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  1. Home
  2. Grow Your Own Fruit & Veg
  3. From Fragile to Flourishing: How to Harden Off Seedlings

From Fragile to Flourishing: How to Harden Off Seedlings

There are several things gardeners must consider when taking their fruit & veggie garden from seed to harvest. One of the most crucial, that new inexperienced gardeners may not be familiar with, is how to harden off seedlings. When growing from seeds to seedlings indoors, before you can begin planting you must give your seedlings time to adjust to being outside all day. If you fail to do this, then you will not allow your plants the opportunity to thrive. So, to give them the best chance of taking root and surviving, just follow the simple steps laid out below. Before you know it you’ll be looking forward to a season filled with fabulous fresh produce.

Before you can plant your seedlings outside, you’ll need to prepare them properly

Why do seedlings need to be hardened off?

Hardening off is the process of toughening up tender plants to prepare them for life outdoors. You do this by slowly acclimating your plants, getting them used to direct sun and harsher conditions by allowing them to spend time outdoors before planting. Don’t put tender seedlings outdoors! If you fail to get your plants ready for the outdoor conditions then they may experience transplant shock when transplanted into the garden. Transplant shock occurs when plants suddenly find themselves in a new, unfamiliar environment. It can cause their leaves to wilt, no new roots to take hold and your plant may even die. That’s why the process of hardening off seedlings before transplanting is so important. 

Keep in mind that hardening off your plants is only necessary if you have grown them from seed and raised indoors. If you purchase nursery plants, they will already have been hardened off. However, if you’re worried about this you can always just ask the seller to make sure.

When should you harden off seedlings? 

You should begin the hardening off process when you notice that your plant has developed a sturdy stem and root system and has a good growth of leaves above the soil. The specific time that this type of growth takes will vary from plant to plant, so there isn’t a ‘one size fits all’ answer. However, if you wait to see this growth and feel confident that the root system has properly developed, feel free to follow the next steps and get your young plants ready to move outside.

Hardening off seedlings will help get them accustomed to direct sunlight

How to harden off seedlings

Step 1: Slowly transition outdoors

As mentioned, your plants need time to acclimatise to harsher outdoor conditions before they move to their permanent location in the garden. To acclimate your seedlings take them out into a shaded, sheltered area and allow them to sit for a few hours. Make sure you don’t choose a windy day or when temperatures are too high/low. You will want to minimise the stress on your fragile fruit or vegetable seedlings. This exercise will introduce them to the idea of growing outdoors without overwhelming them. Remember that your plant is a living, breathing organism and a slow and steady approach is best when hardening off your seedlings.

Step 2: Protect them from any harsh weather

Shielding your young seedlings from any wind or rain is important in the first few days when you harden off plants. However, you can gradually take tender seedlings outdoors on windy days to continue to harden them. Though when it comes to harsher conditions like frost, hail or strong winds extra measures must be undertaken to protect your delicate seedlings. Invest in a covering to keep them protected. This will also serve to protect your seedlings from animals, so it’s a worthwhile investment. Remain vigilant and if you notice a drastic change in conditions you can quickly move the seedlings inside again.

Use a covering to protect your seedlings from snow and strong winds

Step 3: Increase exposure

After the first step having left your seedling outside for a few hours, it’s time to gradually increase their exposure to the elements over the next week. Extend the duration of time they spend outdoors by a few hours each day. You’ll also need to slowly adjust the area where they have been sitting, gradually increasing their exposure to the wind and sun.

Step 4: Increase light intensity

After you initially kept your plants in a well-shaded area or chose to put them out only on a cloudy day, you can now move plants gradually into direct sunlight. Slowly move them into areas with partial sun, working their way up to full sun exposure. This will help them to become more resilient and is a great way to harden them.

Step 5: Repeat for 7-10 days

The hardening off period should last between 7-10 days. Simply follow the above steps each day, extending the time they spend outside and getting them used to the conditions. Take them in each night to ensure they are protected, this step will come later.

Step 6: Adjust watering levels

Outdoor environments tend to dry out soil much quicker than what your plants have been accustomed to while growing indoors. So, as your seedlings are hardened in the elements adjust your watering routine. Carefully check their soil with your finger every few hours. If it’s dry to the touch increase the amount of water it receives. Be careful not to overdo it, as you don’t want your plant to become waterlogged. 

Your seedlings will need more water during the hardening off period

Step 7: Leave out overnight

Just before you are ready to finally plant your seedlings outside, keep them out in your garden overnight. This will allow them to get used to the drop in temperature before being planted. Though make sure to check the forecast, you won’t want to put them out during a frost.

Step 8: Time to transplant!

Congrats, you’re now ready to plant your seedlings directly outside! If you have carefully followed all of the above steps, they should have no problem taking root and thriving in outdoor conditions. 

Now that your seedlings have ben hardened off, they’re ready for planting!

What’s next?

Remember, if you are buying seedlings from garden centres or from us online, this process is not necessary. However, if you are starting your plant from seeds, these are the steps you will need to take. If you’re still stuck on whether to raise your plant from seeds or seedlings you can check out our previous post. Or, if you have any more questions, don’t hesitate to reach out to us on social media (@gardeningexpress), we would love to hear from you!

Keep an eye out on our knowledge hub for even more step-by-step guides on how to create the perfect fruit and vegetable garden. We’ll be covering everything from what tools you’ll need to companion planting.

Updated on January 29, 2024

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