Hardening Off seed starting transplanting seedlings wintersown

Seed Starting – Warm Weather Crops – Adapting the Wintersown Method – Things You Need to Know

I’ve described my modifications of the wintersown method (that I use to get an early start on warm weather crops) in many posts, especially in my recent post and the one at the end of February. But, I’ve received questions from readers that would indicate a misunderstanding of my particular adaptation of wintersown.

The wintersown method of planting in jugs, taping them up, and setting them outside until the weather is suitable for germination, was originally intended for cold weather plants. In other words, seedlings that would be hardy and could take the cold after they germinated and then experienced a change to severe cold.

Altering the Concept of Wintersown

If one wants to get an early start on tender warm weather seedlings like tomatoes, certain adjustments have to be made in the “wintersown” method if you want to assure the seedlings get off to a good start and don’t die from the cold. Thus, I’ve taken the concept of wintersown and adapted it (altered it or changed it a bit using the knowledge of what the plants like) to grow not only my cold weather plants, but to grow my warm weather plants.

A Reason for the Alteration

As I’ve explained previously, the reason for my doing this is because I have neither sufficient room or light for plants indoors. The other reason is to get an earlier start with plants than what I would have if I started the seed outside and had to wait until the weather warmed. (And by the way, I did just that for many years when I first started gardening.)

Short Growing Seasons and Cold into June

Many parts of the country have cold weather until June. Their growing season is very short. Since my method somewhat dependent on the weather, it may not give folks in these colder/short season areas enough time to get the larger seedlings they want for transplanting to the garden to give them a jump on the weather. Anyone in those areas who has the time, space, and lighting may want to start and grow inside and then harden off the larger seedlings when the weather allows.

Starting Warm Weather Crops with My Adaptation of Wintersown

I start the seeds of tomatoes, peppers and eggplant (warm weather plants) inside where temperatures are 60 to 70 degrees F. The optimum soil temperature for germination of these plants is about 77 degrees F although they do well at 68 degrees F.

KEEP IN MIND WHEN YOU PLANT ANYTHING, that every seed has a certain optimum soil temperature for germination.

The percentage of germination will usually decrease greatly as the temperature gets further away from the optimum daytime soil temperature the seed likes for germination. And/or, it will take the seed much long to germinate.

For example, assuming that the seed is fresh:

  • 90% germination rate can be expected from onion seed planted when daytime soil temperatures are about 32 degrees F. But they’ll take about 136 days to germinate! Onion seed, planted when the daytime soil temperature is 68 degrees F, germinate in about 5 days at a germination rate of 99%.
  • 1% germination rate can be expected from peppers planted when temperatures are about 50 degrees F. Pepper seed, planted when the daytime soil temps are 77 degrees F, germinate in about 8 days with a germination rate of about 98%.

You can find this information by copying and pasting this URL into your browser: http://tomclothier.hort.net/ Then scroll and click on Seed Germination versus soil Temperature.

Seed Not Germinating?

If you’re not getting the rate (percentage of) germination that you think you should be getting, get a soil thermometer and check the daytime temperature of the grow mix.

Seed not cured properly or not stored properly can be responsible for poor germination.  Seed that is old can also be responsible.

The minute they germinate, I put the tops back on and place them outdoors under another cold frame IF temperatures are below 50 degrees.

By being outside they get the light they need. Another benefit from this is: they’re hardened off almost from day one!

Different Situations, Conditions, and Reasons

Everyone has slightly different situations, conditions and reasons for doing things. For me, there would be no reason to plant tomatoes in a jug, tape it closed, and place them outdoors in the dead of winter.

They’re not going to germinate until temperatures rise. These plants love warm weather. They germinate in the warmth and they grow in the warmth.

Warm weather plants like tomatoes don’t really like it below 50 degrees, but they can live until it drops to 32. If they do germinate and temperatures in the jug fall to 32 degrees or less, they’re finished.  You don’t have to guess about giving these plants protection from freezing weather.  You either protect them, or they die.

Judging When to Start Seed

In warmer winters, I’ve started tomatoes, peppers, and eggplant as early as March 1st. This year, because of the cold, I waited until April 1st to plant in the jugs. The seedlings are still tiny but everything looks healthy. My guess, based on what has happened in prior years, is that when temperatures get warmer these tiny little seedlings will take off and begin to grow.

If you have a green house or if you have the proper light set up inside your home for seedlings to grow, you can grow earlier with much success. And of course, you have to have the space to care for them when you pot up as they grow. And it’s possible that for all this effort that you may get “fruit” a week or so earlier than I will.

