guides for many plants. These are available online at GLplants.com/technical-guides.html.