Hops are perennial rhizomous plants grown as ornamentals or to harvest the flowers and cones to flavor beer. These plants are heavy feeders and need plenty of water to produce the 20- to 30-foot (6 to 9 m.) vine. In proper soil, with bright light and consistent water, hops are speedy growers that get bigger every year. Try troubleshooting hops problems to find the root cause when hops stopped growing.
My Hops Stopped Growing
Even if you aren’t a home brewer, hops plants make elegant ornamental vines when trained over an arbor or trellis. The plants need at least 120 growing days, nutrient rich, well-draining soil, a soil pH of 6.5 to 8.0, full sun and plenty of water. These twining vines should be female to produce cones and should come from healthy, robust rhizomes. Failure to meet all these conditions can cause stalled growth on hops.
Even with all the proper requirements, hops plant problems like insects and disease may make your hops plant quit growing. Finding the cause of any plant problem can be like hunting for a needle in a haystack. Because growing conditions, disease and pests are all factors in successful growth, the potential causes can really add up.
Hops plant problems usually start with site and cultivation practices. Without enough water, the proper pH, plenty of light and good drainage, the vine is unlikely to thrive. Once you rule any of the conditions of growth out of the picture, you can focus on pests and diseases, of which there are many potentials.
Stalled growth on hops is common in the first year when the rhizomes are building energy and the vine is still too young to produce vigorous stem growth and cones.
Environmental Hops Plant Problems
If you’ve noticed your hops plant has quit growing and it isn’t a first year plant, look at how much water you are giving it on a weekly basis. Some growers recommend watering twice per day in the heat of summer, but this may be excessive, depending upon your soil type. A good rule of thumb is to water deeply, frequently and let the top couple of inches (5 cm.) of soil dry out before watering again.
Feed each plant with a side dressing of ½ teaspoon (2.4 ml.) of 21-0-0 fertilizer in June to add extra nitrogen. Dig in manure compost around the plants in spring. Prune plant vines to two to three healthy shoots to prevent excessive stems and promote cones. Tie the vines to a support structure to enhance sun exposure and strong scaffolding.
Diseases and Pests of Hops
Once you’ve ensured good siting and care for your hops plant, it’s time to look at some other causes of stalled growth on hops.
The most common disease issue is downy mildew, most prevalent in cool, wet weather, and is characterized by vines blackening and dying back. Vine pruning will increase circulation and prevent much of the problem. Spray plants with a mixture of water and baking soda to help prevent development of spores.
Insect pests are harder to pinpoint. Sucking insects cause much of the loss of vigor that stunt vines and diminish growth; aphids and spider mites cause leaf speckling, distortion, vine wither and overall lack of health. Insecticidal soap sprays will usually do the trick.
Big leaf eaters, like cutworms, cause the most damage to young plants. The pests come out at night and can completely girdle a vine as well as chow down on the leaves. Attacked plants look like they came from a Swiss cheese factory and entire stems may be cut off and killed. Hunting with a flashlight and squashing those nasty little organisms is the most expedient and earth friendly way to dispatch the threat.
Cucumber beetles are another common enemy of the vine and are large enough to hunt and destroy in the same manner you treat the cutworms.
Hops are the flowers or cones of female hop plants (Humulus lupulus see fig. 1). Historically, hops have been used as medicine, paper fiber, a salad ingredient, a sleep aid in pillows, and of course, as a preservative and flavoring agent in beer. The first written description of hops being used in beer comes from 12th century Germany (German Beer Institute, 2004–2006). In addition to water, malted barley, and yeast, hops are an essential ingredient in beer production. Hops contain alpha and beta acids and essential oils that contribute to beer’s bitterness and aroma. Brewers can alter the flavor, aroma, and bitterness of beer by adding different hop varieties during different stages of the brewing process.
The hop plant is most likely native to China, but hops are now grown in many temperate areas of the northern and southern hemispheres. Commercial hop production in the United States began on the East Coast in the 1700s, but eventually shifted to the Pacific Northwest, where more than 80% of U.S. hops are currently grown. With the growing appeal of specialty beers and locally grown foods, interest in hops has increased among Michigan farmers, gardeners, and home brewers.
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Why is Calcium Important for Plants?
Calcium plays several important roles in a plant’s growth and development. First of all, calcium is involved in the transport of other nutrients in the plant.
Calcium also contributes to strong cell walls in the plant. A plant with strong cell walls will show stronger resistance to disease and pests.
In addition, calcium is vital for root and leaf development. Strong roots and larger leaves allow a plant to absorb more water and nutrients from the soil, and more energy from sunlight.The root system of a plant.
3. Not Enough Water
Water is one of the essential things that seedlings and all plants need to grow. Water helps the seedlings transport nutrients from the soil and into the roots and throughout the stem and leaves.
