Lilac Care and cultural information

by Frank Moro
copyright 2002-2007
The lilac world is far more complex than the gardener may think. Lilacs have been cultivated for over 300 years and have survived the test of time. Much of their history originates in Asia and Europe. They were brought over to the Americas to become the spectacular plant that is today part of our heritage.
Fragrance, hardiness, bloom, names, childhood memories and even dates -
Everyone has there reasons to feel an attachment to lilacs and that is why it is so widely planted and is part of North American history.
Some past presidents such as Thomas Jefferson made note in his writings about the lilacs in his garden back in 1767 and so did George Washington in 1785.
There are many places that have lilacs that have seen many generations go past them such as the Wentworth-Coolidge Mansion in Porthsmouth New Hampshire and in Makinac Island, Michigan that claim to have the oldest lilacs in North America. Some lilacs have been planted by in the 1600’s
There are 18 species of lilacs that cover over 1800 named cultivars.
The most common lilacs we all know and usually refer to as French hybrids are the Syringa vulgaris. The specie originated in Eastern Europe and was found in the wild for the first time in 1828.
It was previously cultivated for centuries before in Turkey. In 1563 it was brought over to Vienna where many of the nurserymen began to make selections and name clones in the late 1880’s.
One family, the Lemoine’s did many crosses in the late 1800’s and early 1900’s. There total number of named cultivars are about 200.
Since that time many other very dedicated hybridizers have done work on lilacs like Father John Fiala, Fenecchia, Havemeyer, Skinner, Preston, Kolesnikov and numerous others. They have bred many different cultivars that are now just beginning to surface on the market.

There are some main flowering periods that all species can be broken down into:
early, mid flowering, late flowering and very late.
If one would plant a cross section of each specie it would be possible to have lilacs flower for a 5-6 week period.
Recently many new dwarf lilacs have been released on the market and they make an interesting attraction to the garden because of their possibility to stay small. They are from the meyeri, patula or hybrids of these two at times. Example of these would be Syringa patula Miss Kim and Syringa meyeri Palibin. Others would include Syringa x Josee and Syringa x Tinberbelle as well as some others developed by Select Plus Nurseries that will be released in 2001 and 2002.

Syringa hyacinthiflora lilacs bloom about 7-10 days prior to the vulgaris lilacs. They look and smell very often like the vulgaris lilac but have been proven to be more tolerant to warmer climates thus flowering as far as zone 8 USDA.
Later flowering lilacs usually flower 10 days after the vulgaris lilacs and have some very distinct fragrances, leaf shape and growth habits. They have a burnt spicy cinnamon fragrance. Their leaves are longer and thicker as well as they do not sucker at all like the vulgaris and hyacinthiflora’s. They also have a tendency to retain a much fuller look to the ground and grow much more rapid than other lilacs.
The latest bloomers are two species that are large shrubs reaching to 25-30 in height and can be considered tress. They are the Syringa reticulata and Syringa pekinensis. Both of these have creamy white flowers that smell very much like honey and have cherry colored bark.
Lilacs are plants for colder climates and must have a dormancy period in order for them to flower. In warmer climates colors will have a habit to be more washed out also. Lilac lovers who wish to have lilacs flower in warmer zones can activate the equivalent dormancy by depriving the lilacs of water thus forcing them into dormancy. Once water is reintroduced a few weeks later new growth will begin and stimulate the flower buds to flower.

International Lilac Color Classification


All lilacs are broken down into 7 basic color classifications. This color code is taken when florets are 1/3 in color stage.  Lilacs referred to as an example as D-4 refers to a lilac that is double in the class 4 category. S refers to a single flower and D to double.


All lilacs are divided into single or double florets. Single florets usually have 4 petals and double florets look like there are two sets of flowers in the same petal. Today there exists another form of single florets which are quite unique. These can be referred to as multi-petaled florets. Although single the florets may have up to 40 petals arranged in a single row. Examples of these are Rochester, Wonderblue, Flower City, Blue Delft and others. Not all florets will be the same and they are quite exceptional.

