Like most things in life, we utilize the things that are near, available in abundance and reasonable in price. Pottng up roses is no different.
I am interested to hear of the potting soil recipes of other hybridizes,especially people that keep their roses in pots year round. For example do you fish meal or bonemeal in your mix?
Does a mix high in organic matter interfer with the production of blooms?
My climate and conditions are significantly different from yours, Chuck. In mine, moisture holding between waterings is the prime issue. I’ve found moisture control potting soil to work quite well for roses, mixed pots and hanging baskets in my climate. Fir, redwood and peat based potting soils break down much too quickly here and don’t hold sufficient water in my heat and aridity. Coir (coconut fiber) takes two to three years to break down enough to require repotting and it holds enough water to prevent the plants from drying out too far until I can get to them with the hose. I don’t use organic fertilizers at home because I’m on the edge of “wilderness”, complete with all the wildlife you would expect. Few organic fertilizers don’t attract rodents, skunks, raccoons, opossums, coyotes and anything else happening to wander through.
In a significantly wetter climate, this soil is possibly too “wet”, but where there is little rain, much heat and general low humidity, it works quite well.
Even here in New England water is the primary concern for containerized plants.
My potting mix is about 2/3 fine perlite (sold as attic insulation), with the balance being equal parts Agway cedar bark mulch and peat moss. Perlite holds the most water but gives it up quickest to evaporation. Peat and bark mulch hold their water longer against evaporation so act to hedge against neglect and the bark mulch also gives the mix structure and internal strength.
Put about two inches of cedar bark mulch in the bottom of the container before filling it with the mix. Compact the mix strongly as you pot the plant. Leave about 3 cm of depth at the top of the container and fill to the brim with cedar bark mulch to prevent weeds from establishing as time goes by.
Watering takes more patience when the container is filled like this but it’s worth it.
The mix has no calcium or magnesium and is slightly acidic so it is a good idea to flush the container with a quart of limestone saturated water after you pot up the plant (swirl a couple handfuls of dolomite in a bucket full of water).
Feed the roses with Miracle Grow or Jack’s soluble fertilizers or the equivalent. You can use the ‘standard’ formulation rather than anything specific to roses, works fine and you can get it at the big box for cheap. You could also dose them with Rose Tone, which is basically chicken feathers and bacteria (but which is not cheep). That helps to establish the microbes that convert the nitrogen in the chemical fertilizers to a form the plants can use.
Someone recommends me to use here in the South west of France this kind of potting mix : 3/4 sand (not too thin) + 1/4 peat moss with regular watering and keep the seedlings out of full sun. Add fertilizer every 2 weeks starting when the first leaves appear.
What do you think of these recommendations ?