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In general, cannabis likes to grow in slightly acidic soils. Do we have acidic soils in New Mexico? Nope. Our dirt is as neutral as you can get. With a median pH of 7, we barely have soil. It’s like those noncaloric flavored drinks: if you read the label, there’s absolutely zero in them.
I kid. Many plants do just fine in neutral or alkaline soils but a few do better in acidic soil. You don’t see many rhododendrons here, do you? And if your neighbor is growing blueberries, chances are that soil is amended to up the acid content. Cannabis needs a bit more acid, too.
The right pH for a specific plant helps that plant take up the nutrients in the soil so it can grow. Soil contains 14 essential plant nutrients out of 17 but the right pH is needed for the plant to absorb them. Drop off a soil sample to your county cooperative extension service and they’ll not only tell you the pH of your backyard soil, they will give recommendations for growing cannabis. Starting from there, you can amend it to give your personal-use plants some oomph.
Here’s where to drop off your soil sample:
NMSU-Bernalillo County Cooperative Extension Service: 1510 Menaul Blvd. Ext. NW, Albuquerque, 505.243.1386; 844.409.0562
Sandoval County Cooperative Extension Office, 711 S. Camino del Pueblo, Bernalillo, 505.867.2582
The Bernalillo County Master Gardeners Hotline will also answer your questions about how to amend the soil for maximum nutrient uptake. Call them at 505.292.7144 from 11am-2pm weekdays March through October; or call the Extension Office at 505.243.1386 from 9am-3:30pm (closed for lunch from 12-12:30pm) for an in-person appointment. Those folks also have pamphlets on all manner of gardening techniques, so grab a batch while you’re there.
For information on other counties, go to NMSU New Mexico County Cooperative Extension Services and scroll down to Locate Your County Extension Office.
Good soil is about 45 percent mineral matter, 25 percent air, 25 percent water and 5 percent organic matter. This composition allows for good drainage (essential for cannabis) and the oxygenation and feeding of plants and microorganisms. Microorganisms in the soil are nature’s little recyclers and also help to aerate soil. (Ever dig up a peony and discover more ants than you’ve ever seen in your life?) If you’re growing your pot in a pot, these are good proportions to follow as well.
What if you over-acidify? I’ve had advice from an old-school gardener who had been growing pot since before I was born and well before it was legal (*clutches pearls*). His trick was to use plain wood ashes with water – the ratio is one digging shovel of wood ash mixed with five gallons of water. Then mix it into the soil with a garden fork or just let it sit around the plants.