Fresh raspberries make a handy, healthy snack.

Will Dwarf Thornless Red Raspberries Spread?

by Jolene Hansen

Growing your own raspberries (Rubus idaeus) used to require a lot of space and work. Raspberry Shortcake raspberry (Rubus idaeus "NR7") changed all that. The first dwarf raspberry with thornless stems, it was developed with containers and small spaces in mind. Raspberry Shortcake still spreads -- it's a raspberry, after all -- but at a much more leisurely pace. Whether on the patio next to your favorite breakfast spot or in your landscape, fitting this raspberry into your life is a cinch.

1. What to Expect With Size

At just 3 feet tall when fully grown, Raspberry Shortcake is perfect for containers, raised beds or in the landscape. Though well-mannered, it still spreads the same way all raspberries do. New growth comes from its crown and from spreading, underground stems. For container-growing, large pots 24 to 36 inches in diameter up to half-whiskey-barrel size with drainage holes work best. Within a few years, the canes will spread to fill the pot. Without boundaries in the garden, Raspberry Shortcake will continue to widen its reach quite a bit over the years. The plus side is that more canes mean more fruit.

2. Fruit and Other Features

Even though Raspberry Shortcake stays small in height, it still bears full-size fruit. Abundant, extra-sweet berries cover the bush in midsummer. With thornless stems, you don't have to worry about planting it close to walkways or play areas. Kids can grab a quick snack. Hardy in U.S. Department of Agriculture plant hardiness zones 5 through 9, it has a sweet vanilla fragrance and dense, lush foliage that takes on a tint of red -- a perfect accent for a kitchen bouquet, with or without berries intact. Raspberry Shortcake pollinates itself and doesn't need to be trellised or staked.

3. Pruning Needs

Raspberry Shortcake produces new canes every spring and fruits on canes from the previous year. Canes older than this don't bear fruit and need to be removed every year. When winter approaches, let your raspberry go dormant. It may look forlorn, but don't despair. In early spring, you'll see lots of new green canes coming up from the ground and second-year canes with lots of new green sprouts. The old canes with green growth will bear fruit the current season. The new green canes will fruit the next year. Older canes without new growth should be cut back to the ground. Handheld pruning shears do the job well. Sterilize your blades before and after each cut in a solution of one part bleach to nine parts water to prevent the spread of disease.

4. General Care

Raspberry Shortcake doesn't need much attention to thrive and bear lots of fruit. Plant it in full sun with well-drained soil with a pH of 6.5 to 7.5. Fertilizing isn't necessary, but it provides a boost for pots. A fertilizer balanced in nitrogen, phosphorus and potassium -- one with all three numbers the same -- is all you need. Dissolve 1 tablespoon of water-soluble 15-15-15 fertilizer in 1 gallon of water and apply once in early spring and once again in late spring. If leaves start to yellow during the summer, another application of the same fertilizer will help. Consistent moisture is important for berry quality and plant health. For summertime containers, a daily watering may be needed. In the landscape, water two to three times per week during summer months.

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