This cultivar, a hybrid cross between S. japonica ‘Alpina’ and S. japonica ‘Goldflame’, is named for its golden leaves and for its mound-like habit: It matures at two to three feet tall and three to four feet wide. This, and the moderately fast growth rate, also makes it suitable for container growing. It should be planted in the spring or fall. It is rarely bothered by any pests and diseases and deer usually leave it alone. The flowers are suitable for cutting. If you deadhead the first blooms, it may bloom again.
Light
Gold Mound spirea prefers full sun, when possible, but will tolerate light shade. Planting it in a sunny location helps to ensure the best color.
Soil
This plant will grow best in well-drained soil, although it tolerates clay soils better than some other shrubs. Amend the soil with compost as needed. Gold Mound spirea prefers a pH range of 5.5 to 7.5. Mulch for winter protection if you wish to grow them in USDA cold hardiness zones 4 or 5, just to be on the safe side. The plant is hardy to -30 degrees Fahrenheit.
Water
Every week during the summer be sure to thoroughly water this shrub (unless it rains steadily for several days, then you can skip a week). Water until the roots are saturated, but don’t overwater; Gold Mound spirea doesn’t like overly wet conditions.
Fertilizer
These hardy plants should be fertilized in late winter or early spring before new growth appears. A general-purpose garden fertilizer is fine. For the amount to use, follow the product label instructions. Be sure to water thoroughly after applying fertilizer.
Types of Golden Japanese Spirea
Because of the striking color of their leaves, Gold Mound spirea bushes are more suitable for use as specimen plants than is the cultivar Neon Flash, the latter bearing foliage that’s nothing out of the ordinary. You can also use Gold Mound spirea as foundation shrubs or hedge plants. Other cultivars of Spiraea japonica that have golden leaves and pink flowers and that are hardy to zone 4 are the following:
‘Magic Carpet’ is a compact cultivar, ideal for small yards. It grows to just one to two feet tall, with a width of two to three feet.‘Golden Elf’ is even smaller than ‘Magic Carpet’. This dwarf stands at just a little over six inches tall, with a width of one to two feet.‘Lemon Princess’ reaches one and a half to two feet tall and has a width of two to three feet.‘Double Play Gold’ also reaches one and a half to two feet tall and has a width of two to three feet.‘Limemound’ grows to two to three feet tall and three to four feet wide.‘Golden Princess’ also matures at two to three feet tall and three to four feet wide.
Pruning
Deadhead Gold Mound spirea after they’re done blooming. This will foster some reblooming as the growing season progresses. The easiest way to deadhead in this case is by shearing. In addition to removing spent flowers, shearing will help you keep the shrub compact and generate new foliage (the newest foliage being the most colorful parts of this plant). Pruning full branches is usually necessary only to remove suckers (if so desired) or to rejuvenate a mature plant. You can also prune branches to keep the plant extra-compact if you are gardening in a small space. Not all plants respond well to the drastic operation of rejuvenation pruning, but spirea is one that does. If you do decide to prune, you can do so in late winter to early spring without fear of losing your spring flowers because this plant blooms on new wood.
Propagating Gold Mound Spirea
The easiest way to propagate the shrub is by softwood cuttings.
Growing from Seed
Although spirea tends to reseed itself, the seeds won’t produce the same results as the parent plant because Gold Mound is a hybrid. Therefore the recommended propagation is from cuttings.
Potting and Repotting
Because of its compact size, this spirea is suitable for container growing. Choose a container at least one inch wider than the diameter of the plant’s root system or its current pot, and make sure it has large drain holes. Terracotta pots are ideal because they let excess moisture evaporate and they are heavy enough to keep the plant upright in a wind. Like all container plants, it needs to be watered and fertilized more frequently, about one every month during the growing season. Use a diluted all-purpose fertilizer, half the strength of what is indicated on the label.
Overwintering
Gold Mound spirea is hardy to USDA zone 4 and does not need any winter protection when grown in the ground. When grown in a container, on the other hand, the roots are not sufficiently protected from winter chills. You do not need to bring the plant inside but provide additional insulation around the container. You can either build an insulating silo, or wrap the sides of the container with bubble wrap, or burlap and an additional layer of plastic wrap.
How to Get Spirea to Bloom
If your spirea isn’t blooming, it could be that it is not getting enough sunlight; the shrub needs full sun to bloom. Another possibility is over-fertilization with nitrogen, which produces foliage but no flowers. Cut back on the fertilizer, or, when you fertilizer it before the next growing season, use a fertilizer high in phosphorus.
Common Problems
Because Japanese spirea spreads rapidly by dispersing a large number of tiny seeds, and outcompetes native species in natural habitats, such as forests and meadows, it is considered an invasive plant in several US states.
