The hardening off process is an important part of starting seeds indoors and successfully transplanting them to your garden. Do not miss this crucial step! Let’s set the stage: Your seedlings are growing, the weather is getting warmer, and you’re ready to start growing your garden. But before you transplant those tender seedlings outside, remember– while you might enjoy a warm, sunny day for transplanting seedlings outside, sunshine can be the worst thing for your seedlings. Keep reading to learn why!
Seedlings raised in the comfort of a greenhouse, kitchen windowsill or laundry room under the faux sunshine of fluorescent lights, have enjoyed a life of leisure. After some weeks having lazed around with free room, board, and water without a care in the world… they are not prepared for full sunlight, wind and rain.
Like training for a marathon or heading to Hawaii in January, you benefit from a little preparation. Seedlings, too. Which means you need to put them through training… of sorts.
While couch potato seedlings often collapse (face plant?) if you transplant them on a sunny day, cold and wet conditions can spell trouble, too. Fortunately, my 40 years experience starting seeds and growing a large variety of fruits, vegetables, and flowers in my garden here in Kodiak, Alaska has cemented my success transferring seedlings outdoors.
Why Hardening Off is Essential
“Hardening off” is an awkward term that applies to the process of preparing your seedlings by gradually acclimating them to wind, heat, cool nights, and real rain. Transplanting seedlings out in the garden can be the most stressful point in their lives– and it’s also the most critical for ensuring strong, healthy plants! This goes for all bedding plants: flowers, vegetables and herbs.
Skipping the hardening off process for seedlings makes them susceptible to:
- Bolt
- Go to seed
- Succumb to pest invasions like aphids
- Die
Steps to Harden Off Your Seedlings
Here’s a step-by-step guide for hardening off plants:
- Begin a week or two before you plan to set plants in their permanent outdoor homes. Set them outdoors in a protected area, out of the direct wind and sun. Leave them for an hour or so, then bring them back indoors.
- Repeat the process, gradually increasing their outdoor time to 3 hours, then a morning, then a full day and night.
- Keep seedlings damp, but not swimming.
- If frost, heavy rain, or windy conditions are in the forecast, set them in a protected place.
Protip: Use covers or mini-hoops to further protect plants as outdoor conditions improve.
This brings me to the next burning question: What weather is best to transplant outdoors?
Watch the weather. You’re shooting for a cloudy day. Again, you might prefer sunshine, but plants do not. If clear skies are in the forecast, then aim for the coolness of an evening.
Signs Your Seedlings are Ready for Transplanting
Once your plant is showing its “true leaves,” it is ready for transplant to a larger container. Timing your seedlings is everything to avoid killing your seedlings off from transplant shock. Following the above guide ensures the hardening off process is completed and the young plants are ready for outside. Add this blog post to your reading list: How to Time the Transplant of Your Seedlings
