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Ron Smith answers questions about flowers, trees, gardens and shrubs.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I had someone ask me questions about green beans. After the hot weather we have been having, all of the blooms on her green beans dropped off, so she is worried that she will not get any beans. Is there anything she can do to stimulate a second flush of blooms? Is fertilizing when it is so hot and dry a good idea? Would daily watering help? If her green beans will not produce beans, is it too late to plant new green beans? (email reference)

A: Flower abortion on vegetable plants, such as peppers, beans and tomatoes, is not uncommon when the day and night heat gets excessive. It is a shutdown to the reproductive stage of the plant in an attempt to conserve energy. It is very likely the plants will reflower and bear fruit. If she wants to replant the beans, they will sprout almost overnight with the heat and bear fruit by the beginning of September. Whatever she does, a consistent watering regime is needed to get the plants to flourish. No soaking them once a week and then ignoring them to the point of drought stress. Nothing will be very productive under those conditions.

Q: Last fall, I collected acorns from some oak trees in the Sheyenne Grasslands near Kindred. I planted them in plastic plant starters using potting soil. About 60 percent of them made it through the winter and came up this spring. On average, there are a dozen leaves on each plant. When do I need to get them out of the small containers to avoid stunting any further growth? (email reference)

A: Congrats on your success. It probably could have been higher if you had done the float test before planting. Any acorns that float can be discarded because they are nonviable. You said that each plant has about a dozen leaves, which is good because it means each plant is well beyond the cotyledon stage. You can transplant them anytime now. I would strongly suggest that you do it going into the evening hours to take advantage of cooler temperatures and to minimize wilting. Keep the plants watered but not soaking wet and enjoy the fruits of your experiment.

Q: I have a neighbor who has a plant with interveinal chlorosis on the newer leaves. The older leaves at the base of the plant are completely green. I thought I could find a solution in a soils book, but I couldn’t. What is the best thing to do to snap the plant out of its problem? (email reference)

A: This most likely is chlorosis that is caused by the lack of iron due to a high soil pH. It can be corrected in a couple of ways. Apply Hi-Yield Iron as a granular that will be taken up by the plant. The product has a very high percentage of iron and sulfur that temporarily will acidify the soil and make the iron available. Only new growth following the application would show improvement in new foliage color. There are liquid applications of iron products that are chelated and taken in by both the foliage and roots. These products go by the name of Ferti-Lome and Bonide. Both current and new growth typically respond to applications of either product when label directions are followed. All of these products should be available at local garden centers.

Q: We have a question about a young bur oak tree we planted near our cabin on Spiritwood Lake. We planted it six years ago. Since then, it has grown nicely. A few weeks ago, we arrived at the lake to find that a big ash tree had blown over in a windstorm and fallen right on the young oak tree. The oak wasn’t broken off, but it is bent over about halfway up. We cleared the ash away and then straightened and splinted the top half of the oak in hopes that it will recover. However, the top half is now brown and dying. Do we cut off the trunk where it was bent over and hope that new growth will take over and form a continuation of the main trunk or would it work to gently bend one of the side branches and encourage it to grow straight up? Thanks for any ideas you may have. (email reference)

A: The injury from the ash probably tore apart the connecting vascular tissues to the top of the tree. Based on the information you’ve provided, I doubt that this part of the tree ever will recover, so it should be pruned off. If I understand your information, there are lateral branches that are OK. One of those branches will assume apical dominance and begin growing upright. This could result in an interesting looking tree, but a tree worth having nonetheless.

Q: I see a yellow plant in open lots and on boulevards in Moorhead and Fargo. I would like to use it as a groundcover but don’t know where to get it or even what it is. (surface mail)

A: This beautiful yellow flower is a legume known as birdsfoot trefoil. It is a long-living perennial that spreads nicely. In fact, it spreads too nicely in some cases to the point where it becomes invasive. You can try purchasing the seed online from a farm supply company or check local elevators. Better yet, wait until the flowers fade and the seed pods form and then harvest as many seeds as you want. Plant the seeds where you want, but keep in mind that you very likely are going to find it popping up elsewhere on your property. It is used in agronomy practices for forage and soil stabilization because it is a very salt-tolerant plant.

