Tips for the Prevention and Treatment of Stretching in Cannabis Growth
Growing marijuana plants indoors presents a whole plethora of potential benefits. It gives you the freedom to cultivate strains and plants that would never thrive outdoors. It gives you the chance to learn about the fundamentals of plant growth, and offers you finely tuned control over those same fundamentals. You are the one in charge of the amount of nutrients, water, and light your plants receive. Plus, it gives you a hobby that doesn't involve sitting in front of a television screen or computer monitor, a rarity in today's world of intense media addiction.
There are some drawbacks to indoor growing, of course. It requires a lot of electricity. You'll be producing a lot of extra heat, noise, and some really potent smells. That's not even taking space into consideration. Do plenty of research before you begin--- you want to know what you're getting into. One of the most common issues with indoor cultivation is watching your plant grow and grow, stretching up and out and eating up all the space in your grow room. For the most part, this is unavoidable, but there are a couple steps you can take to help minimize the stretching.
Grow bushy marijuana plants
To maximize the space you're using, you'll want to keep your plants as dense and bushy as possible. This can be accomplished through two different practices. You'll want to both minimize the distance between nodes and also promote lateral growth. The distance between the nodes essentially just means the distance between the base of the leaf stems on a plant. The greater the distance between the leaves, the more slender and spindly a plant will appear.
Believe it or not, you don't want spindly plants. If they are tall and thin, its unlikely that they will be able to support the heavy buds that you're hoping for. You'll need to expend extra effort to support the plant, and you'll risk losing your hard-earned buds if any of the stems snap. Not only that, but a stretched plant can easily grow too close to the grow lights. This can cause a whole host of issues: the intense exposure can burn the top of your plants, and lower leaves will receive significantly less light. All of these things will damage the health of your plant, and that means a reduced yield.
As in all things, a preventative approach is best, but if you're already suffering from stretched plants, there may be able to salvage some of the issues by doing some careful pruning on your plants. Don't give up! "Careful" is the name of the game when it comes to pruning. In fact, a lot of professional growers will suggest avoiding pruning entirely. Pruning plants before they mature can affect the flow of various hormones within the plant, including auxins. Auxins are part of the group of hormones that coordinate and organize the way a plant grows. If you can learn to manage and redistribute these hormones away from the main trunk and towards the lateral stems, you'll have a good way of slowing the upward growth of the plant and forcing it to grow outwards.
Now, back to those preventative measures. If we want to prevent stretching, we'll need to know what causes it first. Genetics can play a major role here, but for our current intents and purposes, we can throw it out. Beyond your choice of strain, you don't have much control over the plant genes. What you do control is the environment! The two primary factors you'll be monitoring are heat and light. You'll want to be conscious of these factors from the very beginning, and not just in the period most commonly talked about by growers: 'the stretch', when plants start getting twelve hours of light instead of eighteen. We'll get to that period later.
How to control temperature in your marijuana grow room
We'll start with heat. Temperature is very important. Even if you are getting just the right levels of light, your plants can still get spindly if you don't have the proper temperature levels. Ideally, your grow room will range from 73 to 82 degrees Fahrenheit (23 to 28 degrees Celsius). To help you maintain and monitor these levels, you'll want to make sure you have a decent thermometer. Regularly record the minimum and maximum temperatures in your grow room: these changes are extremely important, as the temperature change between day and night is the primary factor in internode growth. The more the temperatures change, the more your plants will stretch out.
The technique of adjusting day and night temperatures to control the growth of a plant is known by horticulturists as the DIF technique (DIF stands for 'difference'). When the day temperature is higher than the night temperature, you have a positive DIF, and vice versa. The more positive the DIF, the larger the distance between the nodes will be. When night temperatures are higher, you have a negative DIF. This will slow growth, and minimize the distance between the nodes. Maintaining a positive DIF of just a couple degrees will ensure that your plants keep growing, but slowly, with short spacing between the nodes of the leaves and stems.
In fact, the application of a negative DIF can completely inhibit growth in a plant. Commercial growers and farmers sometimes use this technique to force certain crops to 'wait', so that they can harvest everything at the same time. It's unlikely that you'll want to do this, but the information is valuable nonetheless. If you do decide to delay the growth of your plants by applying a negative DIF, be careful: humidity can rise rapidly in a room without lights on. Be sure that your grow room is well ventilated so that you don't risk the onset of mold.
