Is overpotting a myth?

[Walldepartment]

Plant containers – does size really matter?

A few days ago I got a question from Cynthia about “potting up.” For those of you for whom this is an unknown phrase (and no, it’s not a euphemism for a certain herbal activity), it refers to the …

gardenprofessors.com

 

[Paradox]

Not sure what you're asking with posting this?
Did you actually read the entire article?

It concludes that when growing toward a certain size, that it is a good idea to pot up to the desired size for growing out landscape plants for sale.
Bigger landscape plants command more money at the retailer = more money for the buisness. Of course there is a trade off of time and the work it takes to grow it out so the faster you get it bigger within a given time means more money for you.

We already know if you are starting from a seedling, the tree will grow faster in an over sized pot.

Strictly for bonsai:
The question is how much of an oversize to you really need when dealing with a pencil thin seedling.

It doesnt make much sense to put a pencil sized seedling into a 16" x 16" anderson flat to start getting growth when a 6" x 6" will put good growth on for a couple of years then pot up to a 10"x10" and so on.

You are going to want to evaluate and reposition roots periodically anyway and at some point you are going to want to put it into a bonsai pot anyway.

Besides the fact that you're using way more soil than you need to for the tree, putting it in a ginormous pot as a seedling and just leaving it without periodically addressing the root structure will leave you with a large tree with a huge mess of a root structure that you'll have to drastically deal with later. For some species this might be ok, but for others, you'll kill the tree.

 

[Bonsai Nut]

If you step back for a moment and think of horticulture...

Root mass and foliage mass are related. A certain size root mass supports a certain size foliage mass. You can "cheat" the equation by providing a perfect environment for the roots - perfect soil, artificial watering, fertilization - and yet, at the end of the day, you can only go so far. No one would argue that you can keep a sequoia with a 12" caliper trunk in a 5 gallon nursery pot.

The mystery of bonsai is that you can often take a large caliper, older tree, and move it into a smaller pot and reduce the foliage mass at the same time and - success! You have achieved a new balance with smaller root mass and small foliage mass - accompanied by a thick trunk. But you aren't breaking any horticultural rules. You are simply using them to your advantage (aesthetically).

 

[Forsoothe!]

The amount of wood is neutral and almost immaterial. The balance has to be between the feeder roots and foliage. They have to be able to service each other. This principle is demonstrated by bonsai.

 

[Mikecheck123]

We already know if you are starting from a seedling, the tree will grow faster in an over sized pot.

This is controversial if not incorrect.

 

[Walldepartment]

This is controversial if not incorrect.

Exactly. This is not what I have read on bonsai websites. They basically say to start a seedling in a small pot, maybe 3 or 4 inches. After a year or two, move it into a little bigger, maybe 6 inches, and so on. The article makes it seem like you could plant it straight into a 5 gallon bucket and get faster growth.

 

[Walldepartment]

As far as I can tell, what she writes on her blog seems rational. She also writes about how aborist wood chips used as mulch for trees increases their growth rate, more so than compost or fertilizer. Yet I’m betting a lot of people here might say that would tie up nitrogen, bla bla bla.

 

[Paradox]

Exactly. This is not what I have read on bonsai websites. They basically say to start a seedling in a small pot, maybe 3 or 4 inches. After a year or two, move it into a little bigger, maybe 6 inches, and so on. The article makes it seem like you could plant it straight into a 5 gallon bucket and get faster growth.

As far as I can tell, what she writes on her blog seems rational. She also writes about how aborist wood chips used as mulch for trees increases their growth rate, more so than compost or fertilizer. Yet I’m betting a lot of people here might say that would tie up nitrogen, bla bla bla.

The article is talking about landscaping plants, not bonsai trees. There is a difference between a landscape plant that will be in a pot for a couple of months and a bonsai tree that will be in a pot for decades

Under equal conditions of water, sun, fertilizer and health a tree will grow faster overpotted than if it was crammed into a pot barely big enough for it.
It needs to be able to grow roots and foliage that support each other. Its basic horticulture. If it has no room to grow, it will grow slower.
However as I said, it will not grow faster in a pot that is a little bit over potted vs a ginormous pot that could fit 50 of said plants into it.
There is a limit to what over potting can do that is based on the biology and physiology of the plant.

A tree grows the fastest in the ground, not in a pot

 

[sorce]

So if the pot is as big as the ground just skip the whole pot thing.