Q: I’m having trouble with my daylilies. The plants have poor to no flowering and the foliage is yellowing. I had the same problem with my iris plants not opening. What is going on? I don’t want to lose these plants. (surface mail)

A: From all observations, the problem is an ongoing one with a lot of daylily and iris growers. Thrips very likely are causing the blooms to not open or be badly mottled. Aphids also are implicated in this crime. The foliar problems are a virus, yellow streak or rust. If it is a virus, there is little that can be done except to remove the symptomatic foliage. Rust or yellow streak can be kept from spreading by removing the foliage and applying a fungicide that is available at local garden centers. Controlling thrips is a bigger problem than the others because they are difficult to kill with contact insecticides, so look for insecticides with systemic activity such as acephate, cyfluthrin or imidacloprid. These products will control the visible aphids and thrips, which are difficult to see.

Q: We have many oak trees. We just noticed that there are dozens of whitish balls on the trees ranging from the size of acorns to golf-ball size. When we open them, they are a red or pink inside and smell sweet like fruit. However, there is always a small worm in the middle. Any ideas about what the problem is and what we should do? (Texas)

A: Oaks are notorious for attracting gall-making insects and mites. What you are seeing could be oak apple, jumping oak leaf or red pea galls. There are other possibilities. These galls are mostly initiated at the leaf bud unfolding stage when a very small wasp or mite stings the developing leaf and deposits an egg or two within the opening. The hormonal action from the developing larvae causes plant cell proliferation that provides protection and nourishment to the developing insect/mite. Control measures are not necessary or recommended because any application of insecticides after the galls are noted would be the equivalent to closing the barn door after the cows got out. Also, spraying early in the spring would be a timing challenge. Generally, where a heavy gall infestation is noted, predators find them and do the job of keeping the pests under control. Other than cosmetic appearances, these galls do not seriously harm the trees. Consider the galls a biological curiosity.

Q: My coneflowers started looking really weird and deformed, so I looked online and diagnosed them as having aster yellows. It suggested removing the infected plants. Will it be necessary to remove the entire plant or just the infected flowers and maybe some leaves? I hate to pull out all of my perennial cone flowers. (email reference)

A: Aster yellows is a virus disease that is spread by insect activity, especially leaf hoppers and aphids. Allowing the infected plants to remain will act as a vector for the further spread of the pathogen to the rest of the plants. Anything that is visually healthy can stay put.

Q: I have a client who has small green worms on her raspberry leaves (15 to 20 on some) that are eating the foliage. Could they be raspberry sawfly larvae? She started noticing the leaf damage a couple of days ago. When she got done working with the raspberries, her hands were all green from these little buggers. Also, is there a good way to keep toads from digging around the foundation of a house other than removing debris and moisture sources? If she sprayed the foundation for insects, would that get rid of the toads? (email reference)

A: These could be pear slug larvae or raspberry beetle larvae or adults feeding. At this late stage, with no more fruit left to harvest, she can remove the fruiting canes and spray the primocanes to protect them from damage with any number of insecticides such as Sevin or Spinosad. Toads are beneficial and make a huge dent in the creepy crawling characters that like to get into high organic matter environments and eventually work their way into homes when cooler fall temperatures arrive. I would encourage cleaning up around the foundation rather than using insecticides because of the impact on the health of the frogs.

To contact Ron Smith for answers to your questions, write to Ron Smith, NDSU Department of Plant Sciences, Dept. 7670, Box 6050, Fargo, ND 58108-6050 or email For answers to general horticultural questions, go to

NDSU Agriculture Communication – July 25, 2012

Source:Ron Smith, (701) 231-7971,
Editor:Rich Mattern, (701) 231-6136,
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