Gerbera & Roses growing article October 2006
 

Water quality;

With low rainfall in Australia, some growers will not have enough rain / dam water left to get through summer. I would like to advise to already mix the rain / dam water with some bore or mains water; this is to avoid big changes for the plant. When you use a different source of water this could have effect on the nutrients level in the irrigation water, the best thing to do is to analyse the water to find out which nutrients are in the water and adjust the fertilizer mix.

Pythium;

During warm and sunny days, a lot of water is given to the plants and this can cause a saturated substrate. On the other hand the substrate can become too dry when not enough water is given and the over reaction is to give a lot of water. In both cases, the roots are too long in a too wet substrate, root cells burst, and Pythium can infect the plants. For that reason, it is important that the substrate dries up regularly and in this way the exchange of fresh air in the pores is better and oxygen can reach the roots. Watering strategy of many small volumes can saturate the substrate too much, for that reason, a lower frequency with larger amounts can be better but at least a 30-35% over drain has to be given. Pythium is often thought of to be a secondary disease but it can completely infect the root system in a very short period. The circumstances around the roots are very important and a lack of oxygen can cause a quick development of the disease

Flower quality;

In Australia where there is no quality control of the flowers and when the flowers are sold at the wholesale markets, growers are not controlled by an authority and should take quality control more seriously. On the auction in Holland, they have quality controllers who check the quality of the flowers on the following things; Stem length, flower size, bacteria levels in the flower stems, botrytis and damage on the flowers. Below a few tips to get a better vase life for gerberas;

Pick the gerbera from the plant when at least one row of stamen is visible. This is important because raw flowers need much more energy to develop completely and will not last that long.

After the gerbera has been picked, you need to cut +/- two cm off the lowest part off the stem. By cutting off this hard part of the stem the flower can take up the water much better, which is important to avoid breach of the stem and bending necks

Put the stems in clean buckets with clean water immediately after harvesting and place them in a cool area. Before every use, these buckets need to be cleaned / disinfected to avoid the growth of bacteria. Bacteria block the stem so that it cannot take up any water.

Using clean water is very important, the pH of the water may not be too high; otherwise, you create an ideal climate for bacteria. A pH level between 3.5 and 4 is good. Chloride is a good product to be added to the water, because this kills bacteria and makes the pH of the water reduce. Do not place the buckets in direct sunlight, because it will break down the Chloride very quickly.

The flowers take up water more easily if a large part of the stem is placed in water, 10 to 15 cm is ideal. The water temperature may not be too high, because otherwise the flowers would lose too much water through evaporation.

The loss of water in a gerbera flower causes ageing, so this should be avoided as much as possible. Avoiding draught or wind, as well as increasing the relative humidity around the gerberas up to 70% can decrease the evaporation of water by the flower.

During the long period of watering the flowers, special flower nutrition could be added to the water. This gerbera flower nutrition consists of sugars and ingredients to bring the pH down as well as to reduce the growth of bacteria. Sugars have a favourable effect on the durability of gerbera flowers, but if only sugars would be added, this would seriously stimulate the growth of bacteria, so this is not recommendable. A high concentration of sugars in the petals makes it easier for the flower to take up water, which results in a better blooming and durability. We recommend the use of an anti bacterial product (Florissant 500, or Chrysal CVB) to reduce the growth of Bacteria in the flower stems.

Do not put to many gerberas in a bucket when picked in the greenhouse or when transported to the flower market, a damaged gerbera loose a lot of its attraction!

***Although we trust that this information could be of considerable help to the success of the crop, we cannot accept any liability for the results of your crop. All the information in this growing newsletter is without committing ourselves.

This article is written by Job Roskam of Roskam Young Plants Pty Ltd. and also published in the Australian flower industry magazine.