I'm always torn about how best to prepare root-bound nursery plants before planting in the ground. I usually tease apart some roots, sometimes even soaking them in water, or in the worst case take a knife to it and partially cut through some of them. But recently a nursery man told me to leave them be, that they will spread out on their own. This seems counterintuitive to me. What do you folks do? Will appreciate your advice.

That's bad advice. Yes, the roots will spread, IF the native soil isn't too different. For instance, if you plant in heavy clay, and your tree is in a light potting mix, roots growing into the native soil will be difficult for several reasons.

But the worse thing is that roots don't change their positions in the soil. If they are crossing each other, circling in the pot, winding around each other, whatever.... that is how they will stay as they grow larger, and these phenomena will exacerbate. Think of a string permanently around a child's finger. As the child grows, the string does not, and constricts the finger more and more. At best, the finger will be disfigured. At worst, the finger dies!

Rootbound or not, I try to remove as much of the soil in potted/purchased plants as I can as it often times is some sort of spongy wet type of stuff or it is mostly bark/mulch. The spongy stuff, during our cold wet winters, soaks up water, freezes and the plant rots. The really loose mulch type stuff drains too well and is too loose and the plant will still die over the winter. I have best luck shaking and working all that off, and then planting it in the garden soil.

I agree that was bad advice; I would say that what you've done in the past is correct - I've taken a knife to many root-bound plants (some were ones I grew myself ).

It does depend on the plant and the location.
I don't bother loosening bedding plants, like Pansies, because they're not going to be around long enough for it to be a problem.
We don't get freezing weather so I leave the planting mix on the roots.
For trees and shrubs I cut any circling roots and at the bottom of the rootball to loosen.
For monocots, like grasses and palms, the roots don't grow fatter so there's no point in cutting them either.

I appreciate your comments but still would welcome more. I thought the nursery man gave me bad advice too but I figured he must know more than I do. Thanks all.

CPPgardener said: It does depend on the plant and the location.
I don't bother loosening bedding plants, like Pansies, because they're not going to be around long enough for it to be a problem.

Some of those short term plants, I've tried it both ways.
Never saw any real difference.
I think how the planting bed is prepared is far more important.

Even with trees... Grouping them in one large bed that has been well worked and amended, is going to have far better results, compared with one tree out in the middle of a grassy yard.

planting root bound plants in the spring-the plant has all summer and fall to grow out some roots and establish before winter. Planting root bound plants in the fall, may not have good results. Root bound trees I have not had good luck with.

For smaller root bound plants like annuals I use a fish fork to tease the roots apart gently. This is my spare fork. For larger root balls I use the garden claw and give the roots a good whack all the way around to loosen them up.

I've learned recently that plants really tolerate alot harder root-pruning than most people think. I've been taught to straight up sheer the entire outer rootball of a root-bound plant with a breadknife before planting (maybe even remove some of the canopy too).
This might be more applicable to house plants though, I've seen people really hack on the roots of those, ex: https://www.youtube.com/watch?...
I've seen similar methods performed on trees transplanted into the outdoors. Not sure how smaller, more tender, outdoor species would do though.
Personally, I go ham on rootbound plants with a hand rake to really ruffle them up. You can also cut off the bottom 1/3rd of the rootball. I wouldn't recommend this with taproots though.

Here is a hard pruning on a root-bound tree I found interesting: https://www.youtube.com/watch?...

I've done root-pruning on many many houseplants where they're in as big of a planter that fits in a spot, with no ill effects at all. The trick is just don't take off too much, rather 1/2"-1" around the edge and the same off the bottom. I've never lost a plant or even foliage doing that. I've never had to do it with outdoor plants, those should be hardier than indoor houseplants so I can't it imagine it being a problem if you need to do it.

I usually just leave the roots alone though when planting anything outdoors, the roots will reach out into the new dirt whether you rough them up a bit or not.

Thank you all. Those video links that Girthworm send are very helpful.

Depends if we're talking about woody or non woody plants.

The 'trajectory' a root has made doesn't change over time. So a root that's grown in a circle will stay in that circle. Only new growth can go outwards from that point onwards.

For perennials this doesn't matter AS much since most will be dug up and divided regularly anyway to reinvigorate them. Any bad root growth will - with increased reinvigoration over time - be correct until the root system is all outwards.
For shrubs and trees this doesn't apply (or shouldn't). Any bad root growth will stay bad root growth and as secondary growth makes them thicker, they can eventually impede other roots or worse yet, girdle and kill the tree.

In both situations however you can slice the outer edges and bottom off before planting, but with woody perennials this doesn't guarantee a well spread out root system since you can't see what defects are present inside the root ball.

What I do with perennials: tip them out, turn them upside down, push both my thumbs through the middle (on the bottom) and tear outwards creating two 'flaps'. Spread out inside the hole, cover and water in.

