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Gerbera & Roses growing article August 2007

Roses - Stem length and bud size

In South America roses are grown at a higher altitude where the temperatures are cooler. For an example, I have seen flowers of the Preesman variety High & Fantasy from Kenya (produced on +/- 1500 metre high altitude) and Ecuador (produced on +/- 2800 metre high altitude) the result is that the same variety had a much bigger flower bud. The flower size of roses is influenced by high temperatures, so it’s very important to keep the greenhouse temperature as low as possible in summer.

How to improve stem length and bud size? You should prevent stress situations for your rose plants!

1) It is very important to keep the heat out of the greenhouse. This can be done by:

· Use of shade screen with aluminium reflection parts.

· White washing the greenhouse, especially products which keep the heat out the greenhouse.

· In summer start early with ventilation.

· Also in-house misting system (above or under the crop) can help you to increase humidity and reduce the temperature in the greenhouse.

2) The EC of the drip water during period of (extreme) high temperature and low humidity can be reduced to
around 1.2-1.4. E.C. By reducing the E.C. you make the water more easily available for the plant.

3) You can increase the amount of cycles in summer. Water cycles of more than 100 ml per plant per cycle could be used. Make sure that the drain percentage in summer is around 35-40%, but avoid over watering because even in summer you could over water and damage the root system.

4) Especially in extreme circumstances you need a lot of leaves on the rose plant. It would be good if you bend more stems to create more foliage so the plant can build up energy; this also allows the plant to cool itself which generate a bigger bud size, longer stems and a better flower quality.

5) The crop has to be healthy: white roots, no pests and diseases (like Pythium, Phytophthora, downy and powdery mildew, spider mites).

6) Do not allow explosion of spider mites (two spotted mites or red spider), to control Spider mites important items are:

I.P.M.:

	Scouting and instructing workers to mark infected spots.
	Make sure that you have enough persimilis predatory mite on the plants.
	Avoid low humidity, the spider mites like these low humidity conditions.

Chemical:

	Scouting and instructing workers to mark infected spots.
	Spray as soon as you see an infection (on the spot or whole greenhouse)
	Spider has to be in contact with chemical. Spray especially at the bottom side of the leaves
	Use a lot of water (000 till 3000 litre per ha.)
	Spray with a high pressure, with a very fine mist.
	Spray the adult + nymph + larva + eggs at the same time!
	Spray same combination 2 or 3 times, after that it has to be rotated with another chemical group.
	By warm / hot weather the mites multiply very quick, so spray at least every 4-6 days in summer.

Note: With more import roses coming from all different countries around the world (Africa, China, Ecuador, India, Vietnam) Australian rose growers have to improve the quality of their roses to stay competitive.

Gerberas:

The planting season for the Gerberas will start soon; I would like to remind you on the following matters;

	Make sure that before you start planting the new crop, the greenhouse is free of old leaves and that the bench system, pots and drippers are disinfected to reduce the chance that diseases from the old crop could infect the new plants.
	To avoid blocked drippers you should clean the drippers with Acid (removes fertilizer residue) or chloride (remove algae and bacteria). Make sure that you apply the acid and chloride on a different time; together they will give an explosive reaction.
	More and more growers change over to a coco peat mix, but the amount of water you give the new plants at the start is less than when you start with bark or scoria. But it doesn’t matter what kind of media you use, watering the new plants is something to pay a lot attention to.
	When you fill pots, make sure that the pots are clean and sterilized, and take care that the pots are filled 100% or more with the potting media.
	Plants the jiffy pot one third above the potting soil, this will prevent the crown of the plants staying wet.
	The best place for the dripper is in the jiffy pot for the first 2-3 weeks, after that you should put the dripper between the plant and the side of the pot.
	Use some extra shade in the first few weeks when the new plants are planted, too much direct sunlight will make it harder for the plants to grow.
	A good environment around the plant is one of the things you could do to prevent fungus gnats, e.g. when you give the new plants to much water you have more problems with fungus gnats.
	To reduce the chance of diseases you could drench the plants a few days after planting with Agri-fos Supa (active ingredient = Phosphoric Acid) and repeat this drench 5-6 weeks later.

Gerbera – growing 2 or 3 years with a gerbera crop?

	Some growers thinking of growing their gerbera plants longer than 2 years, this is possible but a few thing have to be keep in mind:
	The production in the third year is (much) lower; you will have fewer flowers in the winter when the prices are the highest.
	The flower size get smaller and the stem get a bit shorter.
	Dead plants have to be removed and the open space filled with new plants. This to keep the growing area covered, so weeds don’t have a chance to become a problem.

**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.

Roskam Young Plants Pty Ltd; Supplies gerbera cups, consultancy services, rose plants and gerbera plants to cut flower growers.
Preesman Alsroemeria Preesman Gerbera Preesman Chrysanthemum Preesman Roses

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Gerbera & Roses growing article August 2007

Scouting and instructing workers to mark infected spots.

Make sure that you have enough persimilis predatory mite on the plants.

Avoid low humidity, the spider mites like these low humidity conditions.

Scouting and instructing workers to mark infected spots.

Spray as soon as you see an infection (on the spot or whole greenhouse)

Spider has to be in contact with chemical. Spray especially at the bottom side of the leaves

Use a lot of water (000 till 3000 litre per ha.)

Spray with a high pressure, with a very fine mist.

Spray the adult + nymph + larva + eggs at the same time!

Spray same combination 2 or 3 times, after that it has to be rotated with another chemical group.

By warm / hot weather the mites multiply very quick, so spray at least every 4-6 days in summer.

Make sure that before you start planting the new crop, the greenhouse is free of old leaves and that the bench system, pots and drippers are disinfected to reduce the chance that diseases from the old crop could infect the new plants.

To avoid blocked drippers you should clean the drippers with Acid (removes fertilizer residue) or chloride (remove algae and bacteria). Make sure that you apply the acid and chloride on a different time; together they will give an explosive reaction.

More and more growers change over to a coco peat mix, but the amount of water you give the new plants at the start is less than when you start with bark or scoria. But it doesn’t matter what kind of media you use, watering the new plants is something to pay a lot attention to.

When you fill pots, make sure that the pots are clean and sterilized, and take care that the pots are filled 100% or more with the potting media.

Plants the jiffy pot one third above the potting soil, this will prevent the crown of the plants staying wet.

The best place for the dripper is in the jiffy pot for the first 2-3 weeks, after that you should put the dripper between the plant and the side of the pot.

Use some extra shade in the first few weeks when the new plants are planted, too much direct sunlight will make it harder for the plants to grow.

A good environment around the plant is one of the things you could do to prevent fungus gnats, e.g. when you give the new plants to much water you have more problems with fungus gnats.

To reduce the chance of diseases you could drench the plants a few days after planting with Agri-fos Supa (active ingredient = Phosphoric Acid) and repeat this drench 5-6 weeks later.

Some growers thinking of growing their gerbera plants longer than 2 years, this is possible but a few thing have to be keep in mind:

The production in the third year is (much) lower; you will have fewer flowers in the winter when the prices are the highest.

The flower size get smaller and the stem get a bit shorter.

Dead plants have to be removed and the open space filled with new plants. This to keep the growing area covered, so weeds don’t have a chance to become a problem.