The common lilac (Syringa vulgaris) is a deciduous shrub in the olive family, Oleaceae. Native to the Balkan Peninsula, these plants were first introduced to Europe at the end of the sixteenth century. From there, they were introduced to the American colonies in the eighteenth century. Lilacs are commercially popular as an ornamental plant today because of their bright, sweet-smelling flowers. Lilacs have over one hundred different varieties, making it a very diverse plant loved by many.
When working with plants and cuttings, sanitation is vital. Before you begin, make sure all of the equipment and materials that will be used are sanitized. Even though the common lilac is a softwood, it is a hard to root species. With this information given, the primary method of propagation will be stem cuttings. Because lilacs are softwood species, they can lose water rapidly, so desiccation control is needed.
- Stock Plant Selection – Start by selecting a healthy stock plant. A healthy stock plant should have luscious, bright leaves. Examine the plant to make sure it is free of disease and insects. If any sign of disease or insect infestation is spotted, do not use the plant. You should select a branch with moderate thickness. Lilacs are hard-to-root species so a branch that is too thick or thin will not propagate. Because lilacs are softwood, cuttings should be selected immediately after the plant begins to resume growth in the spring or early summer.
- Cutting Selection – Select approximately three or four stem cuttings from the stock plant to ensure a better survival rate. The cuttings should be between three to five inches in length and contain two to three nodes. While making the cutting, use a sharp pruner or scissors to make a clean cut. Dull blades can damage the proximal end of the cutting. Make sure your cutting is not too old or too young. To make sure that you have a suitable cutting, select a branch and attempt to break it. If it snaps easily, the branch is of suitable age. If the cutting bends and doesn’t break, the cutting is too young. If the cutting does not bend or break at all, it is too old. Desiccation control is crucial for propagating all softwood cuttings, so it is best to plant them in the media as soon as possible.
- Rooting hormones – Once you have a cutting, dip the proximal end into water. After water, use auxin, a rooting hormone. IBA is a common type of auxin and will help to establish and promote root growth. Lilacs are softwood cuttings, so to produce desirable results, use 500-1250 ppm. There are many brands of powder, but as long as they have some type of auxin they should suffice. Tap off any excess powder from the cutting before inserting it into the media.
- Media – Desiccation control is vital when working with softwood cuttings. To ensure drying out won’t happen, use a media that has an excellent water holding capacity. Sand is the primary soil usually used in propagation of lilacs but you could also use peat, vermiculite, perlite, or even a mixture of all four. Fill the pot with the media and wet it down. Use a pot that has holes in the bottom. When water starts to drip through the holes, the soil is moist enough. Use your finger to make a hole in the center of the soil and put your cutting in the hole. Make sure the rooting powder does not come off when you plant it. Water the cutting instantly after it has been planted in the media. This will help to firm the soil around your cutting. Under these conditions, the cutting should root in three to six weeks, but it could take as long as eight.
- Care – The most important part of caring for a cutting is desiccation control. Desiccation can be controlled using a mist system and keep the plant at a cool temperature. Keep the soil moist at all times. If the soil dries out, the cutting will not form new roots. Using a mist or fog system will ensure that the cutting will be watered regularly. If you do not have access to a mist system, a daily, gentle watering will be adequate. Be sure that your soil is only moist, not completely saturated. Overwatering of the cuttings promotes fugal disease, such as root rot, ceasing root growth. A well ventilated soil and pot will prevent this from happening. Temperature during rooting should be between 23-27oC at the base of the plant. If your plant is in a mist system, the air temperature can get up to 30-32oC, as long as there is adequate lighting. Be sure to remove flowering buds from the cutting as majority of the nutrients are taken away from the roots and given to the flowers.
- Bottom heat – Bottom heat can help to induce root growth. Optimum soil temperature for rooting softwood cuttings is between 21-24oC. Commercially, bottom heat can be done in two common ways: with forced air furnaces or a hot water system. If you are not propagating your plant in a greenhouse you can use heating cables or heating mats as an alternative source for bottom heating. On days when the air temperature is warmer than recommended, lower the temperature of the bottom heat. The combination of high air temperature plus bottom heat will cause the soil to dry out rapidly. If you are using bottom heat, pay extra attention to the moisture content to ensure that the plant won’t desiccate.
- Transplanting – Starting checking the plants within the 3-6 week rooting period to observe the establishment of the roots. Once substantial rooting has been made, you may place the plant in a desirable location. It is crucial to prevent transplant shock. Prevent this by slowly reducing the amount of water the plant is getting, by changing intervals and times of the mist system, or manually do not water as frequently. As you reduce water intake of the plant, you will want to simultaneously reduce the air and basal temperatures until they mimic the environment that the plant is going to be placed in. Once transplanted, allow two or more years for the lilac to bloom.
Other propagation techniques:
There are other less popular propagation techniques that can be used on lilacs. Other methods of propagation include propagation by seeds, grafting, air layering, and tissue culture.
- Seeds – time consuming (3-4 years to blossom, 40-60 days of stratification)
- Grafting – difficult for an amateur due to all of the elaborate steps and time consuming
- Air layering – simple and easy. Start by wounding the stem of the lilac plant. Put a rooting hormone in the wound. Then cover the wound and replant it.
- Tissue culture – very difficult to keep free of bacterial and fungi. Need a completely sterile environment.
This lilacs bright, vibrant colors make it a beautiful ornamental tree that is loved my plant enthusiasts everywhere. This plant is relatively easy to propagate using stem cuttings. The most important thing to remember is to prevent desiccation. Do not leave the cutting out of the ground for longer than needed and keep the soil constantly moist. If you follow these steps, you should be able to successfully propagate this lively ornamental shrub.