Propagating Spirea

Spirea shrubs are just as easy to propagate as they are to grow in the garden. There are three methods to multiply your spirea stock: dividing up sucker growth, air-layering semi-woody branches directly in the garden bed, or taking soft and hardwood cuttings from non-blooming stems from mid to late summer.  All of the methods are easy to learn and none involve specialized tools or equipment to obtain healthy new plants

Methods To Propagate Spirea

The easiest method of propagation is to transplant suckers growing from around the base of your spirea. Dig the suckers out, leaving as much root attached as possible, and pot them in containers large enough to snuggly fit the rootball. 

Layering low-growing stems on the surface of the soil is another low-maintenance method to propagate spirea plants. Make sure that at least one leaf node is in contact with the soil by pinning the branch down with a sod pin, a bent piece of wire, or a flat, reasonably heavy stone. 

The most advanced method to propagate Spirea is semi-hardwood cuttings taken in the late summer. This type of cutting will root in a matter of weeks and be large enough to plant in the garden after a year or so of growing in a protected location. 

What You Need To Propagate Spirea

For division: you will need a long-handled transplanting spade, sharpened hand pruners or garden knife, peat-free potting mix without added fertilizers or water-holding gels, and one-gallon pot (or larger, depending on the size of the rootball).

For layering: use a pocket knife to knick the stem, sturdy sod pin or rock to keep the branch in contact with the soil, peat-free potting mix, and a one-gallon pot for growing the new plant after it grows roots. 

For cuttings: use a peat-free potting mix with a 1:1 ratio of perlite or vermiculite or use straight perlite, a sharp pocket knife, a sharpened pair of hand pruners, rubbing alcohol to sterilize cutting tools, and a plastic pot 4-6 inches in diameter.

Best Time To Propagate Spirea

For division: Sucker divisions can be taken at any time of the year. Spring growth is more vigorous and will develop new roots faster. Gardeners in climates that remain mild through the fall (above hardiness zone 7) can transplant divisions until the temperatures fall to the low 40s F. Colder growing zones will have more success replanting divisions early in the spring to give them time to establish before the following winter. 

For layering: Air-layering can be done in the early summer after flowering. The stems need to be flexible enough to bend while still being thick enough to form a strong root system. 

For cuttings: Softwood cuttings of spirea are best taken early in the summer, while semi-hardwood cuttings should be taken in late summer. Avoid taking cuttings from stems that have flowers forming or in bloom. The new growth that emerges after flowering makes ideal softwood cuttings. Only take cuttings from plants that are healthy and free of pests and diseases. 

Steps To Propagate Spirea

Taking softwood or semi-hardwood cuttings is the most reliable method of propagating all types of spirea. There is no need to use a prepared rooting hormone to ensure good root growth. It is more important to take cuttings from non-flowering stems and to keep the cuttings well watered without waterlogging the soil. 

Step 1 - Cut pieces of non-flowering branches that are at least 6 inches long and up to 10 inches. Make the cut just above a pair of leaves, being careful not to harm any developing leaf buds. 

Step 2 - Remove all but the top two sets of leaves from the stem. This will provide more area for roots to form.

Step 3 - Fill a 6-inch pot with a peat-free potting mix or straight perlite and water it well, letting the excess liquid drain out before planting the prepared cuttings. 

Step 4 - Plant the cuttings near the walls of the pot, where they will receive more air circulation and root faster. Allow 5 cuttings per 6-inch pot.

Step 5 - Place the pot in a sheltered location outside where the cuttings will receive partial shade all day.

Caring For Young Spirea 

The cuttings will take 3-4 weeks to start forming a root system. Until that happens, they will require light watering to keep the potting mix damp but not waterlogged. For cuttings and air-layered divisions, new foliage growth indicates the plant has developed roots. Keep watering the new plants until they are large enough to plant out in the garden. 

Layered divisions can be cut from the mother plant when new growth is seen. You can either leave the new plant to grow in place for another year or transplant it into a pot. Lightly feed new plants with a diluted liquid fertilizer if they are grown for longer than 6 months in a pot.  

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 Author Robbin Small - Published 1-2-2024