Horse manure needs to rot down for about one season before you can.
Jul 26, Mulch helps to hold in the priceless moisture for rose bushes and other plants, saving on the amount of watering we need to do. The mulch also stops, or at least discourages, weeds from coming up in rose beds and robbing the moisture, not to mention keeping the weeds and grass from robbing the nutrients intended for rose plants.
Oct 30, Mulching around your roses protects them from weeds and keeps the soil from drying out. For the best results, you should use a 2- to 3-inch layer of organic mulch around your roses.
You can apply mulch to your roses any time of year but it is best in early spring and then again in late summer to early fall. A 2” layer would be considered the minimum application, but a thicker application will need to be applied less often.
We suggest a layer of 2”-4” for best results. Apply a ″ layer of your chosen mulch around the base of the rose, spreading it to the width of the rose canopy. For your mulch material we recommend using a good quality garden compost, composted straw or bark, or well rotted manure from a local farm (manure must be at least 2 years old, as fresh manure can burn the roots of your roses).
The Short Answer Knock Out roses need to be mulched to promote optimal health, vigor and flower production. Without regular mulching, they are more prone to drought stress during hot, dry summers.