The Seeds we have at this point in time are from a Climate of an average of 16-20 Celsius. Here we have regular Heat of 32 Celsius. I started my Seeds from N. America Outside. I Foliar Treated them and put them out into the Sun 6 hrs per day, from under the LED Lighting where they spend most of their time. I am not going to let a Thailand Sudden Rain Storm destroy sever thousand baht of seedlings. Yes they are struggling yet the Father has a bit of experience with this Phenomena.

2 weeks old

So Hardening Off Your Seedlings

If you plan to grow cannabis outdoors, suddenly transplanting your indoor-nurtured seedlings into different soil could damage them and affect their chances of survival. Always use a Transplant Solution. Always! For many growers, outdoor cultivation remains the real ‘gold standard.’ I highly Recommend Viewing the Video Series on Handling of Cannabis Seedlings and Germination (Links at Top of Homepage)

It is the ‘natural’ way of doing things. If you have the private land, and the climate, you don’t need to do much in terms of maintenance. With nutrient-rich soil already in the ground and rainfall, there is no need to feed and water the plants.

Your primary goals are to keep pests and trespassers at bay and check for infections or infestations. At the end of it all, you are generally rewarded with a bountiful harvest of potent buds.

Some gardeners like to grow the seedlings indoors or in a greenhouse before planting them outside. However, if you suddenly take your pampered seedlings and place them into different soil (Temperature or Mix), you could send them into shock.

Plants that aren’t adequately prepared for the transition don’t perform as well as those that are. Remember, in an indoor setting; everything is perfectly regulated. Your seedlings get the right amount of light, water, and nutrients because you set it all up.

Plants that grow outside face a different challenge. There is likely higher humidity and higher winds, extreme Rain, storms, rogue Animals, Insects and more!. It doesn’t take much for plants to get hammered.

As a result, it is necessary to toughen up your Cannabis Seedlings before bringing them outside. This process is called ‘hardening off.’ You need to complete it gradually to give your seedlings the chance to get used to their strange new environment. This “Environment should be what is waiting for them now outside…

Why Is It So Important to Harden off Seedlings?

3 weeks

Seedlings grown indoors and in greenhouses don’t fully develop waxy cuticles that protect lower and upper leaf surfaces from drying out. Such seedlings are not exposed to sunlight or excessive wind. The overall result is faster-growing plants with long, thin cells. They also have longer stems and more fragile leaves. Seedlings not fully exposed to the sun’s UV rays also develop larger leaves than their outdoor counterparts.

Once you plant a young seedling outdoors, everything changes. Now, the plant must keep itself protected from direct sunlight and strong winds and all the exciting things that occur outdoors. It now needs a waxy leaf cuticle to keep water loss to a minimum. Plants cultivated outdoors generally grow more slowly but have more durable stems and leaves. This enables them to survive cold nights, gusts of wind, and droughts. I “stress” my seedlings with a strong fan and gradually turn up the Heat in the grow room or “propagation Room.

The Droplets left on the Leaves may act like a Magnifying Glass. Take a little time and “flick” these off, or do not water at the Suns Peak. I water early in the morning, very early. Once they are over a Meter in Height this is no longer relevant. (Always leave a couple inches of Space from the Top of you Pots for when this time comes. Or you will find that your Soil (Medium) will flow out along with your water! Exposing it’s Roots and Removing the Medium that was being used by the Support Roots.) Plants that are over 3 meters high need to be water 2 times per day. Remember to use well water. Not Treated water.

3 week old seedling

When Should I Harden-off My Seedlings?

The good news is that two weeks is usually a long enough period to ensure your seeds are toughened up sufficiently. It depends on the type of Strain, current weather conditions outside, and how warm the indoor growing climate was. You need to gradually “Acclimate” your Seedlings to what ever is waiting for the out there.

Also, many Growers fail to understand that sunlight’s intensity dramatically exceeds that of an artificial light source. Even Cannabis plants that grow under HID lighting don’t find it easy to transition to the sun’s light.

Some Growers have reported growing seedlings indoors where they had 18 hours of HID or LED lighting a day. They put these healthy seedlings outdoors for a few hours a day in the full sun. (Majeo University, Chang Mai) To their horror, they found that the seedlings were massively damaged. It is sensible to gradually introduce seedlings to sunlight by slowly increasing the duration of exposure. Or Just start them out doors.

I recommend purchasing and starting several hundred seeds. The Plants that make it are the ones you will want to propagate. The Seeds we are allowed to “Purchase” here in Thailand were Bred and Developed in North America. Not here.

As far as when to begin the hardening off process, a lot depends on where you live. Weather and “the Photo Period (length of day, or amount of time to light exposure) are two of the principal factors in determining a successful outdoor grow. Putting plants outside too early or too late will ensure they don’t properly develop.

