Description
Hop,
Humulus lupulus, is a climbing perennial plant in the family Cannabaceae that is grown for its flowers which are used extensively in the brewing industry. The hop plant is a climbing plant with grasping hooks that help it grasp the substrate. The plant climbs upwards in a clockwise direction and has opposing pairs of leaves which are covered in hairs. The plant produces flowers called 'burrs' which develop into scaly cones, or 'hops'. The hop plant vine can grow 6–9 m (20–30 ft) in length and can be harvested for many years. Hop may also be referred to as common hop and likely originated from Central Asia but now grows native in many areas in the Northern Hemisphere.
Hop plants
Hop vine
Hop plant
Hop leaf
Hop flowers
Hop cones
Uses
Hop cones are usually dried and used in the brewing of beer to impart bitterness and aroma.
Propagation
Basic requirements
Hop plants can grow in a wide variety of soils as long as there is adequate drainage, but a loose loam or sandy loam with a high organic content and a pH between 6.0 and 7.5 will produce optimal growth. Hop plants are perennial and can be harvested for many years, they should be provided with adequate vertical space to allow the vines to spread. Hop plants should be grown in full sun and require a tall trellis or fence which is large enough to support 6 to 9 m (20-30 ft) of vine growth. The plants require a period of approximately 8 weeks at low temperature in order to break dormancy.
Propagation
Hop plants are vegetatively propagated from the pieces of rhizome which should be obtained from a reputable breeder. Only female rhizomes should be planted as it is the female flower that is harvested. Plants grown from seed exhibit highly variable characteristics and are not suitable for commercial production.
Planting
Hops should be planted as soon as the soil can be worked in the Spring. The plants can survive a frost but will not tolerate the ground freezing over. Rhizomes should be kept refrigerated until the soil is ready for planting. Rhizomes should be planted horizontally in trenches approximately 30 cm (12 in) deep, leaving 1.5–2.5 m (5–8.2 ft) between plants. Hop plant require a trellis system in order to train the long vines. The support system usually consists of a supporting pole and wire with strings for the plant to grow on. There may be up to four strings per plant which are fixed from the ground to the wire.
General care and maintenance
After the first year of growth, the plants will produce an excessive amount of shoots which need to be cut back once several shoots have been selected and trained to grow on the supporting structure. Unwanted shoots can also be defoliated using chemicals. Mounding earth around the base of the plants will help to reduce the amount of unwanted shoots. The soil around the hop vines should be amended with compost every spring and the vines will also benefit from a side dressing of nitrogen fertilizer later in the growing season.
Harvesting
Hop cones should be harvested before the first frost. Generally, cones are harvested in mid-August to mid-September. The cones will have a papery texture when they are ready and will produce a fine yellow powder and strong aroma when crushed. The lower bracts of the cone may also be beginning to turn brown. The vines should be lowered to the ground and the cones removed from the plant. the cones should be dried prior to storage by threading them out thinly on a screen and allowing to air dry. The cones are fully dry when the inner stem becomes brittle.
Commercial hop production
References
CABI Crop Protection Compendium. (2008). Humulus lupulus datasheet. Available at: http://www.cabi.org/cpc/datasheet/27956. [Accessed 18 November 14].
Paid subscription required.
Drost, D. (20100. Hops in the Garden. Utah State Cooperative Extension. Available at: http://extension.usu.edu/files/publications/publication/HG_Garden_2006-06.pdf. [Accessed 18 December 14].
Free to access.
Mahaffee, W., Pethybridge, S & Gent, D. H. (2009). Compendium of Hop Diseases and Pests. American Phytopathological Society Press. Available at: http://www.apsnet.org/apsstore/shopapspress/Pages/43764.aspx.
Available for purchase from APS Press.
Common Pests and Diseases
Diseases
Category : Fungal
Black root rot
Phytophthora citricola
Symptoms
Blackened and water-soaked areas on the roots; yellowing leaves; wilting stems; blackened leaves which remain attached to the stem
Cause
Oomycete
Comments
Downy mildew
Pseudoperonospora humuli
Symptoms
Stunted, brittle, and light colored shoots; flowers turning brown; curled and/or cup shaped leaves; brown lesions with yellow halos on underside of leaves
Cause
Fungus
Comments
Fusarium canker (Cone tip blight)
Fusarium spp.
Symptoms
Cankers on the base of the climbing stem (bine); sudden wilting of bines at flowering or in high temperatures; leaves at the tips of the cone turning brown; inner supporting portion of the hop cone is brown and dead
Cause
Fungi
Comments
Gray mold
Botrytis cinerea
Symptoms
Lesions on the tips of leaves associated with the cones (bracts) turning tan to dark brown; discoloration may spread from the bracts to the entire cone; gray fuzzy growth on the tip of the cones
Cause
Fungus
Comments
Powdery mildew
Podosphaera macularis
Symptoms
Pale green to yellow spots on top side of leaves; white lesions developing from spots on the leaves, stems, or cones; lesions developing white, powdery fungal masses; slow growth of shoots; shoots covered with white fungal powder
Cause
Fungi
Comments
Red crown rot
Phomopsis tuberivora
Symptoms
Red to orange discoloration of the inner tissue of the plant; uneven root growth; yellow lower leaves; climbing stems developing little side branching
Cause
Fungus
Comments
Sooty mold
Cladosporium spp.
Fumago spp.
Symptoms
Flat layer of black mold on the leaves (including bracts), and cones; reduced cone quality; wilting of the climbing vines; rapid death of leaves
Cause
Fungal complex
Comments
Verticillium wilt
Verticillium albo-atrum.
Verticillium dahliae
Symptoms
Yellowing of leaf tissue between the veins; swollen climbing vines with brown discoloration of the inner tissue
Cause
Fungus
Comments
White mold. (Sclerotinia wilt)
Sclerotinia slcerotiorum
Symptoms
Water-soaked lesions on the stem just below the soil line; tan to gray lesions develop out of the water-soaked region; white fluffy fungus and hard black specks on diseased tissue; yellowing leaves
Cause
Fungus
Comments
Category : Viral
Mosaic virus
Hop mosaic virus (HpMV)
Hop latent virus (HpLV)
American hop latent virus (AHLV)
Symptoms
Yellow and green mottling between the leaf veins; reduced plant growth
Cause
Virus
Comments