Yeah peat and perlite. I would use 1/3 of each. That garden soil is awesome stuff, just not for pots. It has a lot of compost in it too. I used it for my raised beds and they drain great. I mixed 1/3 peat and 1/3 compost with it, and no drainage problems. It truth, it drains a little too fast! The peat will really help. My plants are growing like gang busters in that mix! Here's a strawberry bed with a blueberry in the middle. Awesome product All plants planted this spring.

I've grown roses in containers for many yrs. When we lived in the mobile home park about 15yrs ago, ALL of my roses were grown in pots. I knew at some point we would be moving to a real house and didn't want to have to dig them up (or leave them). Little did I know it would be nearly 11yrs before we'd get out of there. We moved over 600 roses in pots! It was crazy! I've worked in the Lawn & Garden Dept at one of the largest Ace Hardware stores in Northern CA for almost 24yrs. We used to carry Hyponex products but over the yrs we've gotten all sorts of other brands, including Miracle-Gro. I only use our own brand of Ace Potting Soil. Every Ace gets their soil products from different suppliers by region, so not all will be exactly the same. Ours come from a place called Redi-Gro in Sacramento. Their potting soil is composted organic "forest products" with peat moss and a little bit of perlite, and maybe some lime or something like that. It works really well for me. I never use Miracle-Gro soils because I don't like using fertilizer when I first plant the roses. Also, DO NOT use any of the soils that contain water-holding agents. Miracle-Gro Moisture Control is one we carry that I would never use! It sounds good having the time-release water-holding granules mixed in there, but after a time, they settle to the bottom of the pots and hold a lot of water in the bottom, and tend to rot. That may be what others were referring to in the Hyponex soils. They might've added the water-holding granules to some of their soils. If you've never seen the stuff, it's really weird. The granules are tiny little white specks. When you put them in a cup of water, they absorb the water and can grow to hundreds of times their size. One of the guys at work placed a teaspoon in a 16oz plastic drinking cup and kept adding water. The granules grew to these transparent gelatinous chunks well over 1/4" a piece and were practically spilling out the top of the cup. If he'd have put them in a bigger cup, and added more water, they would've kept growing. You figure they probably put several teaspoons of this stuff in a big bag of soil and that can become a big blob of goo.

The reason you can't trust the volume of nursery pots, Jim, is that those black nursery containers are all "nominal" sizes. That means the volume of the pots is vaguely related to the stated gallon size. A "5 galllon" nursery can is 10.5 in. diameter and 12 in. tall. My online calculator says that is only 3.75 gallons if you pot 2 inches from the top of the pot. That isn't large enough for any rose past the first year or so if it puts on vigorous growth. The foot stomping is an old landscaper practice. It's just a cheap way of determining settlement without taking the time to water a plant in. I wouldn't do it. Water your plant in to settle the soil. I've seen people planting roses into dry potting soil. I wouldn't do it. Many potting soils have peat moss which sheds water once dry. Those of you in climates with steady rain year round may not have this problem, but in the desert West, once peat dries out, it takes a concerted effort to dampen it. I open the bag of soil, stick the hose in, fill it up and mix. Then I pot with dripping wet potting soil and also water it in. It's mud pies for grownups. It assures that the soil comes to the optimal height in the pot (about 2 inches down) and fills major air pockets. I unpot roses all the time and have never found an air pocket. I don't drop pots on purpose. Our summers are too hot to grow a lot of roses in pots well. We can't keep the roots cool enough through June and July. I overpot extensively. A 3 x 3 rose goes in an ornamental pot that is 22-24 inches high. I use various decorative pots from the big box store and always buy the biggest size. Why? They bring to rose up to height and look more in scale with a landscape. It's funny how a pot looks big in a store and miniature in the garden. Also, with those big pots I'm approaching the 15 gallon actual size I find any healthy rose needs. I do a seat of the pants volume-of-cone calculation to guesstimate the volume of the pot, taking into consideration the potting soil is probably 3 inches from the top of the container. Here's a nice online volumetric calculator. http://www.online-calculators.co.uk/volumetric/conevolume.php

Wow, it's a small world (or internet in this case). I don't keep up with the conifer forum as well as I do some of the other forums, so I didn't realize this thread was a spin off of another one, but it's still a good idea to have the link to the above article as a reference for any future searches. I agree with Ken, that frequent replanting would go a long way towards solving the issues relating to soil decomposition, except for four things. First, even if you change your soil every other year, most soils will still have some drainage deterioration towards the end of the two year period. Second, if you use your old soil and mix it back in as many people do, that has the potential to cause problems. Third, it's good for everyone to understand how drainage works so that they are better able to decide what ingredients are best for particular plants or circumstances. Different species have different moisture and drainage requirements, and different circumstances (climate, amount of supplemental watering available, etc) require adjustment. Fourth, and maybe most importantly, many people (we know who we are) won't replant frequently enough even though this would be best. As for drainage, as it applies to container culture, being vastly different from drainage, as it applies to in-ground plantings, I'm not so sure. The physics is the same! Only the variable, or circumstances, change. A true understanding of one is a true understanding of both.