Culture Tips for Tango Geraniums
Tango geraniums are characterized by their attractive darkfoliage, very good branching and compact-medium vigor. Like most zonalgeraniums, they are easy to grow if growers pay attention to the criticaldetails of production. These include providing the correct light and temperaturefor good plant and root development, keeping the plants well-fed, effectivelyusing growth regulators and taking care of major insect pests and diseases.
Have transplanting crews ready to go, and try to minimize thetime that cuttings are sitting around. Cuttings that sit around for severaldays, whether in boxes or in the propagation area, tend to stretch, developleaf yellowing, and they are susceptible to fungal root rot. If cuttings can’tbe transplanted immediately, then get them out of their boxes and lay them outon racks or benches to provide good air circulation. If receiving varietiesfrom different suppliers or breeders, try to handle these groups of cuttingsseparately to avoid confusion and to minimize the spread of bacterial diseasesthat occasionally come in with cuttings.
Tango geraniums do great with temperatures of 72° F dayand night for the first several weeks of cropping to achieve optimum growth androot development. Most Tango varieties are not vigorous growers, so it’sespecially critical early in the crop to keep those night temperatures warm toestablish a strong root system and encourage growth and basal branching. Theresults will include a reduced crop time and faster turns, less Botrytis andfungicide applications, strong roots, and high-quality plants that will dobetter for the consumer. These benefits outweigh the increased fuel costs forachieving high night temperatures. More moderate temperatures (i.e., 72-75°F day and 66-68° F night) can be used during the last half of production asthe plants mature and begin to develop flowers.
Optimum light levels for production of Tango zonal geraniumsare between 3,500 and 5,000 foot-candles. The plants can tolerate higher levelsif day temperatures in the greenhouse are kept below 75° F. Hanging othercrops directly above zonal geraniums can reduce light intensity andsignificantly reduce growth and flowering. If baskets need to be hung above thecrop, try to minimize the number of baskets and make sure the shadows moveacross the benches and are not stationary.
To produce nicely mounded plants that are highly branched,plants should be sprayed with Florel at 350 ppm about 10-14 days afterplanting. Plants at this time should be well-established, actively growing andunder no moisture or temperature stress. Most compact Tango varieties, or thosegrowing in small pots with a fast turn-round time, usually only need one Florelapplication. More medium-vigorous varieties (Tango, Tango White, Lavender,Lavender Pink, etc.) or those growing in larger containers do well with two oreven three applications applied about 7-10 days apart. Stop using Florelapproximately 6-8 weeks before sale since Florel aborts flower buds and keepsthe plant more vegetative. If growth control is needed in the later stages ofproduction, use Cycocel sprays at 750-1,000 ppm. Try to avoid very late spraysof growth retardants to prevent small flower heads on short flower stalks.
Keeping the pH above 6.0 is critical for maximizing growthand preventing iron and manganese toxicity. Alternating ammonium-containingfertilizers (such as 20-10-20, 15-16-17, 15-15-15, 20-9-20) with thosecontaining primarily calcium, magnesium and potassium nitrate will produceexcellent plants and help to moderate pH swings. Start fertilizing with 250-275ppm nitrogen and try to keep the EC of the potting mix around 2.0-2.5 mS/cm (insaturated extract) throughout production.
Pests and Diseases
Tango geraniums have relatively few insect and diseaseproblems compared to many other greenhouse crops, although growers might runacross problems during various stages of production. Thrips can attack anddamage flowers and should be controlled as plants go into flowering. Aphids canbecome severe if the plants have not been scouted regularly or have not beentreated with Marathon or another systemic insecticide. Use good IPM practicesand effective chemical sprays to take care of these insects before they get outof control.
The main diseases to watch out for are Botrytis leaf blightand Pythium root rot. Botrytis can be prevented with good air movement,removing dead or dying leaves, high night temperatures and watering early inthe day to minimize leaf wetness. Using sprays of Decree, Daconil, Heritage orSextant (as a replacement for Chipco 26019) have been shown to help controlBotrytis. The best prevention for Pythium is to drench with Subdue Maxx, Trubanor Alliette periodically and avoid over-watering.