How do I encourage vigorous roots?
I would like to know if there is a fertilizer on the market which helps vigorous root growth on young plants ( ie. double/treble the size of plug plants).
I have been buying plug plants from different suppliers and some plants are ok and have good root systemand grow on almost immediately, others after replanting seem to be very slow at developing a good root system.
I've tried additional gritty sand int the compost mix without success.Any ideas would be very welcome. (main plants in question are Fuschias)