Once you’ve decided to start some of your seeds indoors, you’ll want to get together a plan for what comes next. In this getting started guide for starting seeds indoors, we'll cover:
- Planning
- Choosing your growing medium and soil
- Sowing seeds
- Watering tips
- Lighting tips
- Labeling
- Fertilizer - How and when to use
- Potting up
Tips for Starting Seeds Indoors
Planning
Planning is always your first step. Do you have a good space to start your seeds indoors? Some people have an extra room that they can dedicate to their new plants inside, while others start theirs out in a shed outside or in the garage. Make sure you’ve got plenty of room for your seeds and that you can keep them warm and sheltered. Consider how many outlets you’ll need for grow lights and heating pads, and how often you’ll be able to check on your plants.
Choose your growing medium & soil
Your seeds need a growing medium with a fine and loose texture that drains well.
Do not be tempted to reuse potting medium or to use soil from outside.
The indoor sprouting environment is also perfect for fungi and other diseases to flourish. Using a fresh soilless medium that you mix yourself or buy prepared ahead of time is easy and protects your seedlings from this danger.
You’ll also want to make sure your containers are sterilized if you’re reusing them for the same reasons.
Make Your Own Seed Starting Mix
Preparing your growing medium and sowing seeds
Moisten your chosen growing medium and fill your containers evenly. If using a flat, creating rows can keep the seedlings organized.
Plants that need to be planted more deeply will benefit from being grown in individual containers or cells.
Sow your seeds spaced out uniformly according to the instructions on your packages. Different seeds have different depth requirements, so make sure you give each seed the individualized attention it deserves.
Choose Reliable Heirloom Seeds
Watering tips
Water your seeds by misting them gently. A bottom watering system can be a useful way to keep the growing medium moist without washing the seeds away.
Whatever system you choose, make sure your seeds and soil are watered evenly and never fully saturated or waterlogged.
Place a humidity dome over your seeds to keep them appropriately moist for longer. Never place domed plants in direct sunlight. Keep an eye on your seeds and pull that dome off once they’ve sprouted to prevent damping off. Water according to the needs of each seed.
Lighting tips
Provide your seeds with the light and warmth they need to germinate properly. Heating mats and grow lights give your plants a head start on the growing season. Different seeds have different heat requirements, so make sure you take the time to make sure each heating pad is set to the right temperature for optimum germination.
Label your seeds
Don't forget to label each container so you know what you’re growing. Note plant variety and date planted on labels. Using the seed packets can help you to remember the needs of each plant in case you forget.
You’ll also want to date your seeds so you remember when you planted them. This will help you keep an eye on germination and make sure that everything is on track.
Give your young plants fertilizer
After seeds have germinated, they will need some fertilizer. Soilless mediums typically are devoid of any nutrients for the young seeds. Young tender seedlings can easily be damaged by too much fertilizer, so be careful.
Use half-strength fertilizer a few days after germination and watch your plants. After they are more established, you can follow the recommended schedule of your chosen fertilizer.
Pot up as needed
As your seedlings grow, you may have to “pot them up” or move them to a bigger container to give them more room to grow even before they’re ready to move outside. A larger container will allow the plant’s roots more room to grow without becoming rootbound or drying out.
How often you have to pot up depends on the size container you originally planted your seeds in, the type of plant, and how fast it grows.
Enjoy watching your seedlings grow from tiny seeds to thriving plants. As they grow, thin out your seeds as needed to give the strongest plants more room. It won’t be long until you’re hardening them off to move outside for the next stage in their life cycle!
Written by Teresa Chandler
How to Start Seeds Indoors: The Complete Guide
Hardening Off Plants: Toughen Up Your Babies for the Real World
FAQs
The most convenient type to use is one of the commercial soilless mixes (Jiffy-Mix, Pro-Mix, Redi-Earth, etc.) that contain peat moss, perlite, vermiculite, and usually some fertilizer (see Table 1 for a mix recipe). These are specially formulated for starting seeds indoors.
How many seeds per hole when starting seeds indoors? ›
Most seeds prefer a depth of about 2 times their length. The tiniest seeds can be sprinkled directly on the surface. Cover the seeds with a thin layer of soil. Plant about 3 seeds per hole (more if using older seeds) and once they germinate, thin down to leave only the strongest seedling.
When to put fan on seedlings indoors? ›
I keep the fans moving across the surface of seed trays throughout the eight weeks of their development. That's not absolutely necessary. You could opt to turn fans off once the seedlings have developed their first true leaves. I've just found the best success with continued air movement throughout the process.
What seeds should not be started indoors? ›
Seeds for Root Crops Should Not Be Started Indoors
For that reason, it's best to start root crops like carrots, beets, radishes, and even potatoes in the soil where they'll grow.
Should you soak seeds before planting indoors? ›
If you're storing and sowing seeds inside, they won't go through a cold winter, which some need to signify it's time to wake up and grow. To ensure high germination rates, wake seeds up, and potentially speed up the process, soak seeds before sowing them to soften and loosen that outer protective layer.
How deep should the hole be to plant a seed? ›
If you have don't have the packet, a good rule of thumb is to plant the seeds at a depth equal to twice their width or diameter (depending on seed shape). A pencil is a handy tool to make a hole and determine the correct depth. You can measure the point of the pencil ahead of time to denote a quarter or half inch.
How often do you water starting seeds indoors? ›
Most seedlings require water every day or every other day. First, check the soil moisture using your finger by checking the soil color near the drainage hole. If the soil feels or appears dry or brittle, irrigate thoroughly until water pours out of the bottom of the tray, then stop.
What happens if you plant too many seeds in one hole? ›
Q: Can you plant too many seeds in one spot? A: You can! However, you can always thin your multiple seeds that sprout seedlings after they sprout if needed. This will free up space for the ones you leave.
How long should seedlings stay under dome? ›
Humidity domes are meant to stay on the tray until the first sign of germination or once you begin to see the tray sprout. After this, remove the dome and place your trays under light, with proper air circulation. If brought under light too late, seedlings can get leggy.
Should you use a grow light to start seeds indoors? ›
The natural light from a window is seldom enough for good, strong seedling growth. They will usually stretch and lean towards the light and will not produce sturdy plants. Sowing seeds indoors under fluorescent lights is the easiest way for the home gardener to control growing conditions and grow healthy transplants.
You may be able to start seeds without artificial lighting, but seeds that need more time indoors, such as tomatoes and peppers, may become leggy without extra light. High-light areas can be warm, making plants dry out faster.
Do I need grow lights to start seeds indoors? ›
The natural light from a window is seldom enough for good, strong seedling growth. They will usually stretch and lean towards the light and will not produce sturdy plants. Sowing seeds indoors under fluorescent lights is the easiest way for the home gardener to control growing conditions and grow healthy transplants.
Can you use egg cartons to start seeds? ›
Gardening can feel like a very expensive activity sometimes, but starting seeds for spring planting doesn't have to be. You can use egg cartons as a seed-starting tray! Depending on the type of carton you have, you can even cut apart the individual sections and plant them, as the carton will biodegrade.
Do I need a heat mat to start seeds? ›
Answer: Most seeds germinate best when the medium temperature is consistently 70 to 75 degrees Fahrenheit. Placing containers in a warm location in the house, such as on top of a radiator or near a heat register, usually works fine.
Which vegetables should be started indoors? ›
Crops that are best started indoors include broccoli, brussels sprouts, cabbage, and tomatoes. Those with slower root development, like cauliflower, celery, eggplant, and peppers, should also be started indoors.
