do i use an all purpose fertilizer or one of those with a high phosphorous number which is for blooms? read differing opinions. i am using miracle gro potting soil in pots. I also have a few geraniums in the ground .
Hello! Without more information, it’s a little difficult to determine what is going on with your geraniums, i.e. pelargoniums, which are the brightly coloured annuals we like in the summer, as opposed to true geraniums which are perennials that usually have blue or pink flowers.
First, are these new geraniums that you purchased from a garden centre in the last couple of weeks? In that case, they may not be ready to bloom yet. They were likely in a greenhouse having been grown from seed just a couple of months ago. They need to be 3 or 4 months old to be ready to flower. They need LOTS of sun, at least 6 hours, and warm temperatures. Give them sun and time.
If they are geraniums you had last year and have stored overwinter, again, they may not be ready. They should have been repotted in new container “soil” and cut back if they had grown leggy. Mature plants also need large enough pots … at the least a 12 inch pot for a healthy large geranium.
Are the leaves growing and looking healthy? Both the newly purchased plants and those brought outdoors from overwintering inside the house need a period of “hardening off”, that is, introducing them to the outdoors gradually over a period of 10-14 days. If they went out without that process, the leaves can be sun scalded and the plants may be in a bit of shock.
The most common reasons for lack of blooms are 1) not enough sunlight and 2) too much fertilizer.
You mentioned that you are using Miracle Gro potting mix. That product already has fertilizer mixed into it, so I would definitely not add any fertilizer until about 3 months after the pots were filled. The in-ground plants can be fertilized once well-established. In either case, you can use a balanced or high phosphorous fertilizer, but only once a month at most, well-diluted as instructed on the label.
For more information on growing these popular plants, please see our Gardening Guide on the subject here.
Good luck and enjoy those blooms when they arrive!