Culture Tips for Tango Geraniums

February 28, 2003 - 07:58

The Tango series of zonal geraniums offers an array of flower colors, from soft lavenders and pinks to bold reds and violets, and they look great in a variety of container sizes.

Tango geraniums are characterized by their attractive dark
foliage, very good branching and compact-medium vigor. Like most zonal
geraniums, they are easy to grow if growers pay attention to the critical
details of production. These include providing the correct light and temperature
for good plant and root development, keeping the plants well-fed, effectively
using growth regulators and taking care of major insect pests and diseases.


Have transplanting crews ready to go, and try to minimize the
time that cuttings are sitting around. Cuttings that sit around for several
days, whether in boxes or in the propagation area, tend to stretch, develop
leaf yellowing, and they are susceptible to fungal root rot. If cuttings can't
be transplanted immediately, then get them out of their boxes and lay them out
on racks or benches to provide good air circulation. If receiving varieties
from different suppliers or breeders, try to handle these groups of cuttings
separately to avoid confusion and to minimize the spread of bacterial diseases
that occasionally come in with cuttings.

Tango geraniums do great with temperatures of 72° F day
and night for the first several weeks of cropping to achieve optimum growth and
root development. Most Tango varieties are not vigorous growers, so it's
especially critical early in the crop to keep those night temperatures warm to
establish a strong root system and encourage growth and basal branching. The
results will include a reduced crop time and faster turns, less Botrytis and
fungicide applications, strong roots, and high-quality plants that will do
better for the consumer. These benefits outweigh the increased fuel costs for
achieving 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 as
the plants mature and begin to develop flowers.

Growing on

Optimum light levels for production of Tango zonal geraniums
are between 3,500 and 5,000 foot-candles. The plants can tolerate higher levels
if day temperatures in the greenhouse are kept below 75° F. Hanging other
crops directly above zonal geraniums can reduce light intensity and
significantly reduce growth and flowering. If baskets need to be hung above the
crop, try to minimize the number of baskets and make sure the shadows move
across 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 after
planting. Plants at this time should be well-established, actively growing and
under no moisture or temperature stress. Most compact Tango varieties, or those
growing in small pots with a fast turn-round time, usually only need one Florel
application. More medium-vigorous varieties (Tango, Tango White, Lavender,
Lavender Pink, etc.) or those growing in larger containers do well with two or
even three applications applied about 7-10 days apart. Stop using Florel
approximately 6-8 weeks before sale since Florel aborts flower buds and keeps
the plant more vegetative. If growth control is needed in the later stages of
production, use Cycocel sprays at 750-1,000 ppm. Try to avoid very late sprays
of growth retardants to prevent small flower heads on short flower stalks.

Keeping the pH above 6.0 is critical for maximizing growth
and preventing iron and manganese toxicity. Alternating ammonium-containing
fertilizers (such as 20-10-20, 15-16-17, 15-15-15, 20-9-20) with those
containing primarily calcium, magnesium and potassium nitrate will produce
excellent plants and help to moderate pH swings. Start fertilizing with 250-275
ppm nitrogen and try to keep the EC of the potting mix around 2.0-2.5 mS/cm (in
saturated extract) throughout production.

Pests and Diseases

Tango geraniums have relatively few insect and disease
problems compared to many other greenhouse crops, although growers might run
across problems during various stages of production. Thrips can attack and
damage flowers and should be controlled as plants go into flowering. Aphids can
become severe if the plants have not been scouted regularly or have not been
treated with Marathon or another systemic insecticide. Use good IPM practices
and effective chemical sprays to take care of these insects before they get out
of control.

The main diseases to watch out for are Botrytis leaf blight
and Pythium root rot. Botrytis can be prevented with good air movement,
removing dead or dying leaves, high night temperatures and watering early in
the day to minimize leaf wetness. Using sprays of Decree, Daconil, Heritage or
Sextant (as a replacement for Chipco 26019) have been shown to help control
Botrytis. The best prevention for Pythium is to drench with Subdue Maxx, Truban
or Alliette periodically and avoid over-watering. 

About The Author

Harvey Lang is technical adviser at Fischer USA. He may be reached by phone at (303) 415-1466 or E-mail at

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