Basically, water keeps the nutrients moving. Without enough water, even the perfect balance of nutrients in the soil won’t do anything for the seedling because it won’t be able to use them.
When a seedling is dry, it experiences cell damage and grows very slowly, and it will eventually dry. Although you may wait for the soil to dry out before watering some other plants, you should always make sure the soil for your seedlings is moist.
Benefits of Peat Moss
Peat moss offers numerous advantages and benefits to gardeners who wish to make their plants thrive. It has several important characteristics that gardeners need, such as high absorbency, sterile material, acidic ph features, compaction prevention properties, and more.
Here are the most important benefits of peat moss:
- Peat moss is a highly absorbent material. It can retain water much better than other types of soils. This is a great agent to include in your garden soil.
- Sterile medium. Peat moss provides a sterile medium, which is ideal for planting and growing your plants. It doesn’t contain any harmful chemicals, weed seeds and other bad thing you don’t want for your plants. This is why peat moss is ideal starting medium, particularly for tender, vulnerable plants that require a lot of care. This is why it’s a good practice to add a bit of peat moss to any starting mix.
- Acidic pH features. Peat moss is slightly acidic, which means it is great for acid-loving plants. There are many plants you may wish to grow that require slightly acidic soil, such as camellias and blueberries. If your garden soil is not acidic, add a bit of peat moss to make your acid-loving plants thrive.
- Compaction prevention. Peat moss is not compact, which is a great advantage over other organic materials. It is important to prevent soil compaction because such soil becomes less useful. Compaction reduces water absorption and doesn’t provide a good medium for any plants to grow. Peat moss is great because it can easy be re-hydrated and even one application prevents soil compaction for years.
The Threat of Viral Cannabis Diseases
Columns - Growing Pains
Growers worldwide are seeing Cannabis disease symptoms with unknown causes among their crops. Here’s what we know about potential causes, detection and what you can do to stop viral spread.Distorted leaf margins can be a sign of CDS infection.
Around the world people are coming to grips with the health issues and economic fallout of COVID-19. Public awareness of viral contagions is reaching unprecedented levels, presenting an opportune moment to address disease problems within the cannabis industry. As we are seeing with the novel coronavirus pandemic, harmful viruses emerge and adapt, and this is not exclusive to humans. Cannabis growers are increasingly experiencing the negative economic outcomes of decreased vigor, lower flower yields and reduced production of primary target compounds including both cannabinoids and terpenoids. What we are calling “Cannabis disease syndrome (CDS)” exhibits a suite of consistent symptoms, but with no readily apparent single cause. These symptoms, which do not appear to be caused by nutrient deficiencies or other pathogens, are often collectively referred to as “dudding” or “dudders.” (The term originated when growers would think a plant with decreased vigor or stunted growth was “just a dud.”)
Steadily declining vigor in commercial Cannabis clones is not a new phenomenon. As vegetative reproduction by rooting cuttings became popular in the 1980s, growers would occasionally see a clone that became weaker and less productive each time cuttings were flowered. Apart from lowered yield, there were few other symptoms of infection. We tentatively called this a “photocopy effect” based on our analogy that copying a copy of a copy of a copy, results in a faded image that eventually becomes a mere ghost of the original.
We knew that because lost vigor was appearing in asexually multiplied serial cuttings the problem could not be explained by “genetic drift,” which is a shift in the frequency of genes within a small sexually reproducing population. Growers wondered what the causes might be, and even addressed the possibility that simply making serial cuttings might result in diminished vigor.
Soon we realized the symptoms were caused by transmission of an infectious disease that became more and more prevalent through successive rounds of multiplication. (More on this later.) We destroyed clones exhibiting symptoms, carefully sterilized benches, pots and tools, and began to use fresh blades when taking cuttings from each mother plant. There were no known causes, just obvious adverse effects. Yet we found practical solutions, and soon the problem nearly disappeared.
Some similarities exist between the CDS we are experiencing today and COVID-19. Much like the human coronavirus, CDS is difficult to detect at first, as there is a wide range of symptoms. Through our and other growers’ observations of affected plants during the past few years, we have learned that vegetative plants can transmit CDS, while flowering plants are more likely to suffer the consequences. Because symptoms are not readily visible and are easily confused with other diseases, they both lie hidden within populations, and can very quickly become economically impactful. Another similarity between CDS and COVID-19 is that asymptomatic plants can infect the otherwise healthy, with more serious outcomes for some than others. Molecular testing is required to identify potential infections, and there are few laboratories that can effectively identify the causal organisms. Other than practicing social distancing and establishing quarantines, there are as yet no solutions to stopping their spread.
