HOW TO GROW GORGEOUS ROSES,
The nutrients that plants need to grow are available to them in a healthy soil, but from time to time, these nutrients need to be replenished. What, how much and when should we add amendments and fertilizers to our soil? Here are some recommendations.
What to add to the soil. Amendments such as compost and worm castings are added to our rose beds to improve the nutritional content, texture, structure, aeration, pH, water retention, drainage and microbial activity of our soil. Organic mulches that we apply to the surface of our rose beds amend the soil as they break down.
Fertilizers are materials that we add to the soil to supplement the naturally occurring nutrients in the soil. The label on a fertilizer will specify the three primary macronutrients – nitrogen, phosphorus and potassium (NPK ratio) – and any other secondary and micronutrients contained in the package. A fertilizer can be chemically or organically based. For example, the nitrogen in MiracleGro is provided by ammonia and urea. In an organically based fertilizer, the nitrogen is derived from blood meal, alfalfa, fish meal or fish emulsion. Chemically based fertilizers are usually cheaper and provide rapid results, but they can burn our plants, and their constant use builds up undesirable salts in our soil. Organic fertilizers have the advantage of improving the soil, but the nutrients are slower to release, as they need to be broken down by soil microbes for use by the plant.
A How much should we add, and when?
A Basic Fertilizing and Amendment Regimen (BASIC) would include lightly scratching an organic granular fertilizer such as BioStar 3-4-3, Ada Perry’s 2.5-2.5-1 or Dr. Earth 4-6-2 into the soil two or three times a year. The product label will specify the amount to use for each rose. The fertilizer is covered by a layer of compost and worm castings, and a 3-inch topping of an organic mulch. My favorite mulch is A-1 Lifelike 3/8” Screened Compost.
The Basics-Plus Regimen: In addition to BASIC, serious rose growers and exhibitors apply fertilizer every two weeks from March through mid-October. Products they might use and alternate include GrowMore SeaGrow 16-1616, Neptune’s Harvest 2-3-1, Fish Emulsion 5-1-1 and GrowMore Seaweed Extract Liquified Organic Kelp 0.10-0-0.44.
Could less be more? My church planted a very lovely prayer garden three years ago. The garden features low maintenance plants such as grevilleas, leucadendrons, aloes, lavenders, rosemary, succulents and ornamental grasses. In a semicircle in the center of the garden are six Secret hybrid tea roses. This rose was selected for its beauty, fragrance, excellent disease resistance and its extremely frequent repeat-blooming qualities.
I go to the garden weekly to deadhead the roses and check for pests. These roses are fertilized only twice a year, in early February and late June, I do the BASIC regimen, to which I add 2 tablespoons of Osmocote 14-14-14 (a controlled release fertilizer) to each rose. The fertilizers are watered in and covered with worm castings, compost and mulch.
Throughout the year, these roses produce a nonstop multitude of gorgeous blooms. I believe these roses perform even better than the more frequently “fed” and pampered Secret roses in my own garden. Gardens invite us to question and be curious: I had to ask myself whether there was something miraculous about the atmosphere of the prayer garden or was I fertilizing my roses too much? Could perhaps “less be more”?
I sent soil samples from my garden for testing to A&L Great Lakes Laboratories (lab@algreatlakes.com, phone: (260) 483-4759). The $30 test results included a pH reading. (A soil pH test measures the acidity or alkalinity of the soil). The level of nitrogen in my soil was normal. The phosphorus and potassium levels in my soil were found to be in the very high range.
Phosphorus stays in the soil a long time, and plants do not need potassium in large quantities. Linda Chalker-Scott, Ph.D., from Washington State University Extension Service, says there is no scientific evidence that roses need high levels of phosphate or potassium, and she cautions that an overabundance of nutrients can damage our soil, disrupt mycorrhizal development and limit the uptake by the plant of other essential nutrients such as iron, manganese and zinc.
A soil test is a good diagnostic tool if you are doing everything right but your roses are struggling to grow optimally. You may discover a soil deficiency or an excess of a nutrient. An incorrect pH can prevent plants from properly taking nutrients from even a nutrient-rich soil. (The ideal pH for roses is 6.0 to 7.0). With the results of a soil test, you can apply fertilizers to your rose beds based not on a calendar regimen but on what your soil needs.
What amendments and fertilizers should we add?
Nitrogen should be added to the soil periodically, as this macronutrient depletes quickly. Fertilizers high in phosphorus should be used with caution and, preferably, only when soil needs it. Too much fertilizer can be a waste of time and money and, worse yet, could inadvertently harm our soil and our roses. When it comes to fertilizers, more is not necessarily better. Less can be more.