Growing The Yellow Sunny Knock Out Rose

The Sunny Knock Out® Rose (aka: ‘Radsunny’ RAD-sun-nee) is a perennial, deciduous rose developed by botanist Bill Radler of Wisconsin. It is a hybrid member of the Rosaceae family of plants. The plant’s botanical name is Rose Sunny Knock Out ‘Radsunny.’ You may hear it referred to as:

  • Sunny Knockout
  • Rosa Radsunny
  • Knockout Rose
  • Radsunny
Flowering Sunny Knockout RosePin

Sunny Knock Out® Rose Care

Size & Growth

This fast-growing plant has a bushy, upright growth habit. The plant typically attains a height of three or four feet and a width of three to five feet. 

The leaves are semi-glossy and deep green during the warmer months of the growing season. In the autumn, the leaves transition to a very attractive shade of burgundy, verging on purple.

Related: Tips on Growing Roses

Flowering & Fragrance

Vigorous Radsunny blooms abundantly and continuously throughout the growing season, from early spring to late autumn. The three-inch, single, fragrant, citrus-scented yellow buds widen and gradually fade to an attractive creamy white as the season progresses. 

In cooler weather, the flowers stay yellow longer. Finally, in the autumn, the flowers transition into pretty orange/red rosehips. 

Knockout Roses typically bloom in the first year. 

Light & Temperature

Plant Radsunny in a setting that receives at least 6-8 hours of full sun daily. While these roses can bloom with as little as 3 hours of sunlight daily, you will get the best results with full sun. 

Sunny Knock Out® Rose is winter hardy in USDA hardiness zones 4-11. However, in areas where temperatures will fall below 50° degrees Fahrenheit for extended periods, these rose bushes will require special care. 

Watering & Feeding

Rosa Radsunny has average water needs. Soil should be kept moist but not soggy. The best practice is to water deeply and wait until the top few inches of soil begin to dry before watering deeply again. 

Knockout Roses like a standard rose fertilizer. As a rule of thumb, you can fertilize monthly throughout the growing season. Be sure to read the instructions on the particular brand of fertilizer you purchase. Follow the instructions carefully. 

Soil & Transplanting

As with most roses, Rosa Radsunny does best with a moist, well-draining soil mixture containing a high percentage of organic compost and garden loam. It can tolerate any average or sandy soil and can even tolerate some clay content in the soil. 

Be sure to plant your Knockout Rose in an area sheltered from harsh, cold wind but does receive good air circulation. Plant bushes three feet apart. Apply mulch to help retain moisture. Take care not to let the mulch rest against the stem or trunk of the plant. 

Grooming & Maintenance

Knockout Roses are so-called because the new blooms knock out the old blooms. No deadheading is needed. Prune dead or damaged stems and limbs as needed. This is especially important at the end of winter to encourage healthy, new growth in the springtime.

Tips on Rose Growing from Old Time Rose Growers

How To Propagate Roses

You can grow these roses from cuttings. Take eight-inch cuttings at the tips of the stems. Be sure to include an area where a “hip” is forming. 

Make a clean cut with a sharp, sterile cutting implement. Cut at a 45° degree angle. Remove all of the leaves on the lower half of the cutting. 

Once you’ve taken your cutting, you must work quickly and not allow the cutting to dry out. Place it into some water to keep the tip damp as you transport the cutting to its new location.

Early in the growing season, you can start your cuttings directly in the ground. You should have a bed prepared in a sheltered setting that gets ample, bright, indirect sunlight. A wall with eastern exposure is ideal.

Use a pencil or similar implement to poke holes in the soil at a distance of 8″ inches apart. 

Dip the lower half of your cuttings in rooting hormone and quickly place them in the prepared holes to a depth of four inches. 

Press the soil firmly around the cuttings to ensure you have good soil contact on all submerged surfaces. 

Water thoroughly, and keep the soil moist by watering every two days (except for rainy days, of course!) 

Once you notice new growth on the cuttings, you can reduce watering and begin treating your cuttings as mature plants. 

Protect your young plants against cold as needed through the following year. Then, once a full year has passed, you can relocate your young rose bushes to their permanent settings. 

Sunny Knock Out® Rose Pest or Diseases

These specially developed roses resist pests and diseases. As a result, you will have far less trouble with black spot foliage disease, powdery mildew, and rust with Knockout Roses than any other type of rose. 

All types of Knockout Roses are heat and cold tolerant and very resistant to Japanese beetles. 

Knockout Roses are subject to infestation by eriophyid mites which spread a virus known as Rose Rosette. This virus causes the bush to produce bright red clusters of shoots. 

Control this disorder quickly and completely removing the shoots by pruning through healthy green growth. However, you will need to remove and destroy the entire plant if you don’t act promptly. 

Pre-emptive pruning of these plants early in the springtime can help prevent the spread of the virus. Cutting the foliage back by about 2/3 before new growth appears is effective. 

Suggested Sunny Knock Out® Rose Uses 

Radsunny is an excellent choice as a low, fragrant hedge around your patio or porch. It also makes a nice foundation planting. 

Individual bushes are very pretty when included as a focal point in Japanese gardens featuring ornamental grasses and other more austere plants. 

Add one or more of these fragrant beauties to your bird, pollinator, and/or butterfly garden. It is also an excellent addition to a cottage garden.