New Hort Research that Gardeners Can Use, First Edition

by Jeff Gillman, associate professor of horticulture at the University of Minnesota, who's agreed to send us quarterly reports of horticultural research that's relevant to us gardeners.  Coming after his previous guest posts about Gurus Gone Bad,  Compost Tea, and How I Decide What to Research, these quarterly reports qualify Jeff as a Friend of Rant on Steroids, and we thank him. 

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.

 

Fertilizers' Effect on Flowering^1-2        

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….  

Perennials Overwintering in Containers ³

 

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 that ‘Matrona’).    

Demographics of Buying/Researching Online ⁴

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?

Grafting Tomatoes for Disease Resistance ⁵

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.

Organic Produce Really Healthier? ^6-7

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.

The Studies

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.

Comments

[Gardening 4 Life]

Thank you for taking the time to decipher this information for us. I am a Master Gardener and research based information is something I really need to have. The information you gave really made sense. Keep using your degree to translate these articles. It's very much appreciated!

[Colleen]

These were really interesting----thank you Jeff! The information about overwintering perennials in containers is especially useful. And much more do-able than previous advice I've seen about overwintering perennials in containers, which consisted of wrapping the container in insulation and then covering the whole mess with a plastic bag. Who wants to look at that all winter??

[Michele Owens]

Thank you, Jeff. It's interesting that there are no truly definitive studies so far proving that organic produce is more nutritious--it's difficult to control for all the variables. Yet, in my own superstitious way, I'm convinced that flavor and soil quality and nutrition are all connected. And organic produce definitely tastes better. Nobody disputes that.

[Jan]

Wow! Thanks Jeff. This is really helpful. I'm a Master
Gardener and write a monthly article for 2 local newspapers. I'm always looking for studies and like to give credit so people know I'm not just making this stuff up. Great post.

[greg draiss]

Nothing tastes better than homegrown produce organic or not.

There is a definitive link bewtween what goes into the soil and what comes out in food.

Look at the extent wine producers go to just to get the right soil etc. And look at what happens to the crop if the temp and rainfall changes even slightly.

Chile peppers growers are experimenting with soil mositure and nutrient content to see what the effects are on heat in the peppers.

On the nitrogen thing I abhor using gapre juice fertilizers like Miracle Gro Peters(now called Jack's Classic) etc on any crop. The result is an artificial steroid like boost that looks good on the outside but strains the plant on the inside.

While nitrogen may be responsible for increases in ceratin diseases it is an antidote for some turf and plant diseases as well.

I really doubt how much better produce fertilized with organics tastes since the plant knows no distinction between organics and standard fertilizer in the assimilation of such into the plant as nutrient uptake. Plants can't chew on bone meal.

Any dfference in my opinion arises not from the fertilizers applied but how the soil breaks down said fertilizers and releases the nutrirnt content to the roots.

Could one replicate the process of organics by varying the timing and application of chemical forms to mimic the organics? Probably but why waste the time when naturals do the job already.

The (what happened to my mistletoe) TROLL

[Brie]

Awesome! I look forward to seeing these ongoing reports. The part about grafting tomatoes was interesting. And now the next time my mom says "I don't know why won't flower..." I'll say my usual "it probably isn't getting enough light" and add "but try some more nutrients". I always assumed she over-fertilizes but she swears she doesn't.

[Brie]

"I don't know why won't flower..." was supposed to say "I don't know why --insert plant name-- won't flower..."

[Kari]

Great post!! I can't honestly say that it is very useful to me and my day-to-day life, but I found it incredibly interesting. I like to hear what new studies are being done, and I would never be able to decipher a scientific journal myself, nor would I have the time to try. Thanks for doing this. I look forward to your next post.

[Holly Scoggins]

Hi Jeff!
Yay, HortScience!
Thanks for doing this - I've thought how helpful it would be, but never got around to it... possibly too busy churning out more eye-glazing verbiage that I have to pay to have printed. Har!
Keep up the good work and the fine writing!

[MarciBeth]

Jeff, I enjoyed reading your "plain english" version of the research relevent to gardeners. I look forward to reading more.

[DaffodilPlanter]

Jeff, Thank you for this valuable service! Your fluent style, the digests, and the footnotes all make for a perfect package of information. MORE than once a quarter, please?

[gardenmentor]

Please keep these reports coming!

[chuck b.]

Even if there are limited, or no, nutritional benefits to eating organic, there may still be many good reasons to grow organic, many of them ostensibly health-related.

It's never been my hunch that organic farming necessarily produces more nutritious food than the other kind/s. Isn't organic farming more about what's missing (pesticides) than what's added?

As far as that goes, I would be more inclined to think organic meat and eggs offer stronger benefits over organic fruits and vegetables. But maybe I'll exclude root vegetables from that set.

A little bell should ring when scientists say things like "potentially beneficial chemicals". That is extremely flexible language that is potentially useles information.

What's the current level of our scientific understanding of antioxidants anyway? As a medical researcher myself, I know there are still many blanks to fill in in that story (e.g., how much antioxidant to I really need, and what kind of antioxidant, and wherefrom?)

Just going with the idea that antioxidants are per se nutritious, what is the relationship between ripeness and nutritional benefit? What's the antioxidant value of those nearly albino tomatoes picked early you find for sale at Big Grocery, compared to the fully red one I pick in my garden at the peek of ripeness?