Bloom Table of different Species

The gardener must learn to mix species and extend flower times in order to fully enjoy the whole season of lilac time that can spread through 5-6 weeks. There are even some new hybrids that either rebloom or are still under study from Select Plus Nursery that should rebloom and will be released in coming years. Not only  is extended bloom time offered but also either colorful summer foliage or even fall foliage a possibility. There is much to be learned in the lilac world by all.

Early blooming

Syringa hyacinthiflora  Syringa pinnatifolia
Syringa oblata   Syringa Rhodopea

Mid Season blooming

Syringa patula  Syringa meyeri
Syringa vulgaris  Syringa microphylla
Syringa pubescens Syringa x chinensis
Syringa julianae  Syringa debelderi
Syringa x persica  Syringa potanini

Late blooming

Syringa emodi  Syringa x henryi
Syringa x josiflexa Syringa komarowii
Syringa x nanceiana Syringa x prestoniae
Syringa reflexa  Syringa sweginzowii
Syringa tomentella   Syringa Tigerstedii
Syringa wolfii  Syringa yunnanensis

Very late

Syringa reticulata  Syringa pekinensis

20 Of the best Lilacs

These lilacs were chosen either for fragrance, exceptional bloom coloration, or value to the lilac collection for rarity.

chinensis ‘Duplex’: The only double chinensis with lavender red tones. Rare.
hyacinthiflora ‘Lavender Lady: Large fragrant florets and nice fall color.
hyacinthiflora ‘Maiden’s Blush’: The best single fragrant pink in our collection
hyacinthiflora ‘Sweetheart’: A double early, fragrant and has magenta buds with  delicate powder pink florets.
vulgaris ‘Agincourt Beauty’: Dark single violet with petals the size of a dime.
vulgaris ‘Blue Delft’: Multipetaled blue with crisp color and good fragrance.
vulgaris ‘Duc de Massa’: Large pinkish lavender florets that are sweetly fragrant.
vulgaris ‘Krasavitsa Moskvy’: Pale pink buds open to triple polyantha like pure  white fragrant florets.
vulgaris ‘Nadezhda’: Double blue fragrant florets that are paler on the inside.
vulgaris ‘Nebo Moskvy’: Double blue color of a Blue Jay’s shade with twisted florets and extremely good fragrance.
vulgaris ‘Silver King’: A unique lilac that has silvery colored florets.
vulgaris ‘St Margaret’: This lilac puts to shame any double white with panicles  exceeding 15 inches in length and a supreme fragrance.
vulgaris ‘Wonderblue’: Simply the best sky blue you will ever see.
vulgaris ‘Wedgwood Blue’: Beautiful blue with florets showing pink on their  undersides.
vulgaris ‘Windsong’: Seen bloom for the first time ever in 2000, luminescent  bright single pink that is astounding.
vulgaris ‘Yankee Doodle’: One of the darkest single purples available
vulgaris ‘Znamya Lenina’: Huge fragrant dark single red blooms
x ‘Josée’: The only lilac that can rebloom 3-4 times a year
Meyeri ‘Snowstorm’: A dwarf that is pink in bud and opens to a white.  3-4 ft.  high.
prestonia ‘Nike’: one of the darkest purple prestons

Unique Lilac

Over the last 5 years a very unique lilac that existed since 1974 came to my attention. It is Syringa x Josée. A single pink it has the capacity to rebloom 3-4 times per year on good warm sunny summers. I have seen it flower until the end of October. There is a little extra work to be done on it as removing all faded flowers as soon as they dry up. It tens to seed very heavily thus it gets lazy. Also it must be sheared round to even out the plant and stimulate new growth. This will allow the bloom cycle to repeat itself in about 6-8 weeks.

The Perfect Lilac

What is the home owner or lilac lover looking for in the perfect lilac?
The answer varies from person to person. The most common answers are :
-be highly fragrant
-be mildew resistant
-produce or in some cases not produce suckers
-be plentiful in bloom yearly
-not get too overgrown
-have some fall color
Every individual has their personal criteria to be met and there are some lilacs that are better than others.
What may be important criteria for one person may be lower in the list of another’s.
One suggestion is to make a list from most important to least and visit collections and talk to people that are knowledgeable. They will be able to guide you to some better choices. The harder part of the task is to find the suggested plants. Most retail nurseries have been carrying the same lilacs for many years. I suggest to not settle for anything except what you have decided on.
There are many collections across Canada and the USA to visit and you will be amazed of what does exist. Take photos and make records for the lilacs you plant will last many years in your garden.

