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Hosta FAQs: What can go wrong? Hosta viruses...

Dew you know

what to dew?

'Sum and Substance' with virus. Notice the "melted plastic" look of sunken tissue, and uneven discoloration (of what should be a chartreuse hosta).

'Seventh Heaven' is a streaked hosta.

'Revolution' is a speckled hosta. Not virus!

'Undulata' gets "summer uglies," which are not virus.

While there are lots of places online to find information about hostas (see our links), and of course a number of books you can buy for ready references, we didn't feel that there was a good place online for FAQs (Frequently Asked Questions), as experience with the American Hosta Society's Facebook page has shown. We hope you find this useful. The good stuff is at Part I. Here are FAQs on Hosta Virus X, the most serious problem of hosta commerce.

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Use the little ˅ to open (and then collapse) each answer. Be sure to scroll to the bottom for instructions on keeping your garden tools clean.

  • What is a hosta?
    Hostas are a group of plants (genus) native to Japan and eastern Asia. There are about 40 species of hostas, but they interbreed fairly easily to produce thousands of cultivars. (See Lingo page.) While they are often called “hosta lilies,” they are in fact more closely related to agaves (those spiny succulents) than they are to daylilies or true lilies. They are perennial, meaning they will go dormant for winter but should come back year after year. They do require dormant phase — a period of cold temperature — in order to survive year after year, so don’t be tempted to use one as a house plant. They will grow in climate zones 3 – 8 (in North America, that means well into Canada almost to the Gulf coast), provided they get enough water.
  • What is a hosta society?
    Officially, most are 501(c)3 organizations for educating the gardening public about hostas. Informally, they are great groups of people who get together to learn about hostas, to buy and sell hostas (through auctions or open sales), and to see beautiful private gardens that usually feature hostas. There are many local societies in North America, all under the loose umbrella of the American Hosta Society. The AHS publishes a high-quality journal, supports scientific research projects on hosta pests and diseases, manages the registration of new hostas, and supports the national convention of the society. Membership is not expensive, so join up and meet hosta lovers IRL (in real life)!
  • What should I use to fertilize my hostas?
    Hostas are actually pretty efficient at getting what they need from the soil, so if your soil is good, you may need no fertilizer at all. Many people (especially commercial growers) will use fertilizer, though. Any all-purpose fertilizer will do. Milorganite is used by many as it has additional deer-repellent properties. Hostas in pots should be fertilized a few times a season (or with a slow-release formula). Bob Solberg, who knows his stuff, uses a slow-release in the spring, and then a foliar feed with a product designed for tomatoes in early summer. Don't fertilize after mid-summer (mid-July here), as hostas need to prepare themselves for dormancy.
  • Should I mulch my hosta beds?
    For most gardeners in the US, the answer is “yes.” Mulch helps hold in moisture and keeps down weeds. You can use any shredded wood/roots/bark product, or mulch with shredded leaves, pine needles or even grass clippings. In general stone products do not make good ground cover for hostas, although in smaller pots or trough gardens it may be nice. Be sure not to pile mulch up around the crowns of hostas as it can cause rot problems. A nifty way to solve this is to place upside-down nursery pots over the emerging crowns in spring, toss mulch over everything to the depth you want (1-3 inches is good), and then remove the pots to leave an unmulched hole around the crown. The hosta mound will expand to hide the hole. Do beware that voles can use mulch as a nice way to tunnel through your beds to get to your hostas.
  • Should I water my hosta beds?
    Yes, you probably should. In their native habitat, hostas receive as much as 50" of rain during the growing season. While most will handle the higher heat levels they see in North America compared to Japan and Korea, they cannot adapt to low water levels. Commercial growers will see that their hostas get 1/2" of rain three times a week. Hostas in pots will especially need regular watering, but let the soil dry somewhat between waterings so you don't cause rot. On the other hand, hostas can be quite dry in the winter when they are dormant; avoid piling snow on them during winter.
  • Should I label my hostas?
