How to Start Seeds Indoors – A Guide

February 8, 2011

If you are new to starting seeds indoors, you will need to get a few things:

  • seed starting chart
  • A cheap 4′ workshop light and a set of 4′ cool and warm fluorescent lights (a must for those with cooler climates and shorter growing seasons). Don’t get the plant-specific lights as the regular ones are just as good. Alternate the cool and warm bulbs if you are putting more than one set of workshop lights side-by-side.
  • A timer set to turn on 14 hours and off for 10 hours a day (optional if you’re good at remembering).
  • A heating mat (optional, helps germinate harder/longer-to-germinate seeds like parsley and hot peppers)
  • Soilless seed starting mix
  • 72-cell seedling insert trays (breaks down into eight 9-cell packs)
  • Plastic propagation trays
  • Clear plastic domes
  • Used 1” plastic blinds
  • Sharpie
  • Oscillating fan (optional)
  • 4” pots
  • Potting soil
  • A black paint pen

Find out your last spring frost date and plug it into my seed starting chart (keep in mind that my chart is suited towards a USDA Zone 4 growing area, i.e., you’ll need to add more repetitions of sowing seeds if you’re in a longer sowing season). This will give you a schedule of when you should be starting indoors, direct sowing outdoors, transplanting, harvesting and succession sowing as well as sowing for a fall harvest. I just bought an informative book called The Week-by-Week Vegetable Gardening Handbook that also gives tips on other things you should be doing before, during and after the season. However, this book was written by gardeners in Massachusetts and may be skewed towards a shorter growing season.

Buy your seeds online for a larger selection. I mostly buy from Johnny’s Selected Seeds and from local companies. Check to see if there are gardening events in your area. Here in Canada, we have Seedy Saturday where gardeners swap seeds for free and buy from local companies. If you want to save your own seeds, buy open-pollinated varieties and not hybrids.

Don’t bother with Jiffy peat pellets (unless you really like them). I don’t like them as they don’t retain moisture as well, don’t break down in the soil and aren’t re-usable. Instead, get some quality soilless seed starting mix and dampen with water. Fill up your 9-cell inserts with the damp mix and put in your plastic trays. Sow your seeds, one or two seeds per cell, sowing twice as deep as the seed is long. Cut up the blinds into 0.5″ x 4″ lengths and label with a Sharpie to put in each cell. Cover the tray with the clear plastic dome as this will help keep moisture in. Place on a warm area or on your optional heating mat. If you have seeds that are difficult to germinate, try pre-sproutingthem.

Once your seeds sprout, remove the clear plastic dome and place them under the lights. The dome also helps the seedlings remove their seed coat as they push through the soil. If some of your seedlings still have their seed coats on, mist and cover with a narrow shot glass – within a day you should be able to remove the seed coat easily with your fingers. Suspend the lights so that they are two to three inches above the tallest sprout. Plug the lights into the optional timer. Every second day, run your hands over the tops of the seedlings to help them strengthen the stems – this will help prevent leggy seedlings. Or you can place an oscillating fan on them about 3′ away on low for an hour every other day.

Water seedlings from the bottom, not the top to help prevent damping off. I pour enough water in the tray for the seedlings to be standing in 1/3 of water. Remove any excess water from the plastic tray after 10 minutes. I usually water once a week.

Once your seedlings have outgrown their cell inserts, pot them up to 4″ pots with dampened potting soil. Use more cut up blinds to label with a Sharpie. You’ll want to start acclimatizing them to real indoor sunlight at this point. While still indoors, put them in indirect sunlight for a few hours a day. Build that up SLOWLY so that they can withstand full sun. This will take about a week. If you start noticing whitish spots on the leaves, you’ve left them too long in the sun and they now have sun damage.

A couple of weeks before you plant out in your garden, you will need to harden them off to the outdoors. Again, build that up SLOWLY as you don’t want to shock them. Put them outside in a shady, wind-free spot on a cloudy day for an hour or so. Build it up so that they can withstand full sun, rain and overnight temperatures. This takes a while and you’ll have to be patient. Keep an eye out for whitish spots and curling leaf edges as this will indicate sun and wind burn. Keep watering from the bottom. Try not to touch wet tomato leaves as this increases the risk of leaf mold.

Transplant into your garden and use a 6″ piece of blind to label the plant with a paint pen (don’t use a Sharpie for this as the sun will make the marking fade by the end of the season). Don’t fertilize for the first week as your seedlings will be in shock and will need time to settle into their new location.

Remember to succession sow seeds for a continuous supply of produce. Lettuce, radishes, spinach, bush beans, beets and carrots are good for this. Also start a fall harvest of peas, broccoli, cabbage, kale, summer squash, spinach and lettuce.

Also, buy an airtight food storage container to hold all of your seed packets to help keep them dry. Organize them in alphabetical order by Direct Sow, Vegetables, Herbs and Flowers. Keep an inventory if you want to be extra organized.

During winter, get in on seed exchanges or swaps in places like GardenWeb to trade your seeds and try out new stuff.

NOTE: if all this indoor/hardening off stuff sounds intimidating, try your hand at wintersowing, it’s easy and painless.

That’s pretty much all I can think of.  Let me know if anyone else has any tips for a new indoor sower.

(taken from a gardening forum post I wrote)


5 Responses to “How to Start Seeds Indoors – A Guide”

  1. Garden obsessed minds think alike? I just posted something about seed starting and saw yours with the calculator so have linked up. Always wonderful to see you up and garden blogging! I hope we’ll meet at the trade table soon.

  2. Nice guide! One suggestion: use plain pencil on the mini-blind plant tags instead of paint pen. It won’t fade or wash off, but you can rub it off with a bit of work if needed. Plus cheaper than a paint pen. =)

  3. Sandra Says:

    Thanks for the detailed instructions. I have been starting my plants under lights indoors for a couple of years and follow pretty much the same routine though you have given me a few new ideas! One thing you don’t mention and I am always trying to experiment with is how much and how often do you fertilize once the seedlings have been transplanted to 4 inch pots.

    • Kathy Says:

      No problem! I don’t fertilize until the second week of May (when the seedlings start hanging out outside 24/7) and then only twice or so before I put everything in on the long weekend.

  4. Aimee Says:

    Fantastic tips and thorough instructions here – thank you! I’m starting seeds indoors for the first time and have been researching DIY / inexpensive grow light set-ups – the workshop lights are a good idea.

    A friend who gets remnants of blinds for labeling plants just gave me some extra long pieces – perfect timing!

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