Questions about seeds, seedlings and grow

Questions from a fellow grower:

At approximately 45N Lat. I have raised beds in an attached greenhouse equipped with movable shutters to close space at night. Temperature is maintained with a heated (85F) exercise pool. No artificial light. We raise both ornamental and edible plants year round. Glass cover is ordinary 5/32nds glass sloped at latitude down to a vertical glass wall 6 feet high.

  1. If seedlings are started under lights and then transplanted as you describe in your pamphlet, a) will they grow slowly throughout the winter? b) when would I expect them to set buds?

  2. If seedlings are set out in the spring, as we do now with edible plants, how is their growth cycle affected?

  3. Don’t really need heavy production but do want quality product. Decent sunny weather through end of September from mid May. Long enough to make a crop?

  4. What are absolute high and low temps tolerated?

Can’t grow outdoors because of deer.

I’ll give you some basics, until the folks with better experience jumps in. I would then defer to them.

The first thing is, did you download the Grow Bible and check out the Guides section? A lot of what you seek may be there. Granted, you will find differing opinions in different guides / forums; however, I think that is because there is no absolute right or wrong way. Some things work better for tohers, and everyone has their own preference.

You may also wish to give more details about what you wish to grow and how you wish to accomplish it, e.g. the type of strain, the grow medium, *soil / soilless, etc," There is a support ticket that you may find linked in some threadds. That would, imho, a good starting point for the folks to look into your situation.

Per length of time, I beleive it varies by strain and other factors. On a general scale, I would say you could expect the germination to seedling stage to go ~3 - 4 weeks, followed by veg and flower. Some people, I’ve seen, veg for only 3 - 4 weeks, while others take it out to 8 weeks or so. Bloom / Flower is when determined when you take it out of Veg and switch the light cycle to 12 / 12. From there, you change the nutes, and watch for flowering. Each strain has somewhat differing floweing times, and even then, some folks harvest earlier than others. The rule of thumb I’ve seen is that you want to see trichomes mostly milky, with anywhere from 25% or higher turning to amber, depending upon what type of esperience you are after.

Per quality, imho, like anything else, it’s all in the care you give, the attention to detail, and maintaining eveery aspect, e.g. nutes, lighting, etc, to optimum levels. Insufficient lighting, lack of nutrients, too much or too little water, improper pH level of water / nutes and grow medium, will all have some effect upon your final results, with some more detrimental than others.

As far as your setup, everything I’ve seen reccomends the basic 18 / 6 rule of light to dark for veg cycle and then switching to 12 / 12 for bloom / flower. If you are at 45N Lat, will you have sufficient lighting during the winter to maintain the ~18 hours of light? That’s a tough question to help with, without knowledge of what lighting you intend to use. You could also go the autoflower route, where light cycles aren’t an issue; however, even then, I believe that autoflower likes more light versus less light.

I hope this at least points you in the right direction to look into things while waiting for some others to chime in. Good luck in the grow. :smile:

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Since I didn’t post the original question myself, a couple of clarifications:

I was inquiring about the newly released strain. I doubt if anyone other than the staff would have the experience with it fo answer the question.

I state specifically that we don’t use artificial light in the attached greenhouse. Raised beds implies soil. While the temperature is moderated by the 2500 gallons of water in the greenhouse, temperatures can drop to the low to mid 4o’sF during the harshest part of the winter. 45N does not afford even a 12/12 day in the dead of winter.

I suppose the central question can be reduced to this: do these highly hybridized plants simply slow down in response to natural conditions in comparison to those provided in intensely cultivated gardens, or do natural conditions kill the plants or inhibit fruiting?

The question I think only the management can answer has to do with timing planting new seed of the new strain if they are germinated and grown for a month or more under the fluorescent gro-lights we use for our vegetable garden plants.

Thanks for the effort. I have read the “bible” which makes many of the same assumptions you made.


Cannabis is cannabis.

