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planting seedlings indoors

Establishing indoor seedlings gives you a jump-start on food production. A suitable container such as a seed starting tray or plastic cell from an egg carton is key for successful seed planting; they should be sterile enough to prevent soil-borne disease from spreading through their environment.

Staying consistent in terms of moisture is key when germinating seeds; use misting to achieve an equal distribution across your soil surface if necessary.


Seeds require a warm but not hot temperature in order to thrive and grow, or else they risk never sprouting at all. On the other hand, too warm temperatures could make them leggy or cause them to drop altogether. For optimal results, try to find a cool room within your house or garage where germination and starting seedlings is optimal – temperatures in the high 60s should provide ideal germination and growth conditions.

Once the seeds have germinated, they must be transferred into a larger container. A sterile seed-starting mix is ideal, though anything that holds moisture well and allows fine new roots to push through will suffice. Avoid mixes that contain too many dense or large clumps of soil that clog the roots preventing oxygen reaching them – light fluffy potting mixes make transplanting simpler; Burpee offers various solutions such as compressed coir pellets that expand in water as well as loose bags of seed starting formula

As the next step in their growth and maturation, seedlings need adequate lighting. A south-facing window or timed lamp are excellent ways of providing adequate illumination; grow lights should also be set just above seedlings so as to adjust with them as they grow.

Before transplanting seedlings into the garden, depending on their species you may need to harden off their seedlings by gradually exposing them to outdoor conditions over a seven to 14-day period. Each day move them gradually outside into a shady spot while sheltering them from sun and wind – returning indoors every evening if they become cold or damp.

Once seedlings reach two to three inches tall, it’s time to thin them out. Select only healthy and strong-looking seedlings to keep, while cutting away the others with scissors or gardening gloves – this will prevent overcrowding, which may result in leggy seedlings or disease outbreak. Once two sets of leaves have developed, begin fertilizing weekly using half strength organic liquid fertilizer for best results.


Some seeds require ample light for optimal development, such as fluorescent grow lights or an unobstructed window in your house. Consult the seed package for specific instructions regarding light requirements as well as recommended soil types to achieve the best results.

As soon as seeds are planted, they should be lightly covered with a fine-grained, free-draining seed-starting mix that drains quickly. Water the mixture until moistened throughout. If using a kit with lids for air circulation purposes, loosen their grip until your seeds sprout – but remove after that!

As your seeds germinate, they will emerge through the potting mix like little green leaves with stems – these cotyledons serve as food sources until their true leaves develop. Once half of your seeds have sprouted, remove the humidity dome or plastic covering and move your containers to a sunny area in your house.

If you’re growing tomatoes or other plants that require ample light, fluorescent lights may provide enough illumination for seedlings to flourish. Some kits come equipped with them; otherwise you can purchase single fluorescent grow-light fixtures at a reasonable cost.

Keep in mind that the light you give seedlings should be low-heat to protect their delicate roots from overexposure to heat. Also, the temperature inside your house could exceed the ideal seed germination temperatures recommended on their seed packets and cause too rapid of an increase in growth before being ready for transplanting outdoors.

As your seedlings continue to develop, they will require periodic watering from underneath using either a mister or turkey baster in order to prevent dislocating seeds and seedlings or encouraging mold growth. Most sunny locations should only require daily or twice weekly watering of seedlings.


As seeds germinate, they require moist conditions without becoming waterlogged and leading to their death. Finding an equilibrium where soil stays moist but not saturated can be accomplished by misting trays of seeds with water or placing them inside plastic bags or glass/plexiglass covers; once sprouted seeds emerge they should be exposed to light for proper air circulation and visibility.

After the seedlings have germinated and reached 1/2-inch tall sprouts, they require bright light for continued development. Place the trays near a sunny window or use heating mats designed specifically for seed starting – these provide gentle heat about 10 degrees warmer than ambient air to accelerate germination and growth of seedlings. Once their cotyledons (leaflike structures attached to seeds) begin withering away, remove from heat mats and move them to a bright location.

Maintaining moisture in the planting mix is vital to prevent seedlings from growing too tall for available light, or becoming leggy, which leads to leggy seedlings. Generally, planting mix should be moist but not soggy; crumbly yet non-gloppy in texture should suffice. Once seedlings have established themselves, liquid fertilizer diluted at 1/4 strength should be fed regularly to them so as not to overwhelm their development.

Once your seedlings have reached the size you desire, it’s time to plant them outside. In order to ease their transition to outdoor living conditions and help them adjust more easily over time – this process is known as hardening off – it is particularly essential when planting tomato plants as their sensitivity to cold temperatures requires extra care during hardening off. You can help by lightly running your fingers over the leaves to simulate wind, which helps the plant adapt and survive being placed outdoors.


Seedlings require plenty of water when first starting out, but once they develop true leaves (known as “true” leaves) they can access nutrients via photosynthesis and fertilize themselves through photosynthesis. At this stage it’s time to begin fertilization – general purpose liquid or water-soluble fertilizers work fine while those that contain high concentrations of phosphorous such as 1-2-1 N-P-K ratio fertilizers will provide more benefit for seedling growth. Watering from below will prevent cooling the soil or dislodging seedlings while watering from the bottom is best practice to protect their seedlings’ roots.

Many gardeners mistakenly assume that young seedlings require supplemented plant food in order to thrive, when in fact they’re capable of feeding themselves up until a certain point. It is important that gardeners know when it is safe to discontinue giving fertilizer since too much may hinder growth or even result in death of these tender seedlings.

Fertilizer is most beneficial during the germination phase, so most gardeners use specially-formulated starter fertilizer to get their seeds started. Once sprouted and developing true leaves, you can switch over to regular low-strength fertilizer applications: once every few weeks apply a solution of water with liquid or water-soluble plant food mixed at 1/4 strength concentration; alternatively you may simply water your crops as usual when needed.

Prior to transplanting seedlings outdoors, it is vitally important that they receive sufficient light. Without gradual exposure to their surroundings or being “hardened off”, sudden fluctuations in temperature, light, and wind may weaken or kill them altogether.

As part of the hardening process, set seedlings out in a shaded spot for several hours each day in warmer weather and increase exposure as temperatures and light conditions begin to match those inside the home. This allows seedlings to get used to living outdoors before being transplanted into their gardens – use the Planting Calendar to find out when it’s safe!

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