When planted right and in the right spot, Japanese Spirea shrubs are exceptionally easy to grow and care for. 

Japanese Spirea are mounding, deciduous, summer flower shrubs that fits nicely as accents in small garden spaces. In larger landscape borders they are often planted in groupings or mass plantings and are also nice as front facing plants to taller evergreens in home foundation plantings. They can be massed on sunny slopes for erosion control and are welcome additions to butterfly gardens and container gardens.

Here's a breakdown of what you need to know to grow Spirea like the pros...



Cultural Preferences


Soil Preferences

Japanese Spirea are very easy to grow in a wide range of soils. They prefer growing in a moist but well-drained soil of average fertility. 


How To Test Soil Drainage  

If you are uncertain about soil drainage in the area you intend to plant, it's well worth taking the time to test the drainage before planting. 

To test soil drainage, dig a hole 12" wide by 12" deep in the planting area. Fill the hole with water and let it drain. Then, after it drains, fill it with water again, but this time clock how long it takes to drain. In well-drained soil the water level will go down at a rate of about 1 inch an hour. A faster rate, such as in loose, sandy soil, may signal potentially dry site conditions and the need to add top soil, peat moss or composted organic matter to the native soil. A slower rate indicates poor draining soil and is a caution you need to improve drainage or look for plants which are more tolerant of wet or boggy conditions.


Soil pH

Japanese Spirea grow best in an acid to slightly alkaline soil ranging between 5.5 to 8.0 on the pH scale. Most average garden soils fall between a pH range of 6.0 to 7.0. 


How To Test Soil pH  

Soil pH is a measurement of the alkalinity or acidity of soil and is measured on a scale of 1-14, with 7 as the neutral mark. Any measurement below 7 indicates acid soil conditions, and anything above 7 indicates alkaline. 

If you're unsure about the pH of your soil, and whether or not it's suitable for growing Japanese Spirea, it's a good idea to test the soil pH in the planting area. You can quickly test soil pH with an inexpensive soil pH tester probe. To raise the pH (make more alkaline) you can add pelletized limestone to the soil. To lower the pH (make more acid) you can apply Soil SulfurAluminum Sulfate, or Chelated Iron. Adding organic compost to the soil or using compost as mulch can also help to increase acidity and maintain acid soil conditions.




Light Preferences

For the best flower production and foliage density, I suggest planting Japanese Spirea in full to mostly sun, however plants will tolerate part to mostly shade. 



How To Plant Japanese Spirea In The Ground

Scroll down for container planting instructions and care tips


Step 1

Start by digging your planting hole at least two to three times as wide and as deep as the height of the rootball of your Spirea plant. The wider the hole the better. Place native soil removed from planting hole around the perimeter of the hole, in a wheel barrow, or on a tarp.


Step 2

Depending on the type, fertility and porosity of the soil in the planting area you might want to add a soil amendment to the native soil removed from the planting hole. When planting Japanese Spirea in dense clay or poor quality soils it is beneficial to thoroughly mix organic matter such as bagged top soil and/or a good planting mix at a 25-50% ratio with the soil removed from the planting hole. When planting in very sandy or quick-draining soil mixing in some top soil, peat moss and/or compost will help to retain moisture in the soil. When planting in moist, well-drained soils of average fertility there is no need for adding a soil amendment.


Step 3

To remove your Spirea from the container it was growing in first squeeze the sides of the pot to loosen the root ball. The very gently try to remove the root ball from the container. If the root ball is stuck in the container use snips or a utility knife to cut the container away. After having removed the plant from the container, gently loosen some feeder roots around the surface of the root ball.


Step 4

Set your Spirea shrub in the planting hole so that the top edge of the root ball is at or just slightly above ground level to allow for settling. If necessary, add some backfill soil mixture to the bottom of the hole to achieve proper planting height. 


Note:  If the soil is poorly drained (constantly soggy or wet) improve drainage or select a different plant species tolerant of wet soils. 




Step 5

After setting your Spirea in the planting hole, use one hand to hold the plant straight and your other hand to begin back-filling your soil mixture around the root ball, tamping as you go to remove air pockets. When you have filled the hole to the halfway point you can soak the soil. Then continue back-filling to the top edge of the root ball. To avoid suffocating your plant, avoid placing any soil on top of the root ball.


Step 6 (Optional)

When planting your Spirea in a site far away from a water source and in well drained soil, you can use remaining soil mixture to build a 2 to 3-inch high water retaining berm (catch basin / doughnut) around the outside perimeter of the planting hole. This basin will help to collect water from rainfall and irrigation which can help reduce the need for hand-watering. The berm can be removed after a growing season.


Step 7

Next, deeply water the planting area, including the root ball, to a depth equal to the height of the root ball. For an extra boost, you can water your newly planted Spirea with a solution of Root Stimulator, which stimulates early root formation and stronger root development, reduces plant shock, and promotes greener, more vigorous plants.


Step 8

To conserve moisture and to suppress weed growth, apply a 1 to 2" layer of cured, shredded or chipped wood mulch or pine straw around the planting area. Avoid using freshly chipped wood for mulch until it has cured in a pile for at least 6 months, a year is better. Avoid placing or piling mulch directly against the base of your plant as this could cause the bark to rot.




