“When should you prefer seedlings?”, “When is the best time to sow tomatoes and peppers?”, “When do the seedlings go outside?” – Every hobby gardener has been asking himself these questions since January. In this article we explain when to sow which seeds, because properly grown seedlings are the key to a good harvest in the vegetable patch or a profuse bloom in the garden.
Sow seeds and bring them forward: The vegetation cycle begins on the windowsill
The number of warm days in our latitudes is pitifully small for the full vegetation cycle of any plant species. So we start this cycle on the windowsill (preferring seedlings) rather than planting the seeds directly in the garden soil. If there is insufficient light there, artificial light sources can be used. Plant lights, also called phytolamps, are ideally suited for this purpose.
The length of the growing season depends on the speed at which the variety ripens. This varies not only between species, but also between varieties. There are, for example, specially bred early ripening varieties for growing in the conditions of a short northern summer (but those who are impatiently waiting for the first tomatoes will be delighted too).
However, there are still plants that have a very long growing season, such as B. the Chabaud carnation (Dianthus caryophyllus var. Schabaud), the hardworking lizzle (Impatiens walleriana), lobelia (Lobelia), the strawberry (Fragaria ananassa) and others. For them you need to apply additional lighting that artificially increases the light day to 15-16 hours.
So when should you sow the seeds? And when should the young plants go out? The best time to sow varies depending on the stage of plant development. It is important to know how many days it will take for the seedlings to sprout, if and when to pick them, and the recommended age for planting the seedlings. This information and the total duration of the growing season are usually listed on the seed bag – for the respective variety. Everything is clear so far, but what to do if this is your first gardening season? You have never sown tomatoes and you do not know about their germination time and sowing? For your region, May 15th is early spring, but wouldn’t it be too “late” for the sowing then? Try to count the first year strictly according to the calendar.
When to sow which seeds?
The average dates for the most popular vegetable crops are as follows:
(Germination time / age of the seedlings for sowing outdoors)
Cucumber – 2-3 days; 25-30 days;
Tomato – 6-8 days; 45-60 days;
Paprika – 12-14 days; 65-75 days;
Eggplant – 10-12 days; 50-60 days;
Zucchini – 3-5 days; 25-30 days;
Pumpkin – 3-5 days; 25-30 days;
Lettuce – 3-5 days; 35-45 days;
Celeriac – 12-18 days; 75-85 days;
Leek – 12-15 days; 45-55 days;
White cabbage – 4-6 days; 40-50 days.
To determine when to bring seedlings forward, count from the expected date of planting in the ground: 80 days for peppers means sowing seeds in February, 60 for tomatoes = mid-March, 50 for cabbage = late March, and so on.
Being late isn’t a problem either
The closer spring approaches, the longer the daylight hours are, which means the seedlings get more natural light. It has long been observed that tomato and pepper seedlings planted later easily catch up and then overtake the plants sown earlier.
The age of the seedlings is the most important factor for outdoor sowing. And it is better to plant seedlings slightly undergrown than overgrown. Overgrown seedlings are more difficult to transplant, have much poorer roots, and are more prone to disease during the adaptation process. This is one of the reasons why the timing of sowing for seedlings should be calculated individually.
What is the climate like in your region??
When to plant seedlings in a permanent place depends on the climatic conditions in your area. Pay attention to a time with always warm temperatures without renewed frost. It is therefore important for every gardener to know the number of warm days in the month. It is clear that they can change from year to year, but here we can only rely on weather forecasts, the accuracy of which unfortunately leaves a lot to be desired. Therefore, for sowing, one can initially orientate oneself on average values based on long-term meteorological observations.
Where to plant seedlings?
There is a difference whether the young plants are planted outdoors, in a plastic tunnel, in a polycarbonate or glass greenhouse. The times for planting seedlings and sowing seeds in the field and in the greenhouse usually differ by 30-45 days. The higher the bed is, the earlier it warms up. Planting in raised beds can be done 2-3 weeks earlier than in the open ground at ground level. As it turns out, peppers for seedlings in the greenhouse can be planted as early as January.
