Question: I have several roses, both climbers and teas, that have many nice leaves but no flowers. Why, and what is the remedy?
Answer: The lack of flowers may be from improper pruning, shoots arising from the understock, too much shade, too much fertilizer, or severe winterkill.
Prune roses in the spring, just before the leaf buds begin to swell. Remove any winter-protection material, and cut out all dead, diseased, and weak growth that is less than half an inch in diameter. Shorten last year’s new growth by one-third to one-half, but avoid cutting into old wood. At the graft (the bump at the plant base), take out only those old canes with weak growth. Thin out smaller top branches to allow better light penetration and to encourage good air circulation through the plant. Remove any suckers (new canes) arising from below the graft as soon as you see them, for if allowed to grow, they will take over and eventually kill the grafted-on rose.
Grow roses in full sun (a minimum of six hours a day). When new spring growth is fully developed, evenly spread one heaping tablespoon of a complete low-nitrogen fertilizer (such as 5-10-5 or 4-8-6) around each plant. Scratch it in and water well. Feed again if the leaves seem yellow (lack of nitrogen) or grayish green (lack of phosphorus), or if leaf margins turn brown (lack of potassium). Make this second feeding no later than mid-July in northern climes, and not after August 15 in the South.
To protect tea roses for the winter, mount 12 inches of soil over and around the rose crown after the ground has frozen. (Dig and store the soil for mounding earlier in the season). With soft twine, gently tie the canes together to prevent them from thrashing about in winter winds. Place a cylinder of wire around each bush, and fill it with a 12-inch layer of mulch.
To protect climbers, loosely tie the canes in place with twine and wrap them with straw or cornstalks. A more laborious but better method for protecting climbers is the bury them. Loosen the plant’s roots by digging a half circle into the soil, 12 or more inches out from the base. Untangle the canes from their support, then carefully pull them together and tie them with twine. Gently bend the plant down and peg it to the ground with wire hoops (such as old-fashioned croquet wickets). Enclose the prone rose on four sides with boards, cover the entire plant with soil, and mulch with cut evergreen boughs, cornstalks, or any other loose material that neither packs down and smothers nor blows away.
From Horticulture Magazine