Questions on: Hollyhocks

Ron Smith, Horticulturist, NDSU Extension Service

Q: I planted a few hollyhocks two summers ago. They bloomed and flowered beautifully, but now I have tons of plants showing up. Last year I left them alone, but they never produced flowers. I eventually tore them out. I don't know if I bought biennial or perennial plants. I really love them and want them to reproduce, but with no flowers, the plants look like weeds. I love lilacs and have a few of them in my garden. Are lilacs a type of the plant that if I cut off the flowers they will keep blooming? (e-mail reference)

A: I wouldn't rip out all the hollyhocks. Keep just enough plants to keep your garden from looking weedy. You may have biennial hollyhocks that require another cold period before they will flower. Lilacs will flower every year if you harvest the flowers. The flower buds are set for the following year on the subsequent growth that takes place after they flower. If you prune the plants late in the summer, you will remove the flower buds for the following year.

Q: I just wanted to let you know that hollyhock is extremely toxic/poisonous to dogs. Perhaps it is only toxic during the growing season, but not during the winter dormant season. My dog ate a root again today that about killed him. Just thought you would want know. (e-mail reference).

A: Thanks for the information. I'm glad your dog is all right. On matters like this, all I have are a few references, which are research-based and documented by veterinarians or the Poison Control Center. I would suggest ripping out the hollyhock because dogs can be very good companions and loveable to boot, but most are not very bright about learning from bad past experiences, such as chasing cars!

Q: I love hollyhocks, but I have three dogs that dig up the roots and eat them during the winter months. I didn't pay much attention until this morning, when one of the dogs had some kind of a fit. I was wondering if the roots are like a vitamin supplement during the winter, but have a nerve toxin during the spring. Thank you so much for any help you can give me. (e-mail reference)

A: None of my poisonous plant books list hollyhock as having any toxic principles, but that doesn't mean they are harmless. It could be there have been no reported cases of poisoning from this species. I would contact a veterinarian at New Mexico State University's Extension Service to see if he or she can provide you with additional information.

Q: I planted some hollyhock seeds indoors to get them started. I would like to let them grow for a while and then put them outdoors to go dormant. How long should I let the seeds grow before putting them outside? My hope is that I can plant them later this spring and get blossoms this summer! How long is the required vernalization period for hollyhocks? (e-mail reference)

A: I have no idea and none of my references tell me, either! I can't locate any research that has been done on this, so I'll try to make an educated guess/suggestion. I'm assuming you are in North Dakota. If not, modify what I tell you accordingly. When the danger of a killing frost is past, set the plants outside. There is no need for freezing to take place for a herbaceous plant to become vernalized. If spring arrives and there doesn't appear to be any flowering taking place, visit a local garden center to see if it has gibberellic acid. Gibberellic acid is a flower inducer that takes the place of a cold period. Sorry I can't be of more help.

Q: I received some hollyhock seeds from a friend. Do they have to go through a wintering stage before they germinate or can I plant them and transplant in the spring? (e-mail reference)

A: They can be planted whenever you choose. No special treatment is needed.

Q: I planted what I think are biennial hollyhocks this summer. Can I cut them back this winter or do I need to leave the foliage for the plants to bloom next summer? Will cutting them back affect the height they grow to next year? (e-mail reference)

A: Good question. I've never done that and have no references that tell me the answer. I suggest leaving everything alone and see what happens next year, especially if your objective is to get them to grow taller.

Q: We inherited hollyhocks when we purchased our home. We donít like them! We have tried digging them up and killing them with weed killer. Nothing seems to work. Now there are miniature hollyhocks starting to grow in the grass. What can we do to get rid of them? Any ideas would be greatly appreciated. Thanks! (e-mail reference)

A: This is the first time I have heard of hollyhocks being a problem. A good broadleaf weed killer should take them out of your lawn. Trimec is the most potent you can use on home lawns. Wait until they germinate in the spring and then hit the area. That should take care of the problem.

Q: My hollyhocks grow great, but there are not a lot of stalks. The stalks are very long and look gangly. Is there a way to prune them early to get more stalks? I'd rather have the stalks fuller and not as spindly. (e-mail reference)

A: Your hollyhocks are probably not getting enough sunlight or perhaps getting too much nitrogen fertilizer.

