Two species of hops (Humulus spp.) are commonly grown in home gardeners: common hops (Humulus lupulus) and Japanese hops (Humulus japonicus). Both produce similarly showy, cone-like flowers and can be grown from seed. Despite their similarities, common and Japanese hops differ drastically in how and why they are grown. Understanding those differences before attempting to grow them from seed will help you determine if it’s a worthwhile endeavor or a waste of time.
Hops can cause skin irritation in certain individuals, so wear protective clothing and gloves when working closely with the plants.
Type and Climate
As a genus, hops grow perennially in U.S. Department of Agriculture plant hardiness zones 4 to 9, although cold hardiness varies between species. Common hops and Japanese hops grow in USDA zones 4 to 8, along with ornamental types such as ‘Aureus’ (Humulus lupulus ‘Aureus’) and ‘Variegatus’ (Humulus lupulus ‘Variegatus’). ‘Crystal’ (Humulus x ‘Crystal’), a dual-purpose type, thrives in warmth and will grow in USDA zones 4 to 9.
Hops require 120 frost-free days and more than 15 hours of daylight during the summer to produce flowers, so they grow best in latitudes between 35 and 55 degrees.
Hops are dioecious plants, which means each plant is either male or female. Female plants produce the aromatic cones used in beer-making while male hops produce small, pale green catkins.
Seed-propagation results in plants of either sex, so there’s no way of knowing what you’ll get. Also, seeds may not reproduce the favorable traits of specific cultivars such as ‘Aureus’ or ‘Crystal’. For that reason, vegetative propagation is best when growing hops for brewing or when trying to reproduce a specific cultivar.
Grow hops from seed only if using them as ornamentals or start multiple plants to help guarantee both sexes are represented.
Site Selection and Preparation
Hops grow best with full sun or part shade and sandy loam soil. A soil pH between 6.0 and 7.0 is best, although good drainage is even more important. Improve very sandy or clay-based soil with a 3-inch layer of compost worked into the top 12 inches of soil. Hops need a sturdy structure to support their vigorous bines, or twining stems, so prepare the bed against an existing structure or install an arbor or trellis along its northern edge.
Hop seeds need a chilling period at 35 to 40 degrees Fahrenheit to induce germination, a process known as stratification. A minimum of two weeks will work but three months is even better. Seeds must be kept moist during the chilling process. Starting them directly outdoors takes care of the temperature and moisture requirement, while indoor sowing requires an artificial approach.
Hop seeds can be chilled, or stratified, multiple times if the first time isn't successful.
Timing matters when starting hop seeds outdoors. With nature taking care of the hop seeds’ chilling requirement, however, it’s a far simpler process than starting them indoors. Sow the seeds in spring roughly four weeks before the last frost. Sow them at a depth of 1/8 to 1/4 inch and space them 12 to 18 inches apart.
Moisture is critical when starting hops seeds. Water the bed with a misting hose whenever the soil surface feels nearly dry. Do not use a watering can or any other heavy flow of water because it can dislodge seeds.
Stratified hop seeds will germinate in three to four weeks, at which point they should be thinned to one every 2 feet.
In warmer climates, sow hop seeds in autumn to ensure germination the following spring.
Indoor sowing allows for more control over the chilling and germination conditions, but it requires a few more steps and pieces of equipment. Start eight to 10 weeks before the last frost for transplant in spring.
Things You'll Need
- 3-inch peat pots
- Potting soil
- Plastic bag
- Spray bottle
- Heating coil
Fill individual 3-inch peat pots with standard potting soil. Leave the top inch of the pot empty. Moisten the soil thoroughly and allow the excess water to drain off.
Sow two hop seeds in each pot. Press them onto the soil-surface, then cover them with a 1/8- to 1/4-inch-thick layer of soil. Mist the soil to settle it.
Place the pot inside a sealable plastic bag and close it. Store the pot in the refrigerator for two to three weeks to chill the seeds. Periodically remoisten the soil to keep the seeds alive.
Move the pot near a south-facing window after the chilling period. Set it on a heating coil or germination mat set to 70 to 75 degrees F. Remove the plastic bag.
Water with a mist bottle when the soil feels nearly dry on the surface. Watch for sprouts in three to four weeks. Pinch off the weaker of the two hop seedlings at soil level.
Transplant the seedlings into a prepared bed a few weeks after the last frost once the soil warms up. Space them 2 feet apart.
Provide young hop plants with 1 inch of water each week during their first season in the garden. Regular watering is especially necessary in hot climates where summer precipitation is rare. Water only if no rain falls during the week or if the plant is wilting during extreme heat. A 2-inch layer of mulch will help regulate soil moisture; make sure to leave a 2-inch gap between the mulch and the plant's base.
Weekly feeding encourages fast, dense growth. Dilute 1/2-teaspoon of balanced 15-15-15 fertilizer in 1 gallon of water. Water each plant with the solution.
Japanese hops are invasive across the eastern United States.