Questions on: Marigolds

Ron Smith, Horticulturist, NDSU Extension Service


Q: I have a healthy marigold in my front yard. However, the frost soon will kill the plant. I was thinking about getting seeds from this plant for next year, but I'm not sure how to go about doing this. My dad says the seeds are in the flowers. If that's true, do I have to wait until a certain time to gather the seeds? Do I have to dry the seeds? I'm a little confused as to what I need to do, so your help would be appreciated. (e-mail reference)

A: Tie a paper bag over the flower heads and cut them off. As the heads dry, the seeds will fall into the bag (hang the cut-off heads upside down). Next spring, plant the seeds in the soil or in a well-lit room. Hybrids will not reproduce the same type of flower, so don't expect the resulting plants to be like the one you harvested.


Q: I have a large deck and have planted marigolds in planters. They are blooming very well, but the leaves are drying up like cornflakes. This part of the house receives full sun all day and gets very hot. I have them planted in drought-tolerant soil. What am I doing wrong? (e-mail reference)

A: Iím willing to bet the plants are being cooked on the patio. If you can, place the planter in another planter to provide some insulation for the root system. Even though marigolds can tolerate a fair amount of heat, sometimes the direct sun coming in and reflecting off the sides and windows of the house can be too much.


Q: We would like to move some marigolds. Will the move kill them or just slow them down? (e-mail reference)

A: Marigolds are tough plants so go ahead and move them. Move them at the end of the day, going into the evening. Be sure they are well hydrated before digging and keep them well watered after planting.


Q: The leaves of my morning glories and marigolds are being eaten by some sort of bug. The only thing I can find is a beautiful looking gold colored bug that looks exactly like a ladybug. How do I get rid of these beautiful bugs? (e-mail reference)

A: Try an insecticidal soap. If that doesnít work, spray with Sevin. Be sure to spray the underside of the leaves.


Q: I have a large border of marigolds that are shriveling up and dying. I'm not sure if it's too much water, not enough water, heat, or bugs. I can't see any bugs. The leaves start getting pale while the veins stay a little greener but eventually the whole plant dries up. (Fargo, N.D.)

A: It could be any number of things, including those that you mentioned, but it sounds like a white mold fungus. The best thing you can do right now is pull up the infected plants, roots and all, and dispose of them.


Q: I was told that marigolds keep mosquitoes away but I've also heard that they have to be the old-fashioned type because they are more pungent. Where can I buy old-fashioned marigolds? (E-mail reference)

A: It doesn't work so don't get your hopes up. I have seen squadrons of mosquitoes fly out of plants that are supposed to keep them away.


Q: What has happened to my marigolds? I planted nursery plants in pots on the south side of the house and also some in the ground. They have been just beautiful until about two weeks ago. They look like they are drying up from the root up to the flowers. Could I have watered them too much? (Fessenden, N.D.)

A: The marigolds have white mold, a fungal disease that often develops late in the year following a summer of high rainfall or heavy overhead watering. Be sure to clean everything up this fall and try to use drip irrigation next year.


Q: Help! The grackles, crows or black birds of some sort are mutilating my marigolds. They're pecking away at the flowers until there are hardly any left. Any suggestions? (Fargo, N.D.)
A: Every year someone asks me about these characters attacking their marigolds, and all I can say is that they are the mischief makers of the bird world--rampageous, rambunctious, ridiculers of our efforts to have nice plantings! The "Scare Balloon" works to keep them away. Local nurseries have them. The birds think it is an owl or some other bird of prey and it usually gives them quite a fright. They'll have to find someone else's marigold plantings to harass.

Q: I need to know what kind of manure is best to use as fertilizer for a strawberry garden. Also, would marigolds and/or Hoya Carnosa help keep harmful bugs away from my strawberries? (e-mail)

A: The best manure is rabbit. It is clean, easy to handle and, of course, rich in nutrients.

The lygus bug is the big pest with strawberries. It damages the flowers and causes "nubbins" to develop. I doubt the flowers you mentioned would be effective in keeping these and other destructive insects away.


Q. We used certified seed for our potatoes, and we hadn't planted any potatoes for five years. They are scabby with only one or two to a vine. What is wrong? I placed marigolds around my garden because I was told that they would get rid of bugs, but the bugs ate them all up, only leaving the stems. (Jamestown, N.D.)

A. Wow -- you do need help!

The scab on your potatoes is soil borne, and once the potatoes have it, there is nothing you can do. The best defense against this is to get cultivars that are known to be resistant to the disease. Some examples are Goldrush, Katahdin, Kennebec, Red Norland, Red Pontiac, Russet Norkotah and Superior.

You probably had the "nice" marigolds--deodorized hybrids. Next time try the stinky old-fashioned kind, they usually work better.


Q. For the past two years, I have had tiny spider mites (?) choke off my First Lady marigolds by spinning webs all over them—almost overnight. How can I prevent this now before planting, or should I change variety to Cracker Jack marigolds? (Finley, N.D., e-mail)

A. Your problem does not sound like spider mite activity. Spider mites typically do not bother marigolds. And the fact that you use the statement "choke off" by spinning webs almost overnight leads me to believe it may be something else. Spider mites are smaller than the dot at the end of this sentence, and their webs are very minute, almost going without notice, until the plant totally collapses. Finally, they are usually more of a pest on perennial plants that don't get the attention annual plants usually do.

That all being said, what, you are wondering, could be the problem? I believe it is likely Verticillium wilt, since you specify it attacking your First Lady cultivar. Verticillium wilt is a soil-borne fungus that attacks susceptible plants. The Crackerjack marigold may have the resistance bred into it.

I suggest extremely good sanitation this spring, cleaning out the beds before planting anything in them. Then, if you can give up your romance with marigolds and try, for instance, some of the new zinnias or salvias in that spot, practicing crop rotation may make a difference as far as disease buildup goes. If you simply cannot give up marigolds, then plant a different cultivar than First Lady.


Q. Enclosed is a sample of a marigold that I planted in a flower bed on the west side of our home. Every year for the past five or six years something comes and attacks the marigolds and sucks all the life out of them. Eventually the plants look like this sample. Do you have any ideas what I can spray the plants with the stop this from happening? (Garrison, N.D.)

A. There could be one of, or a combination of, diseases that are afflicting your marigolds. Two wilts, Fusarium and Verticillium, are common where the entire plant is wiped out, and gray mold, a species of Botrytis, is also know to infect marigolds.

Here is what I would suggest: First rotate your plantings. Don't plant marigolds in the same spot each year. Generally a three-year rotation is needed. Second, practice fanatical sanitation. Clean up all plant debris in the fall; roam the garden with a plastic or paper bag and discard any faded blooms, or rogue out any sickly plants on the spot. And third, protective spraying with Fore, Zineb, or Captan will help control the spread.


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