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Vegetable Sowing and Propagation – Professional Tips and Techniques

Gemüse Aussaat

The time for the first sowings aproaches. Each year brings a new beginning. But what if things don't work out? Seeds are rarely the cause, provided you have not used ancient seeds. You can easily check this by first conducting a seed test on household paper! Seeds are normally quality controlled and must meet certain strict criteria. In any case, for a seed to successful germinate, it always require four things: moisture, heat, oxygen and soil.

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Water

Only with enough moisture can a seed properly germinate. The decisive factor is the right amount. A seed which has already germinated must be constantly kept moist, even short-term drying can be dangerous. Some summer flowers such as asters, begonia, zinnia and cucumbers are particularly vulnerable tho this. Wetness displaces oxygen, so any germinating seeds which are left dry can rot or are otherwise damaged by bacterial and fungal infestations. With parsley however, the most common problem is mainly due to water-logging.

Some hard-shelled and slow germinating seeds are also bathed in lukewarm water or tea (horsetail, Comfrey) for 24 hours to encourage germination. These include a few vegetables, (spinach, carrots, parsley) but also many windowsill-houseplants. The most hard-shelled of seeds, many woody plants and perennials, can be sanded down with an emery paper or carved with a file for the same effect.

Heat

Zum Keimen braucht man meist Wärme. Die entsprechenden Angaben finden Sie auf der Samentüte. Dabei gilt, je wärmer, desto besser und schneller. Besonders Gurken, Zucchini, Paprika und Tomaten sind wärmebedürftig, 25 bis 26 °C sind optimal. Beachten Sie dabei die Sortenunterschiede. Das Samen höhere Temperaturen nicht vertragen, kommt eher selten vor- und wenn nur im Sommer.  Beispiele dafür sind Kopfsalat und Asia Salate. Wenn nämlich die Temperatur auch nachts nicht unter 15 bis 16 °C sinkt, kann das Saatgut in eine Keimhemmung gehen. Es gibt aber auch Frostkeimer, hauptsächlich Stauden aus alpinen Bereichen, da kommt dann der Kühlschrank zum Einsatz um die Keimruhe zu brechen.

Oxygen

Air, or rather oxygen, is the most important factor for successful seed germination, particularly with regards to the amount in the upper soil layer. As a rule of thumb you can use the size of the seed for the correct sowing depth (cover), the three to four times the seed's size is usually considered optimal.

Earth

The soil should be loose, well-drained, humid and moisture-retaining and should also not contain any plant pathogens or other decomposing microorganisms.T o help with loosening the soil, you can mix some sand in. Some simple playground sand, like what you would find at your hardware or landscaping store will do the trick.

If you want to use compost, only use it after a heat treatment has been conducted. To heat-treat the compost, put it in the oven at 120 to 150 ° C for about 1 hour. Use an old pot or roasting foil for this task.

Finally, it is highly recommend to use a mixture of peat and sand for sowing. You should check the P-value. A low pH can adversely affect germination. A weak acid to neutral reaction is what you're after. In some shops you can also find finished sowing substrates that are ready-made for easy use.

Methods

There are a few options for sowing: either you can sow in rows, or in an area directly on the garden floor, in a cold frame or in a greenhouse. A hobby area also works quite well, as it is always a safe place to conduct pre-culture activities since you do not have tons of other plants in the area.

Prepare your seed trays, multi-pot plates and also your peat strips. The seed trays should be as flat as possible, so that the soil is not able to get too wet or damp. You can find out whether the seed needs to be covered at all or not by reading the seed packaging (pay attention to light or dark germs!). Then, cover with a hood, foil or the installation in a humid greenhouse prevent premature drying out. When filling the soil in the vessel, the edges should be done first, followed by the center. The edge areas dry up faster since they are more compact and in this way you can ensure that the shell dries out evenly. Finally, smooth down the surface. For this part you can use a wooden board with a handle.

When covering the seeds, always apply the soil with a more or less fine sieve, depending on the seed's thickness. It is important to label the sowing arrangements and subdivide smaller areas (such as by placing a marker between the rows). Especially if you want to attract only a few seeds, you should do this with a practical single grain tool. When using multi-pot plates, peat cocos or paper pots this is almost require. As always, give your seeds a little water after sowing.

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Use a multi-purpose sieve to cover the seeds. Sieve the sowing soil finely until it becomes coarser, stopping depending on the seed size.

After germination, the seedlings must be transplanted into another vessel. You can tell they are ready once the leaves are big enough to touch each other.

First prepare the shell for sowing, then set out the individual seedlings. Then, dig a hole a little deep into the earth. You can use a special tool for this, the transplanter tool. This will make a small hole in the ground, but big enough for your seed to grow in to. Uou should lightly press down after planting the seeds.

If you want to propagate cuttings, e.g. from winter geraniums, you should always use a mixture of peat (without mineral fertiliser) 1: 1 with coarse sand. The addition of fine styromull is also useful, but is not essential. Cuttings should not lose a lot of moisture during this process, because they can not retain water without theirs roots.

A cutting creates an identical replica of the original plant. Cuttings can be taken from tissue parts of trunk, leaf or root. Cuttings are cut most often from the shoot of a plant, usually between the leaf nodes (nodules, hence the term inter-nodal cuttings) or below a node (node tailing). Soft cuttings will grow roots faster. When cutting, make sure not to leave too many leaves because this prevents strong evaporation before new roots can form. Cuttings have the best chance at developing roots when they are in certain conditions: like seedlings in propagation beds, under hoods, in foil or fleece. The higher the humidity, the faster the rooting process. Be sure to use clean any tools used for cutting propagation. Disinfect scissors or other equipment afterwards.

The original version of this article was published in the Greenhouse Post, issue 01/2016, text and image: Jörn Pinske.

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