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A closer look a prolonged propagation:

"Those who want larger propagated plants must also invest in higher quality blocks"

The first plants for lit tomato cultivation have already been shipped from Dutch propagator Valstar 's Gravenzande. Lucas Hubert, vegetable plants crop specialist, cultivated the plants - 8.5 weeks old upon delivery - in Grodan Pro blocks for a literally and figuratively solid foundation.

"We supply the plants based on the customer's needs. The plants that we propagated for grower Geert van Ruijven are 8.5 weeks old from sowing, grafted, and come as two plants per block. At least four trusses have already been developed. In the oldest truss the first fruits are already visible," Hubert describes.

There’s a stick of 90 cm in the block to give support to the increasingly heavier plants. At the end of the propagation period, the plant is three times as heavy as a 'standard' propagated plant, the cultivation specialist estimates.

Firm foundation

Hubert sees the tomato plants from the prolonged propagation of vegetable plants as the 'Mercedes' among vegetable plants. "You don’t put a small Fiat engine in a Mercedes. If you want an extremely large plant, you should also invest in the basics and give them an extra high quality block."

His rockwool supplier advised Hubert to go for a larger size Pro block of 10 x 15 x 7.5 cm. The blocks have optimal steering possibilities, keep their shape and are slightly firmer. The extra height allows for more volume and also for additional support for the long poles, which carry a lot of plant weight.

Good cropping traits
The Pro blocks, besides firmness, also have many positive points during propagation. One of the features is the uniformity. "Each pot is similar to the other in terms of strength and weight. We weigh the pots daily to see if we have to begin giving them water. At that moment, it is striking how similar they are. The water content is also a measure of the uniformity of the structure."

To deliver a large plant which is sufficiently generative is a challenge every time. To achieve this, Hubert employs two steering methods: irrigation and increased EC. In the beginning of the propagation Hubert prefers to keep the plants as dry as possible. With the Pro blocks he easily gets back to 30 to 40% of the water content. With resaturation the blocks again become nicely full and the WG is uniform. They then have an EC of 5. The plants draw the water out of the block, so that the EC increases further. After watering, the EC in the block is nicely even again.

Also in terms of rooting the crop specialist is satisfied. "You can see that the plant is growing well. At one point you can see the roots on both the bottom and the side of the block. A sign that they are well distributed throughout the block."

Quick out of production

Dutch grower Geert van Ruijven has a nursery of 6 ha, of which 3 ha are lit and 3 ha are standard. He has been using supplemental lighting for twelve years. For the last four years he has been getting his plants from the plant grower in Pro blocks.

The choice for the large plants to him is a matter of arithmetic. "We want to be out of production as quickly as possible when the tomatoes yield the most. At that moment the additional cost for large plants will be more than compensated. This doesn’t work in another period."

He continues to harvest tomatoes from the 'old' plants up to week 43. The new plants arrived in week 44. The first production falls in week 52 or 1. That is ten days earlier compared to ‘normal’ plants.

He thinks the main advantage of the Pro blocks is their firmness. It takes at least three weeks for the plant to pull on the rope and all that time the plant hangs from the pole. "It is very important that the poles remain firm. If they sag, you will later suffer the consequences."

And of course, for the tomato grower it also applies that there needs to be a good block under it from a technical cultivation point of view. In that respect, he relies on his plant nurseryman, who provides him with a good plant plus block for a successful new crop.

For more information
Harriette Rademakers
Tel : + (0)475 357440
[email protected]

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