Limemound spirea is a low-growing, deciduous shrub that produces an abundance of small, white flowers in early to midsummer. The flowers are borne on arching stems which are covered with dark green leaves. This plant is native to Korea and Japan and was introduced into North America in the late 1800s.
About soil condition, the limemound spirea prefers moderately fertile, well-drained soils, but it is quite tolerant of a wide range of soils except for poorly-drained, heavy clay soils. This plant also prefers a neutral to slightly alkaline pH, but it is tolerant of slightly acidic soils.
Like the other spirea, the limemound spirea (Spiraea japonica "Limemound") is a deciduous shrub that's easy to grow in full sun or partial shade. It's a tough plant that's tolerant of poor soil, drought and even some light shade. The shrub reaches 4 to 5 feet tall and wide at maturity.
The temperature condition that is best for the growth of the limemound spirea is one that is cool and moist. This plant does not do well in hot and dry conditions. The best time to plant this spirea is in the spring or early fall when the temperatures are cooler.
Ideal humidity condition for this plant is around 50%. However, it can tolerate a range of 40-60%. If the humidity is too low, the leaves will start to turn brown and drop off. If the humidity is too high, the leaves will start to yellow and drop off.
The fertilizer, this plant needs, should contain, a good amount of phosphorus in it because that is what, helps the plant to produce, an abundance of beautiful flowers. The roots of the plant, will grow best, in moist soil that is not too wet and not too dry.
Pruning is an important part of keeping your Limemound Spirea healthy and looking its best. This shrub can be pruned in early spring or late fall. For the best results, use sharp pruning shears and make sure to cut at an angle so that water can drain off the cuts.
Propagation is by softwood cuttings taken in late spring or early summer. Cuttings should be taken from young, actively growing shoots and be about 6 inches (15 cm) long. Use a sharp knife or pruning shears to make a clean cut just below a leaf node. Remove the lower leaves and insert the cutting into a well-drained potting mix. Firm the mix around the cutting and water thoroughly. Place the pot in a bright, warm location out of direct sunlight. Keep the soil moist but not soggy. Rooting should occur within 4 to 6 weeks. Once the cutting has rooted, allow the soil to dry out slightly between waterings. When new growth appears, begin feeding with a balanced fertilizer. After the danger of frost has passed, harden off the plant by gradually acclimating it to outdoor conditions. Once acclimated, plant in a prepared bed in full sun.
Usually, the plant growth rate is considered to be fast. This is especially when the shrub is young and continues to to produce new growth each year. The average height and width of an adult plant is between 3 and 4 feet.
Common problems for this kind of plant are powdery mildew, leaf spot, and rust. If you see any of these problems on your plant, you should treat it immediately. Powdery mildew is a white powder that covers the leaves of the plant. Leaf spot is a brown or black spot that appears on the leaves. Rust is a red or orange powder that appears on the leaves.
Source:
Spiraea japonica 'Limemound' habit: UIPLANTS
Spiraea thunbergii - North Carolina State University
Spiraea nipponica 'Snowmound' - North Carolina State University