Propagation of lilacs

1- suckering
2- softwood cuttings
3- grafting
4- tissue culture

Most gardeners have had the chance to dig up a sucker from a friend’s garden with usually good success. This method is basically by severing a sucker or offset form the mother plant. This can be done in the spring or fall. One suggestion is to sever the plant one season prior to the time you wish to move it. This will give the new plant a chance to better establish a stronger root system before transplanting occurs.

Softwood cuttings or tip cuttings can be done in late spring and does require a controlled environment such as a greenhouse and automatic misting system. It can be done manually but is quite a task.

Grafting was used widely by nurseries in the past. Either privet, ash or other lilac species can be used to accomplish this. Upon a 3 year study at our nursery we have noticed that lilacs that are grafted when replanted deeper than the graft union, the grafted scion wood will root on its own and create the original plant. Another advantage of grafting on a established root system is the lilac can flower within 1 year of grafting. This thus brings an advantage to gardeners who would like to see lilacs flower at a younger age. The best understock would be prestonia because they do not sucker and are not invasive as privet may be. Also if any side shoots do grow the leaves are long and of a different texture than the hyacinthiflora or vulgaris species.
A new method that is being used today is tissue culture. This requires equipment that is costly and is mostly aimed at large nurseries to propagate large quantities of lilacs quickly.

Selecting Quality Plants

Selecting lilacs once you have made a choice can be another lesson in itself. There are 2 basic ways to produce plants. One is in field and the other is in a container.
Field grown plants can be sold in different formats. One is called ball and burlap. Usually nurseries who offer larger plants will sell their lilacs this way. It requires digging a ball of soil around the plant and removing the lilac from the soil and placing it into a piece of burlap. This is then tied tightly. The disadvantage of this is that many roots have been cut and even if the plant does flower the same spring it may not reflower for 3-5 years again. Leaves will usually be small and flowers also for that year.
Another way a field plant can be sold is in a freshly potted peat pot. These pots are biodegradable so in time the roots will be able to go through the pot. If a freshly potted lilac is sold in a plastic container be weary of it. If the plant is in leaf and it is early spring it will be very difficult to remove the lilac form the pot without disturbing the root system. This can go as far as having the plant wilt severely and even die in certain cases.
The second way to produce which is more common today is in containers. This method means the plant has been in the pot for at least one year and has a complete set of roots built up in that pot. When removing the pot from the plant the soil should stay intact and roots should be well developed throughout the soil. The advantage is that there will be no stress on the plant when it is planted. Also it will flower earlier since no roots have been cut and that it may continue to grow at a normal rate. It is important to keep records of names of your lilacs so you may let other people know what you have when conversation arises about your plant.

Lilac Care

 There are four basic rules for lilac care; provide good soil, good drainage, plenty of sunlight and scheduled pruning.

Planting site

The location for planting your lilac(s) should be chosen with care.
 Integrate the lilac with other garden plants. You may want to plant according to prevailing winds to make best use of fragrance.
 Make good use of available sunlight; try a south or westerly spot out of the way of doors or windows. Avoid planting along walls or among large trees (or trees which will grow tall). Use complementary shrubs, plants, or other garden outcroppings to enhance the appearance before and after bloom. Lilac spacing should be a minimum of 6 ft. apart, 10 ft. is better. Crowding invites sky reaching and requires more frequent and drastic pruning.


 Lilacs require a minimum of six hours of direct, daily sunlight. The amount of sunlight dictates the appearance, color, and quantity of   bloom. Too much sunlight is better than not enough. When there is a lack of light lilacs will either flower very little or not at all. This is one of the biggest problems gardeners encounter.


Good drainage is characterized by the soil’s ability to retain sufficient moisture to nourish the root system while still being able  to drain off excess moisture.
Lilacs do not thrive in soggy soil. Try digging a hole about 8 in. in diameter by about 12 in. deep and filling it with water. If the water has not drained after 1 hour, consider improving the drainage at the present site by creating a mound about 12 inches high and 2-3 feet round. Plant your lilac in this mound to create a better drainage.

