Report from Spring Trials: Helichrysum and Vinca By Rick Schoellhorn and Erica Berghauer

Learn how to control these popular component plants, as well as which cultivars have the best landscape performance.

At the University of Florida trials, a section focuses onsome of the component plants often used in mixed containers. For 2002, we selectedVinca major and Helichrysum. The idea was to come up with basic productionguidelines for these crops based on southern cultivation and also to evaluatetheir field performance for landscape use. Both of these crops are vigorous inproduction and often get too large before sale. We wanted to determine earlyplant growth regulator treatments that would help keep them under control. Wealso wanted to take a look at them under southern landscape conditions to seewhat their true season was under the South’s high heat and humidity.

Helichrysum

Helichrysum comes from South Africa and is an old-fashionedplant, recently overhauled and put into specialty annual production. There areseveral forms on the market, but all have a felted leaf surface and usually arich gray color. The standard form, sold as Helichrysum petiolare, is the mostcommon, but there are variegated and lime green forms. A separate species withsmaller leaves and a more prostrate form is sold as mini or petite licorice.All of these plants are great for combinations and work well with most mixedbasket recipes; however, in mixed containers, they may have a tendency tooutgrow other plants, so early PGR applications could be helpful.

Growers have several chemical options to control excessivegrowth on Helichrysum. As an example from this year’s trials, we treatedHelichrysum with liner soaks and drenches to 4-inch material. We are learningthat if liners are treated before transplanting, growers save money on theamount of chemical they use and gain control over early stretch. The linergrows out of the liner root ball when transplanted, and the effects of the PGRwear off. Liner soaks are a quick, easy and effective way to control growth.The rates discussed in this article are for plants grown in Florida; othergrowers should make adjustments according to their growing conditions.

Liner Soak.Helichrysum White, Petite, Lemon and Splash liners (EuroAmerican Propagators)were soaked in Bonzi dilution at 0, 2, 4, 8 and 16 ppm. Each root ball wassoaked for 30 seconds and planted into a 4-inch container on January 25. Theseplants were fertilized every watering with 150 ppm of 20-10-20. Data andpictures were taken at five weeks after planting.

The four Helichrysum varieties used in this trial respondeddifferently to the Bonzi liner soak. Helichrysum White responded well to the2-ppm treatment and had reduced plant length of 42 percent, which produces asalable, attractive plant. A higher rate of 8 ppm was effective control forHelichrysum Petite and reduced plant length by 26 percent. Lemon and Splash aremuch less vigorous; as a result, our lowest treatment of 2 ppm was still toomuch chemical. The big message is know your cultivars — not allHelichrysum need PGRs, and northern growers will use less chemical thansouthern growers.

Bonzi Drench. Weevaluated Bonzi drench applied to 4-inch plants. Helichrysum‘Licorice’ (Ball Floraplant) were planted on January 24 andfertilized at every watering with 150 ppm of 20-10-20 fertilizer. The plants werepinched one time at four weeks from planting and treated one week later onMarch 1 with Bonzi drenches at 0, 1, 2, 4 and 8 ppm using two fluid ounces ofsolution per pot. At time of treatment, plant size (average of width andheight) was measured at 3.5 inches. Final data was collected three weeks later.

Bonzi at 2 ppm gave the best results, and plant size washeld to 32 percent of untreated plants. After the 2-ppm drench, plants grewfour inches, showing that plant growth was slowed but did not stop. Higherconcentrations were too strong for quality production, and plants lookedstunted. A rate of 1 ppm might work well under cooler production situations.

Field trials. Thetrial gardens are in full sun; soil was amended with mushroom compost andmulched with cypress mulch. Plants were planted at one plant per one sq.ft.spacing and fertilized withOsmocote 18-6-12 at six grams incorporated per plant.

