Knockout Roses seem to have taken the rose growing world by storm as one of the easiest, trouble-free rose plants to grow. Apparently this AARS award winning rose is the most widely sold rose in North America due to its hardiness and versatility.
This rose was hybridised by Willian Radler and introduced to the world in 1999. It’s a floribunda rose that grows to about 4ft tall (1.2m) and as wide, forming a small compact bushy plant.
Flowers are semi-double and loosely formed, cherry-red fading to pink as it ages. Many clusters of flowers are borne on the plant which have very little fragrance. If they’re not regularly dead-headed they will set hips in shades of orange.
Knockout Roses are a very versatile. They can be planted in rows as a border or hedge, where they look terrific en masse. They are also compact enough to be grown in containers on patios and decks where their non-stop blooming can be shown off to advantage. You can also buy them in tree form as a standard rose.
They are supposedly shade tolerant, resistant to black spot, mildew and rust. Though a lot of this depends on them being planted correctly and having their cultural requirements met - there are cases where this rose does get disease problems but it is less prevalent to disease than some of its fussier counterparts.
Knockout Roses are said to be “self-cleaning” meaning they don’t need deadheading, but to promote continuous flowering I would recommend lightly deadheading this rose bush during the growing season, with the emphasis on “lightly” as the flowers bloom on new wood. If you don’t deadhead, the rosehips use up a lot of the rose’s energy (forming new seeds within the hips) instead of the plant’s energy being used to form flowers.
They are supposed to be hardy down to USDA zone 5, however the occassional loss does occurr in this zone over the winter so I’d be inclined to cover them during that season to prevent any losses occurring with your knockout roses.