I have super phosphate 0-18-0 for my hydrangeas.
Three questions: How much can I can I apply?
If I apply too much can I burn the roots?
Can I put this on other flowering perennials (ie: daylilies, coneflowers, etc)?
Thanks for any info, Gail
Unless your soil is defficient in minerals like phosphate, I would not apply more. Hydrangeas are not heavy "eaters" of fertilizers and amendments like other plants are. An amount as specified in the product label would be safe assuming your soil needs phosphate. Too much of it can eventually decrease mycorrhizal activity. Phosphorus helps roots and blooms develop. It "sinks slowly" in the soil so sometimes, it is recommended that it be applied at the bottom of the planting hole. Some nurseries sell soil kits that give you an approximate indication of how much of the main minerals are found in your soil. A full fledged soil test also gives you this information but is more accurate and should be done once every now and then (say every 5-7 years?)
The package mentions several tablespoons when planting bulbs and 4 LBs when planting a trench row of plants. Sprinkle 6 inches away from plants. That was about it. mysterious. Thanks a lot for replying. Gail