To improve drainage:
1. Remove the topsoil from the actual planting site (an area equal  to 2 to 3 times the lilac’s soil ball/root system)
2. Mix sand and/or fine gravel 6 in. to 10 in. deep into the subsoil (not the topsoil)
3. Mix the topsoil with peat, vermiculite or any other porous additive to cover the root system once the lilac is planted.


The planting hole should be generous enough to easily accommodate the lilac root system. Adding compost is recommended. Bone-meal or ground limestone may also be added to reduce the acidity of the soil. When planting, place the top of the soil ball level with the surface  of the hole. If the lilac is bare-root, the top layer of roots should be a few inches below the surface. When back filling, it is important to   water well, but do not flood, and avoid compacting the soil around the root system. The idea is to remove air pockets, yet keep the  soil well aerated.
If the only available site is always moist or collects rain water that remains for extended periods, lilacs should be mound-planted.
This is a more involved, but successful planting solution.
Remember to water your lilacs regularly throughout the summer.
During the dry season, water more frequently, keeping the leaves pert, not limp. This is when added mulch will pay off. Please remember that a lilac takes 3-5 years to reach full potential color and bloom size. Soil textures and compositions will also play a little on colors. Also warmer climates such as 7-8-9 may expect lighter coloration because of the heat.


This is always a very popular question. Transplanting should be done in spring or fall when the plant is in dormancy. As lilacs have a root system that is very shallow it is important to prune the roots no closer than the drip line of the shrub. Once dug out the new whole must be selected according to our section named planting a lilac. It will be normal for the lilac to have smaller leaves for 1-2 years as well as no flowers for 2-4 years. The plant will need to have all its physiological needs met again and good roots before it will flower. It is also important to cut back the plant by 1/3 when transplanting. Since you are removing roots, this will not make the plant suffer so much. Less roots, less branches to sustain = better chances of quick recovery. A good recommendation would be to use either bone meal or a liquid transplanter such as 15-30-15.

Leaf Spotting and Browning

Some common problems that can occur when there are very high winds in late spring and early summer is leaf spotting and browning. These are only physical damages and will fix themselves. It happens when the wind and heat is just too much for the plant to get up the appropriate amount of water needed. Small brown spots are one indication and total leaf browning a more advanced state. Irrigate the plants in evening or early morning before the heat of the day. Water from ground level is best trying to not wet the leaves if possible


Late frosts in the spring can damage both young leaves and flowers in the spring. If they become damaged they will begin to blacken. The best thing to do is to prune out to 6 inches below the frost as quick as possible. This will permit the secondary buds below bark level to become stimulated and grow. You will lose the bloom for that year but at least the plant will reshoot. It would be good also to sterilize the pruners in 70% rubbing alcohol between each cut.

Lilac Tidbits and Old Tales

True: Lilacs love a sweet soil so adding some horticultural lime in the fall will help not only the ph level but will result in better smelling lilacs.
True: Like a fine wine lilacs depend immensely on the previous years weather to help contribute to their fragrance. If the spring is hot and rainy this will result in poorly scented fragrances. If however the spring was cool and sunny this will increase the sweetness of the fragrances.
False: Kicking lilacs at the base does not help flowering. It only damages the trunk. Lilacs flower when all physiological requirements are met. They are like children they learn to flower as children do for talking and walking; When they are ready.
Pruning and Fertilizing
The best fertilizer is one that has the second number in its composition at least twice as high as the first. This will encourage bloom and not push the foliage too hard. An example of this would be 5-10-5. Fertilizers are different from each company so it is difficult to give an exact number. The fertilizer should be applied at the base of the plant in early spring to help the plant requirements for the year coming. Buds are set the year previous so the fertilizer will work on this years leaves but next years bloom. Mulching lilacs is also important. Using mulch helps reduce the heat stress lilacs have in the summer and will hold water better for them during the summer. Lilacs need regular watering during the summer also. If you see the leaves getting limp or droopy during summer months it is a sign that they need to be irrigated.
Pruning is not mandatory every year on main stems but cutting of faded blooms within a week of when they are spent will help the plant concentrate on preparing more flower buds and not seeds. As any landscape plant pruning should be done immediately after flower period. Once your lilacs have reached heights that no longer are pleasing to view or smell flowers one should rejuvenate their plant over 3 years.

