Annuals, in particular, grow very fast, esp. if growing conditions are good! When I worked in a greenhouse, I remember someone not wanting to buy six-paks of tomato plants, because they were too small. They wanted the 2 quart plants which we sold out of. We said there would be more next week, and they agreed to come back. Later that day we moved a bunch of the six-pak plants into larger containers. After a week, they were MUCH larger and a happy customer purchased several at about 6 times the price of the smaller plants, which would have been equally large if he had bought them and planted them out the previous week. Larger pots give a chance for more natural, uninterupted root growth and a quickly larger plant. Enjoy growing!!!

I just asked my former greenhouse employer this question, taking some examples along to demonstrate, and she explained that plants in smaller pots-their roots will actually dry out before roots in the larger pots will (whether I realize it or not)and when the roots begin to dry like that, the plant will stop growing. Whereas, the larger potted plant has not dried out, and continues to grow. Apparantly, it takes some time for the smaller plant to begin growing again, after it has had this "dry spell"??

Okay, now I make sure my plants are watered when they need it, but apparantly, it must begin to dry out all around the edges of that pot, just as terra cotta pots dry out very quickly. This would make sense to me. I mean, the plants look perfectly fine, but there is some drying going on inside the pot, around the edges.

Can anyone elaborate on this??

I would think this knowledge would be vital to anyone growing plants, to know exactly what size pots to use for what plants. However, you see the exact same size plant growing in all different size pots for sale in nurseries, and apparantly will reach different size growth based upon their conditions when being transplanted. I mean, if you choose to put all seedlings directly into cell packs, from my observation, the plants will grow tall, upright, and rather skinny. I have grown cell plants forYEARS, and used them in all my gardening needs, and they have been fine. This year, I started taking some of those cells plants, transplanting them again into 4 inch pots once they got so big, and the leaves were touching. BUT, what I am examining is, putting them into the cell packs rather than the larger pots causes an entirely different kind of growth. Wouldnt this difference in growth cause the plant to continue growing "differently"??? I mean, a tall skinny transplant is not getting as filled out as the transplants in larger pots; wouldnt this cause an irreversable difference in the two plants??

I know that plant get pinched to cause them to get busy. I pinch the center stems at a certain height. But on the plants in the larger pots, this doesnt even seem necessary, they appear to bush out on their own.

I am also curious what effect using a way too big of a pot will do for a seedling. I mean, will it just continue to grow and grow uninterrupted? I would think too large of a pot compared to a tiny seedling would have major moisture fluctuations in the pot. But I am no expert, that is why I am here asking you!

I would like to understand this from a scientific perspective, like how the roots function in this. I think it is valuable information.

Thank you!

I believe there is more to it than just moisture fluctuations. You could technically set up a small pot with an overgrown plant which is watered with dissolved fertilizers every 10 secs with automatic watering, or you can let a plant in a large pot go fairly dry. The result will still be a larger plant in the larger pot.

I believe it has to do with hormones being activated when root meristems meet obstacles. If you plant a begonia in poorly draining, very moisture retentive soil ("clay") in a 10" pot and you plant the same type of begonia in a high quality planting mix. The result is predictable.

Obviously, the begonia planted in well aerated mixture will experience larger root growth due to water, air, and permability is present.

As you may recall, Auxins and Cytokinins are running a closed loop and balancing the growth of the plants. As long as there is a balance, growth will be rapid. If either top or root growth is mechancially stopped, the plant will adjust the other end of the plant accordingly to achieve balance. Therefore, as long as roots have optimal growing conditions (good mixture of aeration, water, fertilizer, etc) the hormones will instruct the top to grow. If the roots are stressed from being root bound, swings in fertilizer, oxygen, or water availability, top growth will also be stunned.

This is - if not obvious - then logical. The plant must make sure the top growth is kept in check with root growth. Otherwise it would prove fatal to the plant. I believe hormones are the main regulator in this respect.

Here is a link that might be useful: plant hormones - article