Everything is a myth from the right perspective.

Sorce

 

[Forsoothe!]

The only reason(s) plants may grow slower in a large pot is if the pot does not cycle between wet dry wet dry in a manner that keeps it too wet too long (or too dry for too long). That would slow things down. If the plant likes hot roots, a large pot would retain more heat in the evening, too. If the pot doesn't stay too wet too long and matches the needs of the plant, it will grow faster because there will be less root competition among the brother roots and there is never any repotting shock. Exactly what sizes are optimal is another fight.

 

[leatherback]

plants may grow slower in a large pot is if the pot does not cycle between wet dry wet dry in a manner that keeps it too wet too long

This is key.

A pot can be too big.
There is a reason why pot-grown trees in nurseries are not planted in their final-size pot directly, but repotted every so often, even though labour is expensive. Optiomal growth is achieved when the next size up is only a little bit bigger, and repotting happens as soon as the rootball has been established enough not to fall apart when the plant is taken from the container.

 

[Mikecheck123]

Everything is a myth from the right perspective.

This seems like a myth from my perspective.

 

[Shibui]

A pot can be too big.
There is a reason why pot-grown trees in nurseries are not planted in their final-size pot directly, but repotted every so often, even though labour is expensive. Optiomal growth is achieved when the next size up is only a little bit bigger, and repotting happens as soon as the rootball has been established enough not to fall apart when the plant is taken from the container.

I regularly see problems when little tiny seedlings are potted straight into huge pots thinking to simulate ground growing. Most bonsai growers know that pots are not the same as the ground. Drainage and a whole host of factors operate differently in a pot where soil contact is not continuous.
Substrate can become waterlogged, sour and toxic when there are few roots. Really large pots can indeed hinder growth. 2 pot sizes up is usually enough for most plants to cope with at any time.

 

[sorce]

I reckon the truth has to do with the warm zone on the outside edge of the container that roots love to populate.

It's a Mirai thing.

Sorce

 

[bwaynef]

From Plant Production in Containers by Carl E. Whitcomb

When plants are shifted from a smaller container to a larger container prior to stress or stunting, there is no difference in the size of the shifted plant as opposed to the plant placed directly into the larger container, provided the water management of the shallower container is respected and the same rate per unit volume of nutrients is used. Studies of this type have been conducted with numerous species with similar results.

In this section, there is no study cited that I can direct you to, but they do publish a picture of plants that went into a 1gallon then 3 gallon compared to plants that went directly into a 3 gallon. The picture seems to reasonably show plants of similar size. In the preceding section he does state the importance of NOT allowing the plant to slow down due to the stress of rootbound conditions ...and the resulting labor costs required to ensure that doesn't happen.

Also, I don't think the water management part of the quote above can be over-stated.

 

[Grovic]

The only reason(s) plants may grow slower in a large pot is if the pot does not cycle between wet dry wet dry in a manner that keeps it too wet too long (or too dry for too long).

I agree with this; also, from what I've read, the logic behind increasing pot size gradually is to ensure that the soil will dry out to a healthy level. If you overpot, the areas that are not colonized by the roots stay wet for longer, the way I see it, that area acts as a "battery of water" prolonging the time it takes for the soil to dry out.
I think potting up gradually helps you make sure that the soil will dry out as required for optimal growth, but similar results can be achieved if you get right the watering for an overpotted plant.

 

[Forsoothe!]

A pot keeps cooler via evaporation, too, so a pot that stays too wet too long stays cooler which can make for poorer growth. This is of course a sliding scale and is specie specific.

 

[Mikecheck123]

Another, perhaps overly simplistic, way to think about it is: roots are stimulated to explore when the soil is drying out. If the soil remains wet always (as in a pot that's too big), the roots don't have to do anything, and thus, won't.

 

[Forsoothe!]

Another, perhaps overly simplistic, way to think about it is: roots are stimulated to explore when the soil is drying out. If the soil remains wet always (as in a pot that's too big), the roots don't have to do anything, and thus, won't.

You know how I hate to be picky, but this sounds like an old wive's tale. Very old wives.

 

[Mikecheck123]

You know how I hate to be picky, but this sounds like an old wive's tale. Very old wives.

I read it in Bonsai Heresy. So call Hagedorn an old wife, if you like.