1. Target of the crop
To meet your main goals of production and quality it is crucial to have a good start to the cultivation. For that reason, the young plant must be prepared well. Goals for individual businesses can be different like an early production, a high total production or a very equal production per week. Determining this goal has effect on what type of young plant is then required. For an early production quick flowering is essential so the plant must be a very generative one with quite some age. To strengthen this a pre-planting period can be very helpful, needed for that is a larger block volume so less irrigations are required and thus a generative balance is maintained. Meaning to say business goals are strongly linked to the tools used in the propagation process.
It has to be very clear for the propagator what type of plant is desired. The development of a plant is determined by mainly age and temperature; other issues like water and fertiliser are helpful but also logical. The number of days for a young plant to develop to a certain stage is critical and it is different in every part of the world as the amount of sunlight and the day lengths vary enormously. For example, a young plant propagated in the South of Europe will develop 5-7 days faster compared to Holland. Simply copying numbers doesn’t make sense, the strategy must be tailored to the situation as a few days older or younger plants can make a significant difference.
Young plants can grow very quickly in the last week at the propagator and focusing efforts in this time frame can be the 1st difference between good and superb. The local situation is very important as light-levels can vary a lot.
2. Plant types
To reach your goal there are several possibilities regarding plant types; the following ones are possible:
- Single headed;
- Double header on the 2nd leaf;
- Double header on cotyledons.
Worldwide the most popular plant type is a double headed plant pinched on the 2nd true leaf. This type has clearly pushed out the single headed ones. Underneath are described the biggest advantages of the double header on the 2nd leaf, as well as some negative aspects:
Double header on the 2nd leaf
Advantages:
- More generative plants as the 1st cluster is after the 6th leaf of the shoot;
- Less plants needed per ha (12,500 plants per ha);
- Powerful plants as leaf area is big enough for 2 shoots.
Generative heads
Disadvantages:
- Risk of unequal shoots;
- 1st and 2nd cluster quality can be a problem with varieties having fruit weight > 100 grams;
- More sensitive to blinding plants as big leaves are catching too many assimilates shortly after pinching (additional reason why it’s advisable to pinch and de-leaf plants at the same time).
- Increased possibility of realising 4-5 leaves between cluster 1 & 2.
Double header on the cotyledons
Advantages:
- Good cluster quality;
- Normal follow-up of clusters (3 leaves, 1 cluster);
- Less plants needed per ha (12,500 plants per ha);
- Weaker plants, thinner shoots;
- Approx. 1 week’s extra time needed in winter propagations;
- Clusters are initiated and formed well, but weaker as of lower leaf area.
Pinched on cotyledons
Regarding these other 2 plant types the single header has more disadvantages like 25,000 plants / ha, vegetative plant with the 1st cluster after 9-11 leaves. It costs a lot of energy to balance this plant type as fruit load comes in late as well.
But still for some growers it can be an option as it can give a high total production with a lot of power during summer. Another reason can be the variety as some are not easy to develop uniformity over all shoots once pinched, in this case a single headed plant can be an option.
Read more at AIS Greenworks (Hans van Herk)