I sometimes wonder about potentially harmful chemicals naturally present in food, too. There is no reason to believe the plants we eat consist only of beneficial chemicals.

[chuck b.]

"As far as that goes, I would be more inclined to think organic meat and eggs offer stronger benefits over organic fruits and vegetables. But maybe I'll exclude root vegetables from that set."

I'm sorry--that thought was not well elaborated. I was thinking faster than I was writing. Also, it's hard to review one's writing in little blog comments boxes.

My point was that it's a long way between the soil and fruit. Chemicals in the soil do not necessarily migrate through tissue and end up in fruit.

Meat, on the other hand, may be saturated with chemicals that circulate in the blood.

[greg draiss]

Excellent points chuck b.

And what about the temps produce is kept at in the stores. Too hot/too cold what are the effects of the nutritional values then?

At least in your backyard YOU know the stuff that went into and onto the food you grow.

Which brings us back to an interesting point. We all grew gardens back in the day out of necessity with no information that it was healthier it was all there was.

Now in our infinite wisdom (aka brave new world) we are being told to grow our own food out of the luxury it is better for us not because it is all there is.

Amazing we need to modern science to tell us why we do things instead of just doing them in the first place.

How much of this "progress" is really progress after all? Poor rural folks still grow food out of necesity. Seems like us urbanites and suburbanites need a reason to do what others around the world have done for centuries.

Shame on us?

The (prodigal) TROLL

[mr_subjunctive]

More like this, please.

[chuck b.]

Tomatoes are easy to graft? I'm surprised to hear that. It's been a several weeks since I last saw a tomato plant, but I seem to recall those stems being rather soft and herbaceous, and not very round either. Do you graft between first year plants? I know tomatoes are technically perennials (tomatoes that are better perennials; now that would be awesome)--so, would one leave the disease resistant rootstock in the ground for a year to get get woody? Or are we going to do the grafting and harvest all in one season?

[Marte]

Thank you Jeff! This was really interesting.

[arythrina]

Excellent translational work. As a graduate student, I have access to scientific journals of all sorts through my university. But I lack the time and expertise to decipher horticultural research - so keep the summaries coming! Thank you!

[Kim]

Yes, please keep these articles coming. They are interesting and helpful.

The only one I had any experience with was overwintering perennials in containers. I did it with a large number of perennials (for 2 years) and had great success. I didn't lose a single plant (to cold).

Here are the details - just in case they will help anyone or show why my experience differed from the research.

I divided perennials from our garden and potted some up in preparation for a move. I used 1 gallon containers with my own soil mix - a little peat, potting soil, compost, pearlite and vermiculite. I potted up an oriental poppy, multiple daylilies, several coneflower, several toad lily, two monarda, yarrow, sedum (not Natrona), Solomon's Seal, multiple hosta varieties, columbine and oriental lily.

All of them stayed in pots over 2 winters here in the Mid Atlantic except the oriental poppy and the oriental lilies. The one daylily I lost was due to squirrels turning the pot over and emptying it out while we were on vacation. The plant dried out. I lost one of the two monarda to squirrels after it was planted - they dug it up and I didn't notice. Other than that, everything survived. The toad lilies even seeded themselves into a couple of the other pots, as did the sedum.

Most of these plants were kept in dappled shade, grouped together, above ground near some shrubs in a bed in the yard. The yarrow is the only one that didn't look great after I planted it, and it took a couple of years to recover.

Now, I know you have to work hard to kill hosta and daylilies, but what about the rest?

[susan (garden-chick)]

Excellent post, Jeff. I followed the link to your previous post on compost tea and the implication that in most cases beneficial micro organisms already exist in the soil. Are you planning any posts on the effectiveness of mycorrhizal inoculants? This has been pushed by reputable sources in several of the gardening seminars I've attended recently, but if the beneficial organisms are already there, can sprinkling some what powder on the roots really make a difference? If there is some definitive science on this, applicable to the home gardener, I would love to hear about it.

[nandina]

For those wishing to graft tomatoes. Do a search for "ceramic knives". Several companies sell a small folding "jacknife' type for around $30.00. This knife is the best for soft tissue grafting. Works well also for other types of grafting. No need to stop and sharpen your grafting knives any more. Once you have used a ceramic jackknife it will be your constant companion in the field, the greenhouse and the garden.

[Jeff Gillman]

I was concerned that the Garden Rant readership might find this boring -- I'm glad to see I was wrong! I look forward to writing the next installment in a few months.

There were two questions asked that I can answer here. The first was about tomatoes. The most practical and easiest way to graft tomatoes would be to start them in containers, approach graft them together, and then plant out the resulting grafted plant. Look up approach grafting on google and the process I just described will make sense.

Regarding mycorrhizae, there has been quite a bit of research done on those commercial inoculants, and rarely are they beneficial. The reason for this is that the proper type of mycorrhizae is usually already in the soil. In a sterilized soil adding mycorrhizae can help, but few people sterilize their soil. I can summarize an article or two on these products for the next installment (Susan, you'll remind me right?)

[greg draiss]

Thanks for blowing the lid on another jar of snake oil Jeff.
I have seen no benefits to mycorrhizae whatsoever.

Now if we just blow the lid off the fraud of frauds Jerry Baker.

The (medicine man) TROLL

[Susan Harris]

Greg, follow that first link to Jeff's previous guest posts - Gurus Gone Bad - to see him debunk the hell out of old Jerry.