To my mind there is only one good plant food for both outdoor and indoor plants - it costs nothing, and helps solve a perennial problem. NETTLES!! yes, those nasty stinging things. Very simple; cram as many as you can into a bucket (or bigger) - fill to brim with hot water, mash with a stick, cover and leave for a week. Uncover (stand back - IT STINKS !! - then decant resulting green brew into a suitable container (nettle remains go straight on compost heap) DILUTE brew 10:1 and apply to any plant with w.can - do not use neat unless you're planning to build a patio in your flower bed! With houseplants, water around the base. It is natural, full of goodness and works amazingly well (I am told you can drink it but haven't gone that far!) Why pay vast sums for chemicals...? PS Smell soon dissipates.