Starting seeds indoors, or “Pre-growing”, means that you start to grow seeds into sprout indoors, and then – when it’s warm enough, move the sprouts to your greenhouse or garden to grow to full plant. This way you’ll gain precious weeks right at the start of growing season.
Are you one of us who starts to dream about gardening and growing your own veggies as soon as days get longer and spring knocks at the door? It might be still early for your outdoor gardening, but this is the right time to start planning your summer garden: select the seeds, plan the space, and make schedules… it’s all so exciting! It’s also the right time to start seeds indoors, and smart gardens are great allies for you in this task!
In this article we will look into why it’s a good idea to start pre-growing seeds indoors, which plants are good for pre-grow, when to start and how to transplant to get the best gardening experience. You will also get all the tips and tricks you need to know if you want to start pre-grow seeds using hydroponics.
Why start seeds indoors?
Start to pre-grow the summer crops indoors is a rather common habit in the Nordic countries, where pre-growing allows to extend growing season and better exploit the summer months outdoor. Pre-growing is a good habit also in warmer countries where it allows one to get an extra round of cool-weather crops, before the heat of summer.
If you are not an expert gardener, pre-growing indoors also offers an easier start rather than directly planting the seeds outdoors. Indeed, it’s easier to watch your baby plants start to grow, and you don’t have to worry about other unwanted weed plants growing in the same spot and stealing nutrients and water. It’s also easier to take good care of them while they are young and fragile.
If having an easy start is your goal, consider using a smart garden for that purpose. One of the main advantages of using a smart garden is the presence of growing light, which is really important as most veggies need a minimum of 6-8 hours of daily direct sun. Choosing professional agriculture light, like Plantui, also ensures the growth of strong and healthy sprouts which have better chances to grow in beautiful plants.
There are some easy-going plants to start indoors that will give you a nice gardening experience even if this is your first experience: lettuces, kale, beans, tomatoes, chilies/peppers and eggplants. Try melon if you feel ready for a little more challenge.
Another option to sprint into outdoor gardening would be to buy grown-sprouts from the shop directly when the good season starts. This is not our favourite way, so I will not talk about this method here. However, I want to list here for you 3 reasons why starting from seed is better:
- You have more choice of seeds than you have of grown-sprouts, so you can freely choose and experiment with something different every year.
- You are sure your sprouts are strong and healthy when they are moved outside
- Last but not least, you have a unique joy in seeing those little greens coming out, you must admit it!
How to choose what to pre-grow indoors
One of the advantages of growing from seed is the huge number of varieties available. You can definitely follow your fantasy and experiment with something different every year, however, consider that local seeds might have a better chance to grow happy once moved outdoors. Also make sure that you select high quality seeds, with a high germination rate. Plantui selected seeds have more than 95% germination rate and they are ready to be grown indoors. When you select seeds from your favourite store, just make sure to check the germination rate, and if they require pre-growing treatment like soak, scratch, or chill.
Some plants really like a warm and comfy start indoors, while others definitely don’t like to be moved. So, it’s important to choose which plant to pre-grow. Here are some tips:
- Plants with slow growing roots are better to be started indoors: cauliflower, broccoli, brussels sprouts, cabbage and even salads. If you are in a warm country, starting seeds indoors ensures that they are ready before the temperature rises too much, as they might suffer the heat.
- Plants producing tender vegetables like tomatoes, eggplants, and peppers are very susceptible to the cold temperatures of spring, so it’s best to start them indoors and keep them safe. In cold places, starting these plants indoors might be the only chance to get them ripens in time.
- If you are in a cold climate, start also plants like radishes, peas, kale and spinach indoors. They are fast growing and cold tolerant, thus they can be planted directly outside in warmer places, but they don´t mind being transplanted, if you want to start earlier.
- Some plants that might be started inside in the cold climate areas are cucumbers, muskmelon, pumpkins, squash, and watermelon; however they are very sensitive, so need to be careful when transplanting.
Root vegetables like carrots and beets don’t like having their roots disturbed, so it’s usually safer to just start their seeds outdoors in the ground.
When to start pre-growing seeds indoors and when to move outside
The right moment to start to pre-grow/transplant varies depending on the vegetables you grow, your location and the yearly weather.
As a general rule, the seeds of most vegetables should be planted indoors about six weeks before the last frost but remember to check if there are any other instructions for the seeds you choose. Once your sprout has grown, start with the most cold tolerant varieties and slowly move the others when the outdoor temperature is appropriate for them.
Soil condition is very important for a successful outdoor growth. Transplanting on the balcony is easier as the conditions are more stable, thus you are ready to go as soon as it’s not too cold. Remember that heat-loving plants shouldn’t be outside until night-time temperatures remain above 15°C.
When transplanting in a garden it might be good to use a soil thermometer to help deciding when is the right moment to move:
- When the soil temperature is above 8 °C, you can start move outside the cold tolerant veggies like kale, spinach, coriander and lettuce
- When the soil is above 15 °C, it is safe to move outside most of the “warm” crops: radishes, leeks, cabbage, brussels sprouts and peas.
- As the soil temperature has risen close to 20°C ,it’s time to move outside all the sprouts, including cold-sensitive plants like tomatoes and chilies. If you like to have a herb garden outside, that’s the moment to do that too.
Tips & tricks for a happy transplanting outdoors
When transplanted outside, plants need to adapt to the changes in temperature and light, thus it is important to make the transfer as slow and smooth as possible. You should dedicate at least one week to the transition:
- Start by moving the plants outside in a shaded and wind protected place for a short time and gradually extend the amount of time that plants are outside, until they’re staying out all day.
- You can also help the plants to grow stronger seedlings by occasionally running your hand gently over the seedlings, simulating the wind.