Q: Do you know if hollyhocks are safe for animals to eat? Our horse seems to love them, but I can't find anything in horse literature if they are safe to eat. (e-mail reference)

A: Hollyhocks are not listed as a poisonous plant to animals. That means that hollyhocks are not poisonous or that no data has been recorded on them being so.

Q: I read a question and answer on your Web site that sounded like perennials were not as desirable as biennials in the hollyhock family. Is this true and why? (e-mail reference)

A: Desirability is in the eyes of the beholder and where you live. Hollyhocks mostly are classified as a biennial, but in some cases are classified as a perennial. Frankly, the classification is confusing, but I will attempt to clear it up. The Malva alcea, known by the common name hollyhock mallow, is classed as a perennial. We all associate the indestructible plant with our grandparents or great-grandparents’ homes. They appear to tolerate just about any environmental conditions outside of the Arctic Circle to the Tropic of Cancer! The Althaea rosea is classed as simply a hollyhock. While the Malva alcea flowers from June to September, the Althaea rosea flowers from early July through September. There is not a lot of difference, but the Althaea rosea species is said to be able to will survive as a perennial in mild climates. It also is high on the list of desirable plants to eat by Japanese beetles. Apparently, the dependability of this species to be a perennial is in question because it self-seeds, which gives the gardener the impression that it is a perennial, but is behaving like an annual. To add to the confusion, in some instances the plants are biennial because the seed will germinate in the spring, remain as a vegetative rosette that summer and then bolt and flower the following year.
Hence, the desirability of the Malva spp., which is classed as perennial and the more desirable one because of its consistent growth habits. Hope this helps clear up any confusion.

Q: What is the tallest hollyhock on record? Our hollyhock is now at 14 feet 6 inches. (Kingman, Ariz.)

A: I have no idea what the champion hollyhock is! Perhaps one of our readers will know. If that happens, I’ll pass it on to you!

Q: My hollyhocks bloom great, but the foliage looks like lace. What is the problem? Pests? (e-mail reference)

A: Yes, you have pests in the form of the hollyhock weevil or some other insect. Spray with Orthene for control because it has contact and residual effects.

Q: I have been trying to get a nice hollyhock bed going fox six years. A couple of years ago they were great. I didn’t have as many last year, but the bed was still OK. This year I haven’t seen a single hint of one. My soil is very alkaline. Could it be something with the soil? (e-mail reference)

A: You probably have biennial hollyhocks. They are sold in nurseries as annuals, so they will flower the first year. Those that came back were seedlings that most likely were volunteers. The volunteers went through the rosette stage the first season and then came back to bloom. You might get some volunteers this season, depending on where you live.

Q: Last spring I went to a garden auction and bought several trays of hollyhock. I planted them, but all they did was produce several green leaves. Will they come back this year? Will they bloom? Should I dig them up and buy something that I am familiar with? (e-mail reference)

A: You purchased biennial hollyhocks. They grow vegetatively the first year, then flower the next. Unless you are having a brutal, open winter, they should come back with a flourish of blooms this growing season.

Q: What part of the hollyhock is the seed? (e-mail reference)

A: The seed is in the button that forms as the flower fades.

Q: Do hollyhocks and delphiniums give off a scent? (e-mail reference)

A: They are not known for their scents. If roses, marigolds and lavender are considered scented, then hollyhocks and delphiniums are at the back of the pack.

Q: My beautiful wine-colored hollyhocks are turning black when they flower and then die. Most of the buds are drying up and dying and the leaves are covered with brown spots and holes. Do you know what the problem is and will it affect other flowers in the bed? (e-mail reference)

A: Without knowing where you live, it is a little difficult to determine what the problem is. Typically, when the weather is rainy and humid, botrytis fungus is the problem. If you have any more flowers coming, you can attempt to spray with a protective fungicide. If they have finished blooming, then I wouldn’t bother; just clean everything up well this fall.

