Last updated on October 23rd, 2023 at 09:04 pm
Most vegetables and flowers are grown from seed – but that doesn’t always work out the way you think it will. Here we tell you the most common reasons why your seeds do not germinate.
With a few exceptions, such as potatoes, shallots and asparagus, most vegetables and almost all summer flowers are grown from seed. At times, however, the seeds may not germinate at all or may only sprout very sparsely – and hobby gardeners wonder what the reason could be. Here we tell you the five most common reasons
Seeds do not germinate? This may be the reason
Seeds not germinating can be due to the fact that they are simply too old or the seeds have been stored incorrectly. They should be stored in a dark, cool and airy place. Dried, larger seeds can be placed in a screw-top jar. If seeds are sown in unsuitable substrate, too shallow or too deep, germination is usually also unsuccessful. Soil that is too cold, as well as lack of water, will also prevent seeds from germinating. Seed bands and seed discs must be thoroughly moistened before covering with soil.
1) Incorrect storage of the seeds
Especially the self-harvested seeds are occasionally stored incorrectly and therefore no longer germinate reliably. Always store seed packets in a dark place with moderate humidity and cool temperatures between zero and a maximum of ten degrees Celsius. Airy packaging such as a paper bag is important. Foil bags are not well suited, because if the seeds are not yet completely dry, they easily start to mold in them. You can also store well-dried, larger seeds in jars with screw caps. You should also store opened sachets of purchased seeds in a jar with a screw cap or a sealable plastic container.
2) Expiration date of the seeds exceeded.
Pay attention to the expiration date on the packaging, because the germination capacity of many seeds wears off after only a few years: seeds of garlic, parsnips, chives and onions, for example, can only germinate for about one year, carrots for up to two years, fennel, spinach and celery for up to three, beans, peas, lamb’s lettuce, radishes and radishes for up to four years. Seeds of cucumbers, cabbage varieties, squash and tomatoes can still emerge after five years.
To check if your seeds are still germinable, you can do something called a germination test: Place about 20 seeds on damp kitchen paper, roll it up and put it in a foil bag with holes. Keep it at room temperature and after the specified germination period, see how many seeds have germinated. If there are more than half, you can still use the seed, if less than a third, you should discard it and buy new.
3) Unsuitable substrate and wrong sowing depth.
Indispensable for the successful germination of seeds is a good substrate. Deeply loosened, fine-crumb soil with plenty of humus and low nutrient content is best – the less the young seedlings are “spoiled” with nutrients, the stronger the root system will develop. You can also make your own growing soil: A mixture of one-third finely screened compost, one-third sand and one-third screened garden soil is ideal. Very heavy, loamy soil with a low humus content is not well suited for sowing, even outdoors, because the young seedlings can hardly penetrate it. It is essential to loosen it well beforehand and improve it with plenty of humus. For outdoor sowing, it has also proven useful to cover the freshly sown seeds with a fleece until germination – it keeps the heat in the soil and ensures that it does not dry out so quickly in strong sunlight.
The right sowing depth also plays a major role in successful germination of the plant seeds. The rule of thumb here is that the finer the seed, the shallower it must be sown. For example, if the dust-fine carrot seeds are sown several centimeters deep in the soil, the reserve material stored in the seeds is usually not enough for the seedling to struggle to the surface. Conversely, very shallowly sown larger seeds largely end up in the stomachs of pigeons and crows or do not root properly when germinating.
4) Cold or dryness prevent germination
If seeds in the open are very delayed or germinate only patchily, this may be due to the soil being too cold. In spring – depending on the type of vegetable or flower – it is better to wait one or two weeks longer before sowing. Often the young plants sown in the warmer soil overtake the supposed early starters even in growth. Carrots, for example, germinate at around four degrees Celsius, but the optimum germination temperature for rapid emergence is 18 to 22 degrees Celsius. Seeds sown too early are often simply overgrown by weeds because they grow better at low temperatures. They also often simply rot in the soil because they are easily attacked by fungi when swollen.
One of the most common seed killers is lack of water: if the seedbed is not kept evenly moist, the seeds will not swell and subsequently will not germinate. What often only leads to delayed germination can, in the worst case, even destroy the entire cultivation. The seeds are particularly sensitive during the germination phase: if they have already sprouted and then cannot grow further due to lack of water, they will inevitably die.
5) Incorrectly used sowing aids.
So-called seed tapes and seed discs are very popular, especially for plants with fine seeds, because the seeds are already embedded in the pulp with the ideal planting distance.
However, mistakes are often made in the application: It is very important to thoroughly soak the seed discs and bands once after laying them out before covering them with soil. The top layer of soil must be pressed down well and then also thoroughly watered – only then will all the seeds have good contact with the soil and germinate reliably. If you do not proceed as described, some seeds will literally hang in the air underground and their little roots will not find a foothold.
All tips for sowing in the podcast
Whether in the ornamental garden or kitchen garden – sowing plants yourself is an art! Many small details have to work together to turn a seed into a seedling and a vigorous plant. In this episode of Grünstadtmenschen, host Nicole Edler talks to gardening professional Folkert Siemens about sowing seeds. He explains why you should grow certain plants in advance, which substrate is best suited for this, what different types of seeds there are, and much more. Listen in now!