In some years, roses flower poorly for no apparent reason, generally the causes for this are either physiological or environmental.
For example; plants may have been affected by frost, they may be situated in areas subject to severe weather, or are just plain and simply getting too old, i.e. there is predominance of old wood.
Certain signs can often determine the exact problem, e.g. an empty flower case can suggest frost damage.
Blind shoots could mean excessive shade, or lack of fertility.
Poor flowering climbing roses can be due to a build-up of old, weak growth.
To cure these problems, avoid planting out in areas that catch the morning sun, this should reduce the risks of frost damage.
Cut back blind shoots by half to stimulate further growth.
Improve growing conditions by feeding and mulching regularly.
Prune out a large proportion of older wood and this will encourage new growth.