New Hort Research that Gardeners Can Use: December ‘08 Roundup

By Jeff Gillman

Professor Jeff Gillman

Jeff Gillman, associate professor of horticulture at the University of Minnesota, writes quarterly reports of horticultural research that gardeners can use for this website.

They’re shaped like magazines, they have pretty pictures on the front like magazines, they even smell like magazines, but scientific journals are not your typical magazine. Between the front and back covers of these journals lie succinct experiments that researchers have conducted without a shred of fluff or decoration.  I like to think of them as the unflavored tofu of the writing world.  Full of good stuff — if you can force your way through without gagging.

Most researchers don’t read their way through entire scientific journals.  It’s a cruel fact that for most published scientific articles there are only a few researchers in the world interested in the findings (which is a big part of the reason why researchers pay up to $100 or more per page for their work to be published – there are hardly any advertisements in these things).  Perhaps 50 people in the whole world would find work on “Assessing Morphological and Genetic Variation in Annatto (Bixa   orellana L.) by sequence-related Amplified Polymorphism and Cluster Analysis” (recently published in HortScience) relevant to what they do on a daily, or even yearly, basis.

Still, there are a select few published studies that would interest gardeners, but unfortunately gardeners would never find or read them. Subscriptions are expensive (as much as $400 or more a year), neighborhood libraries don’t carry them, and the verbiage varies from eye-glazing to utterly indecipherable without an advanced degree in a very narrow discipline.  To remedy this situation, I’ll be selecting from the journals those few articles that ARE relevant to gardeners and putting them into plain English.  I would love to get some feedback on this.  If it’s useless I’d like to know that, and if it’s useful (or at least interesting) I’d like to know that too.

1-2. Fertilizers’ Effect on Flowering

Over the years we’ve been told that increasing the amount of fertilizer will increase a tree’s growth, but not its flowers.  This is supposed to be particularly true with nitrogen fertilization.  However, a recent study on dogwoods growing in Alabama nurseries showed that heavy applications of nitrogen increased their flower production. Unfortunately, high levels of nitrogen also made powdery mildew problems worse.  Leaf spot was worst with moderate applications of nitrogen (between .2 and .7 lbs/100 sq), while lower and higher levels had the fewest problems with this disease.  So what should you actually do?  It’s up to you; The amount of increased flowering that might be stimulated by increasing fertilization looks impressive, but it might very well be harmful to grass in the area, and, personally, I’m a minimalist….

3. Perennials Overwintering in Containers

So, you want to overwinter your perennials in a container but you’re concerned the plant won’t make it?  Researchers at Ohio State tested 30 perennials that were kept over the winter either in the ground, in containers stored outside, or in containers stored in an unheated building.  They found that of the perennials wintered outdoors in containers only one – Sedum ‘Matrona’- survived.  For most part, the same plants that did well wintering in the ground also did well in containers in unheated buildings. What this means is that if a perennial is hardy in your location, it can probably be stored in a container in your garage, or any other well enclosed outdoor storage area such as a storage shed, as long as you keep the door shut.  Just not out in the elements (unless it’s ‘Matrona’).

4. Demographics of Buying/Researching Online

Here’s some research with results that won’t surprise you, but will confirm some things that you probably already thought you knew – the finding that young, less affluent males were more likely to make online gardening purchases while older, more affluent females were more likely to make in-person purchases.  Also, nearly 28% of consumers had searched for gardening information online at least once in the past year, and, of those people, over 50% searched for gardening information weekly.  Here’s the interesting part.  People between the ages of 30 and 44 were most likely to have searched for gardening information. Married people were also more likely to search for gardening information.  Income, where the people lived, and gender did not affect online searching for garden related information.  I liked this conclusion: “The internet may be an effective means of reaching slightly less affluent males for gardening related product information.”  Who would’ve guessed?

Citations

1. Hagen, A. K., J. R. Akridge, and K. L. Bowen.  2008.  Nitrogen and flowering dogwood I. Impact of nitrogen fertilization rate on the occurrence of spot anthracnose, powdery mildew, and cercospora leaf spot and their effect on tree growth.  Journal of Environmental Horticulture 26(4):197-203.

2. Hagen, A. K., J. R. Akridge, K. L. Bowen and C. H. Gilliam.  2008. Nitrogen and flowering dogwood II. Impact of nitrogen fertilization rate on flower bud set and tree growth.  Journal of Environmental Horticulture 26(4):197-203.

3. Dimke, K. C., S. K. Still, and D. S. Gardner.    2008.  Effect of overwintering   environment on the survival of 30 species of herbaceous perennials.  Journal of Environmental Horticulture   26(4):222-228.

4. Behe, B. K., B. Harte, and C. Yue.  2008.  Online gardening search activities and purchases.  Journal of Environmental Horticulture 26(4):210-216.

5. Rivard, C. L. and F. J. Louws. 2008.  Grafting to manage soilborne diseases in heirloom tomato production.  HortScience 43(7):2104-2111.

6. Caretto, S., A. Parente, F. Serio, and P. Santamaria.  2008.  Influence of potassium and genotype on vitamin E content and reducing sugar of tomato fruits.  HortScience 43(7):2048-2051.

7. Ozgen, M., F. J. Wyzgoski, A. Z. Tulio, A. Gazula, A. R. Miller, J. C. Scheerens, R. N. Reese, and S. R. Wright.  2008.  Antioxidant capacity and phenolic antioxidants of midwestern black raspberries grown for direct markets are influenced by production site.  43(7):2039-2047.

5. Grafting Tomatoes for Disease Resistance

Most of us buy disease-resistant tomatoes, plant them, and are satisfied if the plants just survive and manage to produce a few tomatoes by the end of the season.  But recently heirloom tomatoes have been getting popular and these tomatoes usually aren’t resistant to disease.  Researchers at NC State studied whether heirloom tomatoes could be grafted onto more disease-resistant tomatoes to reduce disease problems and found that the grafting indeed worked.  This is very important, not only to backyard gardeners, but also to organic growers who want to reduce pesticides.  Tomatoes are a relatively easy crop to graft, so, if you’ve never grafted before, this is a great time to learn.

6-7.  Organic Produce Really Healthier?

There were a few articles in the last issue of Hortscience that are worth mentioning because they demonstrate the problems that organic growers (or indeed any growers) have in proving their produce is healthier than conventionally produced produce.  In study 6, done at a university in Turkey, the authors measured the amounts of anti-oxidants and other potentially beneficial chemicals found in black raspberries. The results showed that where a raspberry is grown and which cultivar it is both influence the amount of nutrients in that raspberry.

And in study 7, Italian researchers measured the amount of Vitamin E and other nutrients in various cultivars of tomatoes and at various fertilization levels (they fed the plants different amounts of potassium).  They found that both the cultivar type and potassium fertilization can affect the nutrient content of tomatoes quite a bit.  The take-away message from both these studies is that to get good healthy fruit with high nutrient levels, you need to take many different factors into account.  We don’t know for sure but I would suspect, based on studying these and other papers, that organic production is one of the least important factors affecting nutrient content.

Jeff Gillman is an associate professor of horticulture at the University of Minnesota. He’s also the author of two books, “The Truth About Garden Remedies” and “The Truth About Organic Gardening” (Timber Press).