nurseries – Page 2 – The Garden Professors™

Inspecting nursery plants, part IV

(Note: this is a really LONG post. Not in text – but in photos! Sorry for all the scrolling.)

I don’t know about you, but after spending three weeks on my hands and knees looking for trunk rots, surface roots, and suckers, I’m ready to become bipedal again. So today let’s look at trunks – and what shouldn’t be missing on them.

Many young trees have numerous short branches along their trunk, as shown in the photo below:

Unfortunately, many nurseries and gardeners think this looks scruffy, and respond by pruning these branches off, leaving a tree such as the one in this picture:

Personally, I think these trees look like lollipops, but aesthetics aside, this type of pruning can inadvertently damage young trees. Their bark is often thin and sensitive to environmental stress – especially sunburn. Without those short branches deflecting the sun from the bark surface, the living tissues under the bark can be killed, creating dead patches on the trunk:

How can you tell if the tree you’re considering has been improperly pruned? Just look for those tell-tale pruning cuts, as a close examination of the lollipop tree reveal:

In time, these trees develop thicker bark, and the lower branches are gradually shaded out as the crown increases. Be patient! Let your trees be a little fuzzy when they’re young. They’ll grow out of it.

Inspecting nursery plants, part lll

By now you’re probably ready to stand up, brush off your pants, and stretch your back after crawling around looking for surface roots and root crowns. Not so fast! There’s one more thing to look for – and to avoid.

Take a look at these two photos:

You can easily see the suckers at the base of these trees. Whether or not they are actually suckers (coming from the roots) or watersprouts (coming from the base of the trunk) doesn’t matter. Their presence in single trunked species warns of problems underground. You’ve probably seen landscape trees respond to crown stress by suckering. In this situation, my diagnosis is that the roots are so stressed (buried too deeply, structurally malformed, etc.) that they are unable to provide enough water to the crown. Thus, the plant responds by creating a shorter crown (the suckers) which is easier to keep supplied with water.

In both of the above cases, these were the only individuals of their species in the nursery that were suckering. That makes it easy to avoid purchasing them and their stressed root systems.

This is not such a problem with species that tend to form thickets, like our native vine maple (Acer circinatum) below:

Bottom line: know the natural habit of your trees and shrubs before you buy them. If they are single trunked species, don’t be a sucker – avoid suckers!

Inspecting nursery plants, part ll

Well, I’m recovering from this simply horrific chest cold or whatever it is and feeling brain function returning. The last time we were at our virtual nursery, we were looking for root flare and inspecting the trunk for damage from improper bagging. Since we’re already down on our hands and knees, let’s consider roots. In general, you really don’t want to SEE roots, except where they meet the trunk (the root flare). The presence of coyly crossed “knees” in this photo is a clear indicator of a plant that wasn’t potted up quickly enough:

Likewise, while the fused, circling woody root mass in this next photo might be aesthetically interesting, it sure doesn’t make a functional root system:

It’s pretty easy to avoid these types of plants, because you can see the root problems before purchasing. The hidden root problems, such as those I’ve shown in earlier posts, are tough to find until (or if) you take all the extraneous stuff off of the root ball.

Finally, there is a new production practice that really fries my potatoes. What really makes me angry is that these trees had absolutely LOVELY roots – a nice flare, woody roots spreading radially – and then they were butchered – and left unprotected:

I can think of no legitimate reason for this practice. I’ll be curious to hear my colleagues’ thoughts, as well as those from the blogosphere.

What Makes Growers Change?

Over the last few weeks I’ve said a lot of complimentary things about the Minnesota Nursery Industry and how they’re careful to avoid situations where trees are planted too deeply. What I haven’t mentioned is that there is a reason for this. During the 1980s and early ’90s trees were usually planted deeply with lots of soil over the uppermost roots. It was just common practice. Unfortunately this practice led to roots growing across the trees stems and, when those roots cross the stem, the roots always win (as you saw in Linda’s quiz last week)! Many, many trees planted in that era have trunks which enter the ground looking like the picture below. You can clearly see the roots strangling the tree. This photo was actually taken last year on this campus!

