There are a number of good reasons for starting seeds indoors. I began seed starting indoors for two reasons. You can grow more varieties of your favorite plants instead of relying on what’s available at nurseries. Also, the seed germination rate is higher in a controlled environment than direct sowing outdoors.
Other reasons to start seeds indoors in trays is that growing from seed can save money. There is some expense for the indoor seed starting kit, but in the end it is cost effective. And lastly, one of the best reasons for seed starting indoors is that it is a challenge and a fulfilling experience. Here is how to grow plants from seed step by step.
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Indoor seed starting kit
For starting seeds indoors, you will need a seed starting setup – a cell tray kit, heat mat, lights and seed starting mix. Shop all my favorite supplies in my seed starting essentials guide here.
How to start seeds indoors?
Fill sterilized, plastic cell trays with seed starting mix that contains no soil. If using traditional mix, moisten it first. Try mixing it with water in a large clean container then fill the cells. It is difficult to wet and is messy so I found what I think is a better mix, Miracle-Gro Cactus, Palm, and Citrus Mix. It is easier to work with and gets good results. Fill the cell trays with mix, moisten it with a spray bottle or a very gentle shower of water.
How to grow plants from seed step by step
Next sow 2 to 3 seeds per cell. Plant seeds at the depth specified on the seed package. Some seeds need light to germinate and are placed on top of the mix. A very thin covering of vermiculite may be sprinkled on top, then mist with a spray bottle. If the seeds can be planted deeper, it is easy to just place them on top of media, then add mix on top and mist with water. Label each tray.
Add water to the bottom tray, just enough for the cell tray to absorb or wick up in a day or less. Put the cell tray in the holding tray and cover with the dome. A heat mat is how to germinate seeds quickly and effectively. Place the tray on a heat mat on a shelf with lights hanging a few inches above the cell tray.
Tips
Water only via the bottom tray, to deter disease. Add water to the bottom tray when it is dry.
Never allow the seed tray to sit in water for more than a day. Check it daily.
Seeds need 14-16 hours of light daily. Light should be just a few inches above the seed trays.
An outlet timer is convenient to operate lights automatically.
Remove the heat mat and the cover when almost all the seeds in a tray have germinated.
Plant the same type seeds in a tray because germination rates vary.
Rotate trays daily because the outer edges get less light.
Materials must be clean, washed with soap and sterilized with a solution of 1 part bleach to 10 parts water to deter disease.
If seedlings get leggy, they did not get enough light. They will fall over and do not recover.
A fan or gentle breeze can strengthen seedlings.
Thin and fertilize
Use sharp tipped pruners or scissors to thin seedlings to one plant per cell. Fertilize when seedlings have their second set of true leaves. Use a liquid, water soluble product at half strength. A natural product like fish emulsion is good but any nitrogen source works. Place a fan on seedlings once they have 2 to 3 sets of leaves to strengthen stems.
Potting up and hardening off
When roots are growing out of the bottom, pot up seedlings into an individual pot about 2-3 inches. Use fresh potting mix. Place them in a tray for carrying and continue to bottom water.
Hardening off is at least a week-long process of acclimating seedlings to outdoor conditions prior to planting outdoors. Move seedlings outside into shade during the day beginning with a couple hours and increase the time each day. The last two days place them in bright shade. Always bring seedlings indoors at sunset. Do not leave them out in rain or high wind.
When to start seeds indoors
Timing is everything in gardening. When to start seeds varies depending on the plant and your location. Seed packages may indicate a range of weeks before average last frost. Others may give no directions while some say to direct sow into the garden.
There are a number of vegetables and flowers that can be grown twice a year. In my Texas zone 8b, broccoli transplants can be set out mid-January through February and also mid-September through early November. The growing season in warm climates like Texas can be long, which means there is a long period of time to start seeds indoors, allowing for multiple sowings.
Research the plants you want to grow to learn when to seed indoors. Know the last and first average frost and freeze dates for your location. A soil thermometer is a handy tool because soil temperature is a factor for when cool and warm season plants thrive.
I’ve enjoyed seed starting indoors on my own for a few seasons. I have learned a lot doing it for myself, but I had some previous experience. A long time ago, my job at the Texas A&M greenhouses was to mix the seed starting media and prepare seed trays for the head propagator. And, I taught plant propagation to Master Gardener classes with the assistance of experienced Master Gardeners.
If it is your first time to start seeds indoors, good for you. It is a good idea to start small with just a few varieties and grow with your success. Relax, enjoy the experience and you’ll get better and more confident each season.
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