Answer: Roses do well in full sun and rich soil that is evenly moist yet not soggy and in a location that provides good air circulation but yet is protected from wind -- both winter and summer.
Besides considering the site where you are growing the roses, you might want to run some basic soil tests and see what your soil is (or is not) lacking so you know exactly what nutrients to add. Your County Extension (253-4332) should be able to help you with the tests and interpreting the results. They may also be able to suggest specific rose varieties which are known to do particularly well in your area.
In addition, it is always a good idea to amend the planting area for roses with copious amounts of organic matter such as compost, old rotted leaves, or aged stable manure and bedding to help improve the soil structure. This allows it to hold both air and water better and helps the plants grow healthier. Using an organic mulch such as shredded bark also helps feed the soil when it breaks down, besides helping keep the soil cool and moist during hot dry spells.
In my experience if roses have enough sunlight, the next most likely cause for poor blooming is not enough water or poor watering technique. These plants can use one to two inches of water a week as a rule of thumb, but the best way to tell is to dig down into the soil and see how effective your watering really is. Keep in mind that it is better to water deeply but less often than to water lightly every day. This will encourage deeper and healthier roots.
I hope this helps.
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