Gerbera & Roses growing article April 2008
 

Why do you need to check and register your climate and watering settings?

Quite often growers think that when they put settings in their computer, they don’t need to check the outcome of these settings. Most of the time the computer gives the right readings, but sometimes you could have temperature sensors, flow meters, EC & PH meters, etc. which could be faulty. The earlier you find out problems the less chance you have that things go wrong in a big way.

Keep records of what’s happening with the plant / climate in the greenhouse could be very important for future decisions or when you try to find out why something went wrong with the plant growth. 

The best growers are putting a lot of effort in fine tuning the climate conditions; they often walk in the greenhouse and look around;

1. If the window are at the right opening (not to windy or to warm inside the greenhouse)

2. Check if the heating pipes are warm enough

3. Check the moisture level of the pots / growing bags

4. If everything is working well, if the greenhouse is still in a good condition (no broken windows / plastic covers, screens, irrigation pipes, etc.)

Why does the gerbera production drop in summer / autumn? 

A gerbera plant is a short day length plant which means that its optimal day length to get the highest production is around 11.5 hours light a day. This is one of the reasons that the gerbera production is the highest in spring (the flowers are formed by days with less than 11.5 hours of light) While in summer when the light levels are much higher the production is not increasing but decreases because the daylight is longer than 11.5 hours. 

Since a few years growers in Holland have started tests with black out screens in gerberas (at the moment 40-50% of the growers use blackout screens) to shortening the day length to 11.5 hours in the end of spring, summer and early autumn. 

Advantage black out;

1. The production could increase 10 – 30%

2.  The gerbera plants stay more compact, better balance between leaves and flower production.

Disadvantage black out screens;

1. Cost of installing screens.

2. Temperature under the screen could get to warm in summer.

3. Because of the more compact growth of the plant the stems could get shorter.

How to get a higher winter production? 

1-  Remove all the white wash in early Autumn this to make the glass / plastic as clean as possible before the light levels really go down. Some of the growers wait until the rain remove most of the white wash but then it’s nearly winter and often still a few percent of the white wash is on the greenhouse. In Holland they have the rule that 1 % less light is 1 % less production, especially in Autumn and Winter this is also true in Australia!

2-  Calibrate the temperature and heating sensors so you understand what the real temperature is in the greenhouse, quite often growers are talking about temperatures in the greenhouse while they haven’t calibrate the sensors for a very long period. Also the position of the temperature sensor is very important, the sensor need to give an average of the greenhouse so don’t put it too high, too close to the walls or just above a heating pipe.

3-  With gerberas it’s important that the temperature in the evening is low enough, at 15-16 degrees the plants make more flower buds. For humidity control it’s important that the temperature is raised from four hours before sunrise to 19 – 20 degrees (maximum rise 1 degree per hour)

4-  Try to reduce the amount of fungicides sprayed over the winter period, some of the fungicides could give growth reduction when you use them to much. An active climate with circulation fans will reduce the change of botrytis.

5-  To avoid just before winter a big set back for the plant from deleaving, you have to make sure that most of the deleaving is done early autumn. In winter you could still take a few leaves off the plant but only when it’s necessary.

**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.