Rose fertilization

Asked September 13, 2017, 11:25 PM EDT

What are the best times to fertilize roses? What times should be avoided?

Boulder County Colorado flowers: annuals and herbaceous perennials

1 Response

When to Fertilize
  1. Begin fertilizing when you have 4 to 6 inches of new growth, and can see the first real leaflet with 5 to 7 leaves. ...
  2. Stop fertilizing 8 weeks before you typically get a frost, if you live in a colder winter climate. ...
  3. Fine-tune your applications for optimum rose health.

Fertilize Roses

Feed for Health and More Blooms

How-To-Fertilize-PageGrandiflora In Full Bloom

Roses, in general, are heavy feeders. They love to eat, which positively affects their health. Did you know that a healthy rose not only produces more blooms, but is also better equipped to ward off pathogens too?

Roses can survive without being fertilized, but they struggle. There are exceptions to this rule: Species or near-species roses that are used to growing in the wild and have adapted to neglect. Selections like Rosa Mundi, Rosa glauca, or the Hybrid Rugosas; larger ramblers like ‘Darlow’s Enigma’ and ‘Paul’s Himalayan Musk’ can also fend for themselves. These varieties tend to be once-blooming, but are good choices for rose gardeners that don’t have the time or inclination to fertilize. But, anyone trying to grow repeat-blooming roses, like hybrid teas and floribundas, should fertilize regularly during the growing season.

 Paul's Himalayan Musk Covering a Tree

Rosa-Mundi-bushRosa Mundi Bush In Full Bloom

Nutrients Roses Need to Grow

It helps to understand the basic nutritional building blocks that all plants need. Most important are the Big Three: Nitrogen (N), Phosphorus (P) and Potassium (K). These are the three numbers you see on all fertilizer packages, and are also referred to as the N-P-K ratio.

Without getting too scientific, if you can remember “Up-Down-All Around” you will have a good idea of how these nutrients operate:

  • Nitrogen helps shoots (above ground)
  • Phosphorus helps roots (below ground)
  • Potassium is used by the whole plant (like a vitamin).

More specifically:

Nitrogen (N)Promotes healthy vegetative, green growth. Nitrogen is a component of all proteins and because water washes it away from the root zone, roses require a consistent supply. It is needed to build chlorophyll and allows the plant to use light to turn water and carbon dioxide into sugars to feed itself. Too much and you produce lush plants with few or no blooms. Too little, and the rose will have yellow leaves, no new growth, and small pale roses.Phosphorus (P)Makes for strong roots and abundant flower production. Too little will cause dull foliage, falling leaves, weak flower stems and buds that will not open.Potassium (K)Also known as potash, encourages vigorous growth and makes sure all is in good working order. It is like an immune system booster that helps the plant through stressed times such as disease / insect damage, drought and cold temperatures. Lack of potassium will produce weak steams, poorly developed buds, and yellow edges on the leaves, which turn brown.

Hope this is helpful.