Florel Use on Floriculture Crops; Part II

by Dr. Peter Konjoian
Konjoian's Floriculture Education Services, Inc.

The last issue of this newsletter contained an overview of the effects of Florel on floricultural crops. Today's topic will be more advanced and describe how this growth regulator can be used to achieve higher quality and more efficiency in cropping.

Once a grower has become comfortable using Florel in place of a hand pinch multiple applications will be the next step. Before a plant can be pinched by hand enough fresh stem growth needs to be present so that the cut can be made in this softer tissue. Pinching too soon results in poor branching because the cut is made in hard tissue that will not branch as well as soft. Pinching too late results in a top heavy plant because branching takes place higher up the stem if allowed. The timing of the pinch is usually a week or so after the first signs of active stem growth are witnessed.

A crop that receives three pinches such as fuchsia or lantana hanging baskets will end up receiving four Florel applications in the same period of time because of the principle just discussed. For a single pinch crop such as zonal geraniums the grower has the choice of applying either one or two Florel applications depending on the desired results. If the grower is interested in producing the same size and quality zonal as he produced using a hand pinch then a single Florel application will achieve this result. If however, he chooses a larger, fuller plant two applications in the same crop cycle that called for one pinch will accomplish the objective.

Growers eventually reach a fork in the road as they learn how to use this growth regulator. One of two paths must be chosen. If producing a crop with the same size and quality characteristics as with hand pinching is the goal then replacing each hand pinch with Florel will cut a week or more off of the production schedule. This is because the stem can be chemically pinched with Florel as soon as it shifts into active growth as opposed to having to wait another week for enough stem growth to occur so that the pinch is made in soft tissue.

If producing a crop with added size, fullness, and quality is the goal then the same crop schedule that is used with hand pinching will work. The difference will be that two Florel applications will be fit into the time that was needed for a single hand pinch. The result is the same as growing a double pinched crop only no extra time will be required for this 'second' pinch.

Controlling the dose of ethylene

Another area of research being investigated is the effect of the actual dose of ethylene applied to the plant in a Florel application. Several variables are being studied and include concentration, coverage, and exposure time.

The most common and labelled concentration of Florel on greenhouse ornamentals is 500ppm. Most crops respond well to this concentration but there are several that do not need this much ethylene to cause desirable results. New Guinea impatiens is one such crop and will usually take more than the usual six to eight weeks to bloom after an application. For this reason New Guineas should be treated with 200-300ppm only. Bougainvillea is another sensitive crop and as little as 100ppm will result in leaf drop within a day or two of the application. Even with the leaf drop however, significant branching results several weeks after the application.

With more research in the area of concentration more accurate timing of crop flowering should be possible. While 500ppm causes a six to eight week delay in flowering perhaps 400ppm will cause a four to six week delay, 300ppm will cause a two to four week delay, and so on.

Another variable that contolls crop response is the coverage rate. The standard rule of applying one gallon of solution to two hundred square feet of crop area is practiced with many foliar applications of pesticides and other growth regulators. This is synonomous with the phrases 'spray to runoff' and 'spray to drip'. The lighter spray technique of 'spray to glisten' is closer to one gallon to three or even four hundred square feet. The lighter application spreads the gallon of material over more plants as each plant receives less of the active ingredient. At present there are no plans to use this approach to control crop responses as other variables are more reliable.

A third variable in the dose of ethylene a plant receives from a Florel application is the length of time the material is in contact with the leaf. We are accustomed to spraying a material on a plant and leaving tit here indefinitely. If however, the material is rinsed off of the plant after varying lengths of time can the response be manipulated. For instance, if a 500ppm spray is applied and allowed to remain on the plant for four hours and then rinsed off as with a thorough overhead watering will the plant flower sooner than if the material remains on the plant indefinitely. The answer is yes and by controlling the exposure time crop flowering can be timed as accurately as if different concentrations are used.

The practical implication is that instead of having to return to the mixing area to mix a different concentration of Florel for either sensitive crops or portions of crops that are scheduled for early bloom the applicator can apply the same 500ppm solution to everything and then schedule an overhead watering of those plants requiring less than a full exposure.

As research continues on this growth regulator more choices will emerge once the variables controlling the dose of ethylene are better understood. Learning how to control crop responses through controlling the exposure time to this hormone is becoming a reality. Eventually growers may have the ability to choose the crop response they wish to control and simply use the appropriate exposure time to meet their needs.