How To Plant A Spirea In A Container


Japanese Spirea growing in pots appreciate a moist, but well-drained soil. Constantly soggy soil can and often will cause root rot or other harmful or deadly plant diseases. Therefore, I suggest a container with a drainage hole(s), and a quality potting soil or potting mix, or a 50/50 combination thereof, for planting. Optionally, you can add 10 to 20% pumice or Perlite to the soil mixture to help with drainage.

Choose a container that is large enough to allow for 2 to 3 years of growth before shifting up to a larger size container. This might mean your planting pot would be 6 to 8 inches or more in diameter (width) than the root ball of your plant. 

Container color will matter as well. Not only will you want to pick a color of container that goes well with the foliage and flower colors of your Spirea, you'll also want to pick a container that matches the style of your home or other structures and other plants in the surrounding environment. 

Many nursery & garden centers offer a wide variety of containers to choose from. Before heading out to buy a container take pictures of your home and the surrounding environment. Doing so will help you to choose just the right color and style.


Container Planting Instructions


Step 1

Before filling your container with the soil mix, I recommend lining the bottom with shade cloth or a porous landscape fabric. This will keep the drain holes from becoming clogged with roots and soil. If you place gravel or other materials in the bottom of the pot lay the fabric over it.


Step 2

To remove your Spirea from the container it was growing in first squeeze the sides of the pot to loosen the root ball. The very gently try to remove the root ball from the container. If the root ball is stuck in the container use snips or a utility knife to cut the container away. After having removed the plant from the container, gently loosen some feeder roots around the surface of the root ball.


Step 3

Pour a small amount of your soil mixture in the bottom of the container. Set your plant in the container and make necessary adjustments by adding or removing some soil so that the top edge of the root ball will sit approximately 1" below the rim of the container.




Step 4

Backfill with your soil mixture around the root ball, tamping as you go, until the level of potting soil is even with the top edge of root ball.


Step 5

Water thoroughly until water starts to drain from the holes in the bottom of the container. Add more soil mixture if settling occurs during watering.


Step 6 (Optional)

Apply a 1/2" layer of wood chips or sphagnum moss to soil surface to help conserve moisture. 





Caring For Japanese Spirea


Japanese Spirea plants are very easy to care for and maintain. Following the tips and instructions below will have you growing them like the pros.



How To Fertilize Japanese Spirea


In The Ground:  Fertilize your Japanese Spirea growing in the ground in late winter or early spring with a slow-release shrub & tree type fertilizer or a natural, organic plant food. Before applying fertilizer, always carefully read and follow instructions on the product label.

In Containers:  Fertilize Japanese Spirea growing in pots and other containers in early spring and again in early summer with a slow-release granular plant fertilizer or water soluble liquid fertilizer listed for use in containers. 



How To Water Japanese Spirea


At Planting Time

Immediately after planting deep soak the soil in the planting area to a depth equal to the height of the plants root ball. For an extra boost, to stimulate early root formation and stronger root development you can also water you newly planted Japanese Spirea with a solution of Root Stimulator, which reduces transplant shock and promotes greener, more vigorous plants. When planted during the winter dormant season plants will require less water. So, be extra careful not to overwater during winter!


During the First Growing Season

In average garden soil you should not have to water your newly planted Japanese Spirea every day. More often than not, this causes soggy soil conditions that can lead to root rot and other harmful plant diseases. In the absence of sufficient rainfall, water only as needed to keep the root ball and surrounding soil damp to moist. Keep in mind that deep soaking less frequently, and allowing the soil to dry out somewhat before watering again, is much better than splashing just a little water on the plants every day. 


Thereafter

When established, Japanese Spirea are moderately drought tolerant plants that will require supplemental water only in prolonged periods of summer drought. If you see leaves wilting or curling, or stem tips drooping, this is an indicator your plants could use a deep soaking.


In Containers

Japanese Spirea growing in containers will require more frequent watering, especially during the hot summer months. Use your fingers or a moisture meter to check soil moisture frequently. Provide water when the top 2 inches of soil has become dry. 


Note:  When watering with an automated irrigation system it's best to set your timer to water during the early morning hours and not in the late evening or at night, which can lead to the onset of fungus and other foliar diseases. During the first few weeks after planting, check soil moisture often and adjust irrigation time if necessary to keep the soil moist, not wet. 



How To Prune Japanese Spirea


Japanese Spirea do not require pruning however respond well to and benefit from it.


Late Winter Hard Pruning

In late winter, before or just when new leaves begin to appear, I always give my Japanese Spireas an annual rejuvenation pruning. At this time I use bypass hand pruners or hedge trimmers to cut dwarf varieties, such as Little Princess, Gold Mound, Gold Flame, and Magic Carpet, which grow 1 to 3 feet tall, back to about 4 to 6 inches above the ground. Taller growing varieties are cut back to 10 to 12 inches above the ground. 


Summer Pruning

Removal of spent flowers after the summer bloom encourages heavier rebloom. You can use bypass hand pruners to snip each spent flower cluster stem off just above a set of fresh leaves. Alternatively, you may also use hedge clippers or trimmers to lightly shear plants to remove all spent flowers after the first bloom cycle. 


Maintenance Pruning

Any time of year, bypass hand pruners can be used to cut back stray shoots that are spoiling the shape of the plant. When removing a stray shoot, make your cut  at a point along the shoot even with the main profile of the plant. 

Remove damaged or dead branches as they occur. But back to a point beyond the breakage, or to the nearest healthy branch intersection, or back to the ground if the damage extends throughout the stem.


 



Plant Long & Prosper!

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