Q: I have a number of hollyhocks in my garden that have had their leaves turn a rust color. The leaves eventually dry up and look terrible, but don’t fall off. The stock of the plant has rust/brown, elongated, oval shaped marks on it. What can be done to eliminate the problem? I don’t want it to spread to my other flowers. (Fargo, N.D.)

A: Rust fungi are host specific and need an alternate host to complete their life cycle. However, they don’t carry over to hollyhock. This species of plant has what is known as an autoecious rust because this type has only one known infective stage and is not known to have an alternate host.

To control the problem, cut the plants back to ground level, collect all the leaves and other debris and destroy them. Avoid crowding the plants, water only in the early part of the day and avoid splashing on the foliage. Early in the season, apply a fungicide for protection. Chlorothalonil and Mancozeb are two examples.

Q: My hollyhocks have been beautiful and are about done flowering for the year. Can I cut them back now or do I need to let them go to seed and die back naturally? (e-mail reference)

A: You can do either. If you want them to reseed, allow them to stand. Cut them back if you don’t.

Q: I planted four hollyhocks this year. They get full afternoon sun. Two of them are blooming, but all seem to have spots on the lower leaves that eventually turn the leaves yellow. Do I have some type of fungus? Any other ideas as to what might be wrong? I so wanted to grow them as my grandmother used to have a beautiful garden with plenty of hollyhocks. Any help would be appreciated! (e-mail reference)

A: Rust - hollyhocks are prone to it. You have to get a preemptive fungicide down in the early spring to keep it from developing.

Q: How do you get rid of hollyhock weevils? (e-mail reference)

A: Spray with Sevin, Malathion or Orthene.

Q: We were wondering what type of fertilizer is appropriate for hollyhocks. (e-mail reference)

A: Anything that promotes blooms. Rose fertilizer, for example, will do a good job. It is low in N and higher in P and K.

Q: My hollyhock leaves are turning yellow and getting spots on them. For the past two summers, I have been removing bugs by hand. The bugs seem to be able to fly short distances. Any ideas? (e-mail reference)

A: The insect is the hollyhock weevil, which is related to the boll weevil. Your hollyhock plants could also be getting a rust fungus, which is very common.

Q: I read one of your answers about a hollyhock invasion. I have the same problem, only it's not just in my flower beds. I have it everywhere including in my lawn, garden and under my trees. I dug up every single plant last year which took me weeks to do. I also sprayed with Round-Up. This year there seems to be even more than last year. Is there a stronger weed killer? I'm going crazy because there are literally hundreds of plants coming up. (e-mail reference)

A: Employ the services of a professional lawn care operator that is licensed to handle restricted pesticides which would include herbicides. Since hollyhock is a broadleaf and growing in a turfgrass situation, it can be selectively removed. The firm may have to resort to spot spraying in certain situations where there is a chance of damaging desirable ornamentals.

Q: I am getting a new lamb. Her pen will be along the side of my flower bed that has hollyhocks. Will they be harmful to her? (e-mail reference)

A: They are not listed as being poisonous in either one of my reference texts. That doesn't mean they will not cause digestive upsets if they are consumed. Remember babies have more sensitive stomachs than adults.

Q: I recently planted hollyhocks in my flower garden. Should I cut them down after they have bloomed or just leave them alone? (e-mail reference)

A: I wouldn't cut them until the foliage begins to be a detriment to the quality of your garden setting. I would cut back the spent flower stalks to the highest leaves so they don't put energy into making seed.

Q: I brought back some hollyhock seeds from a friend in Wyoming. How do I plant them? I understand they are great for ground coverage which is exactly what I need. (E-mail reference)

A: Find a sunny location and then scatter the seeds where you want them to grow. Barely cover them with soil and frequently give them a light watering until they germinate.

Q: I have a question about hollyhocks. I had wonderful pastel color flowers last year but this year they are all black. I thought hollyhocks were perennials but now I am told they are bi annual. Is that true? (E-mail reference)

A: Hollyhocks are biennials. I would guess the blackness is some sort of fungus.

Q: Is it okay to mulch hollyhocks or will the mulch increase the chance of disease? (E-mail reference)

A: The risk of increased disease is so minuscule that it isn't worth worrying about compared to the advantages of mulching.

