Choosing an Appropriate Size Container

How large a container ‘can’ or ‘should’ be, depends on the relationship between the mass of the plant material you are working with and your choice of grow media. We often concern ourselves with "over-potting" (using a container that is too large), but "over-potting" is a term that arises from a lack of a basic understanding about the relationship we will look at, which logically determines appropriate container size.

It's often repeated that you should only move up one container size when "potting-up". The reasoning is, that when potting up to a container more than one size larger, the medium will remain wet too long and potentially cause root rot issues, or at a minimum, limited root function. In reality, it is the size/mass of the plant material you are working with, and the physical properties of the medium you choose that determines both the upper & lower limits of appropriate container size - not a formulaic upward progression of container sizes. In many cases, after root pruning a plant, it may even be appropriate to step down a container size or two, but as you will see, that also depends on the physical properties of the medium you choose. It's not uncommon for me, after a repot/root-pruning to pot in containers as small as 1/5 the size as that which the plant had been growing in prior to the work.

Plants grown in ‘slow’ (slow-draining/water-retentive) media need to be grown in containers with smaller volumes so the plant can use water quickly, allowing air to return to the medium before root issues more serious than impaired root function/metabolism become a limiting factor. We know that the anaerobic (airless) conditions that accompany soggy media quickly kill fine roots and impair root function/metabolism. We also know smaller medium volumes and the root constriction that accompany them cause plants to both extend branches and gain o/a mass much more slowly - a bane if rapid growth is the goal - a boon if growth restriction and a compact plant are what you have your sights set on.

Conversely, rampant growth can be had by growing in very large containers and in very fast (draining) media where frequent watering and fertilizing is required - so it's not that plants rebel at being potted into very large containers per se, but rather, they rebel at being potted into very large containers in a medium too slow and water-retentive. This is a key point.

We know there is an inverse relationship between media particle size and the height of the perched water table (PWT) in containers. A PWT is water that fills spaces between soil particles and defies gravity by refusing to leave the pot. As particle size increases, the height of the PWT decreases, until at about a particle size of just under 1/8 inch, media will no longer hold perched water. If there is no perched water, the medium is ALWAYS well aerated, even when it is at container capacity (fully saturated).

So, if you aim for a medium (like the gritty mix) composed primarily of particles larger than 1/16", there is no upper limit to container size, other than what you can practically manage. The lower size limit will be determined by the medium volume's ability to allow room for roots to ’run’ and to furnish water enough to sustain the plant between irrigations. Bearing heavily on this ability is the ratio of fine roots to coarse roots. It takes a minimum amount of fine rootage to support the canopy under high water demand. If the container is full of large roots, there may not be room for a sufficient volume of the fine roots that do all the water/nutrient delivery work, and the coarse roots, too. You can grow a very large plant in a very small container if the roots have been well managed and the lion's share of the rootage is fine. You can also grow very small plants, even seedlings, in seemingly inordinately large containers if the medium is fast (free-draining and well-aerated) enough that it holds no, or very little perched water.

I have just offered clear illustration why the oft repeated advice to ‘resist potting up more than one pot size at a time’, only applies when using heavy, water-retentive media. Well-aerated media are not bound by the same restrictions. As the ht and volume of the perched water table are reduced, the potential for negative effects associated with over-potting are diminished in a direct relationship with the reduction - up to the point at which the soil holds no (or an insignificant amount) of perched water and over-potting pretty much becomes a non-issue.

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Deeper pots are easier to grow in because they have a larger volume of well-aerated soil. The pots below are full of grow medium. The shaded area is saturated soil, a 'perched water table'.

Terra cotta pots or others with gas permeable walls are better (from the plant's perspective) because they facilitate gas exchange and they dry down faster, which is particularly important when using a water-retentive medium.

The pot your plant is planted in should always have at least 1 drain hole. If a pot has no drain hole, the probability of achieving satisfactory results is diminished drastically.