For woody material, the consequences of not correcting root issues at plant out time can be severe, even if it takes many years for the plant to "grow into the problem". The tree below was lifted from the nursery can, dropped into the planting hole, and the hole backfilled. The result were a dead tree several years later as the tree "grew into" the situation where encircling/girdling roots terminated the downward flow of photosynthate through the cambium, which resulted in the roots being starved.


Ideally, growers would buy their trees dormant, so they can plant as soon as the frost is out of the ground in areas that experience frost, and prepare them for planting out by bare-rooting and removing all problem roots. Problem roots include diseased/ damaged encircling/ girdling/ crossing/ roots, roots growing straight up (or nearly so) or back toward the center of the root mass, and j-hooked roots. The planting hole should be large enough to accommodate the root mass and should be back-filled with native soil unless the soil is sandy.

Read more: https://s3.wp.wsu.edu/uploads/...

The most vigorous part of the plant is found in the root to shoot transition area. Unlike humans who age chronologically, plants age ontogenetically, so the newest tissue to grow is the oldest tissue on the plant, and the youngest (most juvenile) tissues will be found at the root to shoot transition, which is how "rejuvenation pruning" got its name - from cutting the plant back to more juvenile tissues. So, pruning roots gives them something of a new lease on life.

When it comes to putting together mixed floral plantings or planting bedding plants in the landscape I follow two practices depending on how rootbound the plant is in the pot or cell-pack it came in. If the soil falls away from the roots, I don't do anything to the roots - I simply plant it in the pot alone or with other plants, or directly into the garden or beds. IF the root/soil mass comes out of the pot intact, that is to say as a unitized mass of soil and roots, I rip the bottom half of the roots off without any thought of being cautious, then work my fingers up into the remains of the soil/root mass to spread it out more horizontally, and plant it. I have been doing this for as long as cell packs and plastic post have been around, and would be happy to provide images of mixed plantings I have put together using that technique. It produces stronger and healthier root systems and happier plants than trying to preserve the roots and go to great lengths to prevent damage. Typically, I toss the roots and soil I remove from the bottom of the soil/root mass into a plastic tub, and use them to stuff around the base of the plantings after they're planted to provide additional stability.
Al

Anecdotally- I can report that a plum tree I bought at big box, and found had all the major roots chopped off at no more than 8 inches, grew amazingly. Honestly, had barely any secondary roots.

It's amazing what a root system will tolerate if you bare root, prune roots hard, and don't allow the roots to dry out while their being worked on. Examples:
Ficus benjamina
From this:

To this:

Boxwood
From this:

To this:

Acer palmatum (Japanese maple)
From this:

To this:

Every spring, I habitually repot some 150 trees that are suffering from the limitations imposed by root congestion/ being rootbound. It's only by repotting and root pruning that the grower can entirely restore the plant to a state in which it is not losing potential due to root congestion. Potting up, even if you trim the roots around the entire perimeter of the root mass (except the top, of course), still leaves the congestion in the center of the root mass as a limiting factor, and only allows the tree to throw off a fraction of the limitations imposed by root congestion.

When you pot a plant up and you see what you determine to be a "growth spurt" ..... it's not a growth spurt at all - just the plant returning a little closer to how it could have been growing all along if not for being rootbound. The limitations begin about the point in time where the root/soil mass has fused into a unit that can be lifted from the pot intact. All 3 examples above were being seriously limited by root congestion. The repot with root pruning eliminated that congestion entirely, not partially, as potting up does.

While it's not necessary to go as far as I did for plants being planted out, something close to that but not quite as severe is appropriate for most woody material that will be grown long term in a pot.

Al

I will add that with bigger shrubs/trees, the rate of failure increases dramatically with age/size, especially in the landscape.
I've done root washing on numerous plants, and I'm not proud to say I lost the majority of them after one season. Even if they survive, there's so much die back that the initial form for which I bought them is gone.

Here's how I had to butcher a Carpinus japonica in the fall of 2021:






After that initial prune + last years' severe drought and high temps for weeks on end, it's lost 70% of the canopy this year, despite all the irrigating I did.
I've pruned most dead branches out (not all) and it looks absolutely mangled right now.
Also, the root flare doesn't look good either. Alot of dead patches (bark cracked etc)....I can see the wounds starting to close, but it'll take years.

My hope now is that since hornbeams tolerate hard pruning well, I can select a new canopy from the epicormic buds that broke into new shoots this spring.

I've made the decision for myself that I'll never again buy a tree of any large size/age anymore unless it's dirt cheap. The survival rate just isn't worth the cost and possible heartbreak.

I'll add a photo tomorrow of how it's looking right now.

Yeah.... A very strong argument for field grown (balled and burlap) vs those horrible container grown.

Better late than never.

The hornbeam:



Bonus tree, Parrotia persica:

I wouldn't even bother with the Parrotia. You'd have to remove so many roots I don't think it would survive. Unless there are straighter roots hiding under those big very curly ones.