It depends ..... From another post: "How large a container needs to be, or CAN be, and how much soil a planting needs/will tolerate before drainage & saturation is an issue depends on the 3-way relationship between plant mass, container size, and soil type. 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 basic knowledge about the 3-way relationship noted, which should logically determine appropriate container size(s). It's often parroted that you should only move up one size in containers when "potting-up". The reasoning is the soil will remain wet too long and cause root rot issues, but it is the size/mass of the material and soil type/composition that determines both the upper & lower limits of appropriate container size - not consecutive volume progression. Plants grown in slow 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. This (smaller soil volumes) and the root constriction that accompanies it will cause plants to extend 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 you 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 or volumes of soil per se, but rather, they rebel at being potted into very large containers with a large volume of soil that is too slow and water-retentive. We know that there is an inverse relationship between soil particle size and the height of the 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 (saturated). So, if you aim for a soil composed primarily of particles >1/16", there is no upper limit to container size. The lower size limit will be determined by the soil volume's ability to furnish water enough to sustain the plant between irrigations." You can grow a very small plant in a very large container if the soil holds little or no perched water (saturated soil). Al

If you examine the ingredients list on a bag of Miracle Gro potting soil, I believe that you will find that it contains "locally" obtained ingredients. That implies that the quality will vary with manufacturing location. I have had bad results using Miracle Gro potting soil bought in the Chicago area. Last year, I used a home made mixture of 2/3 peat moss and 1/3 perlite (by volume) without lime and it worked fine, but, note that my fertilizer solution contained calcium. I buy peatmoss on sale at Menards for about $5 per 2.2 cubic feet. Perlite is $10.23 per 4 cubic feet at http://www.bfgsupply.com/UserFiles/2008Catalog/5_Soil.pdf. That is cheaper than any premix you can buy.

If you have a number of plastic 2-liter bottles or cardboard 1/2 gallon juice cartons, they're quite wide, if width is necessary. Cut the tops off, at whatever height you need. [And if more width isn't necessary, you can also use narrower plastic bottles.] Thinking I can cut the bottom off and fill a new one with dirt then sink them together. Leah, I'm not sure I understand your response. The point of using a taller container is that when you pot up, the current roots can be placed at the bottom of the new container. Snip off the lower leaves and add soil around the bottom few inches of the stem. Additional roots will grow from the currently-above-ground stem, resulting in a larger root system.

True for me. I usually plant out when they are 4" high, but some get away from me, and I don't plant out until they are 8" high. The difference in growth after plantout is obvious. If you don't let them get that big, you don't need to pull off leaves. But I guess you can include that in the instructions when they are sold. "These are too big. Pull off lower leaves and plant deeply!"