Outdoor sowing of cold-resistant and slowly germinating plants (radishes, lettuce, carrots, parsley, dill, radish, cabbage, beets) begins when the soil at a depth of 5-10 cm warms up to 8-10 degrees during the day. At the same time, the first seedlings of heat-loving plants such as peppers, tomatoes and cucumbers can be germinated in the greenhouse. Since Germany is mostly in the cool temperate zone, this means roughly in the period between May 1st and May 10th. For the southern regions from early April to mid-March.
Tomatoes and seedlings of other heat-loving plants should be planted outdoors when the risk of renewed frost has passed and we have stable warm temperatures. Typically this means 10-15 June for northern Germany, the first decade in May for central Germany and the first decade in April for the southern regions.
Tip: Search Google for climate data for your city. View the temperatures based on the data from the past few years.
Sowing seeds: plan after weeks
Make a list of vegetable crops and annual flowers that you want to plant this year. Immediately make a note of which varieties you will be growing and under which conditions, and indicate the expected planting dates. So you know exactly when to plant your seedlings.
It is useful to create a table as early as the planning phase that contains the following information:
- the name of the plant species and variety;
- Planting location – open field or greenhouse (you can immediately plan the specific planting location and the number of plants);
- Days for seedling germination;
- the age at which the seedlings were planted;
- the best time to sow the seeds;
- the dates for sowing the seedlings in the field can now be easily calculated with the data that you have in front of you.
Here is an example:
|White cabbage and cauliflower (early)||3-4||45-55||23.02-2.03||5.05||6-7|
|White cabbage, broccoli, Brussels sprouts, kohlrabi||3-4||35-50||14.03-29.03||05/25||4-6|
|Leek and onion||5-7||50-70||1.02-20.02||05/10||2-4|
|celery root||10-16||60-70||23.02-03.03||May 15||4-5|
* This table is intended for medium latitudes with a moderate climate. If you live in the southern regions, you can start sowing and planting seedlings 5-7 days earlier, while in the northern regions you can start a week later.
It also makes sense to have a separate column with the expected fruit formation (or flowering time for ornamental plants). This can be calculated with knowledge of the growing season of the respective variety. Sometimes the timing of sowing seeds for seedlings is calculated only on the basis of the time of fruiting.
The flowering and harvest times are particularly important for annual plants. After all, that’s why you grow them for this reason. In order to achieve a longer lifespan, not only varieties with different flowering speeds can be used, but also the time of sowing the seedlings can be varied. Due to the variation in the age of the plants, fruit formation will take place at different times. This will also help correct the unpredictability of the weather.
Don’t overdo it either. Remember that it is important to plant the seedlings in the open ground in a timely manner. Consider your options. How many times are you ready to take the time to transplant seedlings? It is more convenient to do this in large quantities for different species and varieties. So it pays to schedule a few planting dates that will suit the weather conditions and are convenient for you. You can use this to calculate the dates for sowing the seedlings so that they are ready in time for the planned planting dates.
Sowing seeds: Calculate sowing dates
Now, using the data entered in the table, you can calculate the dates of sowing for seedlings. To do this, subtract the age of the seedlings and the number of days of germination from the planned planting date. If you have to separate seedlings, you should deduct an additional 4-5 days for the adaptation of the young plants. This will give you a fairly accurate date to plant your seeds. Given the ambiguity of weather factors and different growing conditions, a fluctuation of around 10 days is quite normal.
It would be best if you made your own calendar for sowing and planting seedlings. But in an average form for the cool temperate climate zone, the times will look like this:
Sow seeds: 2nd decade of February – celery, chilli, wild garlic, basil, oregano, parsley, mint, tarragon
Sow flower seeds: sweet peas (Lathyrus odoratus), Levkojen (Matthiola), lobelia, bellflower (Campanula)
Sowing vegetable seeds: 1st decade of March – early varieties of tomatoes for growing in a greenhouse, white cabbage, leeks, arugula, rhubarb
II decade of March – late varieties (for outdoor cultivation) of tomatoes, peppers
III. Decade of March – early varieties of tomatoes for outdoor cultivation, eggplants
Sow flower seeds: Petunia, busy lizards (Impatiens), marigold (Tagetes), delphinium, ornamental onion, phlox
Sow herb seeds: watercress, dill
I. April decade – cucumbers for growing in the greenhouse, cauliflower, broccoli
III. April decade – zucchini, pumpkin, cucumber for outdoor cultivation, lettuce
Sowing flowers: nasturtiums, zinnias, forget-me-nots, cosmeas, marigolds (calendula), decorative sunflowers (helianthus, gerbera)
Sow herbal seeds: thyme, sage
Planting seedlings outdoors or in a greenhouse:
I. Maidekade – cucumber, tomatoes in the greenhouse;
II. Maidekade – leeks, white cabbage, peppers and eggplants in a greenhouse;
III. Maidekade – cauliflower, cucumber, pumpkin, zucchini, celery, cabbage
Planting seedlings in the open ground:
I. Decade of June – tomatoes, peppers
If you take the time to plan and calculate the optimal dates for sowing seeds and planting seedlings in the ground, you can get healthy plants that require less maintenance and provide a stable crop, extend fruiting time and the Make garden work easier and more productive.