    Keeping track of your hostas becomes important one you're bitten by the bug. Visitors to your garden will want to know which is which. One way to keep track is to photograph each bed and use photo software to label each plant. Others use hand- or computer-drawn maps. Labeling the plants in the garden is a matter of preference, but it does help you keep track of who is who during the growing season and the dormant season. How you label is a question of cost and aesthetics. You will likely find that with inexpensive metal markers, you get what you pay for. Top-quality markers using stainless steel wire can be purchased from Kincaid, and DVHS members can contact the webmaster to get the discount code, good for $1 off each bundle of 25 markers. The two best options for fixing labels to the markers are the Brother P-touch laminated label tape, or the Avery "weatherproof" laser-print labels. Both should last for many years in the garden.
  • When is the best time to move/divide my hostas?
    If you’re leaving the hostas intact, you can move them at any time you need. Ideally you get them settled in (don’t forget to water regularly) before the first hard frost. Dividing the clumps causes more stress to the hosta, of course, so it’s best to do that in spring (when they have plenty of time to recover and look nice) or in late summer (when they won’t be looking so nice for the rest of the season anyway). Bob Solberg, of Green Hill Farm in North Carolina, divides most hostas for the purpose of increasing stock in late summer, but believes that siebodiana-type hostas (like ‘Elegans’) don’t like this, and prefer division early in the season. A related question is: Should I divide my hostas? Generally the answer is “no,” as most hostas will get better and better with age. It’s better to move hostas around to make more room, and let them show off, rather than divide them to keep them small. However, some do get crowded (in a border, for example). A good strategy for this is to dig each clump, divide into three or four wedges, plant one back in the original hole with some nice extra soil, and use the other pieces for other uses (like getting new gardeners hooked on hostas). Other big hostas, over time, may develop a “fairy ring” effect with a dying center section. You can dig these up, clean away weak tissues, and reconstitute a single clump.
  • My hosta has a part that looks different from the rest of the plant. What do I do?
    Your hosta has probably produced a mutation, known as a “sport.” (See Lingo page.) If your hosta is variegated but the sport is a solid color, then you probably don’t want it. As a first pass at stopping the conversion to the solid color, see if you can simply snap off the eye (shoot or division) at the base of the plant. If it comes up the next year with more of the solid color, you should dig up the plant and perform a bit of surgery to isolate the part you want to remove (for keeping or discarding). You’ll also want to do this if you want to save the part that’s a different color (say it was a solid hosta but now has variegation). Untangle the roots (by soaking in or washing with water), then use a sharp knife to cut the crown (central structure) around the eye or eyes you want to separate. Some hostas may simply break apart to release the divisions. Then you can replant your original hosta. If you want to compare your sport to what others might have found, use Hugo’s database to search for the original plant, and then look at the list of offspring (sports and seedlings) that he helpfully provides. Note that some hostas, particularly the white-centered Undulata forms, may have color changes through the season, or later flushes of leaves may have a different appearance from spring leaves. Be sure you can tell the difference between normal color changes and true sports.
  • Should I cut down my hostas in the fall?
    Most people will opt to wait until the leaves die back, so you can rake them up when they easily separate from the crown. Yes, if you leave the rotting leaves in place it does return nutrients to the soil, but it can also help spread some diseases. It also can look unpleasant. Better to collect the leaves and compost them so that any pests get cooked out, and then use that nice compost the next year.
  • I don't like hosta flowers. Can I cut them off?