Q: My hollyhocks are beautiful and plentiful -- too plentiful. I have tried to remove the seeds but it is impossible to get them all. The flowers are out of control. They keep re-seeding themselves in all my flower beds. I tried to keep only one or two but when I tried to remove them, it was like trying to remove a small tree, with the trunk as big as my arm. I used Roundup to kill the plants but the plants kept growing, not where I applied the Roundup, but from the roots around the main plant. I tried to dig them up by digging down at least a foot and six inches around the plant trying to get all the roots. However, they keep coming up. The hollyhocks have invaded my iris beds and I can't kill the hollyhocks without killing the iris. Please have a solution for me. (E-mail reference)

A: Hollyhocks are usually biennials, which means that they will bloom in the second year of growth. If you can get to those that are just rosettes this year, they should dig out fairly easily. If you happen to be unfortunate enough to have only durable, perennial hollyhocks, then the use of a herbicide that controls dandelions or broadleaf plantains will work. You need to either remove or cover the iris prior to spraying or else they will be negatively affected by the herbicide. These are the best suggestions I can come up with. I'm surprised that the Roundup didn't do the job. Try using a wetting agent with your herbicide this time. You may have to apply it more than once.

Q: My hollyhocks seem to have a fungus. Do you use sulfur powder on them? If so, where do I find it? Is this the time of year to use it? Also, should I fertilize the lawn yet? (Gwinner, N.D., e-mail)

A: As the hollyhocks start new growth, spray them with All-Purpose Fungicide (Daconil 2787).

It is WAY too early to fertilize the lawn. Wait until some new growth is showing and you have mowed it at least a couple of times. Then apply a fertilizer that is high in nitrogen (N), with a major part of the N coming from sater insoluble nitrogen (WIN) sources, which should be listed on the bag.

Q: How do I clean up my hollyhock bed for next year, specifically quackgrass control and other weeds? (E-mail reference)

A: Quackgrass will need to be treated with Roundup. You can use Treflan or Casoron for other weed control, depending on what they are. Check label for accepted crops before using.

Q: My wife has quite a few hollyhocks that are at least 9 feet tall and flowering. They appear to be healthy. Do you cut or prune these? They are starting to droop to the ground. (E-mail reference)

A: Most people will stake them, but pruning certainly will not hurt.

Q: My hollyhocks seem to have a fungus. Do you use sulfur powder on them? If so, where do I find it? Is this the time of year to use it? Also, should I fertilize the lawn yet? (Gwinner, N.D., e-mail)

A: As the hollyhocks start new growth, spray them with All-Purpose Fungicide (Daconil 2787).

It is WAY too early to fertilize the lawn. Wait until some new growth is showing and you have mowed it at least a couple of times. Then apply a fertilizer that is high in nitrogen (N), with a major part of the N coming from sater insoluble nitrogen (WIN) sources, which should be listed on the bag.

Q. I have hollyhocks that have been growing on the east side of my house for 40 years or more. The past three years the leaves have become spotted and eventually the leaves turn brown and fall off. Please help me get them back to growing and looking nice again! (Sheldon, N.D.)

A. Wow! Forty years in the same location--that's amazing for herbaceous plants.

You've got a couple of fungi working against you: a leaf spot and rust. You can try controlling these problems in several ways: one, good litter clean-up this fall; two, pre-emptive spraying with bordeaux mixture to control the leaf spot; and three, pre-emptive spraying to control the rust--this time using Maneb or Zinebor, or if you can find it, powdered sulfur.

Q. I received seeds from someone who said they were hollyhocks, but I'm worried that they are weeds. Please don't tell me they are thistles! (Kent, Minn.)

A. Beware of those who bear gifts because what you have is light years from being a hollyhock. It is, in fact, sowthistle. Yank everything that looks like that out of your garden before it flowers, as each plant has the ability to produce more than 9,000 viable seeds!

Q. Can you tell me how I can control the spread of hollyhocks all over in my yard? (Maddock, N.D.)

A. Any broadleaf herbicide that you would use to control dandelions or plantain would also coincidently control the hollyhock. If they are in an isolated area, you may use Roundup for their control. Remember, it is a nonselective herbicide, so be careful where you direct the spray.

