How to Transition Plants from Inside to Outside + Our Preferred Method to Save Time in the Garden!

We wish we knew how important this step was when we first started growing from seeds indoors.

We admit, the first time we grew tomatoes indoors, we directly exposed the plants to the outdoor sun, they didn’t make it. Lesson learned, and we found out about an important step called “Plant Hardening”

Hardening off is an important step when transitioning plants grown indoors to their outdoor environment. Without this process, plants can experience shock, sunburn, or won’t survive when exposed to the harsher conditions of the outdoors.

There are many steps to do this, some even recommend to expose your plants for only an hour for the first day. But it can be time consuming to keep moving plants inside and outside each day.

Eventually, we ended up using a tarp and changed our process. Instead of constantly moving the plant, we kept them in one spot and placed a tarp over them. This saved us time and only brought the plants inside if there is an unexpected frost warning.

Our preferred method: Using a tarp or shade cloth

If moving plants in and out daily feels too time consuming, we recommend using a tarp or shade cloth to simplify the hardening off process. This is the method we use, and it has proven to be both effective and efficient. 

How it works:

1. Choose a stable outdoor spot: Select a location where your plants can remain throughout the hardening off process. If possible, this spot should initially be shaded and protected from strong winds.
2. Set up a tarp or shade cloth:
   • Cover your plants with a tarp or shade cloth to shield them from direct sunlight during Day 1 and 2 day.
   • The cover acts as a buffer, reducing the intensity of sunlight and protecting plants from sudden exposure to outdoor conditions.
3. Gradually remove the cover:
   • By Day 3 and 4, gradually remove the tarp or shade cloth during morning or late afternoon sun periods each day. 
   • By Day 5 to 7, your plants should be ready to handle full sun exposure.
4. Water well during this process and open air helps them adjust much faster.
5. After this process, they can now be transplanted in their final spot.
6. Monitor weather conditions: If there’s an unexpected frost warning or extreme weather, bring the plants indoors.

Why we love this method:

• It eliminates the need to move plants in and out daily, saving time and effort.
• Plants remain in one spot, reducing the risk of damage from frequent handling.
• It’s especially useful for gardeners with large numbers of seedlings or limited indoor space.

Step-by-Step hardening off process (Traditional method)

For those who prefer the traditional approach, here’s a detailed guide to hardening off plants by gradually increasing their exposure to outdoor conditions:

Day 1-2: Start with full shade

• Place your plants in a fully shaded outdoor location where they are protected from direct sunlight.
• Leave them outside for 1-2 hours on the first day, gradually increasing the time to 3-4 hours by the second day.
• Keep them protected from strong wind or rain.

Day 3-4: Introduce morning or late afternoon sun

• Move your plants to a spot where they can receive morning sunlight or late afternoon sunlight. These times of day are gentler on plants as the sun’s rays are less intense.
• Gradually increase exposure time by 1-2 hours per day. Monitor plants for signs of stress, such as wilting or leaf discolouration.

Day 5: Evaluate and adjust

• Check your plants for signs of sunburn
• If plants are struggling, continue limiting sun exposure to the morning or late afternoon for another day or two.
• If plants are thriving (green and upright), begin exposing them to more sunlight.

Day 6-7: Full sun

• By now, plants should be ready to handle full sun exposure. Place them in a spot where they receive full sun for increasing durations. Start with 4-6 hours and gradually work up to a full day.
• Ensure they are watered well, as outdoor conditions can dry soil faster than indoor environments.

After Day 7: Transplant to final location

• Once your plants have successfully acclimated to outdoor conditions, they are ready to be transplanted into their final growing spot

Hardening off by growing zone

Since different growing zones have unique climates, it’s essential to adjust the process based on your zone:

Zones 3-5 (Cool Climates): 

• Begin hardening off later in spring when nighttime temperatures are consistently above freezing. Be extra cautious of late frosts.
• Use row covers or frost blankets if temperatures unexpectedly drop.

Zones 6-8 (Moderate Climates):

• These zones typically have a longer growing season, making it easier to harden off plants in early spring. Monitor for sudden temperature swings, especially in transitional seasons.

Zones 9-11 (Warm Climates):

• Plants grown indoors here may need to adjust to intense sunlight rather than cold. Gradually increase sunlight exposure to avoid sunburn, as the sun’s rays can be harsh even in spring.

Alternative hardening off methods

If neither the tarp method nor the traditional approach suits your needs, here are a couple of other options:

Cold frame method

• A cold frame is a small, enclosed structure with a transparent lid that traps heat and protects plants from wind and frost.
• Start by leaving the lid slightly open during the day to allow airflow and adjust plants to outdoor temperatures.
• Over the course of a week, gradually open the lid wider and leave it open for longer periods until plants are fully acclimated.

Partly cloudy days

• Some gardeners prefer to start the hardening-off process on partly cloudy days. The diffused sunlight is gentler on plants, making it easier for them to adjust.
• Gradually increase exposure to direct sunlight as the weather clears.

Tips for success

• Check the weather: Always monitor the weather for unexpected frost or storms. Bring plants indoors or use protective covers if needed.
• Water regularly: Keep the soil consistently moist but not waterlogged. Plants dry out faster outdoors due to wind and sun.
• Watch for stress: Signs of stress include wilting, drooping, or sunburned leaves. Adjust exposure as needed to prevent damage.

Why hardening off is worth It

Taking the time to harden off your plants ensures they thrive in their outdoor environment. Plants that undergo this process are more robust, resilient, and better equipped to handle the outdoors. Whether you use the tarp method, the traditional approach, or another alternative, the payoff is healthier, stronger plants that are ready to flourish in your garden. Just make sure to do this process when the weather is warm and safe from frost.

Let’s grow and eat more plants!