    First is to know that your hostas are free of disease (See FAQ Part IIa) before going from hosta to hosta and cutting off flowers. If tools are not well-cleaned between plants, you can transfer the disease. Second is that many hosta flowers are pretty. If your hostas are mostly Undulata types, then they're admittedly not very attractive. Buy hostas with prettier flowers (or even fragrant ones). Many people see hummingbirds visiting them; I only see happy bees, so consider that as well. Third is that blooming is part of the hormonal, seasonal life cycle of the plant. If you cut off blooms before any open, the hosta can get confused and try to make more blooms, taking energy away. Let a few flowers open on each hosta before cutting, if cutting you must; removing blooms at this point really doesn't affect the growth rate of the hosta one way or the other. Fourth, go ahead and cut the blooms after blooming is finished, unless you want the seeds from that hosta. If you don't have a good hybridizing program, your seeds are unlikely to be really good hostas (compared to those produced by careful hybridizers). But don't let me stop you from having fun by trying to grow some. See FAQ Part III for a brief tutorial. If you do want to collect the seeds, it takes about two months from pollination to the point when seeds are ripe. The pod may still be fairly green at that time, but the seeds inside should be fully black: a small kernel at one end with a long, flat “wing.” Once the pods fully ripen on their own they can split open and spill the seeds—perhaps giving birth to new hostas we call “weedlings”—so if you want to collect them you’ll have to catch them first.
  • Can I grow hostas in containers?
    Sure! Here’s an entire web essay on the topic.
  • Can I grow hostas as houseplants?
    You probably shouldn't. They require a dormant cold period (in case you missed that above), and will die of exhaustion if they don't get to sleep. They would, however, be fine indoors for a few weeks during the growing period if you want to use them for decoration. Some hybridizers bring their prized plants indoors during the blooming period so they can protect the flowers from undesired cross-pollination.
  • Can I grow hostas in full sun?
    This is truly a Frequently Asked Question (or its variation, "What hostas grow in full sun?"). A better question is: Will any hostas thrive in full sun? The answer, in general, is: In our area, they might live but they won't look good. Look for the sun-tolerant hostas at www.hostalists.org, and you'll see a long list, but take the warning that many people who contribute to that list live a good bit further north than we do. So if you ask this question, you should have a good reason for planting hostas in a place where sun-LOVING perennials would be a better choice. Or you should have a really good plan to water, water, water. If you must, start off with a vigorous fragrant hosta like 'Guacamole'. If that grows, then you can try others.
  • Can I grow hostas in deep shade?
    As with the FAQ above, the answer is: not really. Hostas are shade-TOLERANT, but only a few deep green species could be considered shade-LOVING. Deep shade also often means tree root competition or reduced water, which make it even harder for hostas to thrive. In deep shade, try the indestructible H. ventricosa, H. clausa var. clausa, or even 'Undulata Erromena'. It's much better to plant your hostas where they get filtered light (what is known as "high shade"), or where they get 3 or 4 hours of direct sun (morning sun is best) each sunny day.
  • Can I grow a hosta from a leaf cutting?
    Hostas are not like African violets, where you can take a leaf, dip the petiole in rooting hormone, and create a clone. Hostas require some crown (rhizome) tissue to make new roots. (Tissue Culture is a very special case of this.) But if you break off a hosta eye with some crown tissue holding it together, you can, in fact, expect it to grow roots. Rooting hormone helps, and you'll need to support the hosta to keep it upright. It might take two weeks for roots to start forming, during which time you should keep it in deep shade and in constantly moist soil. Indoors would be best.
  • Can I grow hostas from seeds?
    In short, yes. But for a good answer, see FAQ Part III.
  • What are the biggest and smallest hostas?
    Because hosta size depends so much on the age of the hosta and its growing conditions, the only relatively comparable measurements are for the hosta leaf size, as these determine into which section the leaf is placed in a Hosta Show. Based on this, the largest registered hosta is 'Empress Wu', whose registered leaf length x width (in inches) registers a whopping 700, more than 50% bigger than the next largest. And while there are some massive clumps of 'Sum and Substance' and its sports out there (with L x W measurements around 300), it's a good bet that a well-grown 'Empress Wu' will be your biggest hosta. At least for right now; rest assured that hybridizers are literally working on breeding the Next Big Thing! Smallest presents a bigger challenge, as a poorly-grown specimen can have tiny leaves compared to a well-grown specimen, and even a hosta with tiny leaves can spread to cover a considerable area. Per registration leaf size, though, 'Thumbnail' checks in as the smallest, with its L x W measurement registering 0.38, although Hosta Library pics don't show it as that much smaller than some of its tiny relatives like 'Tiny Tears'.

