Arguments for smaller pots almost always revolve around grower convenience.
To promote the greatest vitality in one's plants, free root-run and excellent drainage is key.

And, of course, good light ;)

Josh

One drawback is that with few roots to uptake water, the media will stay damp for a much longer time than I'd want it to. You'd almost be forced to water in sips until the plant was large enough to use enough water to allow you to water fully. Even using a fast mix, such as a gritty mix, if few roots are uptaking water, the soil can stay damp for a week or more. The plant wants aeration; soil drying out every couple days helps accomplish this. It's best for the plant to fully water to promote gas exchange, which would limit aeration.

From my perspective, I'd disagree with point 5. Many plants need root work on a regular basis. It's not damaging them, rather promoting their growth and bushiness. In addition, I want to repot plants at a regular interval to replace the soil that has broken down. This varies on the type of plant and the soil mix I've used. With some mixes, such as the gritty mix, this is less frequent than with a peat based mix.

Growers convenience for me and that of the plants perspective in some ways...

Growers convenience: I like to keep my plants in small pots to make room for more in my house. I also like to keep them in small pots because they are eaiser to carry. I also like to keep them in small pots because certain plants by nature grow shallow roots anyway. I also like to keep many in smaller pots so I can fit as many on my only two sunny window sills..I also like them in smaller pots to contain growth, to keep them from growing to big. Many I like to keep Bonsai size..In the soil I use, I can plant a 2inch plant into a 30 gallon container, but I just don't.

Plants perspective: I guess I have been rather selfish in that department..:-(

Mike

Good morning, Mike!
I utilize small pots for those very reasons, too.
Basically, it comes down to what I can fit on my window-sills.

Lathyrus, I've actually had the opposite problem...I've made mixes that are
too fast-draining initially. I'm thinking of the Buckeyes that I re-potted this
Spring, especially. To keep the mix moist, I had to add extra mulch to the pot,
and I had to set the pot on a tiny dish for a drip-tray. Even after the roots
gripped the mix, I had to water nearly every day.

If I had a pot that was large, that I wanted to water thoroughly, I would just
add a wick to ensure the excess was dripped out.

As for #5 in the original post, I would say that disturbance rather than
'damage' is inevitable. I agree with Lathyrus. By removing the large and
woody roots, one encourages juvenile roots - which are vigorous and efficient -
to re-grow and to conduct all the plant's rootwork.

Josh

The issue I see with all the statements/rhetorical questions, is they cannot be taken at face value w/o a considerable amount of additional qualification.

E.g.:

1) Only SOME water drains away
2) Deep soil doesn't promote drainage, but it does increase the % of soil not subject to a PWT
3) Container (construction) material has no bearing on how deep the PWT is or on water retention. It only affects how quickly water evaporates - or doesn't.
4) Large pots with heavy soils can easily yield a crop of dead plants. Appropriate pot size is based on the size of the pot, size of plant material, and the physical characteristics of the soil.
5) Tight roots limit growth. Attention to roots is necessary in perennial plants to ensure best growth and vitality. A similar example would be 'a gangrenous leg limits our ability to walk, so why further inhibit that ability by amputating it?'

The questions you ask show that you're thinking, but I don't believe you quite have a full understanding of how water behaves in container media.

Al

You need to understand that plants in nature are not in 'a boundless pot'. The outdoor soil system has very little in common with the workings a potting medium and a container. The incredibly complex relationships of a root system and soil system in the ground can never be duplicated within the confines of a container.

Successful container culture can only be achieved if we understand how roots systems behave (in a pot) and how the physical structure of our potting mix determines water movement and root growth.

Looking at your zone, I would assume you are talking about indoor plants. Unless your light is supplemented, over winter, your plants will slow down/stop growing due to lower light levels. Larger containers will stay wet too long and you risk root problems. If growth is slowed, root growth is also. I don't like to repot in fall/winter unless its absolutely necessary and only increase pot size by a small amount.

Reality of growing in containers are what Mike listed. We have to grow plants within our limits. Plants let you know they are happy if they are healthy and robust. I don't know what 'selfish' has to do with anything.

Speaking of roots, orchids (which I grow many) would be happiest having their roots spread all over outside the pots. The reality is, if they were allowed to do that, they would dry up in the low humidity and break every time you moved them. That is the reality of growing in the north-east indoors, without a greenhouse.

Most plants can adapt to your growing limitations and do well.

Jane

Mike - there is a relationship between pot size, plant size, and the physical characteristics of your soil. If you use a heavy, water retentive soil and a large pot, you can expect problems no matter how bright or perfect the light is, the temperature is, the nutritional program is. Roots begin to die very quickly in soils deprived of air. If you have a large mass of soil that is saturated, the plant may not be able to use it before some % of the roots die. This cyclic death & regeneration of roots is expensive to the plant.

On the other hand, if you are using a soil that holds no, or very little perched water, you're almost unlimited in how large a pot you can use. If the soil holds NO perched water, you can safely plant the tiniest seedling in a 100 gallon container if you choose - with no worry for root rot caused by airless conditions. The plant also greatly appreciates the added aeration, and will reward you with more robust growth and better vitality, all else being equal. So you can see that as the soil improves in drainage and aeration, you are less limited in the choice of pot size.

It's probably better not to think of larger soil masses as a superior stress buffer. The plant will eventually be subjected to the same stresses in a large pot as in a smaller container, though again, deeper containers will have a higher % of well-aerated soil when the soil is fully saturated. Buffering against cold is probably of no consideration, and buffering against heat can work for OR against you. Soil masses large enough to heat up slowly also cool slowly .....

