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New England Gardening

Knock Out roses not blooming

15 years ago

my landscaper put in a dozen double red knock out roses last fall. They bloomed beautifully as soon as he put them n last Fall and again earlier this Spring, may-June... but now their leaves are a lime green color (not deep green anymore_ and there are no flowers, no buds, nothing.... I don't see any bugs or black spot. They are on an eastern facing slope in full sun (sun from sunrise to 2:00 or more).

I had also bought six more of these from Mahoney's to fill in the bank some more this Spring - and THESE have bloomed non-stop, have deep green foliage, just beautiful.

I have fertilized all with the same Rose fertilizer (Rose MiracleGro) twice now... and further tried to encourage the yellowed non-bloom ones with more water and an extra application of regular MiracleGro.... HELP!!!

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Comments (2)

tree_oracle
15 years ago
I have found Double Knockout to not be as vigorous as Knockout itself. Having said that, I wouldn't expect them to struggle to the extent that you are describing. Being on a slope, is it possible that the watering that you are doing is just running down the hill and not really penetrating down to their root system? I would dig down into the hole and make sure that they are getting enough water. You also might try digging them up and preparing a better hole for them. I dig a 2 x 2 x2 ft hole for all of my roses and generously mix the native soil with 1 part peat moss and 1 part composted cow manure. That give the rose a really rich but loose soil to get the root system established. It sounds like your roses are not getting enough nutrients so your fertilizer applications are probably not making it down to their root system.
claireplymouth z6b coastal MA
15 years ago
tree oracle is giving excellent advice when he suggests your older roses are not getting enough nutrients because of the way they were planted or are being watered.

Another maybe off the wall possibility - could the landscaper have added large quantities of a slow-release fertilizer like Osmocote to the planting holes? If that is so, then the MiracleGro you added could be activating the slow-release fertilizer.

It sounds a little weird, but I once lost a favorite begonia houseplant when I added fish emulsion to soil containing Osmocote. I later read a report that some fertilizers can dissolve the coating that makes Osmocote slow to release. The effect is to release the fertilizer all at once which the plant cannot handle.

Something like that would explain why the newer roses are OK (they only got a normal dose of fertilizer).

Too much fertilizer can damage a plant as much or more than too little.

Claire
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