Roses
Nitrogen required by rose bushes is mainly in the nitrate form, the importance of chemical fertilizers becomes evident: to supply instantly available nitrogen via nitrate forms; plus nitrogen available within a short space of time via ammonium forms (urea and ammonium phosphates, etc.). A fertilizer containing all three sources – nitrate, ammonium and urea is superior.
Micronutrients (iron, zinc, manganese, copper, cobalt, boron, chlorine and molybdenum) are added in some formulations as well. Percentages are typically small, as roses require only small amounts. Consider a fertilizer with chelated forms of micronutrients as most desirable, as they are the most usable by the plant.
“CHELATED” ELEMENTS (IRON, ZINC, MANGANESE, ETC.) Several trace elements already exist in soils, and are added to fertilizers as an additional supply.
https://youtu.be/6GMnLIT4X0I
https://youtu.be/pop7iWsPn38
Crepe Myrtles
Fertilize in Spring – Begin fertilizing in Spring with the fertilizer of your choice (liquid, slow-release or granules), when the first leaves start to appear. Established, well rooted, Crape Myrtles are heavy feeders. Lightly fertilize every two weeks throughout the spring and summer months. This will promote optimal new growth. Remember, Crape Myrtles only bloom on new growth. Always water your Crape Myrtles after applying your fertilizer.
- When to Discontinue Fertilization and Regular Watering – Discontinue your fertilizing routine in later fall and begin watering less often. This will help the plants “harden off.”
https://www.crapemyrtle.com/fertilizing.html
https://www.crapemyrtle.com/fertilization-for-best-results.html
Hydrangea
Hydrangea fertilization needs vary greatly, depending on your intended bloom color. Certain elements of the fertilizer affect the soil pH, which is a major determinant of bloom color in the pink/blue Hydrangea varieties.
How to Adjust Hydrangea Color
Hydrangeas may produce pink, blue, or lavender blooms, depending on where it’s planted and how it’s fed. The presence of aluminum in the plant ultimately determines the color, and pH affects the uptake of aluminum. Alkaline soils, pH of 6.0 or more, are more likely to produce pink blooms, and more acidic soils, pH 4.5 to 5.5, produce blue flowers.
Pink hydrangeas can be turned blue by applying aluminum sulfate to lower the pH and add aluminum to the soil. Applying lime to raise the pH level will help blue hydrangeas turn pink. If your soil naturally produces very blue or very pink hydrangea flowers, you may need to grow your hydrangeas in containers or raised beds to achieve the desired color. If you do attempt to change the color of your blooms by adding these minerals, dilute them well, and add sparingly. It is very easy to scorch your plants by adding too much. White hydrangeas are not affected by efforts to change bloom color.
https://www.waysidegardens.com/hydrangea-care-guide/a/324/
Plumbagos
Note each paragraph below contains different advice.
Blue plumbago isn’t a heavy feeder and only requires an application of an all-purpose fertilizer blend twice yearly. Apply once in springtime and again in summer while it’s actively growing. Follow package directions for the proper amounts and spread the fertilizer under and around the shrub.
https://homeguides.sfgate.com/growing-tips-blue-plumbago-46137.html
Fertilize plumbago regularly, when plants have a strong root system and full flower heads! Apply a balanced fertilizer at least once per month for the best results.
https://plantcaretoday.com/blue-plumbago-plant.html
