I planted 140 emerald trees in 2014 Easter- long weekend. This year I was told to fertilize and use 30-10-10. My question is what is better the water solution fertilizer or the granules. I do not want to over fertilize.
By “emerald trees” I believe you mean emerald cedar, a good low-maintenance choice – they look lovely in the photo you attached.
You have correctly selected the recommended N-P-K ratio: evergreens require a lot of nitrogen, so 30-10-10 is appropriate. The format of the fertilizer you choose should not be a concern. The only difference is in how you will apply it — remember that it is important to follow directions for the product you select.
Generally, liquid fertilizers just have to be diluted according to package direction and applied; nutrients are available to the plants right away. However, if you don’t follow the directions, the fertilizer can damage the plants. As well, liquid fertilizers usually require more frequent application because they seep deep into the soil, becoming unavailable to the plants.
On the other hand, granular fertilizers are simply sprinkled on the soil surface and their nutrients released gradually – when it rains or when you water the plants. Accordingly, the nutrients are not immediately available to the plants. A disadvantage of granulars is that soil pH (acidity/alkalinity) may impact their effectiveness. Again, if applied incorrectly, granular fertilizer may damage plants.
For more detailed information, take a look at an earlier Q&A posted on our website, “Fertilizing cedar hedges“, which provides practical information for you.
By the way, if you search on our “Ask a Master Gardener” website on the word “emerald”, you will find several Q&A concerning emerald cedars – not just about fertilizers!