Proper place to deadhead lilacs              removing 1/3 of bigger stems

By cutting 1/3 of the main stems that are at least 1.5 inches in diameter down to the soil, this will allow new shoots to grow again. Doing this over the three year period will allow the lilac to continue to flower and refresh its look. If the lilac is a single trunk then it is not recommended to do this. Then remove the 1/3 of the trunks 12-15” above the main break of branches. Lilacs are plants that naturally shoot from the base and this is the best way to encourage the plant to grow. Branches that come from higher in the trunk are generally weaker even if they shoot long growth out. The angle of growth makes them susceptible to breakage in the winter with heavy snows or freezing rains.
If you wish to remove dead flower heads it can be done by cutting just below the flower head.
Lilacs will grow to 15-20 in height if not pruned. A good height to keep them at would be 6-9 feet. Dwarf varieties of course so be kept smaller. This recommended height will make the blooms more accessible to smell, view, and cut. Also younger branches will have a better quality bloom as far as size.


Lilacs are very hardy and don't require any special precautions for winter. It is recommended, however, to protect the trunk of the lilac; lilac bark makes a good meal for hungry rodents.

Lilacs as Cut Flowers

Here are a few good tricks to get your lilacs to do well as cut flowers. Always cut your lilacs in the morning when they are full of water. Make sure to cut with a very sharp knife or pruners and immediately plunge the stems into warm water about 70 degrees or 21 Celcius. When you bring the flowers in, re-cut each flower under water. When flower stems are cut under water, water is pulled into the stems more quickly. Flowers never re-cut after picking can loose up to 60 percent of their potential vase life. This helps it absorb more water. Stems should be scraped a few times to help water absorption. Adding a teaspoon of sugar for carbohydrates into a clean vase will also help. Keep the water and vase clean as scum will block the pores. Changing the water and food often is also an important weapon against exponentially breeding bacteria (aka. scum), which shorten a flowers life span. To optimize their life span, place flowers in a cool place, away from direct sunlight, heat, air ducts.
When the arrangement is complete, the temperature of the display location has a tremendous effect on the vase life of the flowers. Flowers in a 45-º F room deteriorate three times faster than at 35 º F. Therefore, display the arrangement in a cool area out of direct sunlight.

Insects and Diseases

Bacterial Blight
This disease is appearing more often than in the past. Lilac blight as it is referred to, occurs where there are fluctuations in spring temperatures along with cold rains. Plants get what are seemingly blotches on their leaves. These later begin to wilt and turn brown. Leaves will drop and new green shoots will have a sick pendulous look to them. Flower buds may also be infected by turning black. There is little one can do except spray with Benomyl or another fungicide called Bordeaux which is a copper sulfate mixture. Pruning out infected areas is very important and pruning should be done 6 inches below infected areas and pruners must be dipped in 70% rubbing alcohol for disinfecting. A lilac that is kept properly pruned in a open shape and well fertilized will be less susceptible to this bacteria.

Leaf Roll Necrosis
This is caused by air pollutants. The lilac being a plant from the mountains will begin to degenerate when faced with pollution. Branches will die and in time the whole plant will follow. There is not much to be done except to respect our environment. Lilac love clean air.

Lilac Leaf Miner
This problem is becoming a little more apparent in the east. The name of this culprit is Gracillaria syringella. The leaf miner has three cycle periods, the end of May, end of June and once again in the fall. The moths lay their eggs on the underside of the leaves and once they hatch the young insects begin to eat the inside of the leaves. The leaves become a little blackened and they separate like a wafer. If you separate the leave the young worms are visible to the eye. A systemic insecticide is the only control for this pest. It should be applied at the first sign of damage and will control it in 1-2 days. A systemic insecticide will travel through the sap of the plant for a period of 2 weeks. Contact insecticides are of no use.