'Gypsy Rose' with late-season mottling: suspicious but not virused.

hosta edge mist.jpg

Edge misting on a variegated form of 'Halcyon' (probably 'Autumn Frost'. Not virus!

How do I clean my tools to keep from spreading viruses?

Here’s a long and thorough answer from Chris Wilson:

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Shovels: When digging up hostas, especially older/larger ones, you invariably cut into the roots. If your hostas are growing in close proximity to each other there is also the real possibility that when you dig up one plant you are cutting right through the roots of a neighboring plant. If one plant is infected and in the process of digging it you cut through a healthy plant's roots you could very quickly and easily spread the virus to the healthy plant.

 

So to prevent this sap transfer when digging out infected plants we suggest:

1) Dig from the side that is farthest away from any other plants, 2) Dig closer to the crown of the infected plant, and/or 3) Consider digging with a spading fork instead. These have a reduced surface area and instead of cutting out plants they pry out plants, therefore reducing the amount of cut, root to root contact as compared to shovels.

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When you are done digging a known infected plant you will definitely need to thoroughly clean off your digging tools. You must remove as much of the plant sap as possible, which means scrubbing and wiping off the surface of the shovel or spading forks, preferably with disposable rags or towels. You may also want to disinfect the tools to further reduce the chance of virus remaining, especially if you were digging and cutting into a highly infected plant.

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Cleaning can be done with just about any household cleaner, with the focus on removing the dirt and plant sap. If the plant sap is removed, so should the virus. Disinfecting can be done by soaking in bleach or Lysol (or other known virucidal cleaners), although it is still important that you remove the dirt and sap before soaking. Most of the known, tough to kill viruses are neutralized after a 10 minute soaking in a bleach (1 to 2%)** or Lysol solution, and although we aren't certain how long it takes to kill HVX this is probably a safe estimate, especially if you've taken steps to remove all the sap.

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Again, if working with a known infected plant I recommend you thoroughly clean off the dirt and plant sap and also soak in a disinfecting solution. For everyday use it is generally accepted that if you surface clean your tools this will neutralize and eliminate most of the plant sap, and without the sap this will greatly reduce the chances of spreading the virus.

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NOTE: Simply dipping your shovel or pruners in a cleaning solution for a brief moment will not provide any protection from the virus. HVX is a highly stable virus so you must work to remove and neutralize the plant sap first, then soak to disinfect.

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** When mixing bleach you want a 1 to 2% solution to kill viruses. Most bleach is sold in a 3% solution, so you would mix one cup of bleach with one cup of water for a 1.5% solution. "Ultra" bleach is usually a 6% solution, so you would mix one cup of ultra bleach with three cups of water for 1.25%. When cleaning with bleach this can rust metal, so some people like to oil their tools afterwards to prevent rust. The bleach chemical also evaporates quickly from a bucket, so mix a new solution very often or put a lid over the bucket when not in use to prevent it from evaporating too quickly.

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Pruners and scissors: When cutting into hosta leaves and scapes there is a large amount of plant sap transferred to these tools. Even moreso than when digging, although digging into neighboring roots transfers the virus quite easily too. Cleaning your pruners or scissors between cuts must be even more thorough than cleaning shovels.

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For this job one of the easiest ways to clean is using disinfecting wipes. Clorox wipes can be used to both remove the plant sap and provide some surface disinfection.

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Another method is to use a spray bottle of rubbing alcohol or Lysol and lots of paper towels. We purchase 90% rubbing alcohol and put that in a spray bottle for everyday scissor and pruner cleaning, but we also mix up a spray bottle using Lysol concentrate mixed at a very high rate and use that when working with known or possibly infected plants when we sample leaves for testing. Spray the tools down thoroughly and then wipe them off with paper towels. Soak another paper towel and cut through it with the tool to remove sap from the blades and hard to reach areas. Then soak one pair of scissors or pruners in one of these solutions while you use a second one to make the next cut.

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If there is a possibility of having infected plants in your garden you may also want to avoid cutting any leaves and scapes for a while so you can keep a close eye out for possible symptoms.

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Knives: Knives are often used to divide plants. Use a sharp knife to prevent getting sap into serrated edges, making them a lot easier to clean. Again, use rubbing alcohol, disinfecting wipes, or Lysol, and lots of paper towels to make sure you are cleaning thoroughly between plants. [One clever gardener relates that she purchased a dozen inexpensive steak knives at a dollar store, then uses one for each plant, tossing the used knife into a “dirty” bucket. When all the knives are dirty, she washes the whole set.]

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Hands: When working with hostas don't forget to wash your hands. Washing with soap and water will help, especially when working between batches of plants such as in a nursery, then wipe with disinfecting wipes. Disposable latex gloves are also handy, just make sure you change them or wash them between batches and between divisions when dividing multiple plants.

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Final notes: HVX is only spread when plants are damaged and plant sap is released. You have to cut or break an infected plant, get sap on your tools or hands, then break or cut a healthy plant and transfer the sap to through the cut. Just touching plants will not infect them but because we do so much pinching, pruning, and dividing of hostas it is very important to clean methodically between plants. While there is some suspicion that the virus could be spread by bugs or even by the mouths of deer or rabbits, this seems unlikely, although any time there is close contact between wounded plants there is the possibility of sap transfer.

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Thanks, Chris!

 

If you want to read some happy stuff now, consider the FAQ Part III on starting new hostas from seed!

Lemme see Part III!

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