Propagation of

French Hybrid Lilac

(Syringa Vulgaris cvs.)

By Elizabeth Bruins

There is no flower quite as beautiful and aromatic as the Lilac. Lilacs have a strong scent that carries quite a distance. Unfortunately, Lilacs bloom for only a very brief couple weeks in the spring. Weather will have a lot to do with how long your blooms last. Once the buds begin to open, pray for a cool dry spell, as this will prolong the amount of time that the flowers will bloom. Once the blooms are over, you still have a nice shade bush, but you have to wait for up to fifty more weeks to see them again.

Lilacs in the United States date back to the mid 1750's. They were grown in America's first botanical gardens and were popular in New England. George Washington and Thomas Jefferson even grew them in their gardens.

There are over one thousand varieties of lilacs to chose from if you want to have lilacs at your own home. You can enjoy a wide range of colors, sizes and types of blooms. The most common colors are lavender, white, pink, blue, and purple. There is single and double petal varieties. Bushes can grow as tall as 30 feet. And, there are dwarf sizes which only grow about three feet high.

Lilacs are a low-maintenance shrub. Lilacs are adapted to USDA Hardiness Map zones 3, 4, 5 and milder areas of zone 2. They offer good summer shade after they have reached several feet tall. They can be used as a hedgerow, to provide privacy  from neighboring properties. Lilacs do not like to get their roots wet for a prolonged period of time. They do best on hillsides, slightly elevated areas, or level ground where there is good drainage. Lilacs do not grow well in lowlands where water tends to collect for prolonged periods of time.

There are many ways to propagate lilacs. You can propagate them by seeds, cuttings, grafting, air layering or tissue culures.

Propagation by Seeds

Growing lilacs from seed is an uncommon approach. Growing from seed takes time and patience. It usually takes 3-4 years before you will finally get your first lilac blossom. Horticulture greenhouses do plant them by seed in order to use them for rootstock for other methods of propagation. At the end of the season, you can harvest the seed from the dead flowers after they have dried, but before they fall out of the seed pods onto the ground if you would like to try planting your own lilacs. If you are going to do this, you will need to go through a process of stratification (or a cold period) of 40-60 days in order to remove the pysiological dormancy of the seed that is needed for germination.

Propagation by Grafting

The most common type of grafting done to lilacs are either cleft grafts or bud grafts. The process requires a great deal of knowledge and can take several months in a greenhouse or glass-covered frame, where the air is kept moist continuously in order for the grafts to take. Cleft grafting is the most common way of grafting on a commercial basis. Bud grafting is an economical and a very rapid method if you want to grow many new plants.

In order to perform a successful graft you need many things. One of the most important things is compatible stock and scion wood. The stock is the plant that is the base that has the roots and the scion is the plant that is grafted on top of the stock plant that has the leaves and nodes. You also need a sharp knife so that you get a nice, clean cut.

To perform a cleft graft, select good, healthy root stock and dormant scion wood. First split the stock with your knife. Open the crack wide enough to be able to insert the scion without much force. The scion wood should have 2-3 buds on it. Shape one end into a long, tapering wedge. The bark edge of the wedge should be slightly wider than the inside edge. Insert the scions into the wedge, making sure that the cambium layers match. Afterwards, place tape or wax over the union.

To perform a bark graft, first cut the cambium layer of the understock in the shape of a T.

Then cut the bud from the bud stick leaving a heal of wood behind the bud. I like to use a razor blade of the side injector type. Cut beneath and toward the bud. Then make another cut below the bud and away from it to intersect with the other cut. Once the bud is removed insert the bud by gently pealing back the cambium only far enough to insert your prepared bud into the T cut. After inserting, wrap the bud using a rubber band or tape from the top to the bottom.

Propagation by Cuttings

Propagation by cuttings is one of the most popular ways to propagate lilacs. Cuttings should be taken when new green terminal shoots are produced. They should be four to six inches long, but should not be left out too long, because they will wilt easily and die. The cutting should be dipped in a rooting hormone like IBA (Indolebutyric acid) which aids the plant. The cuttings can be placed in a media with peat, vermiculite and perlite. Each cutting should contain 2-3 nodes, which are the growing points where the leaves are attached. The leaves aid in rooting by producing carbohydrates for the rooting plant. The cuttings should never be allowed to dry out and should be kept moist at all times. The cutting should root within 3-6 weeks. Once roots appear, you can place the plant outside in a desirable location.

Propagation by Air Layering

Propagating lilacs by air layering is also very simple and can be easily done. First you need to pick the part of the plant that you would like. Then cut a slit at an angle 1/3 of the way through the stem just below good, healthy leaf growth.  Hold this slit open with a toothpick and dust or spray the cut with a rooting hormone.  Take a length of plastic wrap and secure with a twist tie or string around the stem below the cut you have just made.  Fill this pocket with a big handful of moistened spagnum peat moss and wrap the rest of the plastic around it making sure to over lap, and seal it to the stem above the cut with another tie. Use waterproof tape to seal the over-lapped edges of the plastic.  Make sure the peat moss is in good tight contact with the cut you have made.  Keep the peat moss moist during the rooting process by opening the pocket at the top and adding water when required.  When roots are visible in the the peat moss, cut the stem off below the root mass and pot up.

A figure of the process can be seen below:

Propagation by Tissue Culture

For more than two decades some of the leading nurseries in the US and Europe have been using tissue culture for propagating lilacs. The main reason for resorting to micropropagation is to produce large numbers of selected clones within a short period of time. Propagating by tissue culture is not done by amateurs and needs to be done in a sterile environment.

The most difficult part of the operation is obtaining material free of bacterial and fungal contamination. Succulent terminal cuttings are divided into single node 'explants' and agitated in dilute chlorine for varying lengths of time to try eliminate pathogens. Cleaned plants are placed in nutrient agar under aseptic conditions and stored under lights at a constant fairly high temperature for several weeks.

Plants free of contamination grow for several weeks in the tubes and are then ready for rooting when they make grow to 20-50 mm, or you can further divide the plants and repeat the process until the required quantity is achieved. Leaves at this stage are tiny, resembling those of young seedlings than that of mature plants. After roots are seen you can plant them in regular potting medium and place them a greenhouse.

The stages can be seen below:

As you can see, lilacs can be propagated in many different ways. No matter which way you propagate if it is done correctly you can be sure to have beautiful and great smelling lilacs for many years to come.