How to grow cuttings from seeds: Here are a few basic rules you should know
Before you start sowing, you should calculate how many seedlings you will need. You can still buy the missing specimens, borrow them from a neighbor, or plant another plant in the free space. But if there are too many seedlings, it is always difficult to find a place for them on the property or in the raised bed. This is mainly due to the psychological inability to throw away a living plant. Don’t do extra work – less is better. Here are some other tips to look out for when sowing seeds.
How many seedlings will be needed?
Knowing the size of the greenhouse, bed or flower bed and the minimum distance between plants, you can easily calculate the required number of seedlings. Increase this amount by about 30% to accommodate unforeseen circumstances.
The second criterion for the number of seedlings is the area of the window sills and other suitable areas that you have available for germination. After all, growing it at home takes up quite a bit of space.
The right light for seedlings
Growing seedlings at home requires adequate light. Without them, the seedlings will not develop properly and will grow poorly. Weakened seedlings are prone to various diseases. Therefore, one cannot count on a rich harvest or abundant flowering.
Normal lightbulbs are less suitable for additional lighting of seedlings, but daylight fluorescent lamps (from 5500 K) and growth lamps are. But since the pink-purple glow of the latter is unusual and even harmful to the human eye, they should be used in a set with special mirror reflectors and / or at the same time as the fluorescent lamps.
The light source should be as close to the plants as possible, especially in the first few days after sowing the seeds. Therefore, when installing the lights, take into account the possibility of slightly changing the mounting height.
What should seedlings grow in??
In preparation for the sowing season, take care of the containers for growing seedlings. These are intended to meet a few important requirements. First, they need to have holes in the bottom and a separate tub to drain excess water. Second, choose containers made from a sturdy but lightweight material (wood or plastic) so that they can be moved from one location to another if necessary. They also need to be cleaned and disinfected after use; Plastic is more suitable in this case.
The material of the container must have a low thermal conductivity so that the roots of the plants do not suffer from the temperature differences. Cardboard or egg carton nursery pots are often used, but some gardeners report mold growth.
Note: Do not put the boxes with seedlings directly on the windowsill. Choose a base made of wood or styrofoam. There are also pedestal trays on the market.
Potting soil for seedlings
Growing seedlings at home requires sufficiently well-drained, loose and moisture-absorbing soil so that when watering, the water seeps better and quickly gets to the roots of the seedlings. Most varieties need a pH-neutral soil, but some plants (e.g. gentians, ferns, and conifers) prefer acidic soil – just as they do in the field.
You can buy ready-made potting soil from specialist retailers or you can make the potting soil yourself. The mixture usually consists of lawn and leaf humus and coarse sand. Some gardeners add hydrogel to increase moisture.
The purchased soil does not need to be pre-treated. The self-prepared soil mixture should be poured with boiling water or heated with steam to prevent fungal diseases in the seedlings.
Sowing seeds: the right depth
When all the preparations are complete, you can start sowing. Here you should strictly adhere to the cultivation technology – it is different for each crop. The seeds of some plants (heliotrope, lobelia, petunias, etc.) only germinate in the light, they are simply spread on the surface of moistened substrate. Most of the seeds are planted 1 to 4 cm deep and covered with soil.
Two rules apply to all crops: the seeds should be sown in previously moistened soil, and after sowing they should be covered with glass or transparent film so that moisture is retained. As soon as the seedlings appear, the film is gradually removed.