Q: I am sending you a sample of my hollyhock that has quit blooming. I also enclosed a sample of some violets that have taken over my front yard. (Jamestown, N.D.)

A: The hollyhock has a bad case of rust! Clean up the area completely this fall. Next spring apply a sulfur-based fungicide such as ferbam or maneb. Or, if not available, use Daconil 2787 as a protective spray.

If the violets are really thick and the area shady you might be better off accepting them as the ground cover. To reclaim the grass, use Trimec. It will take two or three applications to completely wipe them out.

Q. I'm sending you some leaves from a hollyhock plant. They have spots that start off a light orange and small, and progress to a large, brown bump. Last year we had the same spots and some broke off, revealing a worm of some kind in the stalk. I have tried Malathion without noticeable results. (Woonsocket, S.D.)

A. There are two "evil forces" at work on your hollyhock: rust fungus, and either a burdock or European corn borer.

Combat the rust with any number of fungicides on the market, and do battle with the borer with a systemic insecticide like Orthene.

Q. Could you please tell me what is wrong with my hollyhocks? They grow tall and flower beautifully, but the leaves eventually get like this sample. What can I do? Thanks for any help you can give me. (Menahga, Minn.)

A. Your hollyhock sample has a bad case of rust. Nothing you can do about it now, but next year before they flower put down a preventative spray of chlorothalonil fungicide, marketed as Dacanil 2787.

Q. Enclosed is a leaf from my hollyhock plant that is infested by something that completely destroys the leaves.

Can you tell me what to use to stop this? (Dickinson, N.D.)

A. Your hollyhock has a bacterial leaf spot disease. Unfortunately, there is no "cure" for this other than continuous sanitation. Clean up debris and leaves around the plants and avoid water splash.

Q.What is wrong with these hollyhocks? The leaves all became like these and die. They still bloom, but have no more leaves. It is like a blight of some kind, but how do you treat it? Please help. (Wishek, N.D.)

A.Your hollyhock is being devastated by a couple of diseases--anthracnose and leaf spot.

Follow good hygiene and spray with protective fungicide Daconil 2787 next year. Be sure all leaf litter is cleaned up this fall and try to avoid water splashing next year.

Q.I am enclosing quite a conglomeration of samples from our yard. This has been an unbelievable year for growing flowers, shrubs and trees. I am about to give up on it all. With late freezes, a very long dry spell and then down pours--I don't think plants know what to do either.

I read your column when you told someone that if their hollyhocks had rust there must be oats nearby. Is this perhaps the cause of some of my problems since I used oat straw to cover almost everything last winter and also as mulch this summer? I have removed it all now and am using baled peat moss as a mulch.

I have sprayed our fruit trees with True Value Green Thumb fruit tree spray, but did not begin early enough. The lilac bushes and Mock Orange bush was sprayed with Fertilome Triple-Action and I used Hi-Yield Captan 50% WP Fungicide on the hollyhocks, but I am sure I did not do it often enough. I quit because I was afraid of what the sprays might do to the hummingbirds, bees, and Goldfinches that frequent these plants.

I did have the soil tested where the bleeding hearts are and it was OK in all areas.

I lost three Orange Glory flowers before they were two inches out of the ground. One had worms all over its roots, the other two just died. This happened with several plants in various locations. A healthy plant in one spot with the neighbor plant dead. I do not understand it.

Any helpful hints you can give on any of this will most certainly be appreciated. (Britton, S.D.)

A. Two of your samples, the maple and highbush cranberry, are showing what appears to be herbicide damage. This could come from spray drift or residue in the oat straw you were using.

The rest of your plants appear to be suffering from a range of maladies: hollyhocks, rust; dicentra and mock orange, aphids and possible overwatering; ponderosa pine, winter damage; crabapple, delayed winter damage; honeysuckle and lilac, powdery mildew damage; haralson apple shows some edge frying from possible excess salts. I am concerned about you horticulture should be ahappy, healthy experience. You are trying too hard. Lighten up a little and I think everything will look better.

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