Considering the conditions on your garden, your knowledge, time and price, you have to decide among sowing outside, growing seedlings or buying seedlings. Each of these has certain pros and cons: direct sowing is cheap and simple, but you cannot control the environmental conditions, and harvest is late. Growing seedlings enables controlling the environment and gradual planting of a few crops at once, but you still need quite some knowledge to do it. Buying seedlings is the simplest, but the most expensive choice.
The crop immunity decreases stress during sprouting and the beginning stages of growth. The success of germinating depends on the seeds – the fresh ones contain more food supply and germinate better. If you want to use older seeds, put them in cold soil, during good conditions, and not during difficult first spring sowing. The soil has to have at least 5 °C (41 °F) for lettuce, peas, broad beans, radish, rucola and cress seeds to germinate successfully, and at least 10 °C (50 °F) for other crops.
Seeds with good germination potential:
- One year only: parsnip, the majority of spices and herbs, black salsify, flowers
- Up to two years: onion, leek, parsley, carrots
- 3-4 years: beans, lettuce, peas, cress, cucumbers, zucchini, melons, Swiss chard, peppers, celery, spinach, tomatoes, radicchio
- More: eggplant, endive, cabbage, most of the other brassica, sweet corn, radish, black radish, beetroot
There is one exception: lamb’s lettuce. Its germination potential is worst in the first year; therefore it’s best to buy it in spring, when the stores still have supplies left from the previous year. You can also put the lamb’s lettuce seed to an unsealed bag and leave in the freezer for a longer time.
Check your whole supply of seeds in spring. Discard the ones you kept sealed for more than 4 years, and the ones you kept unsealed for more than 4 years. Test the germination potential of the seed: put several layers of paper towels on a plate and soak it (pour off the excess water). Spread seeds evenly on the plate. Cover with plastic foil or put in a plastic bag. Put to a warm place; enough light is important only for certain seeds that exceptionally need light. Wait for a few days, for the first leaves to sprout (max. 10-14 days). For the seedling to grow successfully outdoors, it needs roots and leaves.
You can disinfect the seeds by soaking them in (cool) chamomile or sage tea for 20 minutes. The germination can be accelerated if you leave them in any of these types of tea over night.
Handle the seeds carefully. Store them in a dry, cool and dark place (warmth and moist make them loose their nutritional reserves). The seeds can be harmed by:
- exposure to sun (even when in a bag)
- being hit (at the bottom of a shopping bag etc.)
- moist (don’t put a package of seeds on the ground)
When purchasing the seeds, read the information on the package carefully. By only looking at the photos you can easily mistake parsley for parsnip. Check the quantity and the year of production. Before purchase, check the packages stored from the previous season to see which sorts suit you.
Sort, hybrid and genetically modified organism
Here is some basic information on what is a sort, what are hybrids and what are genetically modified organisms (GSO).
Cultivated crops are a result of a long-term work by humans, who were searching, choosing and sowing the crops, most useful to them in a particular time. In this way, in thousands of years, groups of crops have been formed, that are the same at least when we harvest them – technological maturity. This is similar to the descendants resembling their parents. This kind of a group of crops is called a sort. A sort also has to be officially tested and confirmed by the governmental officials to be called a sort. If you cultivate the seeds for your garden on your own, choose seeds of the vegetables that have the most suitable characteristics for you, not the ones that were randomly left unconsumed.
A hybrid seed is a natural phenomenon, when two (sometimes completely uninteresting) crops of the same species give a good descendant. This phenomenon was soon used in the seed industry: the scientists cultivated inbred lines of some types of crops and searched the combinations that gave good descendants. Such crops are more certain, have high crop yield and have better disease resistance. They are, however, more demanding and can fail without enough nutrients or water. Due to a more complex cultivation process, hybrids are more expensive. They are marked with letters F1, mix or hy on the package. These sorts are not good to breed further, as the seeds of the next generation are of a much lower quality.
Genetically modified organisms (GMO)
We get a genetically modified organism during genetic engineering by bringing a portion of genetic material of one living being to the genetic material of another. The consequences of such manipulation are not adequately known yet. Despite the fact that some characteristics are improved (e.g. better disease resistance), there are different GMO-related problems occurring, including allergies.
