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Don Kinzler, Published March 23 2012

Hortiscope: Consider native environment when watering

Q: I have 25 blue and Colorado spruce trees that I bought in containers. The trees grew about a foot last summer, but some are turning brown. How much should I be watering these trees and should I put mulch around the base? What kind of fertilizer do you recommend and how often should it be used? Should I get some insecticide and spray the trees? If so, what kind and how many times? I live in Michigan. Thank you for your time. (email)

A: Think of the native environment spruce trees live in. They don’t need a lot of water to survive or thrive. The same holds true with fertilizer. The mineral nutrients that are available in their native soil will be sufficient 99.9 percent of the time.

There are a lot of things that kill evergreens and other tree plantings. The trees may be planted too deeply. The flare for the roots should be at ground level. Overwatering is a big problem. A good initial soaking at planting time and then monitoring the soil moisture after that during the initial growing season is sufficient. Water when the soil starts to feel dry after you plunge your index finger to the second knuckle. Then soak the trees again. The roots will follow the percolating water. If the roots are kept too wet, they will languish near the upper part of the soil for better access to air. If this regime continues, the stability of the trees during a strong wind could be compromised as they get larger.

There used to be an old saying that one should throw in a handful or two of fertilizer when planting trees. Then they used to make it easier for those of us in the landscaping business by saying that fertilizer tablets should be used. We were told that the number of tablets thrown into the planting hole depended on the size of the tree being planted. We were told to use one tablet for a small tree, two for a medium, three for a large and up to four for a very large tree. This was followed almost religiously by landscape designers and architects and those in the landscape contracting business. However, a professor at Oklahoma State University went through a lot of work proving that such treatment was unnecessary and caused more harm than good in some cases.

This exhaustive answer to your questions is not meant to browbeat you but to provide a basic education to you and others who read this answer. The fact that the spruce trees have put on another foot of growth is a sign that you are doing something right. Keep it up, but temper it with what I’ve said.

As to pesticide use, any pesticide, insecticide or fungicide creates stress on plants. You need to determine why some trees are turning brown. It could be the normal tithe collected by Mother Nature, something in the root area of the particular plants manifesting these visible systems or simply that the plants were lacking sufficient vigor to become established in their new location. I hope you gave the spruce trees plenty of space to expand because most people do not.

If you have more questions, I suggest that you contact the folks at the Michigan State University Extension Service. Go to http://tinyurl.com/

8a36mp8 and click on your county to find a contact person. If the agent cannot assist you, there are plenty of horticulturists, foresters and arborists at the university who can. Good luck.


Q: I have a beautiful Hawaiian hibiscus that has done very well for several years. The blooms are a deep red. We live in the Midwest and have done battle with whitefly infestations through the years. I have found that leaving the plant outside for a time in colder weather kills the flies but is hard on the hibiscus. The plant drops its leaves but eventually recovers. This winter, I’ve noticed a new and disturbing development. As the buds form, there are dark brown to black bugs clustered around the buds and leaves. I quickly remove the buds from the plant, fearing the insects will spread to the entire plant. The bugs look like they might be aphids. They don’t appear to be moving or even alive.

Can you give me a solution? (email)

A: The insects that commonly attack hibiscus flower buds are aphids, thrips, scale and whiteflies. Another possibility is spider mites, but there would be telltale webbing around and on the buds and foliage. Try to examine the buds under a magnifying glass to make a determination.

My guess is that these could be spider mites because they are a common winter pest on many houseplants. There are systemics that can be used. However, for the time being, you are doing the correct thing by physically removing the infested buds. Also, rinsing the foliar part of the plant under a shower of tepid water will help control many household insect pests.


Q: I attended your seminar at the Green Thumb Gardener Exposition. Someone mentioned having success with a chilly chili plant. I am having trouble locating a supplier. Where do you purchase your plants or seeds? (email)

A: Chilly chili plant seeds should be available at your local nursery or discount store. It was an All-American Selection winner a few years back, so seeds should be available locally. If not, check the Gardener’s Supply catalog or go to http://tinyurl.com/

87hhty3.


