Ellen & Jenn - A copy/paste job from a reply I wrote on another thread: 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 soil. 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 parroted 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 soil will remain wet too long and cause root rot issues, but it is the size/mass of the plant material you are working with, and the physical properties of the soil 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 soil you choose. Plants grown in slow (slow-draining/water-retentive) soils need to be grown in containers with smaller soil volumes so that the plant can use water quickly, allowing air to return to the soil before root issues beyond impaired root function/metabolism become a limiting factor. We know that the anaerobic (airless) conditions that accompany soggy soils quickly kill fine roots and impair root function/metabolism. We also know smaller soil 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 soils 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 with a soil that is too slow and water-retentive. This is a key point. We know that there is an inverse relationship between soil particle size and the height of the perched water table (PWT) in containers. As particle size increases, the height of the PWT decreases, until at about a particle size of just under 1/8 inch, soils will no longer hold perched water. If there is no perched water, the soil is ALWAYS well aerated, even when the soil is at container capacity (fully saturated). So, if you aim for a soil (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 soil 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 very large containers if the soil is fast (free-draining and well-aerated) enough that the soil holds no, or very little perched water. I have just offered clear illustration that the oft repeated advice to 'only pot up one size at a time', only applies when using heavy, water-retentive soils. Those using well-aerated soils are not bound by the same restrictions. AL

I did an experiment this spring. I got a rose from a company that was not the right rose, and I already had this rose. They sent the correct rose. I thought I would put the extra band rose in a 3 gallon pot instead of starting it off in a one gallon to see if there was any growth difference. The extra rose started in the bigger pot has made a bigger growth effort than the same size bands I have usually potted in one gallon pots. I use the black nursery pots that I have a lot of. I wouldn't do this with a shrimpy little band that I know would need the smaller pot, but these bigger healthier bands I think might be able to go right into a 3 gallon pot. Of course it might have just been that particular rose...... Seil is in a cooler climate - I note that you are in zone 9, which is quite a bit hotter. Here in Texas, I protect my potted band roses in the heat of summer - I don't leave them out in the hot afternoon sun - they get morning sun and then are shaded from the blast furnace heat we always get in Texas in the hot summer. And don't put them on concrete either - the heat will get them. Good luck, I love growing in pots - love to watch their progress. I have also started putting 6 of those little plastic edging tiles together to form an edging around my bare root roses when I plant them. That way, water goes right to the roots and they get their fair share - so important in the heat of summer. Found that I can removed these the next year, roots are more established. Also, when it comes time to feed them, the fertilizer goes to the roots where it is supposed to. But I don't fertilize much - fish emulsion, kelp, seaweed, and usually half strength, and only when they are up and growing well - and only after watering. By the way, what company did you order your roses from? They look very nice. Good luck! Judith

As to the garbage can idea---if you have it exposed to the sun at all, it's going to heat up. (Think how a car sitting the sun will heat up in the winter.) You don't want that. I'm familiar with zone 6 weather, having lived & gardened there for many years, so I have some idea of what you're dealing with...that is, you need to keep the soil cold when you get those weather warm-ups in mid-winter. i.e., the idea behind the insulation is to keep the heat out and the cold in the pots, to moderate the inevitable wide swings in temperature. (Think 'ice chest'.) If the pots are not in the sun, then the insulation board on top of the pots is prolly going to be sufficient. If the pots get any am't of sun OR are close to a bldg., then you need to think about keep the whole shebang cold. Naturally, you would place the insulation barrier around the pots after it's turned cold, really cold. About the wood tops idea...an inch of wood has an R-value of less than 1.5...compared to R-5 for an inch of XPS (the pink stuff) and R-8 for ISO (the foil faced yellow stuff). So, although wood is an insulator, there are better choices. Of course, you could glue XPS to the wood if you want to. Oh yeh, the pink stuff, XPS, will hold up to the elements much better than the foil faced ISO--it's yellow underneath the foil and is much more brittle than XPS. Also, the R-value of ISO degrades to where it's only marginally better than XPS.

There are several issues inherent in using large fractions of topsoil and coir in a medium intended for use in containers. The main ones are excess water retention and insufficient aeration. The excess water retention can be fixed as easily as judicious use of ballast or partially burying the pot into the ground such that the bottom of the pot is a few inches below the grade level. This turns the entire earth into a giant-size wick and will remove all or nearly all excess water. While this increases o/a air porosity by virtue of the conspicuous fact it removes excess water, it still might not ensure there is enough air porosity to keep the plants content. Coir doesn't retain loft well (it compacts easily), and holds more water than peat. There are also chemical considerations associated with using significant fractions of coir and CHCs in potting medium (more than 10-20%). All coir/CHC products are very high in K, very low in Ca, and have a potentially high Mn content, which can interfere with the uptake of Fe. Several studies have also shown that the significant presence of phenolic allelochemicals in fresh coir/CHCs can be very problematic for a high % of plants, causing poor growth and reduced yields. The pH of coir/CHCs is high enough that the use of dolomitic lime is precluded as a source of Ca/Mg, and both have potential to have excessive EC/TDS (salt) levels. Repotting now would require you free yourself from the dogmatic convention that you should never remove top growth when you repot or transplant. That's fine advice when all you're doing is dropping a B&B tree or a tree fresh out of a nursery can into a hole in the ground, even though that's a decidedly poor strategy as well, unless you bare-root and correct root issues which brings you full circle to the fact it's pretty much necessary to significantly reduce trees' top mass or completely defoliate if you do significant root work, and especially if you bare root. Appropriately reworking the roots requires your tree is healthy enough it has enough in the way of energy reserves to push a new flush of growth. If you fear it doesn't due to recent/current low vitality levels, best bet would be to remove the tree from the pot as is and put it in the ground until just before bud movement next spring, at which time it can be relifted and the root issues corrected w/o need to reduce the canopy. This is true because quiescent buds of deciduous trees tend to remain in that state until the tree's chemical messengers signal plant central the volume of roots is sufficient to meet the water needs of new breaking buds coming on line. Al