It can not tolerate extreme temperatures, too hot or too cold. It can’t tolerate freezing for very long at all. These temperature ranges are covered in the book. Also, all cannabis takes around the same time period to grow. Equatorial sativas a little longer than many, but the total time from seed to harvest is still within about the same time frame, not changing by much more than a week or two more. All this info is in the seed shop, under details about each individual strain.


Here is an article in the blog/guide section that might be of help:

Happy Growing,


At approximately 45N Latitude is a fine spot to be at. All cannabis are short-day plants, excluding auto-flowers (and even autos can be influenced by a shortening day). At 45N your beginning flowering period under natural sunlight will be starting around September, cannabis needs about at least a solid 10 or more hours of darkness to induce flowering. At 45N, peak THC production should be stating around mid/late October and will start decreasing near or after around mid/late November.

Naturally, outdoors, most cannabis is started during the spring, to allow for maximum size and vegetative growth before flowering in the fall.

Hope this helps,


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Watch the pistillate/calyx development to harvest for weight, when all pistillate “hairs” have reddened, or in many strains they turn orange, but generally they are turning “brownish”, and no new pistillate/calyx are developing, the “bud” is finished swelling and putting on weight, for the most part. Watch the trichomes for a more precise way of determining ripeness and the type of characteristics to the “high”. Ideally all trichomes should have turned from crystal clear to a more milky look inside them, as evidence of maximum THC. This milkiness will deteriorate some and turn amber as the buds continue to ripen on the plant, and if too many turn amber the “high” becomes more sedative like, hence the term “couch-lock”.

Here is a link where I recently discussed determining if the buds were ripe enough for harvest, we cover this topic often, and it contains more links where we also discussed it in detail, in a few different ways, recently as well.


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It’s interesting that responses are to what you think I should be asking instead of the question I am asking. I have read the manual/bible which, so far as I can see, describes what is optimum. I don’t have an optimum situation and cannot create one. Ideally, I’d grow for my modest needs out doors. Since I can’d do that, I have to put my few plants indoors. I do have an attached greenhouse which is not set up for artificial lighting. That means, I’m stuck with the sun’s natural, seasonal cycle. Therefore, I cannot achieve 18/6 or remotely close to it unless, as with some plants that respond to even low light levels in terms of their growing “clock” cannabis can be tricked into believing the day is long than it is even though there’s not enough energy in the light to actually promote growth.

I understand what optimum temperatures are as they are described in the bible. My greenhouse is 48 feet long, has a 45 degree south facing glass wall that’s 20’ high that runs down to a vertical glass wall that’s 6’ tall. Both ends are glazed. The entire structure is ordinary glass except that the sloped glass is tempered. I can, and do, avoid black sky freezing by closing articulated louvers on the sloped portion Real world here is a temperature range in the greenhouse at the raised bed level (the entire greenhouse is set up to be wheelchair accessible) that range from 40F-85F. If the sun shines, outside temps are immaterial. In the winter, the temps can go lower than 40F but due to the heated 2500 gal pool, that doesn’t happen. The south facing greenhouse is the heat engine for my passively heated and cooled residence. I did provide power for a Big Ass Fan which helps control mildew and other high humidity hazards. I don’t have the capacity to install HPS lighting nor do I have a convenient way to hang such lighting. If I cannot do it with natural light cycles, I won’t grow weed.

So: what am I asking that’s not in the book that presents only optimum conditions?

I understand that crops won’t mature as fast unless daylight is extended. Does cannabis growth slow down when the photo period is naturally short, or does the lack of light kill the annual plant (assume early spring indoor planting in soil) or cause an immature seedling to bloom prematurely.

I understand that the optimum temperature is an average 85F. Since extremely high temps are not desireable, that means the optimum low temp is fairly high. The question is, what is the effect on the plant if nighttime temps reach as low as 40F? Does that temperature kill the plant (the roots will be soil, in the ground, not in pots and should not suffer anywhere near 40F. At what temperature is cannabis actually killed by cold?