Depth of planting doesn't have an impact on aeration. Roots will colonize all parts of a container that provides a favorable mix of air/water/nutrients. While there are good reasons not to bury the trees buttress roots, aeration isn't one of them.

Larger pots DO postpone the incidence of encircling/girdling roots, but you need to be sure you're not trading one problem for another (over-potting and it's accompanying problems for girdling/encircling roots. Even if you can't see them, you WILL have problems related to incremental and cyclic root death when you overpot with heavy soils. Fast draining, well-aerated soils, as noted, reduce the potential for problems.

Al

Thanks for the additional information. We do have indoor plants, the larger ones being a 4' Gardenia jasminodes and a 2' Osmanthus Fragrans. The plants sit in standard indoor potting soil mixed with 10-30% of construction sand. I have a 20W fluorescent light bulb for plants to supplement the diminished sunlight.

I also plan to overwinter a 6-month-old crabapple and some baby hollyhocks that fail to achieve a good size due to rabbit's visit. People advise me to plant them to the ground now, but my instinct tell me they will die from unforeseen tragic accidents such as critters and neighbors' kids / dogs.

Light is a very important, no, KEY element in determining how well your plants grow, and how they grow insofar as growth habit is concerned, but light isn't enough to trump the effects of a poor or water-retentive soil. Plants have rhythms set to day length and their own internal clocks (search endogenous and circadian rhythms) so they slow down or change growth patterns during a part of their growth cycle regardless of light levels. Even plants that grow exactly on the equator respond to subtle photo-periodic changes and intrinsic rhythms. Slowed growth, regardless of the source, increases the potential of unwanted issues from heavy soils. The supplemental lighting will be very helpful because indoor light conditions are generally considered poor to adequate in most cases, but it simply isn't enough to negate the effects of poor soils.

I can make that assertion based not only on science, but on my own personal experience. Many times I've purchased plants late in the fall and over-wintered them under very good supplemental lighting. It's not that the plants didn't make it through the winter, but I had to be extra careful in how I watered these plants, and they never did as well as the other plants I had in the highly aerated gritty mix I use for everything I have in containers for the long term.

The hollyhocks are biennials and will die after they have bloomed, so keep that in mind. The apple will need a period of cold rest - a dormancy, and will not grow well for you if you try to keep it indoors. If you want to do best by it and protect if from harms, over-wintering it on your garage floor will make it quite happy. Simply toss enough snow on it very occasionally so the soil never dries entirely. It will wake refreshed in the spring & ready to go. Don't forget to think about root pruning. If the apple has ever reached a point where the roots and soil could have been lifted from the pot intact - a root pruning at repot time would be a very good idea.

Good luck.

Al

Well daniel you have outdoor plants, most are full sun plants, that you are attempting to grow in a low light environment. Twenty watts of light is like nothing at all. You need to use a light meter to see just how much light you will have to add to have a chance at success. Al

Totally agree with Calistoga. Those plants will need stronger light. A screw-in solution, look for about 50W-worth of compact fluorescents. I use octopus-type floor lamps but you can get cheap, clamp type fixtures which you can attach to bookshelves. Buy the highest watt fluorescent you can find. Big-box stores carry them in packs.

Jane

Daniel, where exactly are you going to set your plants for the winter? What kind of light will they get? What kind of temps will you provide? How far from the window will they sit? Especially the Gardenias and Osmanthus, in which I am curious? I have a few of these and find growing them in zone 5 very easy...

Also your choice of mix could do without the builders sand especially for them. Don't you have access to washed vrey course sand if sand is what you desire to use? Do you have access to perlite or some other material not as fine as that?

Selfish? Here is an example...

Using MG potting mix on my Orchards no matter how much light they get, because I was too lazy to go out and get what I know what is best for them..An Orchard bark mix, what is best for them, from their needs:-)
For sure they would die of root rot, even if they had the best light in the world..

Thanks for all your concerns.

Our over-winter window will be two sets of baywindows facing south-southeast, receiving ~3 hours of direct sun in the morning. The window covers the plants' entire height. The window is doubled-layered and is filled with argon in the middle.

The room becomes quite warm on sunny days. The indoor temperature will be maintained at 20C (68F) or above. And the moisture content will be maintained at 50% or above. We can mist spray the leaves if necessary. The plants will be about 0.5' from the window glass, or farther away if it is too cold.

We currently use automatic watering glass globes, which is staked to supply water from slightly under the root ball of the plant. The plants sit in "smart-pot" fabric bags on top of plastic trays. The construction sand we added actually drains faster than our potting mix.

We will be looking for stronger supplementary lights if necessary.

As for the crabapple, I studied some online information about plant dormancy and the plant hormone abscisic acid (ABA). I realized that the primary danger of keeping the otherwise cold-hardy plants indoors is that there might be still enough stress (lack of sunlight) to stimulate the production of ABA to push the plant into dormancy, but not enough cold hours indoors for the plant to naturally break down ABA for it to emerge from dormancy. On the other hand, if the plant faces no stress at all, ABA is not accumulated and the plant simply keeps growing.

So my plan is to try to satisfy the baby crabapple's various needs as best as I can. I will have a plant bulb shining right on top of it for at least 6 hours a day. However, if the plant starts to drop leaves, I will let it go completely dormant in the garage for a few months, so it can take its time to break down ABA and wake up from sleep in the spring. (But I will be in trouble if the tree decides to sleep when spring begins!)

;o) Good luck - be sure to keep us posted.

Al