Buddleja black knight is an ornamental plant that is known for its black leaves and flowers. This plant is native to China and Japan and was introduced to North America in the early 1900s. The black knight buddleja is a deciduous shrub that can grow up to 10 feet tall and wide. This plant prefers full sun to partial shade and well-drained soil. The flowers of this plant are black, purple, or blue and bloom in the summer.
Related plant:
Buddleja Davidii Nanho Blue
Related plant:
Buddleja Royal Red
About soil condition, black knight buddleja prefers well-drained soil that is rich in organic matter. The plant is quite tolerant of different soil types, but it will not perform well in waterlogged or extremely dry conditions. For best results, apply a layer of compost or organic matter to the planting area before adding the black knight buddleja.
Similar to other Buddleja, the Black Knight requires full sun to partial shade in order to thrive. It grows best in well-drained soil, but is tolerant of a wide range of soil types. This shrub is moderately drought tolerant once established.
The temperature condition that is best for Buddleja Black Knight is warm weather. This plant does not like cold weather and will not do well in it. The plant needs to be in an environment that is around 70 degrees Fahrenheit or above to thrive. If the temperature outside is too cold, the plant will not be able to grow properly.
Ideal humidity condition for this plant is around 50%. If the humidity gets too high or too low, the plant will suffer. Too much humidity will cause the leaves to droop and the plant to become floppy. Too little humidity will cause the leaves to turn brown and fall off.
For the fertilizer, usually the plant doesn't need much. A light dressing of an all-purpose fertilizer in the spring is all that is necessary. As for the root, it is best to keep it moist but not wet and to fertilize regularly.
Pruning your Buddleja Black Knight is an important part of keeping your plant healthy and looking its best. Pruning helps to encourage new growth and can also help to control the size and shape of your plant. When pruning, be sure to remove any dead or damaged branches and stems. You can prune your Buddleja Black Knight in late winter or early spring.
Propagation is typically by stem cuttings taken in spring or summer. Remove a length of stem with some leaves attached and pot up in moistened, well-drained propagating mix. Place in a propagator or warm, bright spot out of direct sunlight to keep the compost moist and encourage rooting. Once rooted, pot on and grow on in moist, well-drained soil in sun or semi-shade.
Usually, the plant growth rate is about 1-2 feet per year, but can be as much as 3-4 feet in rich soils with good drainage and regular watering. They are fast-growing, heat and drought tolerant, and relatively low-maintenance once established.
Common problems for this kind of plant are that the leaves may turn yellow and the plant may not flower. The reason for these problems is usually due to too much water or fertilizer. If you think your plant has these problems, you should check the soil to see if it is too wet or too dry. You may also need to adjust the amount of fertilizer you are using.
Source:
JC Raulston Arboretum - Photographs of Buddleja davidii 'Black Knight'
Buddleia alternifolia | Landscape Plants | Oregon State University
Managing Pests in Gardens: Trees and Shrubs: BuddleiaUC IPM - ucanr.edu