An alternative option is the 'morning pulse'. To use this technique, you let the temperature in the room drop by a couple degrees for the first two to three hours you turn the lights on, then maintain a positive DIF afterward. This will have an effect similar to the negative DIF, but you won't have to worry about rising humidity. The easiest way to apply this technique is through the use of an air conditioning unit or a temperature-controlled fan.
The best marijuana grow lights
After temperature, you'll want to choose lights for growing marijuana. First, make sure you are getting enough light in the space. If your plants aren't getting enough light, they will stretch out as they grasp out for more light. In a perfectly managed situation, all of the bud sites on a plant will receive the same amount of light, at the exact same intensity. Even, balanced lighting will produce dense buds all over the plant.
If you use artificial lighting, you'll need to remember that the power and intensity of the light diminishes exponentially with distance. We won't get too deep into the math here, but distance from the plant to the bulb will swiftly reduce intensity. This is the main reason that plants grown indoors will develop smaller, less dense buds on the lower sections of the plant. Artificial light just can't provide the same power across an entire plant.
It's most common for growers in Europe to use a single 600 watt HID lamp per square meter of growing space. This is definitely enough, but if you aren't mindful of details, you can still get stretched out plants with this set up. Make sure that the bulbs are always as close to your plants as they can get without burning them. To go along with this, you'll want to use reflectors to help dissipate heat. You have a couple of options in this regard: parabolic reflectors, air-cooled reflectors, adjustable reflectors, etc. If it dissipates heat, it will work for you. Just make sure that the surfaces on your reflectors are being kept clean, otherwise they won't work.
The exact distance you'll want from your plants to your light source will vary, depending on the environment, equipment, and strain of plant being grown. In general, you'll want about 35-40 inches from a 600 watt lamp to a young plant. As the plant matures, you can reduce the distance to around 18 inches. If you're worried about this, an easy tip is to just put the back of your hand above the top of the plant for awhile. If the lamp burns you, it will probably burn your plants, too.
Prevent marijuana plants from stretching
Another factor to consider is space. Through it can be tempting, don't overcrowd your grow room. This is an easy way for plants to stretch out as they fight with one another for light. Overcrowding will get worse as plants grow, too, since the lower portions of the plant might get almost no light at all. The light they do receive will be richer in infrared, which will cause the plant to stretch even further.
Before you get started, take the time to plan out and organize your space. You want plenty of room for all the plants: they'll take up more space as they grow, and you don't want to grow yourself into a corner. The type of light you're using will also affect the plant growth. We won't go too deeply into the different types of light you can use, nor the different parts of the spectrum you'll want to use as the plant matures.
Though you might be tempted to use a window sill to take advantage of direct sunlight, only do this if you have absolutely no other options. In direct sunlight, young plants can easily get too hot and wilt. On the other hand, if there isn't direct sunlight, the plants will end up stretching out in the attempt to get more light. For young plants, it's a good idea to put some money into a T5 or PL propagation light. These bulbs are cheap fluorescents that you can put right onto a propagator. They put out the cool white light that young plants require for steady development.
When your plants reach the vegetative state and begin to leaf out, you'll want a blue compact fluorescent (CFL) or metal halide (MH) bulb. Both of these types of bulbs produce white-blue light, which promotes vegetative growth and thickness while minimizing stretching and vertical growth.
When your plants begin to flower, you'll want to begin reducing their light exposure from 18 hours to 12 hours. During this time period, the plants will undergo rapid vertical growth: there is almost nothing you can do about this. Since plants require nitrogen for this sort of growth, you might expect that you could diminish it by cutting off nitrogen, but don't do it! Your plant needs nitrogen, and trying to cut it off will just damage its health.
Your white-blue lights can still be used through the first several weeks of flowering to help keep the distances between nodes short and minimize stretching. Be careful about switching to a sodium bulb too early during flowering. Although these lights help encourage bud growth, they can also cause stretching in the plant if they're used too early.
Above all, don't forget to plan as carefully as you can. As the old saying goes, "Measure once, cut twice." It's much easier to take care of any issues by giving yourself wiggle room and expecting issues before they actually arrive. You should always expect some stretching to occur. In addition to the initial growth, your plants will likely double in size once they begin flowering and you change the amount of time they are exposed to light. Make sure you are accounting for all of this growth when you plan out your space. For example, if the maximum height in your grow space is four feet tall, make sure you are switching your plants to flower at 2 feet.
The bottom line is this: if you want to make sure your plants grow at a reasonable rate without experiencing extreme stretching and damaged stems, make sure you get plenty of light and don't let your night temperatures vary too far from your day temperatures.