I was raised on a farm: orchards. I’ve been a gardener most of my life, so I have a nodding acquaintance with what it takes to make a crop. Marijuana, with which I have no experience, seems to be an exception to most crops. It’s in a vegetative state throughout since it is not allowed, by breeding or culture, to produce seeds. Most non-fruiting crops, in the winter and early spring, will continue to grow at a slow rate. Some are selected to continue to produce: chard, kale, even beets and lettuce. Patience is a requisite.

I originally asked the question about that newly announced strain because I’m not about to plunk down $10 or more per seed if I cannot produce a crop under the conditions I’m stuck with.

If anyone knows the answer, please contribute - I’ll be grateful. If staff is paying attention, I’d love to hear from you since it appears the answers I need are not considered in your book. I’m not in a hurry to make a crop nor do I have to have huge per plant production. If it can be done, though, I’m intrigued by the description of the new strain.


I am staff.

I actually answered your questions pretty directly and not about just what is optimum. Cannabis is cannabis.

Yes if it doesn’t get significantly more than 10 hours of light during veg, plant growth will be significantly slowed. 85F is not the optimum temperature, it is a little high. About 70-75 is the optimal temperature. This is true indoors or outdoors. Outdoors, shade cloth might need to be employed if temps are getting too high. If you can keep the soil, the root-zone near the ideal, then the stems and leaves will withstand influxes of temperatures outside these ranges.

And again, much of this info was also in the link I shared:

“Most outdoor varieties can endure temperatures as low as 50F (10C) without any problem. That being said, fifty degrees is still not an ideal temperature because it tends to slow down tissue growth and photosynthesis later in the day. Anything below 40F (4C) can result in damage to the tissue. Gas patio heaters can keep gardens warm on frigid nights. Maintaining a temperature of 60 degrees will promote plant growth substantially.”

Something to think about, technically all cannabis is a outdoor plant, as all plants are naturally. I wouldn’t pay a lot of attention to outdoor vs, indoor strains, except if you need higher heat tolerances, but do pay attention to the details for any significant info that might be related to your questions.

You keep mentioning a new strain, I suppose you mean Robert’s Gold leaf, again cannabis is cannabis, I have grown this strain and it is just like any other strain, the flowering expected days/weeks is also listed and is about average in length.


I’ll tag @latewood to this conversation as he’s the greenhouse expert here, but I doubt he’ll have a lot different to tell you. Cannabis needs what it needs, and I’m sorry if your natural conditions can’t meet the minimum requirements.

Happy Growing,


At 45N, actually you do get 12/12 around September, during your actual equinox which is not far off from most commonly celebrated equinoxes in September in the Northern Hemisphere.

At 45N you won’t get 18/6, but you do get a little “remotely close to it”. Around June, and especially near the summer solstice, around June 22 – you’ll be getting around at least 15 hours of sun. As I stated above, starting and planting in the spring is how it is done with natural sunlight in most places and should work fine for you.

You’ll probably need to look into training the plants if you have limited ceiling space and you plan to grow a large plant over a long spring/summer schedule, you can start later for smaller plants, and determine by your own known temperature ranges, and with what I’ve told you above about how cannabis will react at 45N to the expected daylight conditions, if your plant will be ready before it gets too cold.

At 45N it does seem your plants should be pretty much ripe by the end of October, under natural sunlight – from the ‘cannabis specific’ latitude maturation charts I’m looking at. If it gets too cold before the end of October to early/mid November, then it might just not be possible.


All I have to say is: If you cannot control your environment, then you are wasting time and money. If you are outside, or in a greenhouse; You must time your grow perfectly or you will suffer setbacks, or low yielding plants. The only other option is to fabricate a shelter inside greenhouse or Outdoors in order to allow for heating, or extra lamps to allow for a longer day.