Hopefully someone else will answer, too. I have been mixing Osmocote and some alfalfa pellets with the soil.

My rooted plants in gallon pots get a teeny bit of water soluble fertilizer with every watering, and a few times a week they get a drop of Superthrive in their water.

Happy Gardening,
Michelle

A little Superthrive is fine. What you must never do is mix a generous amount of organic fertilizer mix into regular peat based potting mix at the time of potting up rooted cuttings. The mix will heat up and cook the cuttings. We learned this the hard way. We put nothing in the mix. We do use SuperThrive and various foliar potions at diluted rates. After they've gotten roots showing at the bottom and some new growth at the top it seems to be safe to give a sprinkle of pelleted slow release fertilizer. Apex (Evergreen) 20-10-10 with micronutrients (important) sold by obcnw.com claims to be a 12 to 15 month fertilizer in cool climates (the PNW). In warm climates it is 8 to 9 months. A fifty pound bag is about $53. The 20-10-10 balance is perhaps not the optimum for roses, but it seems to work.

We are a squeaky Zone 8a and our roses often do not go truly dormant in the winter, with climbing canes lengthening dramatically sometimes. This type of fertilizer has so far not stimulated excess new growth in the winter which would most certainly be lost in one of our freezes. It does seem to sustain the plants through the winter rains which leach the pots too much if there is nothing for the roses to take in.

I used to use a mix that I made up that had a lot of compost and bark for the potted roses. Nancy Lindley offered the comment that a more porous mix that drained well might be better. She was right. I now use a mix that is just peat and perlite and the roses are better for it. Well, I do put in a couple of shovels full of commercial potting mix per wheelbarrow load because the wetting agent in the bagged mix helps with the initial hydration of the peat.

The need to add fertilizer is a good thing because you can adjust the amounts to the weather conditions. I use a time release product in the spring and then go to a dilute liquid program.

Most of the growing season here the pots need water at least once a day. The time release fertilizer that claims 3 to 4 months of service will not last anywhere near that long with that kind of a watering schedule. I get a month - six weeks at best.

One year I used a brand of time release that had little green BB's in the mix. I thought that as long as I could see the green pellets on the surface of the pot that there was undisolved fertilizer left. My roses got mighty hungry before I discovered that the pellets were some kind of plastic that was just used as a carrier of sorts.

Regards,

Charles