Q: I have a question about garden soil that I hope you can answer. We live in West Fargo. We have alkali soil, and when it rains, everything drains toward us because we are the lowest spot in the neighborhood. Through the years, we have added barnyard soil to the garden with good success. We also have added recycled grass, peat moss and various other things that nurseries have told us to use.

For the past few years, our neighbor has drained his sump pump at the edge of his yard, which is very close to our garden. Because of that, our garden is getting worse. However, I’m sure all of the rain we received last summer had something to do with it. New neighbors moved in last fall and told us that the previous owners had drained their water softener into the sump. Was it the salt that destroyed our garden and is there any hope for ever having a good garden again? I hope you have an answer. (email)

A: When the snow melts, go to your garden site and get a sandwich bag full of soil and either mail it or bring it to me. I’ll have it tested for salt levels and nutrient status. Frankly, I don’t think what little salt may have been channeled into your garden would have a very detrimental effect. Last year was a lousy one for garden soil unless you were on a crest that drained magnificently.

Our own personal garden did the poorest ever. For example, our raspberries that had been producing fruit for 20 years rotted out from the perpetually soaked soil. My take is that your garden soil will be OK unless we have a repeat of the rain events of 2011. However, I’d still suggest getting the soil tested.


Q: For the past five years, we have had a company fertilize our lawn and spray for weeds. The first two summers, we were pleased. We did some remodeling and had some sod put down in 2010. Last summer, the lawn just didn’t flourish at all. In fact, it looked pretty bad because it dried out and did not look lush.

Our neighbors were experiencing the same thing on their lawns. One person who sells sod said it was because the company was using liquid fertilizer instead of granular. The company just contacted us about this coming season. What do you think would be the thing to do? We definitely need weed killer because we don’t want a lot of dandelions growing in the lawn. Should our new sod be aerated? (Crookston, Minn.)

A: Your problem does not stem from the use of liquid fertilizer. Such a statement is nonsense and is not backed by any credible research. The misapplication of liquid or granular fertilizer can result in the same damage. I would communicate with your lawn service company to see if it had any complaints about last year’s applications. I also would ask if you and your neighbor were some of the first ones getting the treatment for weed control. Sometimes the applicator will make up a solution the night before, which may cause it to settle and mess up the intended dilution. It could be that you and your neighbor got a higher dose than intended because of this insufficient agitation of the herbicide solution.

The same thing can happen with fertilizer applications. Your lawn care provider is a reputable company and would want to know of any problems you experienced so it can exercise better quality control. I’m sure your lawn grass will recover this season with the proper application of fertilizer and timely herbicides.


Q: My question centers on a bag of saffron crocuses that I missed last year.

Even with the bag on, they went through their bloom (there are dead flowers on top). What are left are long, brown stems with large tufts of leaves on top. A few weeks ago, after I discovered the plants, I put them in potting soil mixed with 5-5-5 fertilizer and then put the plants under grow lights. They look good and healthy, but the corms are not as firm as before.

Should I try to plant them outside now or keep them under the grow lights? I don’t know how fragile they are at this point. While inside, I can control the light, humidity, nutrients and temperature. If I plant them outside at the normal planting depth, they will have much of the brown sheath above ground, but I’m not sure if that will hurt or help the plants. (email)

A: The corms are bound to lose some firmness as they produce new growth. I would encourage you to move them outdoors gradually. Leave them there through the summer to allow the foliage to make more food for storing in the corms. Once you’ve spent a good week moving them in and out to toughen them up somewhat, go ahead and plant them somewhere permanently. Enjoy the beauty and unique flavoring that saffron brings to Mediterranean dishes.


