Q: Last week, you said to fertilize flowers that aren't blooming. My rose bushes are supposed to bloom all summer, but they have stopped. Can I fertilize them or is it just too hot?
A: Roses come in several groups and some only bloom once in a summer, including may old-time roses and many climbing roses. Most new varieties will bloom several times over the summer, but may rest for a few weeks in between.
"Most of the major commercial rose production in the U.S. occurs in the Central Valley of California and outside of the Phoenix area in the hot deserts of Arizona," said Brian Correiar, Manager of Production/Operations Research and Quality Control for Weeks Roses, the largest commercial rose grower in the country.
Summer heat is probably not the problem, but sunlight and watering might be. Roses bloom on the ends of new growth. If the plants are in too much shade, they don't grow as fast and take longer between blooming times.
Roses don't like to have their roots in very wet soil, but they do like damp soil. If your area is hot the roses can dry out, and again, their growth rate slows. They like deep soil. Before planting a rose bed, add compost and create a good soil as much as 12 inches deep. This gives the roots a large volume of soil to soak up water. If the rose bed has shallow soil, water more often to keep the soil damp.
Soaker hoses and timers deliver water to the roots where it is needed. Overhead watering with the hose or an irrigation system can get water on the leaves and that helps create unhealthy conditions that promote diseases. Morning water before the heat of the day is better than in the afternoon when the plants are already wilting.
Adding as much as 4 inches of organic mulch helps hold the water in the soil. It also keeps the soil cool. Gravel mulch doesn't help the soil organisms or help fertilize the soil the way organic mulch does, but it is better for the roses than bare soil.
Since roses are actively growing and producing flowers during the summer, they need more fertilizer than most other types of shrubs. Follow the directions on the slow-release fertilizer package for best results. Typically, if your area gets a killing freeze in the fall, the last fertilizer application should be applied at least six weeks before the average first-frost date.
From the rose plant's point of view, the object is not to grow flowers, but to grow seeds. We call them rose hips. If your plants are growing hips, the plant will spend its energy growing seeds and not growing more flowers. It is okay if you want to harvest some rose hips, but if you want flowers, you will need to prune off the hips. We call the removal of spent flowers deadheading. Some modern roses don't grow many rose hips and don't need much deadheading.
If your roses have rose hips, prune that branch back. The rose bush will want to send up a new stem to about the same height above the ground as the original one. If you just snip off the hip, the plant will send out a new branch with a rose on it that is only a few inches long. If you clip the branch back closer the ground, leaving only a couple of leaves on the stem, the plant will produce a long stem with a flower on the end.
Check your roses for insect or disease problems. Aphids and Japanese beetles can damage the new growth to the point that flower buds are eaten or destroyed. Diseases also slow the growth of the plant and that means a longer time between flowers.
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Copyright 2016 Jeff Rugg, licensed to Creators Syndicate.