Sowing seeds outdoors
There are some requirements for successful sowing:
- well prepared soil (without large clods or crust after raining; moist but not too wet – should not stick to your gardening tools)
- proper depth (2 to 3 times the size of the seed; more shallow during winter, deeper during summer)
- soil temperature (best germination temperature is described on the seed package or in the description of crops; soil temperature is monitored by your local agriculture organizations; shade during summer, warm during spring with a dark garden fabric
- space between rows and space between plants (according to the description of crops or on the seed package)
- hoeing and tilling of soil (when the soil is dry enough after rain, till the soil crust)
- direction of rows (in the direction of the most common wind in summer, especially the wind after the rain).
The sowing depth depends on the size of seeds. Herbs seeds can be just spread on the surface. Root crops, onion, brassica crops and leafy vegetables can be sown on the surface and then spread with a little soil with a rake. Legumes and fruit vegetables are sown 3-5 cm (1-2 in) deep and covered with soil. Potatoes are planted to 10-20 cm (4-8 in) deep ridges and covered with soil. Onions and garlic should be planted at least 5 cm (2 in) deep.
Why (or when) to grow seedlings instead of directly sowing outdoors:
- crops from warmer climates need higher germination temperature
- summer heat can be too high for young crops
- small seeds germinate worse in a bad, heavy soil
- seeds develop easier in a controlled environment and grow into strong crops with better yield
- price of seeds (use less seeds)
- you can grow seedlings for almost all vegetables and flowers
- transplanted flowers bloom earlier.
The seeds can be sown to seed trays and later transplanted (pricked out) to larger pots or trays – or directly to pots of proper size (without separating). Pots from the previous years should be disinfected with hot water and have to have a hole on the bottom for excess water. If you plant to larger pots, you get seedlings together with a root clod. If you pricked them out to a greenhouse, pull the seedlings out of the soil beforehand – because this way the seedlings stop growing for a short time and the harvest is later. Sow more seeds at ones, as not all will germinate. The seeds don’t need light, but more or less constant temperature is vital. When seeds germinate, however, move the seed trays or pots to light. Thin out the germinated crops if needed. Pricking out is useful for some crops (fruit crops develop better root system) and harmful for others. If you prick out the seedlings, the soil does not have to be very nutritional, as crops need less time to grow. Prick out, when the germinated leaves get into horizontal position.
When purchasing seedlings:
- check quality: evenly dark green leaves, all leaves of the same sort the same color (tomato and yellow pepper plants have lighter green leaves, as well as some sorts of cabbage)
- buy where you know the seed quality is good (they are kept properly and strengthened)
- check if the root system is strong (light and well grown root, no smell of decay)
- it is better that plants are smaller but have well-branched roots than vice versa
- check the leaves (especially the lower sides) for possible disease or insects (but some squash sorts have characteristic white spots)
- check that the plants’ leaves are not too wide apart (except for some lettuce species where this is normal)
- regardless the weather, put the early purchased transplants into a sheltered space (they have to adjust to outdoor conditions)
- high air moisture and excess watering are two major transplants enemies. Air the room where you keep them every day, when temperature is above 0 °C (32 °F).
- you can also buy grafted transplants with better root system. This is especially reasonable with watermelons, melons and tomatoes that can be grown with more stalks
Care and transplanting of seedlings
Seeds require higher temperatures to germinate, but seedlings should be moved to a cooler place after germination to grow strong. Water them with a sprayer and not with watering can to avoid excess watering. Seedlings do not need fertilization until transplanting. Once transplanted, they need fertilizers richer in potassium and phosphorus, and with less nitrogen. You can use sea algae extract or calendula, dandelion, sage or chamomile tea.
Before planting outside, strengthen the seedlings: leave them in a room with windows open during the day for 10 days, when temperature is above 0 °C (32°F). 3 days before the transplanting let the room open during the night as well. Purchased seedlings are already strengthened and should not be put to a closed space again.
Plant the seedlings to moist soil and not on hot sun (best in the evening). Poke a hole in soil, at least as deep as the roots are long, and place it in.
Plant fruit vegetables (pepper, tomatoes and eggplant) a little deeper than they were in the sowing tray or pot – it will develop side roots on the stem. Other crops should be planted exactly as deep as before (this is especially important with celery, lettuce, endive and radicchio). As for grafted crops, the grafted spot has to be above soil, otherwise it will grow roots.
Do not rush with planting fruit vegetables too soon; they need warm soil, as cool soil can stop their growth.
After transplanting, water the crops well and keep watering carefully until the roots outgrow their root clod (approx. 10 days).
Cucumbers, zucchini, melons and watermelons don’t take pricking out well, but you can help them grow a strong root system by filling only half of a pot with soil at first, and fill up the pot to the top a day or two after they grow.