How About Cucumbers and Squash?

Plants like cucumbers and squash grow very quickly.  Most of the time they are direct seeded into the garden.    If you want to start the seed in a flat or container you can, but they will be ready (with the right temperatures) to transplant much more quickly than tomatoes, peppers and eggplant.

Final Thoughts

Be aware of thoughts caused by the subtle brainwashing in our society. We, as a society, are so use to seeing warm weather plants for sale in April (even if it’s 40 degrees outside), that it’s easy to think warm weather plants are suppose to be lush and green and grow in April even if conditions are not favorable.

A good part of being successful with any kind of seed starting program is to know under what conditions those seeds and the seedlings they turn into would thrive.

Best of luck, keep planting, and let me know if you still have questions.


Related Posts:

Warm Weather Crops and the Winter Sown Method

Wintersown Variables – A Readers Questions – Natures Principles


All content including photos is copyright by TendingMyGarden.com.  All Rights Reserved.


  • I used this method to start my tomatoes, peppers, basil, eggplant, chamomile, and wormwood this spring. Usually I start seed indoors under the lights. This year I started them in the milk jugs indoors at the same time I usually do–mid-March for Middle Tennesee. After they germinated, I moved them out to a sunny covered porch with southern exposure. At night, if it was going to dip below freezing, I brought them in. Another thing I did different this year is using a mix of 3/4 organic seed starting mix to 1/4 bagged organic potting mix that contained worm castings to start all the seeds in.

    This year I’ve had the best luck with my starts and I used no indoor lighting! They were sturdy-stemmed and hardy. All are in the garden and doing well except for the eggplant, which I’m going to plant a little later this year to see if I can avoid whatever eats the leaves to “mesh” early in the season.

  • Thanks for this great report Betty. I too love this method because of the sturdy seedlings that result from it.
    More than likely it’s flea beetles that are eating your eggplant leaves to “mesh.” I can’t put them in the ground until they get some size on them or the flea beetles demolish them.

  • Hi Theresa
    As an experiment I took my first 3 Mortgage Lifter tomato plants out of the greenhouse & transplanted them (much earlier than usual) to the garden. It’s been so unseasonably warm at night here in Hyampom (CA) that I felt justified. I’ll “jug” them up if I suspect a temp below 50 degrees, tho. Am going to transplant 3 Cherokee Purples tomorrow & 3 more of the others daily til gone (about 45 heirlooms in all). I’ll let you know the results.
    Cheers, Dick Messenger

  • Dick, have you grown Mortgage Lifters previously. If so can you share some details on how they did?
    I’m growing them for the first time this year because Sandra (reader in Maryland) spoke so highly of them.

    In spite of the fact that I thought to wait until mid May to plant any tomatoes in the garden, I looked at the nice 10 day forecast with temperatures above 50 and decided to put in a few of the larger seedlings. Saved me from having to pot up to the next size.

    Let me know too how your Cherokee Purples do. I’ve tried those and they didn’t do well for me. Seems certain tomatoes like certain conditions and if you have those conditions they do great.

    Thanks for commenting, Dick.

  • Theresa, I live in Central Florida and my only good garden is a fall garden. My question is when should I start my seeds to plant in August or September. I do not have room for setting up racks and lights to start seeds inside, outside is very warm but my seedlings get leggy. Is there anything I can do about that? We have very hot Octobers, should I cover my garden with sheets to guard the plants from such heat? I would love to grow gallon size tomato plants to put into the garden, when should I start those seeds?
    So many questions……….thanks, Bonnie

  • Bonnie, when you start your seed depends on what you want to plant.
    Sounds like you’ve gardened for a while — so you probably have a feel for how long it takes your favorite veggies to reach transplant stage. If you don’t, start “doing” and keep a few notes for next year.

    I’m able to start a tomato plant if the weather is right and put it in the garden in 3 or 4 weeks. (It’s a rather small transplant at that stage.) When folks start tomatoes for early spring planting here in Va. they usually grow them 6 to 8 weeks before planting. So as you can see, times can vary.

    For those gallon size tomato plants you want – you’ll probably need 8 to 12 weeks.

    If your seedlings are outside in nature’s light, they should not be leggy unless you have them where they can’t get enough sun. The only time I’ve had leggy seedling outside, is when I let the plants outgrow the pot.

    By covering your garden with sheets — I am assuming you mean set up the sheets as shade.
    Some type of shade covering is good in severe heat.

    Hope this helps.

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