Q: Is there a compelling reason to estimate the leaf-out date, such as spraying for insects or disease? Any forecast would require using weather forecasts, which are a bit iffy at times. I don’t see a major economic benefit like we have for numerous other crops where it’s useful throughout the growing season to predict crop, insect or disease development. I suspect the development of a growing degree date (GGD) model would take many years of daily observations of the trees and the air temperature in the vicinity. After that, it would take significant research, with several years of data, to come up with a base temperature for certain species of trees. I also wonder what use this information would have. However, I am wondering if such a relationship exists. (email)

A: We use phenological indicator plants. This is a term that is used to indicate the time frame for any seasonal biological phenomena. For example, the appearance of blooming lilacs is strongly correlated with the initial germination of annual grassy weeds, such as crabgrass. Because many such phenomena are very sensitive to small variations in climate, especially to temperature, phenological records can be a useful proxy for temperatures in historical climatology, especially in the study of climate change and global warming. For example, viticultural records of grape harvests in Europe have been used to reconstruct a record of summer growing season temperatures going back more than 500 years. Viticulturists in America are doing the same thing. In addition to providing a longer historical baseline than instrumental measurements, phenological observations provide a high temporal resolution of ongoing changes related to global warming. The concept of growing degree days contributes to our understanding of phenology. While GGDs are related to phonological studies, there is no nailing down of a specific accumulation of GGDs that can tell us when a certain species will leaf out, flower or germinate.

The study of phenology in horticulture is totally absorbing and is strongly encouraged for serious gardeners. Having a historical record of your locality of when the oaks, maples or lilacs start showing activity, fruit set and senescence, would be of value to the understanding of climatic changes that are taking place on your property. It then can be tied with annual weed emergence, destructive insect arrivals, pine pollen production and more. It is one of the very best ways to become your own self-taught expert!


Q: I am emailing you because my cactus plants are dying and I really want to save them. My mom made me a cactus garden for my birthday last year and passed away two weeks later, so they are very important to me. The plants are in a large terra cotta pot that has peat and some sand in it. The surface is covered with small gravel pebbles. There are four types of cacti in the pot. The first is an old man cactus, while the second is a tall, thin cactus with lots of spines. However, I can’t figure out what it is. I also couldn’t figure out a name for the third plant, but I found a photo of it at http://thundafunda.info/2 /widescreen-wallpapers/flowers2/download/Red-Cactus-flowers-pictures-flowers-wallpapers.jpg. The fourth cactus looks similar to the prickly pear cactus but has smaller, finer spines. They were growing well until about a month ago. At that time, the stem of the red cactus became very moist and fell over. It then shriveled up and turned brown. I managed to save a small baby that was growing on top, but I don’t know what to do with it. Can I grow a new plant from this baby? The second plant I described became very thin and shriveled as if it had lost all its water. The same happened with the old man cactus. Both still are firmly rooted. I dug up the spot where the red one was planted to feel the soil because I thought maybe it was too moist, but it was very dry. I put the soil back and added a small amount of water. I read cacti go through seasonal changes. However, I’ve never seen any of my mom’s cactus plants do this and she had a green thumb. (email)

A: The red cap from the one cactus will grow eventually. Place it on clean, dry sand and only give it a small amount of water. I would suggest moving the surviving members of the cactus garden your mom made to a new planter. Use fresh cactus potting soil and avoid the temptation to overwater, which causes the death of most houseplants, especially cactus. Be sure the planting has good, bright, indirect light from a window. If not, provide a supplemental light source. Set the timer for 14 hours of light per day. I don’t know what else to tell you. This should save at least some of the plants that are alive. If there is no life in any of the remaining cacti, I wouldn’t bother planting them.


Q: I had a cottonwood tree removed several years ago. Since then, long trenches have developed in my front yard. I started digging in the problem area and found that rotting roots from the cottonwood tree was causing the problem. Should I remove the roots or just mulch the area and fill the trench with dirt? (email)

A: The roots will continue to sprout and attempt to grow unless you get them all removed. You could treat the sprouting shoots like broadleaf weeds and spot spray them with a weed killer or you can continue to dig out the roots as you discover them. The call is yours.


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 ronald.smith@ndsu.edu.