As we’ve transitioned from spring to the official start of summer on June 21, our hops have been going through all sorts of physiological changes. Technically speaking, hop plants go through a number of growth phases throughout the year, called “phenophases.” Back in 1995, German researcher Rossbauer and colleagues published an article, outlining specific phenological growth stages of hops, as follows:
- Stage 0: Sprouting
- Stage 1: Leaf development
- Stage 2: Formation of side shoots
- Stage 3: Elongation of bines
- [They did not include a stage 4]
- Stage 5: Inflorescence emergence
- Stage 6: Flowering
- Stage 7: Development of cones
- Stage 8: Maturity of cones
- Stage 9: Senescence, entry into dormancy
While knowing when these individual phenophases occur may help us better fine tune the timing of our management practices, we generally lump hop growth into two phases–vegetative and reproductive. And, because hops are photoperiod sensitive (meaning that day length drives their production), the summer solstice generally marks the transition from their vegetative growth to reproductive growth.
During the spring months, hops focus their growth in the main bines, which climb upright, as well as the leaves growing on these bines. While the day length continues to get longer, the plant is pushing to get the main bines as tall as possible. The amount of vegetative growth ultimately determines how much the plant will yield, so it is important to manage plant health aggressively during this time.
By June 21, hopefully the main bine has reached the top wire of the trellising system (16 feet) since after that point, the length of day gets shorter, and the plants will transition to the reproductive growth phase. The plants may grow a bit taller but vertical growth generally slows. Instead, the plants focus on growing lateral shoots extending from the main bines where the hop cones form. From this point, we’ll see the production of burrs which develop into flowers and then cones.
And in a couple months, before we know it, we’ll be harvesting our hops! Until then, keep calm and hop on…