Repotting vs up potting: disturbing roots vs chopping roots

[gjantzer]

I have a dozen or so young plants in 4" containers that I want to get into 10" pond baskets but the buds have opened up into small leaves. Some of the plants are already in a similar substrate to what I will be using. Other plants are still in nursery soil so I would need to remove most of the old soil before getting them into the pond baskets. If I am not removing roots is the timing still not recommended? The general consensus is that repotting be done by the time that buds open, but how does that relate to disturbing roots as opposed to chopping roots off? In other words, what is the general rule for up potting vs repotting?

 

[0soyoung]

So why don't you organize a little experiment and figure it out for yourself?

Think about what the consequence is of removing all the roots --> your plant is effectively a cutting. It would have no capacity to take up water until the plant could generate roots. But, if the relative humidity of the air is less than 100%, water will be lost from the plant to the air (i.e., transpiration). So you would put the plant in humidity tent or terrarium that would keep the air around the leafs very humid. Cover it in transparent/translucent plastic, for example and put it in the shade (photosynthesis can still happen in shade).

Before you go this deep for a rescue, you wait until you have a rainy/high-humidity week in the forecast. If they immediately start wilting, move them to shade, if they aren't recovering /then humidity tent rescue'. Use this sort of qualitative response as your metric and I think you can learn a lot and not lose a plant. But they are young plants - so what if you lose a few = cost of learning.

 

[Adair M]

It sounds like these are deciduous trees. You mentioned leaves. Why are you putting them in pond baskets? That's a pine technique.

Generally speaking, deciduous trees we want a flat, thin root system. Different techniques are employed.

 

[GroveKeeper]

It sounds like these are deciduous trees. You mentioned leaves. Why are you putting them in pond baskets? That's a pine technique.

Generally speaking, deciduous trees we want a flat, thin root system. Different techniques are employed.

You can plant on a board or tile in pond basket/colander and get the benefits of air root pruning,

 

[sorce]

Do it!

Sorce

 

[Vance Wood]

Specifically what kind of trees are you talking about?

 

[gjantzer]

Specifically what kind of trees are you talking about?

I am mostly curious about the rule in general. If I don't cut the roots can i repot later into the spring? This spring I want to repot some Trident Maples, Korean Hornbeam and some Quince. I purchased several seedlings last year and put some of them in 4" pots and some in the 10" pond baskets (with only 3 or 4" of soil used - giving me a 10" training flat). The ones in the 10" pond baskets are growing much more quickly than the ones in the 4" pots. I am wanting to know if I can move those still in the 4" pots into my pond baskets if I don't cut up the roots.

 

[Adair M]

Yes, you can up pot.

Tease out 1/2 inch along the sides of the current root ball so that when you add the new soil, they'll be "in" the new soil. That way, they will start growing in the new soil.
A common mistake is to simply stick a rootball in, and backfill with new soil. The roots will be reluctant to grow into the new soil because it's so different.

Of course, the best approach is to bare root young seedlings and arrange the roots out radially, eliminate the downward tap root(s) and attach it to a board so that the roots grow out, not down. Merely setting the tree on a board will help, but the root really want to grow down. And they will push the trunk up if they can! So, a screw inserted up from the bottom of a board into the trunk prevents that.

Colanders really don't help. A large (wide) relatively shallow box works well. Put 1/2 inch of coarse soil (or pumice) in the box. Then place the board with tree attached on the pumice. Secure the board to the bottom of the box. Leave an inch or two of space between the sides of the box and the edges of the board. Roots will radiate out from the trunk horizontally until they get to the edge of the board, then go down, then will grow in the pumice below the board. Cover the board with a couple inches of soil. Yes, deep. The radial roots will develop and fatten and fuse better if they're buried. They will develop slower if they are exposed.

Leave for two years.

In two years, dig it up. Cut off the roots where they start growing down at the edge of the board. Wash lol the old soil off. You can then rearrange roots that cross. Use a nail driven into the board to hold them in place.

Replace the pumice, secure the board back in place, rebutted. Wait another two years.

Repeat until you're happy with the nebari.

Meanwhile, work the top.

You may have to use a new board every couple repottings.

Colanders, provide no benefit. At least, not for deciduous. For pines, they work great. They provide no benefit for junipers, either. Junipers naturally produce fibrous root systems.

 

[Vance Wood]

It is my understanding that Quince should be repotted in the Fall due to a fungal disease they can contract when the roots are cut in the Spring. Most the trees you have mentioned are normally repotted in the Spring if you are cutting the roots et.al. However if you are only slip potting the tree you can pretty much do that any time of the year unless the tree is frozen in the pot. Yes you can move the 4" trees into the 10" pond baskets if you don't disturb the roots. However if you wait till near the end of June you can open up the soil ball and straighten out the roots before putting them in the 10" pond basket.

