Nandina domestica ‘Obsession’, often sold as ‘Seika’, is a compact shrub favored for its dynamic foliage color and tidy growth habit. This cultivar is popular in residential and commercial landscapes due to its smaller, more manageable size compared to older heavenly bamboo varieties. The plant is named for its vibrant, fiery red new growth that emerges in spring and persists through much of the year. This dense, upright form makes it suitable for foundation plantings, borders, and container gardening.
Expected Growth Rate and Mature Dimensions
The ‘Obsession’ nandina is categorized as a dwarf cultivar with a slow to moderate growth rate, making it a low-maintenance selection. Growth speed varies based on climate and care, but the plant typically adds a modest amount of vertical growth annually, often ranging from a few inches up to a foot in ideal conditions.
The shrub generally plateaus at 3 to 4 feet in both height and width. This manageable size is achieved over several years, with the plant reaching its full density in about three to five years depending on the environment. Its predictable growth ensures it will not quickly outgrow its designated space, which is a benefit for small-space landscaping.
Optimizing Growth Through Environmental Conditions
The shrub thrives best when planted in a location that receives full sun to partial shade. Full sun intensifies the signature red coloration of the new foliage, though afternoon shade can prevent leaf scorch in the hottest climates. The ideal planting medium is rich, well-drained, and slightly acidic soil. While the plant tolerates various soil types, it may develop chlorosis (yellowing) in strongly alkaline soils.
During the first season, deep and regular watering is necessary to establish the root system. Established plants are drought tolerant and require only moderate watering in hot, dry conditions. Applying a balanced, slow-release fertilizer in early spring supports robust growth throughout the season.
Maintaining Desired Shape and Size
The naturally compact and dense habit of ‘Obsession’ means it requires very little maintenance pruning to maintain its shape. When pruning is necessary, the goal is to encourage new, colorful growth and rejuvenate the plant, rather than reducing its overall size.
The preferred method is renewal pruning, which involves using hand pruners to thin out the oldest, tallest canes at the base, cutting them down to the ground. Removing up to one-third of the oldest canes in late winter or early spring encourages fresh stems to sprout, which display the most vibrant red foliage. Avoid shearing the top of the plant, as this damages the natural, upright character of the foliage and leads to an unnatural, brushy appearance.