Breaking Garden Rules: How to Harden Off Seedlings - Do You Need To? -AlboPepper.com (2024)

FAQs

Do you really need to harden off seedlings? ›

If you don't harden off your seedlings, their growth can be seriously stunted, setting back your harvest possibly for weeks. Even worse, they can die, wasting all the time and money you spent germinating seeds and caring for your seedlings.

Put them outside for an hour and then bring them back in. Then the next day, put them out for 2 hours. Do this for a few days and continue to slowly increase the time they are exposed to full sunlight until they are "hardened off" (capable of sitting in the sun all day long). Seedlings grown in weak light stretch.

After weeks of pampering in the cosy warmth of a greenhouse, young tomato plants can get a fright if they are exposed to cold weather outside. This is why it is important to harden off tomato plants before moving them outdoors.

Hardy plants can be hardened off when the outside temperature is consistently above 40° F. Half-Hardy plants may be hardened off at 45° F.

Problems. The most common problem is damage from cold temperatures, or even a late frost. If this happens, cut out the damaged growth and continue to harden off. In warm weather pests such as greenfly might multiply and need controlling.

Day 0: Start hardening off seedlings when they're a couple inches tall with their first set of true leaves. That's right: the process of hardening off seedlings should start indoors first.

Begin hardening transplants 1-2 weeks prior to setting out plants in your garden. The easiest way to harden transplants is to place them outside in a shaded, protected spot on warm days, bringing them in at night. Each day, increase the amount of sunlight the transplants receive.

How big should seedlings be before transplanting? Seedlings should be at least 2-3 inches tall before transplanting and should have their two "true leaves."

Tips to start indoors

In previous blog posts, we've discussed tips for starting seeds indoors. Adding a fan to the room where your seedlings sit is a great way to strengthen them as they grow. A fan makes the hardening off process easier for them to adapt to outdoor growing conditions.

Tomatoes really love water and do not like to dry up too much! It's hard to overwater a tomato plant, but even a water-loving plant can get overwatered. Always feel the soil before watering - it should feel a bit dry or moist but not wet.

Do peppers need to be hardened off? ›

Hardening Off Your Pepper Seedlings

Harden off the seedlings before transplanting. When the seedlings are about 7–8 weeks old, they should be 6–8" tall. Ideally, they will have some buds but no open flowers. Harden off the plants by decreasing the day temperature to 60–65°F (16–18°C) for 1 week before transplanting.

As the name suggests, warm season crops such as tomatoes, peppers, zucchini, and cucumber prefer warmer weather and are less cold hardy than cool season crops; these are the plants that hardening off is most important for.

In general, begin the hardening process 7-10 days before the date you intend to plant them out in your garden and once the danger of frost has passed. If your growing zone generally recommends that starts don't go outdoors until the last week of May, begin hardening seedlings a little more than a week before.

There are three ways to skip hardening off. 1. If you are growing in a high or low tunnel you don't need to worry about acclimating your plants. UV rays can't penetrate most tunnel/greenhouse covers and extreme wind and temperature are also moderated, so simply transplant on arrival.

Seedlings, with their tender new leaves, often give up the ghost when temperatures dip to 32-33°F. Tropical plants have differing low-temperature thresholds. Some keel over when temps fall to 40°F; others crumble at 35°F. Other plants are just hardy by nature and can withstand temperatures as low as 18-20°F.

If you don't harden your plants, the tender plants will get burned by the sun, the shock of cold, or the wind. Some plants may recover from burn (even fully), but their growth will be set back a few weeks while they recover.

Cold frames and greenhouses are not required for acclimating plants to outdoor life, but these structures make hardening off plants easier. Plants can be hardened off in greenhouses and cold frames by simply opening the doors of these structures during the day and closing them again at night.

Only do so when the soil is looking dried up a bit. Your seedlings will be just fine without “moist” soil for a few hours, even a day or more. Just don't let it go on too long, check your seedlings at least once a day!

As a general rule of thumb, your seeds will sprout even if you don't soak your seeds before planting, but with soaking, the germination time decreases, and the germination rate increases. Seeds that have a continual flow of moisture to uptake have much higher chances of success.