Adair's approach is good as well. There are more than one way to fry chicken.

 

[GroveKeeper]

Yes, you can up pot.

Tease out 1/2 inch along the sides of the current root ball so that when you add the new soil, they'll be "in" the new soil. That way, they will start growing in the new soil.
A common mistake is to simply stick a rootball in, and backfill with new soil. The roots will be reluctant to grow into the new soil because it's so different.

Of course, the best approach is to bare root young seedlings and arrange the roots out radially, eliminate the downward tap root(s) and attach it to a board so that the roots grow out, not down. Merely setting the tree on a board will help, but the root really want to grow down. And they will push the trunk up if they can! So, a screw inserted up from the bottom of a board into the trunk prevents that.

Colanders really don't help. A large (wide) relatively shallow box works well. Put 1/2 inch of coarse soil (or pumice) in the box. Then place the board with tree attached on the pumice. Secure the board to the bottom of the box. Leave an inch or two of space between the sides of the box and the edges of the board. Roots will radiate out from the trunk horizontally until they get to the edge of the board, then go down, then will grow in the pumice below the board. Cover the board with a couple inches of soil. Yes, deep. The radial roots will develop and fatten and fuse better if they're buried. They will develop slower if they are exposed.

Leave for two years.

In two years, dig it up. Cut off the roots where they start growing down at the edge of the board. Wash lol the old soil off. You can then rearrange roots that cross. Use a nail driven into the board to hold them in place.

Replace the pumice, secure the board back in place, rebutted. Wait another two years.

Repeat until you're happy with the nebari.

Meanwhile, work the top.

You may have to use a new board every couple repottings.

Colanders, provide no benefit. At least, not for deciduous. For pines, they work great. They provide no benefit for junipers, either. Junipers naturally produce fibrous root systems.

I'm sure your approach works very well, but why do you say that colanders are no benefit to deciduous trees? Especially for trees in the early stages of development, having more roots will increase the number of options you have when trying to develop your lateral roots.

 

[Adair M]

I'm sure your approach works very well, but why do you say that colanders are no benefit to deciduous trees? Especially for trees in the early stages of development, having more roots will increase the number of options you have when trying to develop your lateral roots.

The colander technique was developed because pines don't like to have their roots disturbed very much. So putting them in a colander would allow them to grow pretty much uninhibited for 4 or 5 years without them having to get dug up very often.

Deciduous trees, at least elms and maples, are more more tolerant of being bare rooted. Even every year! So, you can be more aggressive with the roots and arranging than you can with a pine.

Pines prefer dryer soils. The exceptional drainage offered by a colander works very with them. Deciduous trees in the height of summer are carrying a lot of leaves and can dry out quickly in a dry wind. They generally prefer soils that stay more uniformly moist. A colander will dry out around the perimeter. D trees don't like that.

Colanders are the wrong shape for D trees. We don't want deep root systems, we want more shallow, broad root systems.

All that said, you can grow a D tree in a colander.

But I think you would get better results using the Ebihara technique, which I described in an earlier post.

Edited to add: and I wouldn't nail a pine to a board. I'd use a colander.

 

[GroveKeeper]

The colander technique was developed because pines don't like to have their roots disturbed very much. So putting them in a colander would allow them to grow pretty much uninhibited for 4 or 5 years without them having to get dug up very often.

Deciduous trees, at least elms and maples, are more more tolerant of being bare rooted. Even every year! So, you can be more aggressive with the roots and arranging than you can with a pine.

Pines prefer dryer soils. The exceptional drainage offered by a colander works very with them. Deciduous trees in the height of summer are carrying a lot of leaves and can dry out quickly in a dry wind. They generally prefer soils that stay more uniformly moist. A colander will dry out around the perimeter. D trees don't like that.

Colanders are the wrong shape for D trees. We don't want deep root systems, we want more shallow, broad root systems.

All that said, you can grow a D tree in a colander.

But I think you would get better results using the Ebihara technique, which I described in an earlier post.

Edited to add: and I wouldn't nail a pine to a board. I'd use a colander.

The colander technique may very well have great benefits for pines, but that doesn't change the fact that deciduous trees still benefit from air root pruning. With how aggressively some of them root, the air root pruning effect can create an incredibly dense network of feeder roots in a short amount of time. That's the benefit you get from planting anything in a colander/pond basket/Vance pot.

