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Hortiscope

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

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I have a row of emerald green arborvitae. I use a soaker hose to water the plants once a week for an hour. I sprayed Miracle-Gro on them in April. I had a leaf miner problem so I sprayed acephate on them. The arborvitae came back strong, except on one tree there is a single branch that went from a beautiful green to a bright golden yellow (dead) in a week. That was a couple of weeks ago. Recently, I noticed the same color in another tree. In both cases, the dead foliage is only connected to one branch. I never have seen this color on dead foliage before. Usually it is a dull brown, grayish color, not bright, almost fluorescent against the emerald green. Any ideas? (Long Island, N.Y.)

A: Plant tissue death can result in different colors. It depends on how the death took place. In some cases, it is through a fungal canker growth that slowly girdles the stem causing a gradual reduction in nutrient uptake. In other cases, it could be from girdling bark beetles that suddenly accomplished a complete girdle of the branch in question. The presence of the carotenoids suddenly appearing seems to indicate a sudden change within that particular branch that caused an almost immediate chlorophyll breakdown and revealed the yellow pigmentation beneath. For whatever reason, during a slow death, brown (tannins) is the typical color. I encourage you to examine the affected branches to be sure something isn't getting started that could decimate all of your beautiful arborvitaes. These are just intuitive guesses and subject to change if more information becomes available. Let me know what you find.

Q: I would like to plant tulips and daffodils in bulb pans. I want blooming to take place the second week of May (Mother's Day). When should they be planted and how should I prepare the bulbs for planting? (e-mail reference)

A: This requires a skill that has been gained through a lot of trial and error or from being passed on by the previous generation of growers. This is something I never have attempted for good reason. More experienced people have it down to a science and can do a much better job than I'd ever hope to do. What you want to attempt would require the precise timing of temperature and light, plus other cultural requirements. Quite frankly, greenhouse operators have decades of practice perfecting the timing. If an experienced grower wants to share secrets on how to accomplish this timing, I gladly will pass them on to the readers of the column. Sorry I couldn’t help more.

Q: Is rhubarb safe or good to use this time of year? A client heard it could be toxic this time of year. (e-mail reference)

A: I must answer this question at least a dozen times every year. Sooner or later I will have reached everyone. Rhubarb is as safe to use now as anytime during the growing season. Toxins do not accumulate in the stem tissue as the summer wears on. The stems do get tough and stringy at this time, which makes the rhubarb a little more difficult to work with than when the stems are tender and succulent in the spring and early summer. The reason for discouraging harvest at this time is because of the assimilative growth that is going on at this time. The plants are accumulating carbohydrates in the crown and root system, so excessive removal of the stems cuts down on that function and may weaken the plant for next season. The oxalates are contained in the leaves in toxic levels all through the growing season, so the leaves never should be used in food preparation.

Q: I'm going to be moving day lilies from the lake to Fargo. Do I cut them back now before I move them or wait until a frost kills the foliage? (e-mail reference)

A: I'd suggest waiting until we have at least one soft frost, which means the temperature dipping down to 32 or 30 degrees. This helps shut down foliar activity. I'd move them foliage and all if possible.

Q: I was reading through your posts about eating hollyhock flowers. We have two desert tortoises who love the flowers. They aren’t so keen on the leaves, but the flowers are munched on the moment they are handed over. We’ve been feeding the tortoises these flowers for nearly seven years because they are listed on the edible plants for tortoises list. Our llamas and goats also will nibble on the leaves and flowers. (e-mail reference)

A: Thanks for the information. What is one man's poison is a favorite meal for someone else. In this case, it is your tortoises. I'm not surprised about the llamas and goats eating the flowers because I've seen them eat amazing junk and still thrive. I have no idea what would be considered poisonous to them. In my other life as a seed salesman, I had set up a vegetable and flower seed display at a garden center where they had goats that were free to roam. I came back the following week to find that every seed packet was gone. The owner said two goats discovered the display and ate everything. Some were treated seeds, but apparently the goats were not affected by anything they ate.

