Planting Weed in Spring in Latin America: A Guide for the Tropics and the Southern Cone

A spring planting guide for weed in Latin America

In Latin America, the best time to plant cannabis in spring depends on whether you're in the tropics or farther south: in the tropics you can germinate at the start of spring, once days pass 12 hours of light, while outside the tropics it's better to wait until the second month of spring so photoperiod plants don't get confused. Either way, wait until nighttime lows stay above 10 °C (50 °F). The region is huge and packed with growing environments, from mountains and valleys to dry highlands, coastlines and tropical islands, and cannabis thrives in all of them.

Cut by the equator, Latin America spans both hemispheres, and apart from the Southern Cone (Uruguay, Chile and most of Argentina), most of it lies between the tropics. Taken as a whole, the region offers every kind of climate a cannabis grower could ask for.

Like any plant on Earth, weed needs certain conditions to thrive. If you want to grow outdoors, keep these two in mind:

1. Temperature: cannabis plants stall when temperatures drop. Ideally, don't start your outdoor grow until nighttime lows stay above 10 °C (50 °F).  

Spring can look very different from the north of a region to the south, and temperatures at sea level aren't the same as at 1,000 m (about 3,300 ft). That's why it pays to check your local spring lows.

2. Hours of light: feminized and regular (photoperiod) seeds need specific hours of light to grow and to flower. In the Northern Hemisphere, most commercial strains get enough light to grow from May on and to flower from August on.

If you want strains that grow regardless of day length, go for autoflowers. Despite being famous for that trait, they still need lots of light to grow well. The upside is you don't have to wait for the days to shorten for them to start flowering.

Laws vary from country to country, and cannabis enjoys different levels of tolerance across much of Latin America, so check the rules where you live. When it comes to the best climate and temperatures for growing, though, a little local knowledge and a solar and lunar calendar go a long way. For the Tropic of Cancer, we use Guatemala City averages; for the Tropic of Capricorn, Lima's; and for the southern regions outside the tropics, Santiago's.

When spring arrives, here's the data to keep in mind: 

TROPIC OF CANCER

• Average day length: March: 12h 03m, April: 12h 28m, May: 12h 48m

• Average temperature: March: 26 °C (79 °F), April: 27 °C (81 °F), May: 26 °C (79 °F)

TROPIC OF CAPRICORN

• Average day length: September: 12h 01m, October: 12h 20m, November: 12h 40m

• Average temperature: September: 19 °C (66 °F), October: 20 °C (68 °F), November: 22 °C (72 °F)

SOUTHERN REGIONS

• Average day length: September: 11h 52m, October: 12h 54m, November: 13h 51m

• Average temperature: September: 19 °C (66 °F), October: 20 °C (68 °F), November: 21 °C (70 °F)

The first month of spring begins with the vernal equinox, the point after which every day until the fall equinox has more than 12 hours of light. That's key for a healthy vegetative stage.

In the tropics, you can germinate cannabis at this point. Seedlings will sprout and take off fast in the tropical heat. When growing here, picking the right strains matters a lot, especially ones that resist bacteria and fungi, a big plus in humid climates.

As for strains, sativas and sativa-dominant hybrids will do fine and flower without trouble. Indicas will grow well in veg but may struggle to switch into flower, since the nights don't lengthen fast enough to trigger it. In that case you may need some light deprivation (covering plants to give them longer nights) to make sure the more photoperiod-sensitive strains flower.

Outside the tropics, the days get longer faster, but it takes longer for the sun to give cannabis the full exposure it needs. Germinating in the second month of spring sets you up for a strong veg stage and the best final results. Germinate too early and photoperiod plants can get confused, cutting yield and quality at the end of flower.

In that situation, the short days tell young plants it's flowering time. A few weeks later they have to switch back to veg (revegging), only to flower again when fall comes. Revegging plants can still look impressive, but their flowers will be lower quality and the harvest pretty thin.

If you want big plants in places with a short veg season, germinate your seeds before spring starts and give them artificial light to stretch out the veg stage. Once established, plants can go outside when days pass 12 hours of light. After two weeks in partial shade to harden off, they'll take off once they hit full sun.

Early spring is the perfect time to start topping (cutting the main tip so the plant branches out) to shape how your plants grow. Well-trained, well-kept plants usually respond with vigorous growth and multiple bud sites. An even canopy with open, cleared-out branches underneath keeps plants healthy.

This is also the time to start spraying organic foliar solutions, like natural pesticides and fungicides such as neem oil, and growth boosters like seaweed or aloe vera. Ideally, spray in the late afternoon or evening.

Finally, late spring is the right moment to amend your soil again to prep for summer's vegetative explosion. That's when plants push hardest to develop as many bud sites as possible.

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