Cannabis disease syndrome cannot be attributed to a single pathogen, although there is a primary candidate for its cause (more on this later). In symptomatic plants, several infectious organisms may be involved, making accurate diagnosis and effective control even more difficult. If CDS killed more of its hosts rather than simply making them sick, then it would have been noticed much earlier, and should not have already spread so widely. As we also have observed while studying affected plants, the cannabis disease syndrome spreads most quickly by taking cuttings from infected plants, using them as mother plants, and thereby multiplying the disease through future generations.
What causes CDS?
In the Spring of 2019, two laboratories independently identified hop latent viroid (HpLVd) within a number of California sinsemilla clones, and this pathogen is the prime suspect in our search for the causal pathogen of the CDS we experience today. Originally discovered in Cannabis’s closest relative Humulus lupulus, the source of hops cones used in brewing beer, it is unclear how it spread to Cannabis. Unlike viruses and other diseases with more readily apparent symptoms, HpLVd is symptomless in most hop cultivars, affecting only the most susceptible. And, co-infection is often first indicated by the symptoms of opportunistic fungal pathogens that infect hop plants weakened by HpLVd, or plants weakened by HpLVd may become more susceptible to fungal or bacterial diseases, similar to the situation we face in diagnosing its infection of Cannabis.
CDS causal organisms travel through the plant’s vascular system, spreading from lower parts of stems (on the left) upward toward younger tissues (on the right).
How can we know if our plants have CDS?
Infected plants vary from the healthy norm. CDS symptoms are subtle and difficult to perceive and are therefore most noticeable in clones with which a grower has intimate familiarity. The foremost outcome of a CDS infection is lowered productivity resulting from a loss of vigor. Plants grow more slowly, flowers are smaller, and resin gland development is slowed. Lower branches appear to grow away from the central stalk more than usual and sag, while the main stem grows erect. Other common symptoms include brittle stems that easily break when bent, distorted leaf growth, variegated and chlorotic leaves and overall stunted growth, resulting in drastically lowered expression of terpenes and cannabinoids.
Although the presence of HpLVd may initially be asymptomatic, as it progresses, additional symptoms begin to appear such as stunted growth, general yellowing of the foliage, discolored mosaic blotches or streaks, interveinal yellowing, deformed leaf margins of younger leaves and discoloration within the stems, all characteristic symptoms of possible opportunistic coinfection by fungal or bacterial pathogens.
Adding more confusion, HpLVd-infected plants may actually exhibit symptoms that can be perceived as favorable, such as darker green foliage and increased branching, which complicates detection and control while increasing its spread through the propagation of seemingly healthy cuttings. Molecular testing by experienced laboratories is the only way to verify the presence of HpLVd.
Viral infections spread internally from infected to clean parts of the same plant, making sampling difficult. Only part of a plant might be infected, maybe just one or a few limbs. Since HpLVd may hide in a minute portion of the vascular system, the only way to know for certain that a plant is healthy is to test tissues from several parts of the plant before destroying it. Sampling each clone for pathogens, and verifying that the cutting remains clean, can be a costly process.
How can we control CDS?
Long before scientists discovered that a human immunodeficiency virus (HIV) is the primary cause of acquired immune deficiency syndrome (or AIDS), health care organizations were already advising people of preventative measures: use condoms, do not reuse needles, sterilize razors, etc. They understood the severity of AIDS and how to curtail its spread long before they knew its cause. As with human viruses, awareness, mitigation and suppression are the key elements in the control of plant pathogens. Once awareness is raised throughout our community, testing must begin to learn the causes of the disease and the extent to which it has spread. Infections must be traced back to their sources, and diseased plants either quarantined or destroyed. If the spread of CDS is stopped, it may eventually die out, or at least reach levels that do not cause widespread economic losses. There are several steps that growers should take to prevent the spread of pathogenic diseases in general, and specifically CDS.
1. Control pests.
Viral vectors include common Cannabis pests such as aphids, whiteflies, thrips and mites that transmit and widely spread viruses and other pathogens by first feeding on an infected plant, and then feeding on an uninfected plant. Effective pest control should be a part of every grower’s strategy.
HpLVd infection also attenuates flower and resin development. These plants of the same cultivar are the same age and grown under identical conditions.
2. Keep it clean.
Each time you take a cutting, the plant’s vascular system is susceptible to infection. When establishing new mother plants, use fresh, sterile blades directly from the package or use sterilized scissors for every cut to assure you are not transmitting a disease. Viral and fungal infections can also spread via contaminated containers, benches and growing media. Household bleach diluted with five parts water is an inexpensive and effective sterilizer. Spray clean tools, soak scissors, drench containers and wipe down benches. Use sterile media for rooting cuttings and growing flowers. Wash and sterilize your hands or change gloves before moving on to the next mother plant. When possible, buy clean stock from a trusted nursery.