The shape of the root system is beside the point as you can plant a tree on a board as easily in a colander as you can in a pot. The "Ebihara technique" and air root pruning are not mutually exclusive. In fact I think they would probably work better in unison.

And while some deciduous trees might not prefer being in a container where the edges get too dry... that is a pretty broad prescription. There are so many different types of deciduous(or broad leaved trees if you prefer) trees that I don't see how you can make such a generalization. Even the small number of natives I have collected from the same range respond very differently to the same techniques.

 

[just.wing.it]

Interesting stuff yall...

 

[Adair M]

The colander technique may very well have great benefits for pines, but that doesn't change the fact that deciduous trees still benefit from air root pruning. With how aggressively some of them root, the air root pruning effect can create an incredibly dense network of feeder roots in a short amount of time. That's the benefit you get from planting anything in a colander/pond basket/Vance pot.

The shape of the root system is beside the point as you can plant a tree on a board as easily in a colander as you can in a pot. The "Ebihara technique" and air root pruning are not mutually exclusive. In fact I think they would probably work better in unison.

And while some deciduous trees might not prefer being in a container where the edges get too dry... that is a pretty broad prescription. There are so many different types of deciduous(or broad leaved trees if you prefer) trees that I don't see how you can make such a generalization. Even the small number of natives I have collected from the same range respond very differently to the same techniques.

Fine. Do what you want.

 

[barrosinc]

Fine. Do what you want.

So, what about a box with side mesh and wooden base?

 

[0soyoung]

So, what about a box with side mesh and wooden base?

Air pruning, regardless of what form of mesh container that one uses and regardless of what species is planted, will prevent roots orbiting along the pot wall. A wood box with mesh sides will work (this is what Vance Wood got a patent for). Pond baskets will work. Colanders will work. A mesh bag tied around the root ball will work. Air pots will work. Etc.

Roots must be pruned (by some means) to develop ramification, just as branches must be pruned to develop branch ramification. One can use root pruning to do this OR one can unpot, root prune, and repot (i.e., 'repotting'). The process of physical root pruning abruptly, but temporarily, reduces the capacity for loading mineral nutrients and adsorbing water. Thus, an increased growth rate with air pruning versus repotting may be very real.

 

[markyscott]

The colander technique may very well have great benefits for pines, but that doesn't change the fact that deciduous trees still benefit from air root pruning. With how aggressively some of them root, the air root pruning effect can create an incredibly dense network of feeder roots in a short amount of time. That's the benefit you get from planting anything in a colander/pond basket/Vance pot.

The shape of the root system is beside the point as you can plant a tree on a board as easily in a colander as you can in a pot. The "Ebihara technique" and air root pruning are not mutually exclusive. In fact I think they would probably work better in unison.

And while some deciduous trees might not prefer being in a container where the edges get too dry... that is a pretty broad prescription. There are so many different types of deciduous(or broad leaved trees if you prefer) trees that I don't see how you can make such a generalization. Even the small number of natives I have collected from the same range respond very differently to the same techniques.

An important component of success in using the Ebihara technique to develop a spreading root base is that the roots need to grow straight, long, and radial to the trunk. They need to expand and fuse to become part of the nebari. It seems to me that air pruning the growing tips to form a bunch of feeder roots would be counter productive. But I might be wrong. Never tried it with a colander.

 

[GroveKeeper]

An important component of success in using the Ebihara technique to develop a spreading root base is that the roots need to grow straight, long, and radial to the trunk. They need to expand and fuse to become part of the nebari. It seems to me that air pruning the growing tips to form a bunch of feeder roots would be counter productive. But I might be wrong. Never tried it with a colander.

It might be counterproductive in the later stages. Early in the development though, air root pruning will give you multitudes of roots to choose from. It might even be really advantageous if you're going for the fused root pancake.

 

[markyscott]

It might be counterproductive in the later stages. Early in the development though, air root pruning will give you multitudes of roots to choose from. It might even be really advantageous if you're going for the fused root pancake.

I want them to look like this:

Early: Late:


I've only ever done it or seen it done in a box, but I'd love to see it successfully carried out in a colander. The trick is promoting long, straight, radial roots - when they hit the end of the box, they wrap underneath and grow below the board.

 

[Adair M]

It might be counterproductive in the later stages. Early in the development though, air root pruning will give you multitudes of roots to choose from. It might even be really advantageous if you're going for the fused root pancake.

The thing is, they won't get air pruned until they get out to the edge of the colander. When I have done the Ebihara technique, I get tons of new small roots on top of the board. Racing to get to where they can drop over the edge. They don't continue to grow straight out. They go down. So, there would be no airpruning until they hit the bottom of the colander.

I'm not sure there's any real benefit.