This tree is one of the lucky ones. These girdling roots were removed, the layer of soil over the crown was removed, the crown of the tree was inspected, and it was determined that this tree could survive. Many others planted during the 80s and 90s are not so lucky — in fact, many are suffering or dead.

An outcry over the last dozen years or so, mostly from cities (St. Paul and Minneapolis), led to changes in harvest by the nursery industry, and by the landscapers who install the trees. Yesterday I received a plan for planting trees up and down a major highway here in St. Paul to review. The specs were very specific — and similar to the specs that we see now across the Twin Cities and most of Minnesota. Root flare must be at, or even above, the surface of the soil.

I don’t want anyone to get the wrong idea. There are still those who sell nursery stock with the root flare buried deep under soil in the ball, and there are landscapers who dig a hole twice as deep as the depth of the ball before planting, but it’s becoming less and less of an issue as, in general, we seemed to have learned from past mistakes.

Inspecting nursery plants, part 1

I’m frequently asked to give seminars on selecting healthy plants at the nursery, especially trees and shrubs which can run hundreds of dollars. (Nobody seems to want a seminar on how to pick out a flat of petunias.) I routinely visit nurseries with my camera so I can record examples of good and not-so-good choices. What better forum to share these than on our blog? I’m also curious whether the problems we see in the Pacific NW are found elsewhere in the country, or in the world for that matter. So today we’ll hunker down on our hands and knees and inspect root flares.

The root flare (or root crown) is the point where the trunk meets the roots and should be wider than the rest of the trunk. The photo below shows this clearly:

In balled and burlapped trees and shrubs, you might not be able to find the root flare as soil and/or burlap cover the root flare. The tree below is burlapped far above its root flare:

Over time, many trees and shrubs buried too deeply will develop trunk rot. You can inspect for rot by gently peeling back the burlap from the trunk and looking for damage. Don’t worry, this doesn’t hurt the root ball or the trunk:

The tree in the above example already has some red flags – the presence of weeds on the soil surface suggests that it’s been in this pot for a long time. (And no, you don’t want to buy this tree.)
The most dramatic example of the problems that can occur is this weeping larch, which has been completely girdled by the rot induced by the burlap and twine around the trunk:

Lesson: It’s cheaper to wash your now-dirty pants than it is to buy (and eventually replace) a poor quality plant.

Chad and Jeff’s Excellent Nursery Adventure

About 3 months after I started my job in Minnesota I hired a technician to help me run the nursery and to manage research plots. His name is Chad and he stands about 6 foot 4, has shoulders that threaten to pop the sides of the skid steer loader whenever he enters it, and he knows his stuff because he needs to (and even if he didn’t know his stuff you’d be scared to tell him that because he looks dangerous with his frightening Fu-Manchu moustache). Currently Chad is responsible for day to day operations in the nursery as well as writing publications. In other words he’s indispensible. When you read a post from me, particularly when it’s regarding nursery or landscape research, you’re usually reading a combination of both of our thoughts.

Over the years Chad and I have seen a lot of nursery stock; some of it good, and some of it bad. Between us we’ve seen poor pruning, unhealthy root systems, pot-bound plants, trees planted in soil that was much too alkaline or acidic for them, trees planted in the wrong zone, trees sold that weren’t close to the size that they were supposed to be, trees that were girdled by critters, root systems completely eaten by voles and even a tree shot with a handgun. I once saw a whole field of Japanese maples topped (basically topping is when you cut horizontally through a trees canopy to give it a flattop – talk about competing leaders and narrow crotch angles!). Seeing that field almost made me cry – A planting worth $20,000 – $30,000 wholesale almost instantly became worth the price of kindling. But we agree that none of that can hold a candle to Sara’s Nursery (Named after the owner’s daughter).

I received a call a few years ago from a nursery in western Wisconsin (which, for those of you who aren’t familiar with this part of the world, is much closer to the Twin Cities than to Madison, WI where the University of Wisconsin is). The caller was very concerned that the plants in the nursery which she had been hired to run were failing. Basically, their leaves were dropping and she couldn’t figure out why. This was even happening to plants that we usually consider “indestructible” like potentilla. I had never heard of such a thing, but it sounded like a soil problem and so I asked her to have some soil tests done and to send me the results. She agreed, but she was distraught and asked me to come and take a look at her operation. I balked at first, but after a few minutes of begging I gave in. I asked Chad if he’d like to join me on a trip to the nursery the next day; he agreed and we were off.

