Feeding My Roses with Colorburst

behlgarden(9)February 15, 2012

I bought this 15 lb Colorburst 15-30-15 Fertilizer from Home Depot for my roses.

I read that roses like 1:2:1 ratio of NPK. My Organic way to Roses stops at not using any chemical pesticides/insecticides. For Fertilizer I believe I don't do any harm to bees correct?

Anyone used this and how were the results?

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mike_rivers(z5 MI)

I havn't used Colorburst but it has slow-release nitrogen and resembles some forms of Osmocote except for the high phosphorous analysis. Dr. Linda Chalker-Scott at Washington State U has made the following points about high-phosphorous fertilizers: 1) There is no evidence, anywhere, that phosphorous stimulates either root growth or flower production. 2) Phosphorous does not leach readily and tends to accumulate in the soil and interfere with iron uptake - likely to happen especially with roses. 3) Most seriously, high phosphorous fertilizers tend to destroy the beneficial mycorrhizae on a plant's roots.

I use both alfalfa and Osmocote to fertilize my roses and I always look for a brand of Osmocote with the lowest possible phosphorous analysis such as 19/6/12 - which is almost exactly the N/P/K ratio of 3/1/2 found in most plant tissue. Truth is, I'd prefer an even lower phosphorous number.

    Bookmark   February 16, 2012 at 10:25AM
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michaelg(7a NC Mts)

As Mike Rivers says, it's a widespread myth that extra phosphorus promotes blooming. Or, in the case of advertising claims, it's a lie. I've linked a study using annual flowers that shows no benefit to extra P. It did find a benefit from extra nitrogen, contrary to horticultural folklore.

It is OK to use the package that you have bought. Follow directions. It will have no effect on the bees. But in future, choose a fertilizer that has more nitrogen (first number in the three-number sequence) than phosphorus (second number). It is possible to permanently damage soil by long-term excessive application of phosphorus.

Here is a link that might be useful: fertilizer experiment

    Bookmark   February 16, 2012 at 10:35AM
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Thanks. most articles and suggestions that I read on Google search suggest NPK ratio of 1:2:1 for Roses, so I picked up the 15:30:15 for this case.

I would love to hear folks over this high "P" content benefits or disadvantages of using it. High Nitrogen what I heard causes a lot of foliage and not enough blooms.

    Bookmark   February 16, 2012 at 11:33AM
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michaelg(7a NC Mts)

Well, here is another science-based link.

As I said above, and your Googling confirms, there is a widespread belief that extra P promotes bloom. This belief is repeated in many non-scientific garden books and articles. It just happens not to be true. Roses can only use 1/3 as much phosphate as nitrogen. They use NPK nutrients in the ratio of 3-1-2. Some other plants such as tomatoes use the ratio of 2-1-2. No green plant is known to use more P than N.

A ratio of 1-1-1 (found in Miracle Gro etc.) is fine for pots because soilless media (American potting soils) are low in P and do not retain P as well as normal soils. Also potting soils are only used for a year or two before discarding.

In the garden, unused phosphate builds up in the soil, and, in extreme cases, can cause shortages of other nutrients by binding them in insoluble compounds. University of Florida reports cases of this and recommends using less P than N for roses. However, it takes years of over-fertilizing to cause a problem with excess P. That has allowed the myth to survive.

Not trying to close off other peoples' comments, though.

Here is a link that might be useful: Chalker-Scott

    Bookmark   February 16, 2012 at 3:28PM
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seil zone 6b MI

ANY well balance fertilizer will work just fine on roses. They do not need anything special and do not need extra "P" to bloom well. Some extra organics to feed the soil will probably do a lot more good than anything else. Healthy soil will give you far more bloom power than extra fertilizer.

    Bookmark   February 16, 2012 at 3:41PM
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OK folks, thanks for chiming in. My plants are 10 year old and last year I used this http://www.homedepot.com/h_d1/N-5yc1v/R-202052195/h_d2/ProductDisplay?catalogId=10053&langId=-1&keyword=vigoro%20fertilizer&storeId=10051

its Vigoro 12-6-10, cost $12/20 lb. Color burst that I got is also by Vigoro http://www.homedepot.com/h_d1/N-5yc1v/R-100074761/h_d2/ProductDisplay?catalogId=10053&langId=-1&keyword=vigoro&storeId=10051

this one costs about $15 for 14 lb.

What I read here, "P" should be less than "N" for roses. if that is the case I should go with the 12-6-10, is that good enough OR use 15-30-15? I can return the 15-10-15

    Bookmark   February 16, 2012 at 5:03PM
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The 12-6-10 is a good mix for roses.

    Bookmark   February 16, 2012 at 5:34PM
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strawchicago 5a IL(zone 5a)

I'm glad to hear from Mike_Rivers and Michaelg, both sources I trust and learned much from - thanks. People reported BAD phosphorus burn with liquid fish-fertilizer like Alaska MorBloom with high phosphorus (0-10-10). A decade ago, I burnt and killed a young white pine with too much bonemeal (4-12-0), and am cautious about phosphorus ever since.

In alkaline soil, phosphorus is bound up in complexes with calcium or magnesium, and no matter how much phosphorus you feed the plants, it's going to be tied up in alkaline clay. University of Coloroda extension specifies that neither bone meal nor rock phosphate should be used at pH above 7.

It's better to lower the pH, so the phosphorus is released from the soil. Tap water is usually made alkaline so it doesn't corrode the pipe. If you have well water like mine in a high limestone area, the water pH is above 8. Here's a post in Garden Experiment Forum regarding the problem with high pH water:

Posted by aznative40 z7bAZ (My Page) on Fri, Oct 24, 08 at 12:38

"Alkaline water?....Come here to Cornville AZ I will give you all you want. I'm on a private well and grew my garden the first year with compost, manure, and well water. The first year everything went well, the second year everything was stunted. Okra grew a whopping 8 inches tall, cukes were yellow and hard at 2 inches, and even Zuccinni which will grow everywhere, was hard and yellow even at a few inches long. They looked and felt like gourds. I did a pH test before first year planting, 7.1 at the end of second year 9.2. Left the ground fallow for 2 years and will try it again, with a filter "

    Bookmark   February 17, 2012 at 10:12AM
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