Making Light of Time
When to transplant
By Mike Martino | Cover Image by Dakota Rains
Those of you who drive Highway 36, 299 or the 101 on the regular, may have noticed an increase in enclosed trailers on the road, and U-Hauls as well. That’s because it’s the springtime push, and people are taking cannabis plants they’ve started in town under grow lights out to the hills to be planted for this season’s crop. You may have even seen some of those plants waving hello to you on the side of the road as you drive by with flashing blue and red lights in the background. Due to the time of year, I thought it would be interesting to go over the factors that go into deciding when plants should be taken outside, when supplemental lighting should be turned off, and general considerations one should take on a strain-by-strain basis.
The first thing to take into account when bringing plants outside is the weather. Many growers when planting their full term have already move their plants outside some time in April or May. The weather varys from warm to sunny, to cold and rainy or even snowy. I’ve always preferred to take my plants out when the weather is mild, the cloudier the better. The reason being is that grow lights cannot replicate the intensity of the sun. When moving plants outside directly into the full sun from inside, it’s common for the plant to be stressed by the intensity of sunlight. The most common symptom is leaves bleached white, in effect killing those leaves. I’ve also seen new growth die, or entire plants die, but that only happens when taking plants out on hot days and placing them directly in the full force of a hot sunny day. This makes it important to have a strategy for plants to avoid stress and maintain vigorous growth throughout the transition phase. If due to timing one is forced to bring plants out on a sunny day, there are a couple of options. My preferred method is placing plants in a greenhouse covered in a couple of layers of Reemay or Agribon. This thin cotton cloth can cut the intensity of the sun by about half. It’s cheap and available at all local garden stores. This will avoid plants from being sunburned. About a week under cloth they can be moved outside without any worry of sun stress. The only other method I have seen, and it’s pretty old school at this point, is placing plants underneath a tree for a few days and then placing them under the full sun. There are disadvantages to this that I will explain shortly.
As I mentioned before most growers take their plants out in April or May for the growing season. At this time of year there are only 13 to 14 hours of daylight, ideal conditions for plants to start flowering. Therefore it’s important to run supplemental lighting from sunset until about 11pm to prevent plants from prematurely flowering. That is why I don’t like the tree shade method for transitioning plants. In greenhouses, it’s easy to hang supplemental lighting that will keep plants from flowering. Also, weather can vary substantially during this time of year and in cases of rain or extreme cold, your greenhouse can be heated to protect plants. This is important because any stress on the plant takes away from plant vigor and the goal at this time of year should be to get plants as big as possible, as quick as possible. Greenhouses go a long way in helping to accomplish this goal.
The last part of the transition process is deciding when to turn off supplemental lighting and start planting in their final container or bed. When this should occur depends on two primary factors: weather and strain. It’s not uncommon on the North Coast for Summer to be late in appearing in terms of consistent warm, dry days. Just because it’s June 5th it wouldn’t make sense to plant in the full sun if there are wet windy days in the forecast. Assuming that the weather is appropriate, when to take plants off of supplemental lighting is very strain dependent. A basic rule one can go by is that the later in the Fall a strain finishes flowering, the earlier in the Spring it can be planted. For instance, Sativas like OG, Blue Dream, Sour Diesel and Ogre, which finish late October to early November, can be planted in the last week of May, weather permitting, with little worry of prematurely flowering. Strains like Mr. Nice, Black Berry Kush, and Purple Trainwreck, which finish late September to early October, should be planted as near the Summer Solstice as possible. Early flowering strains are the ones most susceptible to premature flowering, so I’ll give you a great tip that will help to prevent that. When you have these plants under lights, don’t do the standard 18 hours on, 6 hours off. You want only 16 hours on and 8 hours off. This makes sure that when they are planted and are only getting 15 hours of light a day they are not stressed into thinking its Fall and start flowering prematurely.
Many gardeners may already have an understanding of what is discussed. If you are new to the scene or you have not come across this information in the past these tips will go along way to ensuring you have a successful Spring, because remember, you can’t come back from a bad start. Have fun in the garden and good luck to all you gardeners out there.