The start of growing tomatoes, sweet peppers and aubergines starts with sowing in plugs. Both tomatoes and aubergines also require rootstock, as these crops are almost 100% inoculated. This advice tells you how to make optimal use of Grodan plugs in this process.
To create to create the highest possible seed germination rate of the seeds and an even development of the plants in the trays.
The first step the trays undergo on the sowing line is the initial wetting of the plugs. This is an important moment as the seeds germinate due to temperature and because they absorb water.
The best way to wet plugs is to offer water several times (= repetitive). This means on a sowing line that there should be several spray bars (5) from which the water comes.
The water should run over a tray at a gradual speed to allow time for it to sink through the wool. An optimal situation occurs when the beams are 50 cm apart. Large amounts of water will flow over the plugs, so it is better to offer the same amount of water in several passes at a gentle speed.
It is very important to weigh the weight of the trays structurally and randomly after initial wetting. Then also note this on the seed list; a (240- or 252-hole) tray in which the plugs are well saturated with water weighs 2.2 -2.3 kg respectively. If trays weigh less than the lower limit, this is a signal that the plugs have not become sufficiently wet. It is important to take action on this right away. Is the water offered irregularly? Is the water pressure sufficient and constant? If the plugs are not getting wet properly, this immediately leads to growth retardation and unevenness. It is therefore important to check and ensure this process regularly. Also note that the temperature of the water used for initial wetting should definitely not be too low (<18 degrees). Too low a temperature hinders good uptake by the fibres in the plug.
Seeds germinate primarily on the basis of temperature and moisture. Of course, light also plays a role in this. The EC and pH of the water are important preconditions in the germination process. The plants use minerals such as nitrate, calcium, potassium and phosphate in the various growth processes such as rooting, cell division and cell elongation. These minerals are eventually well absorbed by the plants at a Nutrient solution pH between 5.5 and 6.
The fertiliser value needed by newly germinated seeds to grow is small, an EC of 1 mS/cm² is sufficient. However, often a higher base supply is given along, ranging between 1.5 and 2.5 mS/cm², to create sufficient buffer.
Sowing the seeds in the plugs is a precise process in which it is very important that the seeds are centred in the middle, at an equal depth in the plugs. They then have the largest volume of water available after germination, and they have the largest possible volume of stone wool to grow in.
For plugs with a sunken seedling pit, it is important that the seeds are at the bottom of the pit, so that the tomato rootstock, for example, anchors itself nicely and stably.
The central location of the seeds increases the emergence rate and uniformity of the whole lot.
The amount of vermiculite sprinkled on the seeds of various Crop plants is not always the same. The differences between rootstock and sweet peppers, for example, are obvious. With both the Grodan Pro plug and the Grodan Plantop Plug, due to the good central location of the seeds, there is a similar layer of vermiculite on all seeds in the tray. This ensures the same germination conditions for all seeds, allowing rooting and growth to be as uniform as possible. All these aspects ultimately clearly promote uniformity in a batch of plants.
An alternative to using plugs with vermiculite is the Grodan Plantop Funnelplug, which does not require the use of vermiculite. Propagating without vermiculite requires adaptation to the climatic conditions in which the plugs are placed. Ask the Grodan propagation specialists about the possibilities of a vermiculite-free plug.
The filled trays are placed in the germination room after the sowing process. Take care during manual handling. Trays are heavy due to the initial saturation, and may break due to the large weight. Always handle them with 2 hands. This will eliminate the chance of breaking.
The Plantop and Pro Plugs have excellent resaturation. Should edge effects occur because the outer trays dry out faster, these plugs are easy to resaturate and will be nice and evenly moist again after wetting.
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