The nursery that we found was a retail operation on a road which was once a major thoroughfare, but had been reduced to a minor highway when the interstate, which ran parallel, had been expanded. Still, it seemed like a pretty good location for a retail nursery in terms of customer traffic. After we parked the car Chad hopped out and began inspecting balled and burlapped evergreens while I joined the manager to look at their container stock. It was a mess. It was the end of summer when we visited, but the leaf drop made it look as though we were in the late fall.

I popped a potentilla out of a container and could find no roots reaching the containers edge. Taking a closer look I quickly discovered one major problem. These were bare root plants planted into containers filled with soil. Soil is almost never a good thing to put into a container because it’s usually too heavy and prevents air from working its way down to the plant’s roots. The gentleman who owned the nursery (not the manager – in most cases she just seemed to do what the owner wanted to do) was a farmer who had decided that it made sense to save money by using this soil which grew his field crops so well. This nursery was buying bare-root plants, popping them into containers filled with field soil, and then selling them at quite a mark-up (by the way, this is considered an unethical practice).

This field soil was obviously a problem, but, while plants usually suffer because of the use of soil in containers, I didn’t think it was likely to cause the carnage that I was seeing. I asked about their fertilizer and watering practices. Both of those seemed reasonable and unlikely to cause a major problem.

Meanwhile, Chad came back to report on the evergreens. Almost all of the evergreens (which showed signs of repeated shearing – good for Christmas trees — not good for the long term health of landscape trees) were missing needles close to the base of the tree and appeared to be suffering somewhat. I thought it might be a water issue, particularly if city water were being used, and asked where it came from. The manager told me that all of their water came from a well on site. In this part of the world we frequently have issues with well water being too alkaline, but it usually doesn’t cause the type of damage that I was seeing here. I filed water away as a possible, but unlikely cause.

I was pretty stumped, as was Chad. Obviously we saw problems, but these just didn’t seem sufficient to cause what we were seeing. The manager offered to show us the potting operation, we followed. The first thing that struck me about the potting shed was that it seemed old, and yet the timbers themselves hardly showed any rot which is kind of unusual. We asked when the shed had been built and the manager indicated that she had reason to believe that the shed had been built in the 1940s or 50s.

We entered the shed and noticed a large pile of what we assumed to be soil. Nothing special. Then our eyes began to adjust to the dim light and we realized that this was no ordinary pile of soil. It was mostly white. We were confused. The first thought that went through my head was “what is this, cocaine?” Then I thought, no, it must be perlite. I looked at Chad. His eyes were big and round. I went over to the pile, poked my finger into it, and then touched it to my tongue.

“What the EXPLICATIVE DELETED is this place?” I asked Chad (OK, I may not have used those exact words, but it was something close). The manager must have overheard.

“Well, it’s a potting shed now, but it was built to store salt for the highway” she responded. “That’s just a pile of leftover salt. We stack our soil against it when it comes in.”

We tested both the soil from the pots and their irrigation water. Both were ridiculously high in salt (and, not coincidentally, sodium levels). In fact, salt levels were high enough in the irrigation water that it would literally burn foliage off of the plants.

Shortly after visiting this nursery Chad became a Buddhist and my beard turned more gray than brown. I can’t swear that it was this nursery that caused these changes, but I can tell you that I haven’t been the same since.

Bare Root Trees

For the past 11 years I’ve been running a nursery at the University of Minnesota called the TRE (for Teaching, Research, and Extension) nursery where we research all kinds of fun stuff like Dutch elm disease, the dangers of mulching, and what happens when you plant a tree too deeply. One of the most interesting things we’ve done recently, though, is to install Missouri gravel beds into the nursery. Missouri gravel beds are called Missouri gravel beds because they were invented by Chris Starbuck, a professor at Missouri State. He mostly works with gravel beds above the surface of the soil, while here at Minnesota we work with gravel beds below the surface of the soil (the gravel bed below is 60 feet by 10 feet and filled with about 2 feet of pea gravel — we do have a system for recirculating the water — which we sometimes use and sometimes don’t because of clogs, algae buildup, etc.).

