Bob Solberg talk at Midwest Convention

thisismelissa(z4a-S Twin Cities MN)July 16, 2012

So, Bob Solberg gave a talk this weekend and it was kinda funny. This was the first I'd ever heard him speak. He was quite fun!

Growing hostas... the bigger the better.

He talked about key components of gardening hostas. Water, light and nutrients.

He basically said that you cannot overwater hosta. Interesting. We've had members of GW who've grown hostas alongside a water feature, so it didn't surprise me that he said this.

Light. Well, remember my recent post about having moved hosta into the sun here in my z4 garden and how they're flourishing. He explained something here. He said that in his NC garden, at his longitude, hostas grow quite short. But "you guys up here [referring to Minnesota] can grow 'em tall"

Nutrients. No surprise here, he recommends lots of nitrogen. Early in the season, he recommends at least one application of a fertilizer with 18-24 in the Nitrogen number. He also recommended a foliar feed as the 2nd set of leaves are emerging. This will grow nice big leaves.

He said Osmocote is rendered ineffective when temps rise.

With the high nitrogen fertilizer, he said to also look for a significant amount of Magnesium too.. (higher up on the list of active ingredients. I think he said this aids in development of color.

So, there ya have it!

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ken_adrian Adrian MI cold Z5

He basically said that you cannot overwater hosta.

==>> hmmm.. sounds vaguely familiar.. lol ...

have heard him many times at hosta college.. and various group meetings ... his catalog/newspaper [if he still does it] is a font of great information..

one of the prime professors... and all around good guys ... just a pleasant person.. willing to share knowledge ...

if you ever get the chance.. make time to hear him speak ...


    Bookmark   July 16, 2012 at 7:43AM
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Mellisa, I too felt it was a great talk. He is well organized, informative and entertaining. By the way, I believe he mentioned using Epsom Salts for Magnesium. I didn't take notes. Do you happen to remember when or how to apply them. I have some sitting in my garage doing nothing.


    Bookmark   July 16, 2012 at 12:19PM
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irawon(5a Ottawa)

Thanks for passing on the hosta growing information. Good to know about using a foliar fertilizer with the second flush of leaves and the bit about the magnesium.

    Bookmark   July 16, 2012 at 12:21PM
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So what are the types of foliar fertilizer? Just Miracle Grow?

    Bookmark   July 16, 2012 at 12:36PM
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Steve Massachusetts Zone 5b

Fish emulsion or compost tea for the organic types.


    Bookmark   July 16, 2012 at 1:11PM
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Like I stated in another thread......the northern gardens do grow bigger hosta over all..... it is a fact.

Jeff White

    Bookmark   July 16, 2012 at 4:26PM
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hosta_freak(z6 NC)

Bob Solberg talks about the fact that hostas grow taller up north,in his newsletter,which I get every spring. He may be right,but he lives in the piedmont of North Carolina,and that may be true where he lives. Here,in the mountains,and my garden,the hostas grow very tall,due to the high shade in the woods. Just a little tidbit,which you all don't want to hear anyway. Phil

    Bookmark   July 17, 2012 at 9:15AM
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Solberg indicated that 95 degrees was approx temp that Osmocote dumps all its fertilizer. Also stated that most important time to water is as hosta are leafing out in spring - so unless you are getting good regular rains, you should be watering at this time. And Melissa, do you have a photo of the red leaved hosta?

Phil, your mileage may vary (ymmy) is true about gardening as it is in many areas. Bob's point was that more sun yields shorter plants and angle of sun as move south equals more sun.

Some of the other speakers-

Interesting talk about behind the scenes look at TC production from Rob Mortko. Seeing hosta growing without roots and then changing hormones to change to root growing mode. Levels of care to start with clean tissue and maintain clean working area.

Don Dean talked about variety of plant types for color and form in the shade garden....and then morphed to what is coming down the line....some nice tri-color hosta and blues.

Keynote Speaker - Don Engegretson, Landscape Design for Shady Spaces. Very entertaining speaker. One of his first principles is to evaluate every tree and shrub from how it works/fits - if it gets a thumbs down (from either spouse) getting rid of it - slash and burn approach.

Color is last consideration of design after Function of space, Maintenance considerations, and Cost to install and maintain. We do it backwards by looking at visual impact first. Also suggested benches, bird baths, fountains, pathways, boulders, and sculptures are all best when placed in shade. Benches should afford a view that is only(best) seen from that vantage point.

His website-


    Bookmark   July 17, 2012 at 12:21PM
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irawon(5a Ottawa)

Paul, thanks for the additional information about the importance of watering hostas as they are leafing out. I will have to remember that as our irrigation system is often not opened soon enough.

" Solberg indicated that 95 degrees was approx temp that Osmocote dumps all its fertilizer." So, Osmocote is heat activated. I thought it was water activated. Did Solberg say at what temp Osmocote begins to release fertilizer? Are you saying that the remainder of fertilizer in Osmocote is dumped/ released into the soil at 95F?