Optimal temperature for seedlings
For every culture there are optimal, minimum and maximum temperatures for germination and subsequent growth. For example, begonias and petunias germinate at + 22-24 ° C, while the optimal temperature for cabbage is + 8-10 ° C. You can find all the necessary information on the Internet or in specialist literature. In any case, you should reduce the temperature by 2-3 ° C after germination so that the plants can take root better and only then continue to grow.
Note that lower temperatures are also desirable at night. This is because photosynthesis and the respiration of plants depend on temperature. Since photosynthesis stops at night, but the plants continue to breathe, the need for high temperatures is lower. Even with little light, the following applies: the less light, the lower the room temperature should be.
How should I water my seedlings?
Watering also depends directly on the amount of light. On a hot, sunny day, sprouts, especially those with large leaves, should be watered morning and evening. With a few hours of daylight and cloudy weather with a low air temperature, 2 to 3 waterings per week are sufficient. Make sure that the soil in the container remains moist, but that no waterlogging occurs.
Watering should be done with tap water. At the beginning of growth, seedlings and small seedlings should be watered with a spray bottle so as not to damage the weak stems and leaves.
Prick out cuttings
Growing plants should be transplanted into individual cups so that they do not compete for nutrients and light. With good care and sufficient light, most plants are ready to be singled out as soon as two to three leaves are present.
Seedlings can easily be transplanted with a table fork or a special pricking fork by taking a few plants out of the seed pot and carefully pulling the roots apart. You can also shorten the central root with scissors so that the lateral roots develop better. The branched root system enables the plant to absorb nutrients more intensively and over a larger area. This way the root system remains superficial. The plant needs frequent watering as the roots do not go deep into the soil to provide moisture for themselves. Shortening is not recommended for plants with a taproot system.
And this is how pricking works: Earth is poured onto the bottom of each cup and moistened abundantly. The pricking fork is then used to poke holes in the substrate. These should be so big and deep that the roots of the seedlings fit into them without kinking them. Now the seedling is put straight into the hole and covered with earth.
Sometimes the small seedlings are transplanted like a bouquet, a few plants in a cup. This way the roots are less damaged and the plants get a decorative look faster.
Transplanting is carried out on a cloudy day, and then the seedlings are shaded for a couple of days. In this way, the plants weakened by the transplanting can acclimate and start growing again.
The cultivation technique stipulates that the seedlings are hardened a few days before being transplanted into the field – this way they get used to the outdoor conditions.
Hardening of the seedlings is carried out in warm, cloudy, windless weather by placing them outside for 10-15 minutes for the first time. Little by little, the time outdoors is increased. At the end of the week, when the weather stays consistently warm, the seedlings can stay outside overnight, allowing them to get used to the daily temperature fluctuations. To avoid sunburn, the seed pots should be shaded and protected with covering material at night. Hardening the seedlings prepares them for transplanting.
Transplanting seedlings outdoors
As a rule, heat-loving plants are grown from seedlings, so that transplanting into the field is only possible when the risk of renewed frost has passed. The prepared hole is filled with the necessary fertilizers and abundantly watered. When the soil has dried a little, the seedlings are carefully taken out of the cup and lowered into the prepared hole together with the clods, covered with soil and compacted.
Extra-long tomato seedlings can be planted at an angle and, after cutting off the lower leaves, covered with soil to a height greater than that in the shell. Side roots will then form on the stem below the surface, and the plant itself will assume an upright position after a few days. Other plant species should preferably be placed at the same depth as in the cup. After transplanting, mulch the soil, shade the seedlings and leave them for a few days without watering to allow the roots to spread and grow in search of moisture.
A few more tips
Of course, if you are not satisfied with the seedlings you have grown, you can also buy ready-made ones. When buying, pay attention to their appearance: the seedlings should be strong, deep green in color and free from external injuries and signs of disease.
Do not forget to mark the seedlings when sowing and transplanting, indicating the type of plant, variety and date of sowing. It is also worth recording this information on your sowing calendar.
When growing seedlings at home, keep them away from cats and other pets. They all like fresh greens and will not miss the opportunity to explore the taste of the seedlings. So make sure that you plant the seedlings in a place inaccessible to animals.
Some species can be transplanted during the flowering period, e.g. the wild pansy (Viola tricolor var.hortensis), petunias, marigolds and a few others.