We take bare root trees and place them into these beds in spring (when bare root trees are available from nurseries) to encourage root growth and then plant them out into the field later in the season. The amount of beautiful fine roots for transplanting is just incredible, and the resulting plant can be planted bare root any time of year, instead of just spring when bare root plants in our area are usually transplanted.

Now to be a little more specific: I’m a tremendous fan of planting bare root plants, but I’m not a fan of planting larger plants bare root (at least not without Missouri gravel bed treatment), particularly what are known as B&B trees — trees that are harvested and held in a burlap and wire cage, such as those being harvested below from our nursery.

The reason that I don’t like taking a B&B tree and planting it after bare rooting it (by removing all of the burlap as well as the wire cage and then washing off the soil that surrounds the roots) is that, no matter how gently you wash off the roots, fine roots tend to be destroyed. When you harvest a root ball for a larger tree you are removing about 80-90 % of the roots. The additional roots that you remove by washing the ball will often make the tree non-viable. This is something that have I learned from experience with individual trees, as well as from replicated experiments using hedge maples and Turkish filberts. We used trees with a stem diameter of about 2 inches with standard sized root balls for that size tree, washed off the root ball for half (five trees of each species) and planted the other half using our more standard system (we removed the top portion of the burlap and wire, but not the bottom portion so as not to disturb the ball). All of the trees which we bare rooted from B&B died after planting and all that we didn’t bare root lived. This is further supported by some research coming out of the University of Illinois earlier this year by Andrew Koeser (and coauthors) which shows that handling the balls of B&B trees just isn’t that good for them.

So why am I spending so much time with this? Simple, this is an area where researchers disagree. In fact, based on what Linda has written in the past I’ll bet that she disagrees with me. And that’s a good thing. People always want the quick and simple answer, but often there isn’t a quick and simple answer. I can’t deny that sometimes bare-rooting a B&B tree before planting might be a good thing. But I think that, in the majority of cases, it’s a mistake. In terms of containers — We’ve got a big research experiment going on that right now — we’ll have results next year.

The other side of nurseries

As some of you know, my background is somewhat different from most faculty members in Horticulture in that my roots (no pun intended) are deepest in forestry. I’m sometimes asked to compare and contrast various aspects of horticulture and forestry. There are certainly differences – some of which I’ll get into in later posts – but there are also a lot of similarities. One of the truisms that seems to pervade both fields goes something like this: “When all else fails, blame the nursery”. Whenever a tree dies, whether it’s a 2-0 bare-root seedling or a tree that was spaded in with 60” tree space, the first reactions is “Must’ve been bad nursery stock”. Um, could it have been that the tree planting crew left the bundle of seedlings in the 90 degree sun all afternoon or that 5” caliper red oak really doesn’t belong in a bathtub? I bring this up because often we see suspicion, if not downright hostility, aimed at landscape nurseries. I thought of this as I was touring J. Frank Schmidt and Sons nursery this week near Boring, Oregon (yes, there really is town called Boring). J. Frank Schmidt and Sons is one of the largest wholesale producers of shade trees in the country. If you walk into virtually any garden in the northern half of the US, chances are you will see trees that began their life in the Schmidt’s fields under the shadow of Mt. Hood. J. Frank Schmidt nursery is among the most progressive nurseries in the industry, investing in new plant development, in-house research, and supporting university research through the J. Frank Schmidt Family Foundation and donating thousands of trees for research trials. During the tour, our host. Jim Ord, was excited to show us an air-slit container that Schmidt had developed for to reduce circling roots in container-grown trees. As I mentioned at the outset, we are often quick to blame nurseries for causing problems, here’s an example of a nursery working to solve problems. And this is just one example, Schmidt and other nurseries are working to develop and promote new elms and other species to provide a wider array of trees to replace ash trees in the wake of the Emerald Ash Borer. In some ways Schmidt is unique due its size and progressive stance but other ways it is very similar to a large majority of wholesale nurseries which with I interact. While there are certainly issues that trace their roots to problems in nursery production, most nurseries take great pride in their products and work constantly to refine and improve their growing techniques.