Set up a sterile quarantine area for any new arrivals to your facility, and keep new additions isolated within until you become confident that they are not infected. (Again, the only way to be entirely sure a plant is healthy is testing.) Flower a few cuttings in isolation and watch for disease symptoms before multiplying your mother plants. Better yet, do not accept any foreign plants. As we have observed time and again, most grows become infected by taking in cuttings from others.
4. Limit visits.
An infected plant can touch an uninfected neighbor and spread diseases, and humans who come into contact with infected plants can also spread diseases. Prevent the spread of CDS by keeping people who may have been in contact with potentially infected plants, especially other growers, out of your quarantine and propagation areas.
5. Destroy affected plants.
The easiest, cheapest and most effective strategy is to destroy any mother plants you suspect are infected. Always label and number cuttings so you will know which mother they came from, then later each cutting can be traced back to its source. Should cuttings prove to be infected you should destroy the entire clone—the mother plants and all of their cuttings.
Stunted growth, as seen on the right, can be observed in plants where HpLVd has taken hold. These plants of the same cultivar are the same age and grown under identical conditions.
Can I get rid of CDS?
Once CDS is suspected and/or confirmed in a crop there are several possible solutions for its control.
1. Outgrow it.
Viral and fungal infections translocate through the vascular system of the plant and may be left behind in older tissues as plants develop, so it may be possible to simply outgrow the problem. Under vegetative daylength (more than 16 hours of light each day), transplant small mother cuttings into fresh sterile media, feed them well, and grow them rapidly under strong artificial lighting, or better yet, under full natural sunlight. Take small cuttings from the uppermost meristems or growing tips of the fastest growing plants and root them in sterile media or an air rooter with sterile water. The more cuttings a grower roots, the higher the chances of selecting a clean one.
Unfortunately, many of society’s most popular clones, some of which have become industry standards, have the highest chance of being infected. By now they have been through countless vegetative propagation cycles, and each cycle exposed them to possible infection. Whenever feasible, replace potentially infected cuttings with an earlier version of the same clone. Smaller growers who focus on fewer varieties may have started with and still maintain an uninfected clone. Quarantine any new arrival and be sure it performs better before replacing your old favorite.
There are other possible solutions that should be outsourced unless a grower has the resources to try them on their own. Micropropagation of meristems in vitro has been touted as a way to clean an infected clone. Many confuse micropropagation with in vitro culture of callus or undifferentiated cells, the plant version of stem cells. Meristems are the last place pathogens reach as they spread through a plant, and the smaller the cutting, the less chance it will be infected. Micropropagation protocols root tiny meristems in sterile conditions, much smaller cuttings than can be rooted in a typical commercial nursery. Once a clean clone is maintained in sterile culture it remains clean, and when multiplied under sterile conditions its offspring will also be clean.
Micropropagation alone does not remove pathogens. However, nurseries are developing protocols to reduce and possibly eliminate pathogen loads by passing meristems through a series of conditions that kill disease organisms without killing the plant. Although theoretically possible, no company has shown that this process actually works, and results in a disease-free plant that also retains its favorable characteristics. One can only know if cleanup has been effective by first testing to be sure a pathogen such as HpLVd is present before treatment, and then cannot be detected following treatment. A clone that has been “cleaned” should also exhibit the favorable traits it had before it became infected. Before spending money, one must decide whether their clone is worth attempting to recover, or whether it would be more efficient to restart with clean nursery stock or seeds.
The localized chlorotic yellowing of leaves can be caused by HpLVd infection as well as other opportunistic fungal and bacterial pathogens associated with CDS.
2. Sow your seeds.
Unsanitary cuttings are the main root of Cannabis diseases, and rather than trying to clean an infected clone, growers can simply sow seeds. Seed and pollen transmissions of viruses and viroids have been shown for several crops but are unconfirmed in Cannabis. Traditional seed propagation interrupts a pathogen’s life cycle, allowing a fresh start each year. Seeds provide the best chance of procuring clean plants and establishing a new clone. Who knows? You might even discover the next OG Kush!
CDS rarely kills individual plants, which is one reason for its silent spread, but it may well be lethal to our industry. We have no measure of how fast it is spreading. We are only beginning to examine the problem, and as our awareness increases and growers begin to experiment, more effective solutions will certainly appear. As cannabis is increasingly commercialized, disease control will become the responsibility of licensed and certified nurseries that will preserve and distribute clean stock, like all clonally based commercial agriculture from potatoes to berries.
It is high time for our industry to be proactive. CDS as well as other diseases have become part of our industry and are likely here to stay. As with viruses within our human population, we will learn how to live with them and manage them efficiently.