It is spring, and the weather is getting warmer. If your seedlings are big enough and the weather is favorable it might be the right time to harden them! In this article, I will answer some of the most asked questions regarding seedlings and their transitioning from the indoors to the outdoors.
Plant hardening is a process of acclimatization of the plants, and seedlings. It is a transition process of the plant from a protected and controlled indoor environment to a harsh, uncontrolled environment outdoors. It is exposing the plants gradually to temperatures, sun exposure, wind, and rain.
Is it necessary to harden off plants?
Yes, it is necessary to harden off the plants before they are transplanted directly to their permanent place outdoors. By exposing the tender and protected plants gradually to the outdoor environments and climate conditions, the plants are being helped to acclimatize and use harsh sun exposure and other natural elements. By this gradual exposure the plants become tougher and more weather resistant and face the transplant shock better.
What happens if the plants are not hardened off?
If the plants are not hardened off, they might face a harsh transplant shock which can lead some of the tender seedlings to a slow recovery, set back their growth, and some plants might not recover. Some plants might get sunburned. Plants might recover from sunburn but their growth will be slowed down which might lead to a few weeks of recovery rather than growing, maturing, and preparing for harvest. This will delay your harvest. Some plants might not recover at all.
Why do plants need to be hardened off?
The plants need to be hardened off to help them gradually adjust to the outdoors natural elements and to toughen up. By starting the seedlings indoors, they are in an ideal environment and do not need to toughen up because indoors the plants do not face the harsh natural sun with different intensities and temperatures. The plants do not face the wind or harsh rain. By gradually exposing the tender plants to the various elements, the plants can adjust and toughen up before they are placed outdoors permanently. Allowing the plants to toughen up, they will be able to withstand the various elements better and pass the transplanting phase much faster. Once the seedlings are hardened off, they are fully ready to be planted outdoors and thus continue their growth smoothly. If the plants are not hardened off, they will face a transplant shock and instead of putting all their energy into growth, maturing, and fruit production, their energy will be put into adjusting themselves and recovering from the shock.
If you want your plants to continue growing smoothly after being transplanted outdoors, I strongly recommend hardening them off, so they have the best chance to just continue growing and bring fruit at the right time.
How long should hardening off last for most seedlings?
Most seedlings take about one to two weeks to harden off. Seedlings can be ready to be planted outdoors after a week of hardening off if the weather is favorable. However, if the weather is not favorable and has a dramatic drop in temperatures or an increase in rain, it can take up to two weeks to harden the plants off.
If your seedlings will still face frost after the transplanting, plan to protect the plants if they needed it by covering them when occasional frost happens. You can help your seedlings face frost by covering them with frost cover. I use a fleece garden cover for protection. A plastic cover or a tarp overnight can be used as well. Seedlings can be also protected by sheets of newspapers layered over them, but the wind might blow them off. Ensure the protection is attached well to the ground so the wind does not move it.
At what temperature should I harden off the seedlings?
Cool-weather seedlings can be hardened off at consistent temperatures of 45F and above. Warm-weather seedlings can be hardened off at consistent temperatures of 60F and above. Do not harden off the seedlings at freezing temperatures.
When should seedlings be hardened?
Begin hardening off the plants for about a week or two before transplanting them outdoors. Most seedlings need at least a week to harden off if the weather is favorable.
How to harden off the seedlings?
Start the hardening-off phase by bringing the seedlings out only for a couple of hours on the first day. Place the seedlings in the shade for a few hours. Then bring them indoors again. The next day increases the hours outdoors in the shade. Each day increases the outdoor exposure and adds on the sun exposure. Increase sun exposure daily as well. Check the seedlings are doing while being exposed outdoors for adjustments needed. Keep the seedlings well-watered as they are exposed to the sun. Since the root system is confined in the seed trays, they have nowhere else to get water from but your provision. Keep the seedlings well-hydrated during this transitioning phase.
When are the seedlings ready to be hardened off?
The seedlings are ready for hardening when they have at least two sets of true leaves and the root system is large enough to be able to hold the soil around them well.
How big should seedlings be before transplanting?
The easiest way to tell the seedlings are ready to be transplanted outdoors is when they have at least two sets of true leaves and their root system is large and strong enough to hold the soil around them. You can gently pull the seedling out of the seed cell and if the roots are large and hold the soil well around them, and there are two sets of true leaves, you can start hardening them off, and then transplant them outdoors.
How long can seedlings stay in trays?
The seedlings can stay in the seed tray as long as their root system has enough space to grow into. When the roots start to peak out of the seed tray or start to grow into a circle at the bottom of the tray, it is time to transplant the seedlings. The seedlings can be transplanted into a larger pot if the weather outside is not favorable. The seedlings can be handed off and then transplanted outdoors in their permanent place.
In conclusion, do not rush the hardening-off phase, and give your seedlings enough time to adjust sufficiently before they are planted outdoors. Plant them outdoors when the weather is favorable for the plants and be ready to protect them if they need protection.
A GOOD READ
Is April too late to start seedlings in zone 6?
What seedlings to plant outdoors in April in zone 6
The best way to start seeds outside
How to start seeds and care for seedlings
What do hardiness zones mean and how to determine yours