Lilac Scales
There are two kinds of scale; oyster scale and San Jose scale. These must be taken seriously for they can eventually kill a plant. These scales can be brought to your lilacs via hosts such as birds and other kinds of plants such as willows and ash. Mites are brown scales that attach themselves to the bark. They are hard to kill and must  be sprayed at the right time. Spraying must be done at over 60 degrees Fahrenheit when the insects are on the move. Diazinon or Malathion can be used. A systemic insecticide can also be used. If branches are very infected one may choose to cut it out completely and discard it.

Phytophthora Blight
This is a soil born fungus that kills the root sprouts and shoots. It is found most often in wet weather areas. Once on the plant, it can spread by raindrops or water droplets splashing from one leaf to another. Copper sulfate is an excellent way to control this fungus.

Witches Broom
It appears mostly on late flowering lilacs where the growth is congested or dwarfed. It usually does not happen in the home owners gardens but mostly in large collections. If pruning these plants it is important to disinfect the shears before cutting other plants.

Lilac Borer
The lilac borer is one of the hardest insects to catch. They usually make their way into the plant at its base through old wounds. The borer makes its way into the cane, eating the cambium wood, which is the wood that lets sap flow. As the wood gets eaten around the branch of the old trunk, the specific branch becomes weaker, leaves begin to yellow and the branch will die. The only visible external signs is sawdust deposits at the base of the plant and a entry hole at the trunk. The best way to control this is to cut the weakened branch and destroy the larva.

Mildew is caused by a fungus called Microsphaera alni. It appears in the later part of the summer and leaves a white powder on the leaves.
Spores are most active when the weather is hot and humid. Certain lilacs are more susceptible than others. One can use a sulfur wettable powder to control naturally. Another product that can be used is Benomyl which is a systemic fungicide and should be applied right after flowering. It knocks out the spores and prevents the symptomatic white cast.  I am sure you can find organically based alternative fungicides also.  Preventative measures such as
removal of infected fallen leaves reduces subsequent infections.  Pruning the lilac shrub with a slight degree of openness allows a greater airflow through the shrub, thereby reducing the amount of spore inoculation.  Warm, moist, environmental conditions favor the development of the fungal spores, so some years will show worse infections than others. This is only a cosmetic fungus and will not harm the plant. In the fall clean away the dead leaves after they fall is another way to control this.

Rodents and Deer
In some areas these animals can be a problem. Rodents will usually go after lilacs when they are young. This can be avoided with some wrapping of the trunk with tree wraps sold at garden centers. As for deer a number of ways has come to my attention. One is to have a solar powered light with a motion detector in the garden that will light up at night. It will have to be moved on a regular basis or they will get used to the location. The other is to hang strands of human hair in the lilacs. This apparently puts out our odor which can discourage them to come around.

Lilacs are water loving plants but do not like to sit in water. In the summer if the leaves lose their shine, borders of leaves brown a little of the leaves look limp it is a sign of a lack of water. Irrigation would be needed. In warmer climates water withholding can be used as a tool to initiate dormancy and have plants flower in the spring.

The most popular lilac questions:
Why doesn't my lilac flower?

-      Usually a lack of sunlight can be an initial problem. A minimum of six hours of sun is needed per day.
Too much nitrogen (the first number in a fertilizer) can be a problem. Often lilacs are planted in the lawn and fertilizers used to green up lawns are too high in nitrogen. This causes beautiful green foliage but little bloom. Avoid going around the plant and use suggested fertilizer.

No bloom after first year. Lilacs are sometimes purchased as bareroot or ball and burlapped plants. These will flower the same year but not reflower for 3-5 years. The flowers were made from the previous year and it is normal that the plant will have to make new roots and get settled in for a few years before it reflowers. The best way to purchase lilacs are containerized plants. These are lilacs that have passed at least one year in the container it is in. They will have a complete root system and will reflower at an earlier age.

Improper pruning time often is another problem. Some lilac lovers prune their plants at the wrong time. They should be pruned after flowers are faded within 2 weeks. Any other pruning will result in the cutting of flower buds.
Lilacs should take 2-3 years to flower once planted if they are in full   sun and are well drained. If they don’t talk to a specialist.

With all this in mind lilacs are still very easy plants to grow and enjoy for years and unlike other some other plants require very little care.
Offer one to a child so they may have the same fond memories as we do about this heritage plant.