When using a collection saucer, the pot should not rest on the bottom of the saucer as that arrangement ensures the effluent that exits the drain hole has a pathway by which it can make way back into the grow medium, thus defeating the reason for flushing the soil when you water.

The pot should be positioned well above the high water mark in the saucer.

As a bonsai practitioner, I have several hundred pots from cheap plastic training pots to very expensive pots by well known potters. I keep all of them handy for a wide variety of reasons. The only time I discard a pot is if it's broken, or in the case of plastic training pot, to badly damaged by the sun (too fragile) to be usable. I think this will vary significantly from person to person.

Thoughts?

Al

how about a pic or two ..

i would slip it out of its pot.. and look at the roots.. to help me decide if the roots were circling ... or whatever ...

i try not to fix things that arent broken.. and the only way to do that.. is look and see if there is a problem to solve ...

how much fert do you use.. and how and when do you apply it ...

how much light does int get in your house.. and is it usable light .. is it etoliated???

its really hard to give much more.. without seeing the plant and pot.. and btw.. if you slip it out.. take a pic of the roots and show us that ...

ken

The roots (rhizomes) need lateral space to expand. Otherwise, there will be enormous pressure from cramming against the pot, and against each other.

https://garden.org/plants/photo/161371/

https://garden.org/plants/photo/454665/

It just occurred to me that I failed to say that the dimensions of its current pot are 10" WIDE and 4" DEEP. But when I see pictures of other snake plants I never see them in anything remotely similar, so I was wondering if it was something else I needed to fix. If it needs lateral space as opposed to depth, tho, then it sounds like the current pot might actually be fine and there's no reason to shock it by repotting right now. But that was the real reason for my question.

Ken, I promise I'm not ignoring you, I just don't have everything you're asking for at the moment. But I'll try.

Light: eastern, direct. Blinds are down about 60%, and kept closed in the morning or else my apartment becomes a solar oven in 3 of the 4 seasons. But once the sun is overhead I twist open the blinds. Snake plant is about 8 feet away up on a set of drawers, as no plant can stand up to Snacking Cat who also likes the window (my other plants are in a lighted shelf framework to the side of the window where We Have Agreed She Can't Get Them, so long as I keep one of her Offering Plants on the floor).

Fertilizer: 1 c of diluted Cactus Juice at present, whenever the meter reads 'dry', so along with its regular waterings. I may up it to 2. Previously it has had regular (about every 2-3 months) sprinkling of 1-2 tablespoons epsom salts, and many drops of Miracle Grow cactus food. Should I continue the epsom salts?

This is where it was previously, in my bedroom on a high shelf with no direct light, in April:

This is where it is NOW, in my living room where its getting more light:

I cut the longest leaf up into about 8 pieces and tried to root them - half of them seem to still be alive.

--GW

Popmama - just tried to update my profile with my Zone, which is 7b in western WA, but Houzz won't let me. Guess I was away for too long and will have to hash it out with admin when I don't have anything to do. Back when I had an apartment with a balcony and previously one with a patio, I put my plants out there and they loved it. Here, no patio, no balcony, I have a garden plot but its 8 floors down so I don't feel safe leaving them out there.

How well do snakes do with those lights you can stick in their pots? I'm thinking of getting one for my flf, and wonder if the snake might benefit from one as well.

--GW

Aww I'm sorry you lost your outdoor space! That stinks.

I honestly don't think the pot is the issue here. I see your little succulent is also very stretched from lack of light. So I'm going to guess that Mr. Snake wants more light. Snake plants are the type of plant that tolerates lower light but doesn't thrive in it. Tolerate means it survives which is sort of what I think is happening here.

The pot doesn't appear to be a problem.