Q: I have a question about dieffenbachia plants. I acquired one that is very rich in leaves, but when I got home, I noticed that two of the biggest leaves have curled a bit and the ends seem somewhat limp. I have watered it with warm, filtered water and moisten the leaves. Is the plant suffering because of the location change? If so, what can I do to help it? I'm wondering if one of the causes is that the plant didn't have much light in the supermarket. It gets full sun from a south-facing window. It's my first plant, so I'm clueless. (Romania)

A: You have the distinction of being the first person ever to contact me from Romania! Thank you for writing. Dieffenbachias are pretty tough plants, so I don't think you have anything to worry about. If the leaves respond to your warm, filtered water treatment, then let your concern rest. If not, then it is in a temporary pout or funk about being in a different location. Keep in mind that this plant does not need full sunlight. In fact, it will wilt if put in full sun all day. Perhaps this is what is causing the reaction you mention. You've moved it from a relatively low, filtered light source to one where you have it in a south-facing window that gets direct, strong sunlight for six or more hours. If so, just move the plant back from the window so that it isn't being impacted from the direct rays of the sun.

Q: I have two Miss Kim lilacs growing in sunny spots here in western Arkansas. The lilacs were purchased two years ago. The lilacs bloomed but almost all the leaves get scorched and some of them turn completely brown by the middle of the summer. I tried spraying them with an insect, disease and mite control every week, but it didn’t make a difference. Is our climate too hot for the lilacs or is this problem some kind of a disease and there is a solution to this problem? (e-mail reference)

A: You are right at the maximum level for heat tolerance, so you might have the lilacs in a microclimate that cooks the plants to above that heat range. I'd suggest moving the lilacs to a spot where they will get morning sun and dappled shade in the later part of the day.

Q: We had a very hot summer here in New Jersey. My hydrangea always wilts in the afternoon sun but recovers when we water it. After the blue fades, we are left with a beautiful faded color. However, this summer it turned brown and ugly. I cut off all the brown flowers, but I am always wondering about pruning. How much, when or should I not prune at all? My husband pruned some of it two years ago, so we did not have many flowers last season. This year, we had an abundance of flowers. I have read many of your posts and it seems some people prune back to 12 inches. What is a good rule to follow? (e-mail reference)

A: Apparently your hydrangea blooms on last season's growth. I would recommend selective instead of wholesale pruning. Cut back the tallest branches to the desired height and allow the rest to remain. This will give you a better flower show next season. Do this selective pruning every fall or spring while the plants are dormant. You shouldn't have to go a season without the beautiful flowers.

Q: I'm hoping to improve my lawn by doing some work this fall. I'm not sure of the sequence and timing of applying Trimec, fertilizing and overseeding. I have creeping Charlie and a nitrogen-depleted lawn. I also don't like to water the yard, but that hasn't been a problem with all the rain. What type of fertilizer would be best? Do you have an opinion on a type of seed I should use? I guess my plan is to spread seed on the lawn after a vigorous raking. (e-mail reference)

A: Here is a quick outline of what I would suggest. Also, check out the information at http://www.ag.ndsu.edu/pubs/plantsci/landscap/h1311w.htm. The broadleaf weeds are particularly vulnerable to herbicide treatment at this time. Trimec, Weed-B-Gon, Tzone and Q4 are the ones that will be effective in controlling the weeds. Make an application now and again next spring when active growth resumes. Fertilizing is recommended at this time. However, I suggest power raking, cleaning up the duff the rake pulled up, fertilizing, seeding and spot treating the areas that have weed infestations. Assuming you live somewhere north of the Mason - Dixon line, I would recommend a bluegrass mixture of 55 percent Kentucky blue grass, 35 percent creeping red fescue and the rest perennial ryegrass.

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 e-mail ronald.smith@ndsu.edu.


NDSU Agriculture Communication

Source:Ron Smith, (701) 231-7123, ronald.smith@ndsu.edu
Editor:Rich Mattern, (701) 231-6136, richard.mattern@ndsu.edu
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