Your location significantly impacts the photoperiod. In the Northern Hemisphere’s ‘southerly’ parts, such as America’s southeast and southwest, the longest days of the year seldom exceed 14.5 hours. In Seattle and other Pacific Northwest areas, the longest summer day is around 16 hours. In Anchorage, Alaska, it is up to 20 hours! Ideally, you will live in an area where the longest days are 18 hours. Here in Thailand it is Typically 12 Hours per day. If you seek a larger Yield you will need to supplement the Photoperiod.

Here in Thailand you must adjust the Photoperiod if you want a yield of more than 100 Grams per plant. Thailand has a Photoperiod of 12-12. I use street Lights on all my Farms on Timers.

Now, let’s look at a few ways to harden up your Cannabis seedlings.

Gradual Outdoor Exposure

As the name suggests, this is a slow and steady process. Begin by placing the seedlings outdoors up to 10 days before your pre-determined transplant date. Put them under trees, so they benefit from the protection of the shade.

You can leave them in this relatively safe position for 3-4 hours a day to start with. Do Not Leave them unsupervised. Remember they are Babies. Slowly increase by an hour or two a day or week. When you bring the seedlings back indoors, put them in a warm place, like a porch or heated garage at night.

After several days, you can decide to expose the plants to the full intensity of the sun. It is probably best to wait until the plants have at least five sets of real leaves. At this stage, only put the seedlings into the glare of the morning sun. Avoid exposure from 11 am to 2 pm in particular.

If the temperatures remain high during day and night (at least 50 degrees Fahrenheit), your plants should be ready after 7-10 days. Keep a close eye on the seedlings, however. I keep Mine in a Safety Cage. Make sure the soil in their pots never goes dry, and account for any sudden changes in temperature. The best time to make the full transition is on a cloudy day. Water the seedlings well after planting using a hormones’, seaweed, B-12 diluted solution. Make sure the PH is correct and the Soil is good..

You can make the process easier by using a wheelbarrow to bring your plants in and out of the garage. It is also essential to place the seedlings on a higher surface, such as a table. If you leave them on the ground, slugs, snails, and other animals could damage them. In Thailand the Chickens will destroy your seedlings!

Withhold Water Temporarily

This is a little on the ‘tough love’ side of things, and for Professional Growers to try only. Seedlings are very delicate. but some gardeners do it! Around a fortnight before the transplant date, stop watering your seedlings. Wait until they show initial signs of wilting. Make sure you pay close attention. If you leave it too long, you could seriously damage your plants. The process shouldn’t take too long because there isn’t much soil in a seedling pot.

Start watering them as soon as they begin to wilt. Then, allow the young plants to wilt once more. After two weeks of this process, your seedlings should have the desired toughness. Again, make sure you complete the final transplant on a cloudy day and water the plants well. This is Dangerous and will affect the Growth Rate of your Seedlings. I recommend this to seasoned Growers.

Using a Cold Frame

A cold frame has a glass top where you grow and protect small plants without artificial heat. (This is a N. American technique), It is ideal if your goal is to harden up young plants. Again, this is a gradual process. When the seedlings are in the cold frame, put the device in a southwest or south-facing spot (if in the Northern Hemisphere). The design of the cold frame box means your plants are kept at lower temperatures but still enjoy a semblance of protection.

Keep the box closed for up to three days to give the seedlings time to adjust. Then, open the windows on top of the frame halfway to let a bit of Light in. You can do this during the day and at night, but only during good weather.

The best conditions are when it is dry and relatively warm. The goal is to keep the seedlings in a temperature range of between 40- and 50-degrees Fahrenheit. This is the ‘sweet spot’ where they continue to grow while adapting to the changes they face.

Keep the frame closed tight if the weather is a little colder. If the temperature drops significantly, add a layer of bubble wrap on top of the box for added insulation. If the weather gets really bad, it is a wise idea to abandon the process temporarily. During hotter days, leave the box fully open during the day. Otherwise, leave it half-open.

After a week, you can begin leaving the cold frame open during the day and night. You can consider transplanting the seedlings once you believe you can leave the frame open 24/7.

Always Use a Small Fan

There are other ways of conditioning your Cannabis seedlings for an outdoor grow while it is still inside. One of the easiest methods involves a small fan. Use it to circulate air around the seedlings. This process can help toughen the stems and prepare the plants for the wind they encounter outside.

Make sure you don’t overdo it, however. Too much air movement could cause the seedlings to dry out or get damaged. Keep the fan from pointing directly at the seedlings. The goal is to blow air around the room, not straight at the seedlings. Now I use the “Swing” feature of the Fan. I let them get beat a bit by the wind, yet not to much. After you have done this a few times you will develop your own methods.

You can keep the seedlings’ moisture content at a steady level by using a spray bottle to water them. Consistent moisture helps early leaf development and germination. The seeds I received from N. America 16 Celsius are struggling. Yet I will see to it they make it. We all will lose 20-30 depending on how many you start. This does not matter how good of a grower you are, or how many crop you have done. It is a fact of Life/

I am Hitting my Seedlings Hard. These are some “Special Forces” CBD Seedlings for sure!


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