Yeah, the little succulent is the sole survivor from a multi-succulent pot I bought at a plant sale at an elderly support center 10 years ago that I transferred to a handmade creamer I bought in Hawaii; this is also after a severe haircut of dead leaves and 'roots' (the little strings hanging down for rooting into soil that I'm forgetting the name of) I did earlier this year. I'd have also moved it to better accommodations a few years ago but the rootball is pretty solidly in there and I don't want to risk breaking the creamer. It gets a little water, a little fertilizer, and keeps on trucking even if its not as happy as I'd like. It would definitely be in the window if not for the cat. Let me add, too, that the succulent has been in this spot as long as the snake - since April. Previous to this it was actually under light, tho it was dimmer than I should have had it, and it also had been moved several times before then. I'm glad to see the new growth in just the last several days.

Might be fun to hang it in the window and see what happens...hmmm!

--GW

A lot of pots cannot contain Sansevieria when it gets root bound - plastic, clay, even glazed will break under too much pressure. I even have one plant out of its broken pot this summer and it is doing fine. It will need something to house it before I move it back indoors for winter.

A plastic bowl works well for multiplying but then what?

Then it's time to give some away, or compost if you don't have any takers.

It just occurred to me that I failed to say that the dimensions of its current pot are 10" WIDE and 4" DEEP. But when I see pictures of other snake plants I never see them in anything remotely similar ..... Shallow pots require that the grower is very careful when choosing the grow medium being used. The pots below are all filled to the top with the same medium and the shaded area represents excess (perched) water held between soil particles and resisting gravity.

Most media based on very large fractions of fine ingredients (peat, coir, compost, composted forest products, sand, topsoil, ...... support several inches of perched water. The norm is 3 to 6 ". As you can see, when using a pot 4 " deep and a grow medium that supports 3" of perched water, only 25% of the soil will be hospitable to roots. Should the medium support 4" of perched water, 100% of the shallow pot would be saturated and wholly inappropriate for the roots of almost any plant.

It's not that you can't grow sans in pots as shallow as yours, it's just that they require a medium that holds very little or no perched water in order that they might realize as much as their genetic potential as possible. Too much water in the root zone limits root's ability to function normally, and can set the stage for fungal infections of roots.

There are some tricks you can use which will limit how much excess water a planting can hold. Ask if you have interest.

..... just tried to update my profile with my Zone, which is 7b in western WA, but Houzz won't let me ..... Mouse over "Your Houzz" on the Houzz menu bar - upper right corner, then select "Edit Profile and Settings". Scroll down to "Profile Information". See the text boxes "First Name" and "Last Name". You can enter your user name and location/ zone in the first name text box, or you can leave your user name as is and type your location/ zone in the last name text box; then tap "Update" below your last profile option below.

Al

Yeah, I'm not new to this whole Internet forum thing. ;) Just turns out that my adblocker extensions like to beat up on naughty invasive Houzz. ;) ;) ;)

I added a lot of perlite during the soil refresh because there was some rot previously and there's been no problem with that since. Also using the meter before watering helps.

I'm still pondering getting one of those lights that you stick in the pot for my snake, or if I happen to find a secondhand desk lamp that can hold a grow light properly. Is it 6500 lumen that's best? Given that its high above on drawers to the left of my desk, how harsh is that powerful a light on human eyeballs?

--GW

The number 6500 on packaging of lights or bulbs can refers to the color of the light on the Kelvin scale, thus the 'K', or the output in lumens. The 'color' of daylight is approximately 5200K. I use 6000K LEDs at 6500 lm for foliage plants (trees). 6500 lumens isn't so bright that it will burn your eyeballs to a cinder at a glance, but neither is it comfortable to stand a few feet from and stare directly at the light. Light diminishes very quickly as the distance from source increases, and this can be determined by using the Inverse Square Law. The formula is Intensity=1/Distance² . So, at 2 ft from source, 1/4 of the light available at 1 ft would strike the plant. At four ft, only 1/16 of the light available at 1 ft would strike the plant, and at 6 ft 1/36. The unit of measurement (ft, meter, mile) doesn't matter.

Al