Knockout roses seem sluggish this year after the first flush...I think they need fertilizing. Do you use a regular fertilizer or bonemeal, bloodmeal, etc? When, how much?
I suspect most roses will be a bit sluggish after the first flush. Since they usually have a built-in "rest and recuperate" schedule, there doesn't seem to be much one can do to shorten that time-out period, but after all the energy a rose has to use for a big flush of blooming, it only makes sense to feed it again during the rest cycle in preparation for whenever it decides its next bloom period will be.
I often go one of two ways (depending strictly on my mood and energy level): in the spring I feed with Osmocote, a 4-month continuous feed--perhaps supplemented near the end of the season by a short-term quickie feed if the roses look like they need some help in, let's say, September.
Alternate method (but I'm usually too lazy to follow through): Feed the rose monthly (per package instructions) one of the organic --Tones (RoseTone, Plant-Tone, etc.). Variation on this method: Feed the roses RoseTone before and directly after the first bloom cycle, ignore the hot summer months (roses often go semi-dormant in that heat anyway), and then supply a final feed of Rose Tone in September.
Actually, I'm rather erratic in practice--depends a lot on the weather and my energy level. I think I concentrate more on watering them rather than worrying very much about fertilizer. Sometimes I just toss on whatever fertilizer happens to be on the shelf--often just a general 10-10-10 or something like that.
And I think sometimes I just don't get around to feeding them--sometimes. They bloom anyway.
I follow the schedule suggested by E.B. Stone (organic fertilizer company).
Feed with their rose & flower food: March, May, August
Alfalfa in Feb. and August
Sul-Po-Mag: Feb. and Oct.
As with Dublinbay above, years have gone by when they got little or nothing, and sometimes my schedule is a little "off" the above plan, and everything seems fine anyway. I suppose just feeding after each flush of bloom would work too. In other words follow what the roses tell you to do, not the calendar. It's why roses are so wonderful, they bloom and carry on in spite of us.
I do not fertilize anymore so I can't help you in that department.
But I'd recommend keeping them well watered...
I scratch in a slow release dry fertilizer right after spring pruning. After that I use liquid foliar feeds about once a month. Potted roses may need some more often, like every 3 weeks.
But Kate is right, they do naturally take a rest after that first big spring flush. And if your weather was odd this spring and they bloomed late and now things have already started to heat up there they may be even slower to regroup.
Thanks for all your input! We didn't fertilize at all last year, with no major spring pruning, and had a very colorful summer. This year, I did the big clean up pruning at the right time in February, and seem to have less flowers now despite fertilizing after the new growth in early spring. Maybe I just need to be patient.
Here in NY its a lot different the fertilizer schedule. Here we wait till the roses leaf out completely and then I use Espoma Rose Tone around each plant -- I either wait for rain to be in the forecast to wash it in or if you do not mulch, you can scratch it into the soil. I also apply my 1st application of Epsom salts around each rose too. Figure about a half cup of the fertilizer and salts around each rose.
In May, June, July and August I feed again with the Rose Tone and in July I do my 2nd application of Epsom salts.
They do pretty well with this routine.
Jim I am a little surprised to hear that you don't fertilize anymore lol. Your roses always look so beautiful! You must have wonderful soil then! :)