Encouraging more root growth
Hi everyone, some advice please for a beginner
I took about 50 geranium cuttings last September and I have had them in a heated propagator with grow lights above since then. approx 40 of them took and a lot of them were quite bushy with lots of leaf and I had to keep pinching out flower stems as I wanted to promote root growth and intend to use these to take more cuttings later in the year so that I can build up a stock of about a 100 plants which I can use for cuttings each year.
Given that these seemed to have quite a lot of growth when I started to transplant to 3.5" pots I was surprised by the lack of roots which seemed very weak.
Is there a trick to promoting strong root growth, is there a root feed that one would use in this situation?