I have four 3-year old rose bushes, which are growing in full sunlight. I just water them regularly and they seem to be fine and healthy. But this year only one is showing any signs of flower buds. What is the reason they are not going to bloom?
There are a few reasons that roses sometimes come up “blind”, i.e. without flower buds. The most common reasons are environmentally issues (sunlight, watering, temperature) and also lack of nutrients.
We did have a terrible winter, with brief periods of warmth, such as a 20 degree day in early April, followed by more freezing weather, snow and ice. This kind of warm / cold weather cycling results in freeze damage that doesn’t kill the rose canes, just leads to blind shoots.
Prune out the blind shoots and the new growth that appears should be normal.
You say you are diligent about watering and that they are in sunlight. But you make no mention of feeding them. Roses are heavy feeders. Choose a fertilizer with a higher centre number, such as 5 10 5, which will encourage blooming.