‘White Licorice’ (EuroAmerican Propagators),‘Licorice Vine’ (HMA) and Helichrysum Licorice (Ball Floraplant)were trialed. All lines did equally and showed vigorous early season growth,reaching 2 ft. high x 3ft. wide.For early season color, this form was excellent. However, as soon as summerevening rains began in late June, all began to show signs of Botrytis andinsect damage.

‘Licorice Splash’ (EuroAmerican Propagators) and‘Variegated Licorice’ (HMA) were the variegated forms evaluated,and ‘Lime Licorice’ (HMA) and ‘Lemon Licorice’(EuroAmerican Propagators) were the green forms trialed. All of these cultivarsdid poorly in full sun and never achieved a good look. Green forms scorched,and variegated forms showed reduced vigor, scorching, stunted growth and areversion to solid leaves as the season progressed. These plants needed alittle protection and probably would have done best in partly shaded plantings.

Several Helichrysum microphylla cultivars were trialed:‘Mini Licorice’ (HMA) and ‘Petite Licorice’(EuroAmerican). Again, not much difference between the two cultivars. Greatearly season performance and strong color in the landscape although not asbright as the larger-leaved forms. Both cultivars began flowering in June, andthis really detracts from appearance. Foliage problems set in with warm nightsand rains.

Vinca major

Vinca major is a challenging crop for three reasons: Itgrows quickly and becomes tangled with other plants; it requires severalshearings to keep it under control; and long branches that hang over the potmake shipping difficult. By using PGRs, growers can reduce stem length, whichcan make for a higher-quality product.

Liner Soak. In ourspring trials, four cultivars — Vinca major ‘Expoflora’,‘Variegata’ and ‘Maculata’ and Vinca minor‘Illumination’ — were treated with a Bonzi liner soak. OnJanuary 25, entire root balls of plugs were submerged for 30 seconds in 0, 1,2, 4 and 8 ppm Bonzi dilution.The plants were potted into 4-inch pots and fertilized every watering with 150ppm of 20-10-20. Data was collected after five weeks.

Variegata and Maculata were the most vigorous. A liner soakof 2 ppm Bonzi reduced the cascade length by 23 percent compared to untreatedplants. Maculata required only 1 ppm of Bonzi to reduce elongation by 21percent. At higher rates, Maculata appeared over-regulated. Illumination andExpoflora do not require any plant growth regulators. Bonzi did not have anyeffect on Illumination; the plants grew as though untreated, while Expofloraappeared to develop at a manageable rate without treatment.

Vinca has a running habit, and as with many plants of thistype, using PGRs cannot control growth once stems begin to hang over the edgeof the pot. With all the varieties we trialed, once the branches were pointingdown, all bets were off on control.

Field trials.Variegata (HMA & EuroAmerican Propagators), ‘Wojo’s Jem’(Wojo’s Greenhouse), Maculata (HMA) and Expoflora (HMA) were the Vincamajors trialed. We really didn’t expect Vinca major to do well in fullsun, but these cultivars surprised us by growing luxuriantly and quicklycovering their plots. Maculata, both lines of Variegata and Expoflora allshowed similar vigor and growth habit. Wojo’s Jem took almost twice aslong to cover its plot but was beautiful when it got there. None of thecultivars flowered throughout the summer, and all have rated consistently highmarks throughout the season and were still impressive in late July.

The only Vinca minor trialed was Illumination (EuroAmericanPropagators). Without comparison varieties, it’s a bit difficult to givesummaries, but we were unable to keep lower leaves on this plant even in ourgreenhouse studies. The plant has a striking yellow variegation and isdistinctively different from the other Vinca in the trial. However, under fullsun in the landscape, all variegated leaves scorched, and there was somereversion to solid green. This cultivar definitely needs shade in productionand you should avoid over watering, as it is not a vigorous plant under Floridaconditions.



Rick Schoellhorn and Erica Berghauer

Rick Schoellhorn is assistant professor of horituculture and Erica Berghauer is a graduate student in the Department of Environmental Horticulture at the University of Florida. They can be reached by phone at (352) 392-1831 x364 or by E-mail at rksch@ufl.edu.



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