A few months ago I purchased a beautiful flowering plant. (forgot the name)
It was already a good-sized plant. I decided anyway to transplant it from its rather small pot to one of my very large pots. I think 15 or 20 gal pot?

The plant instantly started to wither. For the next week, I watered often and it would perk back up. After that, it continued to go downhill. After a month I finally just tossed it since there was no saving it. The roots were already flooded with too much water. This confused me because if I didn't water the plant often from its initial transplant shock, it would wither.

With all that being said I am just wondering if just starting a plant or even a seed in a large pot at first is the better thing to do. I have grown a lot of sunflower seeds in the past and some of them would not make it after transplanting to a larger pot. Maybe I am missing something, but would love to hear everyone's thoughts.

It's likely your plant died from transplant shock. One light watering after a transplant and just wait and let the plant "come around" on its own is my policy there.

When upsizing pots, it's better to just move up 1 size, as too much soil around the plant, when watered often (as you did), just waterlogs the roots often causing root rot and the plant to gradually die.

Best approach, IMHO, is to leave it in the original pot where it's happy and set that down inside a larger one (for visual/size aesthetics) until the plant has a chance to adjust to YOUR home's temperature and light settings, at the very least. They undergo shock merely when we buy them and bring them home, in other words. A rapid transplant to a new pot is a double whammie shock for most plants. Setting the old pot down into a larger new one is the safest way to keep your plants happy and you happy at the same time. Sorry you lost this plant, but you have a better plan for your next one.

Peggy8b said:
When upsizing pots, it's better to just move up 1 size, as too much soil around the plant, when watered often (as you did), just waterlogs the roots often causing root rot and the plant to gradually die.

with Peggy, I think this is the key. When you put a small plant in a too-big pot, the little roots can't use all that moisture contained in the pot so it becomes sodden and anerobic. If it were in the ground, the water would naturally drain away. You might also look at your choice of potting soil. Moisture-retaining products or excessive peat moss can contribute to root rot.

Edit to add. There's always a "but." I often park new, small nursery plants — ones that will eventually get big — into large outdoor ceramic pots at the beginning of the season, because I don't want the bother of multiple repottings. The key, for me at least, is using a fast-draining potting soil and finessing the watering regime. Much of the latter is experience and experiment. Also being familiar with your plant's needs is vitally important. I've also planted seeds in large pots. That's a situation when you don't want to obey the rule of saturating all of the soil. Just a spritz on the surface until they are well sprouted.

I appreciate all the responses! It makes more sense to me now :)

I was curious because I myself usually do start seedlings in my larger pots. But I can definitely see why instantly repotting my prior plant was a bad idea.

How important or critical pot size is depends on the physical characteristics of the grow medium (and the size of the root mass of the plant being repotted or potted up - and there's a difference between the two practices. Media that hold an excessive amount of water make our choice of pot size critical; whereas coarse media that hold very little water in the large spaces between soil particles offer growers plenty of margin for error.

The easiest medium to grow in will be one that holds all or almost all water on the surface of soil particles, in the internal pores of porous particles, and at the interface where soil particles contact each other, leaving the spaces between particles full of air, top to bottom of the pot. Media comprised almost entirely of fine materials (peat, coir, compost, composted forest products, sand, .....) will hold a great deal of water in the spaces between particles. This is the water that robs plants of the oxygen they need to drive root function, resulting in roots that function poorly, or worse, fungal root infections.

The images below are what I make/use for my own purposes. The second image, the one that looks like gravel, drains well enough that there is no upper limit to the size of the pot you could use to start a seed in, and still not worry that the new plant would be over-potted. You could also unpot a plant from a pot that holds a pint of soil and move it into a pot that hold several gallons w/o concern about root issues.



Al