Effect of pruning on the growth and development of Protea 'Pink Ice' (P. compacta R. Br. x P. susannae Phill.)

Nieuwoudt, Gerrit (2006-04)

Thesis

ENGLISH ABSTRACT: The main purpose of producing cut flowers is to earn a satisfactory income with the first endeavour normally to increase the total number of flowers produced. This has limits due to the number of flowers that can be produced per plant or per area planted. Another method is to get the bulk of the crop in the longest possible stem length category to earn better prices. A third option is to target the seasons or times of the year when prices are naturally higher due to a positive ratio between demands and supply. Most of the protea cultivars grown commercially in South Africa flower outside the period September to January when prices and demand for proteas on the European markets are high. Previous work established that the flowering period of some protea cultivars could be modified to more favourable marketing periods through the timing of the pruning operation. Plants of Protea ‘Pink Ice’ were pruned at monthly intervals from January to December 1999. For the first crop after pruning the highest yield was achieved for plants pruned in June. Flowers borne on an autumn flush needed 4 to 6 weeks longer to complete their development than for spring flush borne flowers. However, since flower initiation in autumn occurred earlier by more than 3 months than on the spring flush, this difference in time accounted for the earlier flowering of the former in spite of a longer period to complete the flower developmental process. The effect of cropping this cultivar in a biennial system was tested against actual prices to test the validity of the finding that the June treatment resulted in the highest number of harvestable stems. It was found that the June treatment also gave the best income and the phasing of production resulting from a June pruning in a biennial cropping system fitted this cultivar the best. Orchards should be divided in two blocks with one in the ‘on year’ and one in the ‘off year’. The length of the shoot stub left after a shoot has been pruned determines the nature of the regrowth. Four-year-old plants of Protea ‘Pink Ice’ were pruned to four different bearer lengths in November 1999 or February 2000. Plants were pruned that either a half, one, two or three flush length bearers were left on the plants. Plants with the two longer categories of bearers took the shortest time to sprout buds from axillary positions on the bearers and also had the most buds developing into shoots. The longer bearers produced more flowers per plant but the average length of the flowers was shorter than the plants with shorter bearers. The average total income was more in the instance of the longer bearers due to more flowers and the earlier harvest resulting from buds sprouting earlier.

AFRIKAANSE OPSOMMING: Die hoofdoel vir die produsering van snyblomme is om ‘n bevredigende opbrengs te lewer en normaalweg word daar eerstens gepoog om soveel moontlik blomme in totaal te kweek, maar daar is beperkinge op die aantal stele wat per area of per plant geproduseer kan word. Nog ‘n metode is om die langste moontlike stele te lewer uit die grootste gedeelte van die oes aangesien langer stele beter pryse realiseer. ‘n Derde opsie is om die grootste deel van die oes te lewer gedurende die periodes wanneer die pryse die hoogste is as gevolg van ‘n positiewe verband tussen vraag en aanbod. Die meeste van die Protea kultivars wat in Suid-Afrika gekweek word blom buite die periode van September tot Januarie wanneer vraag en dus pryse vir Proteas op die Europese markte hoog is. Vorige navorsingswerk het gevind dat die blomperiode van sommige Protea kultivars geskuif kan word na die beter bemarkingsperiodes deur die regulering van die snoeityd. Plante van Protea ‘Pink Ice’ is op ‘n maandelikse basis gesnoei vanaf Januarie tot Desember 1999. Die plante wat in Junie gesnoei was, het met die eerste oes die meeste stele gelewer. Blomme wat aangelê is op ‘n Herfs groeistuwing het tussen vier en ses weke meer tyd nodig gehad om oesryp te raak as die blomme wat op ‘n Lente groeistuwing ontwikkel het. Die blominisiëring op die Herfs groeistuwing het egter ongeveer drie maande voor die op die Lente groeistuwing begin en hierdie verskil in tyd het die vroeër blom verklaar ten spyte van die langer ontwikkelingstyd. Die effek van ‘n tweejaarlikse oessisteem vir die kultivar is getoets aan werklike markpryse om te bepaal of die Junie snoeidatum, wat die meeste stele opgelewer het, ook finansieël die beste gaan presteer. Daar is gevind dat die Junie behandeling ook die beste opbrengs opgelewer het. Boorde behoort verdeel te word in twee blokke met een deel in die produksiejaar en die ander deel in die groeijaar. Die lengte van die stompie wat gelaat word nadat die loot gesnoei is, bepaal die aard van die hergroei. Vierjaar-oue plante van Protea ‘Pink Ice’ is gesnoei na vier verskillende draerlengtes in November 1999 of Februarie 2000. Plante is gesnoei sodat daar draers van ‘n halwe, een, twee of drie groeistuwings op die plante gelaat is. Plante met die langer draers het die kortste tyd geneem voordat knoppe in die blaaroksels begin groei het en hulle het ook die meeste aantal knoppe gehad wat begin groei het. Die langer draers het ook die meeste aantal blomme per plant geproduseer, maar die gemiddelde steellengte van die blomme was korter as dié wat geoes is van plante met korter draers. Die gemiddelde totale inkomste per plant was die hoogste in die geval van die plante met die langer draers, as gevolg van die groter aantal stele asook ‘n vroeër oes wat gerealiseer het, omdat die knoppe vroeër begin groei het uit die blaaroksels.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/21689
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