GROWING INSTRUCTIONS FOR EXACUM ( PERSIAN VIOLET )
Plants should be grown under full sunlight in Winter months. During the Summer months, a light shade should be applied (3500 to 5000 foot-candles). During the Spring and early Fall, plants should be grown in full sunlight, but light shade should be applied when plants start to flower. Shading at this time will produce darker colored blooms. Excessive light and heat will cause flowers to be faded or prematurely set bud in late Spring and Summer production.
During Winter and the cooler periods of Spring and Fall, Exacum grow best at 60 to 65 degrees F. at night, and 72 to 77 degrees F. in the daytime. But in the summer, they respond with much faster growth because of warmer temperatures and longer days.
Exacum grow best in a loose, well-balanced soil mixture containing plenty of peat and perlite or styrofoam for good aeration.
Exacum is a moderate feeder. We have found they grow best by alternate use of a 15-16-17 peat-lite special and calcium nitrate, at the rate of 2 pounds per 100 gallons, every third watering. Constant feedings of 150-250 ppm of Nitrogen can also be used. Lower strength in Winter, higher strength in Summer. If desired, Osmocote 14-14-14 may be incorporated in the growing media at the rate of 1/4 to 1/2 teaspoon per 6" pot or 1/8 to 1/4 teaspoon for 4 1/2" pot of soil. Some growers have experienced an excessive leaf curl or crinkle. This seems to be related to excessive light, and possibly a low copper level in the leaf structure. A foliar spray using Phyton 27 at 15 to 20 ounces per 100 gallons, applied two weeks after potting, has been very successful in reducing crinkle on Exacum. A second application should follow 2-3 weeks later.
Exacum respond well to the use of B-9, which helps control size and quality of the plant produced.We suggest slightly different methods for regulating LITTLE CHAMP and the CHAMPION and ROYAL series. For all varieties we recommend that B-9 at .25% solution (regular Mum strength) be applied one to two times, depending on light conditions. Even under high light we find one application makes a superior plant that is stronger and better shaped. Exacum can be grown without growth regulators under good growing conditions (light and temperature).For the CHAMPION series and ROYAL series, one application can be applied one week after potting. A second application may ne needed two to three weeks later under low light conditions. Height is also controlled quite well by regulating the amount of water received. If small plants are desired, they should be allowed to dry out more between waterings. Be aware that excessive B-9 can significantly delay flowering.Although LITTLE CHAMP is selected for its compact growth habit, one application of regular Mum strength B-9 (.25% solution) should be applied 14 days after potting. This encourages side branching, producing a compact, well-branched plant. A second application may be needed two to three weeks later under low light conditions.The growth regulator Bonzi shows promise as a growth regulator on Exacum applied as a spray 2-3 weeks after potting at 1 ounce per gallon of water - good height control is obtained. As with other species Bonzi is absorbed through stems and roots. Either a drench of appropriately applied spray will give good control.
Winter seems to produce more growing problems than Summer. Apparently the lower light levels and shorter days make a softer plant that can be easily injured and attacked by disease. This must be compensated for by lower fertilizer levels and reduced watering to make a "harder" plant. Starting around October, pots should thoroughly dry out between waterings. If media remains constantly moist during the Winter months, a media with more aeration is needed. Water early in the morning, so foliage is dry by late afternoon. Provide good air circulation around plants, and reduce fertilizer levels by one half. Overwatering and high nutrient levels, besides promoting disease, cause delayed flowering. Exacum require much less fertilizer and soil moisture than Pot Mums, Lilies, or Poinsettias. And they respond poorly if fed with high levels of fertilizer, especially ammonia. Again, remember that to accelerate Winter flowering of Exacum, one should lower fertilizer levels and make sure plants dry out between waterings.
During the warm long days of Summer, Exacum will flower very quickly. It is important to fertilize plants regularly and not let plants go under moisture stress too often or plants will flower prematurely.
Exacum react according to the total light energy received on the leaves. Flower bud initiation is not affected by day length, but a more uniform and earlier flowering will occur under long day conditions - therefore the use of supplemental lighting in the Winter is beneficial. Lighting such as H.I.D. lights or even Mum type lighting of 10-20 foot candles used 4-6 hours a night from dusk can decrease production time by two weeks during the Winter period.