    Bookmark   July 17, 2012 at 1:27PM
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irawon(5a Ottawa)

Paul and Phil, can I extrapolate from your comments re sun/shade and height of hostas that generally hostas grow taller in shade? Could that be because they are stretching for light?

    Bookmark   July 17, 2012 at 1:32PM
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Once the ambient temps reach 95F or the soil temp reaches 95F? "Osmocote dumps all its fertilizer" - does that mean that the time release quits working and the whole shebang releases into the soil? Wouldn't that render it virtually useless in southern summers? (By "virtually useless", I mean not more useful than a non-time release fertilizer.)


    Bookmark   July 17, 2012 at 2:03PM
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Steve Massachusetts Zone 5b

I think your suppositions are correct bkay. I knew that the time release stuff (Osmocote,MG, etc) was temp controlled but I didn't know that all of it was released at 95 degrees F.

Paul, did Bob talk about the organic slow release ferts like Plant Tone, Milorganite, or Soy Bean Meal? These are not temp controled.


    Bookmark   July 17, 2012 at 2:39PM
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"...did Bob talk about the organic slow release ferts like...."
Bob's talk was not about specific brands. As Melissa said he likes a heavy nitrogen hit early in season around 18 - in his area 15 is what's available.

"Wouldn't that render it(time-release fertilizer) virtually useless in southern summers?"
Yes, it would seem to defeated time-release factor if you get hot temps early.

irawon - not sure about your extrapolation, since obviously most in south are growing in shade already and his comment was general in nature. I would tend to think more in terms of trying to conserve water that transpires (hope I have correct word) through the leaves. Smaller leaf surface means more conservation of water. Width is probably affected, but width is also a function of longevity and # of eyes.


    Bookmark   July 17, 2012 at 3:21PM
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hosta_freak(z6 NC)

Irawon,hostas grow taller I guess because they are reaching up for light. One thing I do know,though. Hostas grow bigger,but less leaves in more shade,and they grow more,but smaller leaves in more sun. There are a lot of other factors,but they grow,according to their environment a lot. My garden is on a hillside,while most people up north are on flat ground. This makes a big difference in how much water remains around the hosta roots Water ,from rain drains downhill from my plants. The trees keep them shaded,so they don't lose too much moisture. Does that help? Phil

    Bookmark   July 17, 2012 at 4:57PM
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Ludi _PA_7a

This is a great little font of knowledge we got going here. I was also unaware that certain time release fertz will âÂÂpopâ at the right temp.

I am excited to be able to provide visual aids for Phil's comment on hosta leaves growing bigger and less of them in shade versus sun. I am still new to the genus (and the resulting addiction) but am happy to contribute where I can.

Both pictures are of the same cultivar ⦠Elegans (she has been getting a lot of feature time since being ID'd ⦠thanks again Steve). They are both around the same age and at least 8 years old.

In pic 1 the clump is growing almost completely under an Azaliea, Rhody, Pieris.

In pic 2 the clump is in substantially more light and away from anything that might bump into it or grow over it.

Hope this helps,


    Bookmark   July 17, 2012 at 6:01PM
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irawon(5a Ottawa)

Ludi, that's a great visual aid to illustrate the points made by Paul and Phil comparing leaf size and number of leaves of a hosta in sun as opposed to in shade. Is the Elegans in shade per chance a bit taller?

    Bookmark   July 18, 2012 at 4:59AM
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Osmocote does indeed dump at 90-95 degrees, which makes it great for the first three months of spring and summer when things are just bursting out of the ground, but after that the organic stuff that you should be side-dressing and/or fertilizing your plants with should be taking over to carry them the rest of the summer and into fall.

One of the things we learned at garden product seminars was to hand out a small bag with a tablespoon of Osmocote as a starter fertlizer with every perennial we sold.


    Bookmark   July 18, 2012 at 10:35AM
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A while back I rescued my little Dream Queens and potted them. I made the mistake of adding a small amount of Osmocote not knowing about the temperature/release relationship. I rarely have ever used the stuff. Then I put the little 4" pot in a shady spot with 7 days of new record high temperatures so far this month. The largest leaves on each tender little plant has now yellowed and is probably dead - perhaps due to over-fert. if Osmocote dumped. I am going to repot in fresh mix and zero fert and hope to save them.


    Bookmark   July 18, 2012 at 1:19PM
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idiothe(4 MN)

You need to read the package... not all time release products are the same. They usually say something like Up to Four Months or Up to Six Months... there are products with differing technologies. Bob specifically said something like "don't use one of those 180 day products if your temperature..." In Minnesota, if we spread the stuff at the very beginning of the season... like April 1... it will be pretty much exhausted before the heat hits in July - if it is 120 day. The 180 day stuff would still be about half active.

And pots are the particular problem. A black pot on a bench in direct sun on a 70 degree day can easily warm the soil to 90 or more and cause "the dump." I have stopped using time release in any pots.

    Bookmark   July 18, 2012 at 2:03PM
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