The Cannabis Pre-Flower Stretch Phase: How Tall Will My Outdoor Plants Get?

10-Foot Plants in Mid-August: What to Expect During the Pre-Flower Stretch Spurt

As daylight hours begin to shorten in mid-August, outdoor cannabis plants shift gears from vegetative leaf production into the initial pre-flowering stretch phase. This transitional surge is when plants explode vertically, often adding anywhere from 30% to over 100% of their total vegetative height before bud formation sets in.

Currently, the tallest plants in my garden are already brushing 10 feet tall, and the pre-flower stretch is just getting started! How tall can these plants get??

The Double-Edged Sword of Fast Growth in Living Soil

When cannabis taps into deeply amended organic living super soil, the growth rate can almost be too fast for the plant’s own good. Cell division happens so rapidly that the vascular walls cannot mature…(turn woody and hard) as quickly as the plant stacks on top-heavy mass.

This creates thick, succulent stems that are vulnerable to snapping under heavy late-summer gusts before they fully harden off. A massive 10-to-15-foot canopy acts like a giant green sail in the wind, which means structural protection can become important! My plan from the start of this grow was to grow these plants as I have countless 15 foot tall plants guerrilla…no support at all.

Minimal Support: T-Posts, Two Ropes, and a Wattle Fence

While modern grow guides often advocate for extensive cages and multiple layers of plastic trellis netting, cannabis is naturally a rugged, durable plant capable of thriving without complex support. But, that did not take into account just how fast these plants would be capable of growing.

• Backside Line Support: Instead of boxing plants into cages, a row of sturdy T-posts running the length of the plot paired with just two long strands of rope provides a simple, effective backstop. To stop the wind from laying them all the way over.
• Wattle Windbreaks: A low wattle fence in front of the bed disrupts ground-level wind gusts, breaking up the force of mountain winds right at the root zone.
• Natural Flexing: This minimal setup allows the main stalks to move naturally with the breeze—which builds strong root flares and thick woody bases—while preventing sudden micro-bursts of wind from leveraging and snapping brittle main branches. Gusts in that country can get up in the 40 MPH range.

Zero Bottom-Pruning for Seed Production

Many growers spend hours lollipopping and stripping undergrowth to direct energy exclusively into top colas. In this plot, the lower canopy remains completely un-pruned from the ground up.

If one grows in an area of high humidity stripping that lower growth is paramount…but here in the foothills of the Simcoe Mountains I enjoy a very arid environment, and molds, and mildew are not much of a problem.

• Practical Time Investment: Manually thinning out the bottom branches of a wall of 10-foot-plus bushes would easily take 10+ hours of tedious work with zero benefit to the end goal.
• Maximizing Seed Yield: When growing a crop for open seed production, every single lower branch, node, and calyx is valuable real estate. Dense lower growth translates directly into more seed yield.

Managing Moisture on a North-Facing Slope

Conventional growing dogma usually advises against north-facing slopes, citing lower sun angles and damp, trapped moisture. However, hillside topography offers a distinct microclimate advantage: continuous convective air drainage.

As cooler mountain air moves down the slope, it creates natural air movement right through the dense lower canopy. In a dry late-summer climate, this steady airflow clears out stagnant pockets, keeping mold and mildew risk virtually nonexistent despite the lush, un-thinned foliage.

Conclusion

I am having a ‘How Tall Can They Get’ contest, so stop by and give me you best guess….Read to the end of the post for the contest.

It is funny, but after growing this plant for over 50 years I am still learning during certain grows….this one for sure. I have not used super soil much over the years opting instead to simply feed my plants when I water…as I can assess their needs easily.

I have not had plants bush like this much…especially after only topping them one time. This is a direct result of the nutrients readily available to them in that super soil! I will be creating more of these hugelkultur super soil planting beds up at Stony Oasis for sure. I am debating making them just a couple feet apart for a large garden. Am thinking about planting veggies in them with drip irrigation.

I can only imagine what a crop like winter sqaush, or pumpkins would do in one! I cannot wait to experiment more with them!

Have you ever used them? Tell us about it in a comment. I would love the input.

Here are prior updates on this grow…

How to Grow 10lb Cannabis Plants Off-Grid: The 2026 Super Soil & Dryland Hugelkultur Guide

Dryland Hugelkultur Cannabis Grow Central Washington

Early Summer at Stony Oasis: Hugelkultur Cannabis Grow Update

Mid-Summer Explosion: How the Hugelkultur Bed is Feeding My Cannabis Plants

How to Grow Massive Harvests: Techniques & Heavy-Yielding Strains

Creating Massive Growth in Cannabis Plants With Organic Super Soil

Can You Grow 10lb Cannabis Plants in the Mountains? My Dryland Hugelkultur Experiment

Off Grid Living Soil Cannabis Grow Update: Growing Dryland Cannabis