Most of the disease problems of Exacum seem to be related to botrytis (gray mold). It may show up as a gray lesion at the soil line or small gray lesions at the branches. In either case, that area of the plant becomes soft and dies. This form of botrytis is actually aggravated by excess fertilizer, too much water, or water left on the plant and leaves in the late evening and overnight. Specific botrytis-control chemicals such as Chipco 26019 (Rovral) at 16 ounces per 100 gallons, Ornalin at 8 ounces per 100 gallons, as a foliar spray only, will help control this problem. But less fertilizer strength and less water are also needed. Pythium and Phytophthora can be controlled by Cleary's WP at 16 ounces per 100 gallons combined with Subdue 2E at 1 to 1 1/2 ounces per 100 gallons.
After potting - apply a heavy spray which moistens the entire plant as well as the top 1/4" of soil with Chipco 26019 at 1lb per 100 gallons of water. Three to four weeks after potting, drench with Cleary's at 16 ounces per 100 gallons plus subdue 2E at 1 to 1 1/2 ounces per 100 gallons. Four to six weeks after potting spray again with Chipco at 1 pound per 100 gallons of water. Seven to eight weeks after potting or 1 week before flowering, spray with Chipco 26019 at 1 pound per 100 gallons or use Ornalin at 8 ounces per 100 gallons. When using Ornalin be certain plants are not under heat or water stress of Ornalin may burn. Ornalin should only be used 1-2 times per crop.
The most damaging insect to Exacum is the broad mite. Usually found on the upper parts of the plant, they cause the leaf and growing tips to become yellow and distorted. Buds will fail to open. Broad mites can be controlled with Avid 0.15 EC, or a combination of Avid/Talstar. This product does not injure open flowers. Pentac, Kelthane, or Vendex can also be used to control Broad Mites, however, flower injury may occur. Worms can be controlled with Thuricide or Resmethrin aerosol. Thrips, which attack growing tips, can be controlled by using Orthene, Mavrik, or Avid.
Exacum should be placed next to a window or some artificial light source for long lasting quality. Low light conditions will cause flowers to fade. Exacum may also be placed outside on a patio or in a semi-shaded area. They are hardy to 32 degrees F.
1) Use a well drained soil especially during the Winter months. Exacum that stay wet over long periods of time are susceptible to stem canker Botrytis.
2) Plants collapse immediately after potting - caused by stem canker Botrytis. Apply a heavy spray immediately after potting with Chipco 26019 and avoid injury during transplanting.
3) Too much growth and lack of flowers in Winter are the result of excess nitrogen.
4) Too little fertilizer in Summer works in the reverse and causes premature flowering on small plants.
5) Water on foliage or late afternoon watering can cause botrytis injury both at the soil line and on upper branches as well.
6) Excessive use of B-9 causes leaf burn (rates higher than 2500 ppm) B-9 also burns open flowers when applied too late.
7) If Exacum are grown in greenhouses that are under artificially short days (such as Mums), flowering will be delayed.
Timing of the crop is seasonably variable with a marketable 6" flowering plant being produced in seven to eight weeks in the Summer and up to twelve to fourteen weeks in mid-Winter. Smaller plants grown in 4 1/2" or 5" pots for mass market sales can be produced in less time and on less bench space, since Exacum can be forced to flower at an early stage. No pinching is necessary, because they are a self-branching plant. In case of premature budding of small Exacum, larger plants can be produced by removing the earliest flowers and increasing fertilizer.
Summer Spring/Fall Winter
Wks. to finish from...
2 1/4" Cells: 7 - 8 10 - 11 12 - 14
1 1/2" Cells: 8 - 9 11 - 12 13 - 15
200 Plugs: 10 - 11 13 - 14 14 - 16
Wks. to finish from... Summer Spring/Fall Winter
2 1/4" Cells: 6 - 7 9 - 10 12
1 1/2" Cells: 7 - 8 10 - 11 13
200 Plugs: 9 - 10 11 - 12 14 - 15
Summer Spring/Fall Winter
Wks. to finish from...
1 1/2" Cells: 7 - 8 9 - 10 11 - 12
200 Plugs: 8 - 9 10 - 11 12 - 13