What I Learned This Summer (part 2): Pot Recycling, a Photo Essay

A big “score” at a great garden center or nursery results in guilt. Not about the money I spent, but the giant pile of pots and tags left in the wake of the planting frenzy. I plan to provide a more thorough review/discussion on this topic in the future – but for now, I want to share what I learned in a visit to the Missouri Botanical Garden’s (MOBOT) recycling center in St. Louis (part of the Perennial Plant Association’s annual conference). As one of the public gardening world’s leaders in conservation and sustainability, their program is truly revolutionary and apparently very successful. In place since 2006, they’ve kept hundreds of thousands of pots out of the landfill.

Dr. Steve Cline,recycling guru and dynamic Director of MOBOT’s Kemper Center for Home Gardening, explains the system to our group.

Start with your basic pile o’ pots, knocking out loose soil, beer bottles, whatever they’ve accumulated.

Deliver them to either a participating garden center (there are several) or the garden’s recycling location and place in the appropriate bin.

If off site, pots get hauled to the garden’s Monsanto Center for recycling. Garden staff and volunteers then send them off to the great and loud Pot Chipper in the Sky…

resulting in pot confetti…
Woo hoo! (flings in air)

…which gets shipped to manufacturers of cool things like plastic lumber!

Voila. Guilt relieved; IF you garden in the greater St. Louis area. I’ll be talking about alternatives for the rest of us in a future post!

Bad roots and deceptive marketing

I guess today’s blog should be entitled “The Cranky Garden Professor.” Really, I’m not always cranky, and when I am I go outside to do something constructive in my garden. Last weekend I finally tackled a 5-gallon container of lavender that I’d bought several weeks ago. I had intended to wait until fall to transplant it, but I was watering it every day to keep it from wilting. I figured I might have better luck getting it into the soil where a good mulching would help keep the soil moist without daily watering.

So I carefully slid the lavender out of its pot and into my root-washing tub (Figure 1). (If you’re not familiar with root washing trees and shrubs, be sure to check out my web page. I’ve got a fact sheet and some myth columns on why it’s important to bare-root containerized and B&B woody plants before installing them in the landscape. Please visit www.theinformedgardener.com to access the entire site, or this link for a fact sheet.

Figure 1. Five little lavenders.

As I worked the potting media out of the root mass, I suddenly discovered why I was using so much water to keep the lavender happy. It wasn’t one plant. It was 5 separate lavender plants all placed in the container to LOOK like one large plant. Worse, all 5 plants had some of the crummiest root systems I’ve ever seen (Figures 2-6). They were poked into the pot like little carrots. Most of the pot was filled with untouched potting media.

Figures 2-6. The beehive is back!

What you see in these figures are root systems that look like upside down beehives. They were obviously left in their original small pots too long and developed circling root systems. So rather than growing outwards into the soil, they stayed in these little spirals and eventually would fuse into woody knots. They don’t miraculously straighten out when they’re put into larger containers (or the garden). If they did, they would have rapidly spread throughout the big container to soak up all that water I was pouring on daily.

Sigh. Now I was cranky again. These lavender roots were just like those I’d seen on hundreds of landscape plant failures over the last 10 years. Since these roots were so tightly woven together there was little hope of untangling them. So I made one vertical cut through each of the root masses (Figure 7), spread them out horizontally (Figure 8), and planted them (Figure 9).

Figure 7. The cut. Figure 8. The spread. Figure 9. In the ground.

This is the worst possible time of year to transplant trees and shrubs (it’s August, after all) and I most definitely put a world of hurt on these roots. But I will say that since I moved them I have been able to reduce irrigation, since the soil holds moisture better than the potting media. I’ll keep track of their progress through the next 12 months. I’m hoping they make it through this summer – if so, they stand an excellent chance of growing a decent root system over the fall and winter.

Back to the cranky part. I really resent nurseries that deliberately bunch small shrubs together in one pot to make them look like one big plant. It certainly cost more to buy this one pot than to buy five smaller pots. If this isn’t deceptive marketing I don’t know what is.