- Make sure the soil is moist at all times during this period, but try to water them less/ less often and slowly reduce the fertiliser, if you use any.
- If possible, transplant on cloudy days or in the early morning, when the sun won’t be too harsh. You can also help the transition by using a partial shade for the first period.
- Younger plants with smaller roots adapt better to the new environment, thus transplant them as soon as the conditions outside allow it.
Remember also to prepare your soil for welcoming the new plants: get the right soil, peat moss, or coir and if needed a source of nutrient like compost or manure. If you grow in the garden, check that the soil is not too wet, make sure you remove weeds and get ready with mulch for protection from water transpiration.
Transplanting from hydroponics – tips for happy transition
Starting seeds indoors in hydroponics is a very good choice to start easy and clean. Some plants germinate much better with this method than in soil (e.g. some low germination rate chilies) and there are less chances of soil-borne diseases.
The transplanting however needs a little extra care as the plants need to adapt to a new completely environment after they have been moved. The roots especially need to grow thicker and longer to search for nutrients and water in the soil. So here are some tips on how to do it safely:
- If you can, transplant the sprout to a pot, even if the final destination is the outdoor garden. Choose a pot with a diameter of 10-15 cm to have space for root growth. If you are preparing for the summer balcony you can already use the pot you have chosen for them.
- Prepare a loose and well draining soil to reduce shock to the roots, and make it moist but not too wet to welcome your transplants.
- Just before transplanting water the plants. You can add a Vitamin B rich nutrient, to help roots grow in soil. You can also sprinkle the wet roots with dry soil.
- Make a hole big enough to fit all the roots or the pre-growing pod. Adding mycorrhiza (beneficial fungus) in the hole will help plants absorb nutrients from soil. Don’t put too much pressure on the roots while covering them with soil.
- Act calmly but fast to avoid roots shock; that means move your plants directly to the soil and don´t leave naked roots laying around exposed to light and air.
- Young sprouts adapt easier than older plants. If you are transplanting plants that have already grown quite big, consider cutting up to ⅓ of the leaves to reduce the amount of water and nutrients the plant needs to find in the soil.
- Water your seedling immediately after transplanting and then slowly start reducing the watering and fertiliser in the next few days. If you have a well draining medium, at the beginning you can still water quite often and remove the extra water. Over the days reduce the watering, until you only have to water when the top of soil is dry (this will take about 1-2 weeks).
- If the plant looks happy in soil, this is also the right time to gradually adapt the plant to the direct sunlight and the outdoor conditions as suggested earlier. At this point you are ready for place your pots on the balcony or transfer the plant to the garden.
- If you need to directly jump from hydroponic to garden, try to adapt your hydroponic plants, for instance by reducing watering and fertiliser and gradually expose the hydroponic plants to the sunlight and outdoor breeze. After you move the plants in soil, make sure to give plenty of water until they adapt to the new environment and still provide nutrients for a while. Try also to shade your plants at the beginning. All the tips given before are still valid!
After you have transplanted your plant from hydroponic to soil don’t panic if the leaves are yellowing or falling off (especially for bigger sprouts), just make sure the soil is wet and the direct sun is not too strong; they will recover. New leaves will emerge as the plant adapts in a couple of weeks.
How to equip your Plantui to start pre-growing seeds inside
Get ready in time with all what you need for pre-growing with your Plantui:
- The plantui smart garden 6 is the best option to start pre-growing seeds indoors as it can be equipped with a pre-growing tray fitting 12 seedlings.
- Our selection offers some plants which benefit from pre-growing and are easy to transplant outdoors: lettuce and other salads, kale, 2 different cherry tomatoes and chilies.
- The experimental capsules, meaning empty stoon wool plugs, are what you need when you choose your seeds from your favourite store.
And here are some more tips for creating an outdoor garden from your Plantui:
- Take advantage of the germination light to speed up the start of your seeds, but remember to add one height block for at least a few days before transplanting. The blue light that the plant will get after adding 1 heigh block strengthens the roots and this is very important for growing healthy plants in soil.
- The younger the better. You can transplant your plants as soon as they have few leaves and roots coming out from the stone wool pod. On average you can happily grow your plants in Plantui for 1 month before moving the plant outside.
- Cold resistant crops, like kale, can be moved earlier in the spring than fruit producing plants like tomatoes. If you start to pre-grow a mix of them, and move some out of the Plantui earlier, remember to cover the empty holes in the smart garden. You can also start a new plant in that hole, even if you have one height block, but the germination will be slower as the light is not ideal.
- Before moving the plant to the soil, make sure to leave only one plant per pod to ensure they have enough space to grow into full plants. You can try to remove the extra seedling holding them with tweezers from the base and slowly pull them up; if the full roots come out you can plant that too, but it’s not always the case.
- You need to remove the plastic holder, but the stone wool plug can be placed directly in soil. You can open up the plug a bit by cutting it with a scissor, but make sure not to damage the roots.
Last few things you need to know – as Plantui uses the hydroponic method to grow plants, you can use the tips given in this article and move the seedlings to a pot before planting them into the garden. If you move your plants directly from Plantui to the garden you can adapt them by unplugging your smart garden and moving it in the sun/outside, in this way the plants will get less water and get used to the sunlight. If the leaves are wilted in the evening make sure the plant gets water by reconnecting the device and manually activating the pump (keep your hand on the device for 15-20 seconds until the pump starts -you’ll hear it). Remember also to reduce the amount of fertiliser. You can for instance start to grow your seeds using only 2 l of water + 2 spoon of nutrient and 10 days before moving them out start adding to the plantui bowl water without nutrient.
Hope you feel ready to start your summer gardening adventure!
Martina & Plantui team