Photoperiod & Strain Selection For Outdoor Marijuana Growing

Understanding Photoperiod & Strain Selection For Outdoor Marijuana Growing

Why are some marijuana strains better for outdoor marijuana growing than others?

Because some marijuana strains are more naturally resistant to pest, disease, daylength, and environmental issues associated with outdoor marijuana growing conditions.

Note when I talk about “outdoor marijuana” I’m referring to marijuana grown outdoors from early seedling or clone to harvest—not marijuana grown totally in a controlled space like a greenhouse.

The reason I exclude greenhouses and other controlled-space outdoor growing is if you do a controlled-sapce marijuana grow properly, you control for pests, contamination, and diseases almost (but not as well) as if you’re growing in a properly sealed indoor hydroponics marijuana grow room.

You can alter light cycles when you grow “outdoors” using a controlled space.

This article is mostly focused on growing marijuana outdoors, where your plants are at the mercy of whatever Nature throws at them.

It’s also applicable to marijuana plants grown in your back yard so you can get to them immediately every day.

Some marijuana strains are resistant to problems common to marijuana grown outdoors.

But other marijuana strains are especially susceptible to molds, mildews, and bugs that may be in your growing location.

And some marijuana might not start to flower, or finish flowering, at “the right time” where you live.

Let’s start with marijuana resistance to common pests, diseases, and growing condition problems.

For example, some marijuana strains have long, narrow-diameter Sativa-dominant buds instead of fat thick buds with more Indica or Afghanica influence.

What difference does that make outdoors? If you live in an area with high humidity and/or significant rainfall during bloom phase, the thinner buds are less likely to develop gray mold (the evil mold that ruins your cannabis crops in bloom phase).

Read this great article about stopping gray mold.

Another example…some marijuana strains produce resins that naturally resist powdery mildew, mites, molds, thrips, aphids, and other bad things.

Knowing what cannabis strains work best outdoors where you grow is specialized knowledge usually held by long-time growers in a local marijuana growing area such as microclimates within Northern California’s Emerald Triangle.

There, growers have been working with specific marijuana strains for years and can tell you pearls of wisdom such as: “This one never gets mites even if every other strain does.”

Outdoor marijuana growers worry about matching their strains to the specific geographic latitude and climate zone where they’re growing.

That’s because marijuana plants respond to “photoperiod,” which is the length of visible light per day and the length of darkness per day.

The north-south orientation of your location relative to the earth’s equator greatly affects the length of day and night in your area, which directly affects your marijuana plants.

When your marijuana plants are outdoors full-time, they notice that from late March until the Summer Solstice in June, the amount of light per day is increasing by small amounts.

If you’ve planted the right genetics at the right time in the right geographic location, your marijuana plants will start in and stay in grow phase until they sense later in the year that the sun is up less and less hours.

Eventually, this triggers them to start flowering.

Your cannabis plants notice that after Summer Solstice, the amount of light per day decreases.

Your outdoor marijuana plants will start flowering when the amount of light per day triggers it. Usually, this happens in late summer.

Unlike hydroponics indoor grow rooms where you have 18-6 or 24-0 light cycles for the first weeks of growth, and then abruptly shift to 12-12 to trigger bloom phase, your outdoor marijuana plants watch the total length of light and darkness per day based on natural conditions.

Outdoor marijuana plants in the Northern Hemisphere most often start flowering when daylength drops below 13-14 hours per day.

With some marijuana genetics, if your young plants are in a geographic location that has less than 14-15 hours of light during the early days of springtime, your plants could become confused.

They “think” that it’s autumn.

This means they might not put on regular vegetative growth, but instead stay short, and may show pre-flowering when they’re only a couple of weeks old.

However as day lengths increase in May and June, these marijuana plants revert to vegetative growth, getting larger, developing more root mass, and gaining height until day lengths start significantly decreasing in August, September, and onwards.

Other than procuring cannabis seeds or clones known to flower and be ready for harvest outdoors before the end of October in your geographic location, you really are at the mercy of genetics and conditions.

Ask marijuana seed breeders what strains they recommend for your specific area as regards photoperiod and flowering times, and as regards resistance to pests, diseases, and environmental conditions specific to where you grow marijuana outdoors.

My technique for getting the right outdoor marijuana strains includes doing research to see if I can get seeds or clones meant for where I live.

I also choose several strains with different lineage. For example, a Haze, a Kush, a pure Sativa, and a hybrid Indica-Sativa 50-50 split.

Put those different marijuana strains outdoors, and observe carefully to see how those strains handle your specific growing conditions and needs.

If you want to do the extra work and are willing to sacrifice root size, you can plant your outdoor cannabis in containers, and then move them into a dark space every day so they only get 12 hours of ambiant outdoor light.

Marijuana growers in areas where anti-marijuana helicopter patrols start flying looking for flowering plants in late summer and autumn can force their plants to flower and finish in summer using that technique…but it’s a big hassle to do it.

In our next article, we’ll be giving specific outdoor marijuana strain recommendations.

Also look at our outdoor marijuana master grow guide article that contains super-useful outdoor growing information and links to other outdoor marijuana articles.

Happy outdoor marijuana growing!

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