I use pro mix BX for mine--well really I use it for most plants--but any soilless mix that drains well will work. Geraniums don't like to have wet feet so wait until the pot feels very light before you water

I think I'd rather buy the mix ready made. By the time you buy all the ingredients to mix your own it will cost as much as mixing your own.

Thank you very much, very useful answer.

Is your Pro-Mix BX with Biofungicide and Mycorrhizae? I saw that there is also a Pro-Mix Brk with lower water retention and I wonder if you tried this as well. I also would like to know if you add any compost to this mix.

As fertilizer I have an all purpose 20-20-20 from Jack's. What do you use and how often do you fertilize your plants?

Thank you very much again.

Pro-mix does not have either of those. I have never heard of pro- mix Brk but I do know that Pro-mix Hp has less water retention. I tried it but didn't like it because it dried out too fast and I was always watering. With the BX watering depends on the size of the container and I have no set schedule for watering. I let my fingers or the weight of the pot tell me if the plant is dry. I press a finger into the soil and if it feels wet I don't water. If the container is light in weight I water. big pots get watered less often

I fertilize the pots in the greenhouse about twice during their 2 month stay there. They get no fertilizer when they are young plant that I've started from seed but the larger plants do. I use water soluble 15-30-15 but your 20-20-20 will be fine if it's water soluble.

For pots outside I use a time release fertilizer at the time of planting but If you want to use the water soluble then fertilize every 3 weeks to a month

In my area standard potting mix is the default, and the only thing you could have done is select one among few brands with varying qualities. It is, however, a good substrate for most hybrids (the lion's share in the market). If you choose soil mixes with better drainage, the cost of making your own is a small price to pay compared to the rewards. In general, this is my conclusion, based on the available materials and my climate:

- coarse tuffa and peat mix: I have used this mix with P. Radens, P. Denticulatum and P. Mollicomum. My mix is 50/50, but you may try different mixes to improve it. The idea is taking ground tuffa (used for roof gardens and raised beds in public gardens), and sieving it through a fine mesh, leaving the grains with the size of coarse sand grains and larger. This is messy and makes lots of dust, so you'd better put your face mask on.

- Coarse sand and peat mix: I use the same 50/50 ratio, but coarse sand is a rare commodity in my area, so I use the former.

- Mixes with finer sand (builder's sand/ dune sand) and pure peat may work well with non-glazed clay pots. Those mixes are problematic on the long run as they trap much water and displace air from around the roots. Again, non-glazed clay eases the stress of water saturation.

The coarse tuffa mix works well in winter (when it rains most) and has to be kept moist by more frequent watering in summer, but that's not a big deal.

I've been growing Zonal Pels since I was a kid. I've used all sorts of soil mixes, and they do fine. I think they are one of the easiest plants to accommodate. Right now I use the same compost for all my plants (Pels, cacti,bonsai, ), it all depends on what I can get. I add vermiculite or perlite to the mix in various ratios, or grit, with gravel for a drainage layer. Pels are easy. They do really well for me no matter what I use! And I've created my own pale pink hybrid!