Light: 5 to 8 hours Daily Nutrient pH -6.0. EC 2.0-3.5 PPM 1260-2450
Carnations are among the most popular cut flowers, they are pleasing to the eye and if grown in a reasonable volume can also provide a cash crop. The petals are edible and pleasantly sweet with a perfumed aroma. There are roughly 300 species of Carnations, they come in a myriad of assorted colors. There are also annual, biennial and perennial varieties..
In soil they take 2 to 3 weeks to germinate from seed, a properly maintained hydroponic garden expedites this process slightly. In addition to seed, they can also be grown from cuttings which is the most popular method used by commercial growers.
Light- In nature they require about 5 hours of sunlight daily [minimum] , which is not difficult to duplicate in a hydroponic scenario.
Support - They reach 1.5 to 2 feet in height, taller varieties will need support to prevent them from toppling over.
Air temperature should be in the ballpark of 55-65 F day cycle and 40-45 F night cycle. Solution temperature should be within a few degrees of 70 F..
Although the plants are sometimes perennial, if you plan on growing them in hopes of turning a profit they should only be kept for 1 to 1.5 years, after that their quality and productivity wanes and they should be replaced..
Starting Carnations from Cuttings
Tip cuttings should be harvested from a healthy plants or acquired from a reputable supplier. They should be between 3 and 5 inches long. If they are too large they are harder to root. A dry, aged and Desiccated cutting does not allow for the process of cellular regeneration that takes place in cuttings.
Cuttings can be rooted in the hydroponic media as soon as harvested or can also be cold stored for up to 2 weeks before rooting. Perlite, vermiculite, coconut coir, sphagnum moss will all work. My personal preference is a 50/50 perlite/vermiculite blend. Some growers use oasis cubes or root cubes. .
Distilled water or Reverse osmosis water is advisable but not absolutely necessary. See: Hydroponic Water Quality
Rooting hormones are purely optional but can be helpful. If you decide to use one a gel IMO, works best. If you want to keep costs down you might want to consider using pure unadulterated honey. It has natural antiseptic and anti-fungal properties. Cover any cut areas with honey to create a thin layer over the damaged tissue and it will stimulate growth and feed the plant. See: Honey as a Rooting Agent
Cuttings should be inserted with about 1/3 of their height in the media. Cut any leaf nodes. Leaf nodes are small swellings in a plant stem from which leaves emerge. The area of the leaf node contains plant tissue known as meristem. Meristem is undifferentiated plant tissue from which new cells are formed and from which new roots can also emerge.
Daily misting of the cuttings is advisable.
Do not allow the media to dry out completely at any time in the rooting process.
Do not use any nutrient solution for the first 7 to 10 days, after that a very mild nutrient solution, 1/4 strength to start out with gradually bumping it up to full strength when the cuttings are complete. Rooting should be complete in about 3 weeks.
During the rooting process the air temperature should be a few degrees above the norm for growing mature plants. So 75 to 80 F is optimal for the day cycle and 4 to 5 degrees less at night.
Starting Carnations From Seed
Carnations used in hydroponic systems are generally from cuttings, however it is possible to start from seeds. In fact if you are using a deep water system it is advisable, it also works well with Ebb and flow.
Mediums such as rock wool, coconut fiber, peat and oasis cubes or other rapid rooter plugs serve as a seed starting medium, keep in mind that when the seedlings emerge they should be transplanted to a complete hydroponic setup.
Oasis cubes are sterile and light weight and they have a good air to water ratio. Rock-wool is also popular for seed starting. Rock-wool requires more diligence as it is alkaline. Maintaining watering and nutrients with a more acidic pH level rectifies this.
Although the seed itself naturally contains all the nutrients it will need to start life. Pre-treating the hydroponic media with a 1/4 strength nutrient solution is helpful as the seeds germinate.
Do not over water the seeding medium, moderate amounts of water combined with misting works best. If the medium is too wet, particularly in the case of rock wool the seeds will fail to germinate.
Place your media, be it cubes, pellets or what have you in a shallow tray, I like to save the clear dome topped containers from rotisserie chickens and other take out foods for this purpose. Put about 3/4 inch of water [preferable distilled or Reverse Osmosis] in the bottom, leave the lid on and keep it in a warm dark location till sprouts appear.
Disease Problems of Carnations
Carnations are prone to fusarium, none are immune but some are less susceptible. Arbel and Scarlette cultivars have the highest known resistance.  Jade, Springfield, Mandalay, Ormea are several other cultivars of varying colors which are being bred for resistance. When growing carnations it is advisable to not re-use rock-wool and thoroughly sterilize media such as clay pellets before reusing.
Stem rot can sometimes be an issue when grown from cuttings. It is caused by soil borne fungi that can and will survive in a hydroponic setup. It is essential for successful carnation production that you begin with clean plant material and propagation media. Fungicide application on a regular basis will also help.
Sanitation is essential to avoid plant disease especially with cuttings which are in a weakened state. Sanitizing any tools after each and every 'surgery' is essential.
1. Pacific Northwest Plant Disease Management Handbook
2. New additions to fusarium resistance carnation program.