Organic Garden Guide: Growing Garden Lilacs

You need to consider several things before you choose a lilac. First of all, you need to select the color of lilac flowers and also the site where you will like to grow the plant. While these are important aspects, the climate is even more vital provided you are living in a region that is on the periphery of areas where some of the best lilacs are found.

In fact, lilacs or Syringa are the solitary shrubs that come in amazing variations and also offer the gardeners living in areas having extended cold winters a wonderful choice. Majority of the lilacs need more or less 1,000 hours under 50°F (10°C) to stimulate the growth of their flower buds. Generally speaking, lilacs possess the aptitude to endure colder weather conditions even less than 50°F. Both the hyacinthiflora lilacs as well as broad-leaf

lilacs (S. oblata) are reasonably resilient. These lilacs bloom quite early in the season and, hence, their flower buds are susceptible to damage by frosts occurring late in the season. Therefore, it is important to plant your favourite lilacs on an elevated ground and not in frost pockets to allow the cold air to rest. This is particularly important if you are growing the plants in colder peripheries of lilac hardiness zones. As mentioned earlier, a majority of the lilacs require a cold winter to encourage their bud development and bloom. For instance, lilacs like S. x hyacinthiflora, S. x chinensis, S. pubescens subsp. patula, as well as a number of cultivars of S. vulgaris, will produce flowers in temperatures ranging between 10°F and 20°F (-12°C and -6°C). However, the plants may be susceptible to mildew in places having humid summers.

When to Plant

Spring is the ideal time for planting lilacs. It should be done immediately when the soil becomes warm and is workable. Be careful not to plant lilacs in soils that continue to be moist from the melted snow. Preferably, you should undertake planting lilacs during the latter half of April. Planting the lilacs early helps their roots to start growing before the onset of summer and protect them from heat and drought. In addition, spring is the time when you will get the best lilac selections. It is important not to plant lilacs very late in the season. The growth of the roots retards after the soil temperature falls to about 41°F (5°C) during fall. If you plant lilacs very late, the growth of their roots will be so sluggish that the plants will only establish themselves just before the onset of winter.

Lilac Requirements

Lilacs need a few things for optimum growth and prolific flowering – sunlight, adequate space and a well-drained soil.

Sunlight: These plants need full sunlight for no less than six hours daily. If you are growing lilacs in northern gardens, the more the sun the better it is for the plants. On the other hand, if you are growing lilacs in southern gardens, the higher and brighter the sun shines the better it is for the growth of the plants. However, lilacs have a natural preference for partial shade. When the plants are grown in some shade, it prevents the colors of the flowers from fading quickly, especially those having different shades of pink and darker hues.

Space: Lilac shrubs or trees require adequate space for proper growth. Lilacs grown in arboretums and botanical gardens are planted at a distance of about 6 feet (1.8 meters) from one another. It is better to grow lilacs 10 feet (3 meters) apart if you are growing lilacs in your lawn and using a riding mower. However, you can grow them more closely when you are using lilacs as a hedge.

Soil: Lilacs or Syringa require soils having a proper drainage system. Barring the Himalayan lilac (botanical name Syringa emodi), all other lilacs will die when the soil is waterlogged. In case you have no option but to grow lilacs in grounds where the water generally forms a puddle or the ground generally becomes damp during spring and fissures during summer, plant them in elevated beds.

If the soil is well drained, you can grow lilacs in almost all types of soil – ranging from somewhat acidic to reasonably alkaline. In fact, lilacs grow well in poor soils. The plants may not bloom when grown in extremely fertile soils or soils mixed with heavy amounts of fertilizers. Traditionally, we know that lilacs grow best in alkaline soil. This is because these plants have the ability to tolerate even bare limestones. Rather than a preference, it is a quality of their survival. However, lilacs do not survive when grown in very acidic soil – with a pH below 6.5. If the soil in your garden is too acidic amend it by adding half a cup (125 ml) of horticultural lime blended with the soil in the planting hole before planting the lilacs. Also, make sure that you spread a handful of the lime at the base of lilac plants every year during spring.

Planting Lilacs

Having selected a very aesthetically pleasing spot in your garden that either receives full sunlight or is a partial shade and has a well-drained soil with lots of space, you need to get rid of the entire stones and sod from the area where you intend to grow the lilac. Next, dig a planting hole that is roughly 50 percent wider compared to the plant’s root ball. Keep the soil excavated from the hole aside. Ensure that the planting hole is sufficiently deep so that the lilac can be planted to the same depth as it was earlier in. The hole should also be deep and wide enough to accommodate all the roots of the plant. Prior to planting the lilac, fill the hole with water.

If you are planting a potted lilac, remove it from the pot sometime before replanting it in your garden. Even pot is made from fiber should be cut or opened by tearing to free the lilac before replanting.

On many occasions, the potted plant will slide out of the container without much effort. Even in such cases, never lift the plant by holding its stem or pull it out of the pot harshly, as doing so may damage its roots. It is advised that you apply some pressure on the sides of the container with a view to slacken the root ball and subsequently hold the pot upside down or at an angle downward so that you can easily take the plant out of the container. Provided the lilac shrub or tree is considerably large and in case it is bound by its roots, you may require stepping on one side of the pot to slacken the grip of the roots. Next, slide the lilac gently out of the container and raise it by placing your hands below the root ball. In fact, you may require some assistance to keep the lilac stem in a vertical position while you move the dug out soil around its roots in the planting hole.

Generally, the roots of the relatively large lilacs are balled and wrapped with burlap after they are dug up from their original place of growth. In addition, it requires a minimum of two persons to handle a large lilac shrub or tree dug out for transplanting. Often burlap is treated to defend against decay and, hence, it should be removed before planting the lilac. Unfasten the burlap in the region of the stem, lift the lilac using the burlap, and gently slide it into the planting hole. Once you have positioned the lilac in the planting hole, get rid of all labels, wires or twines.

After positioning the lilac roots in the planting hole, fill the hole with the soil removed while digging the hole. Keep the soil level a little higher than the ground level, as some of the soil will be compressed into the hole. Be careful not to include any fertilizer or additive like peat moss, as the lilac will grow better if it is not planted in a rich soil. In fact, planting the lilac in a fertile soil may retard the growth of the roots and prevent them from growing beyond the pocket wherein it is planted. Press the soil around the plant lightly with your foot to make it firm and water the plant properly. Providing a plant with one bucketful of water should be enough. After watering, don’t press the damp soil down. If you are growing the lilac in a very windy spot, provide the plant with a stake – but only for the first year of its growth.


Whether you should mulch your favorite lilac or not, is a matter of personal choice. Mulching the plants is good in a sense that it helps to keep weeds away and also retains the soil moisture. At the same time, mulching protects the plants from girdling mishaps caused by trimmers and mowers. Mulching also looks beautiful provided it spreads only as far as the external periphery of a mature plant. The general labor-saving practice involves applying the killer grass 2.4-D (Roundup) directly to the sod circle around the lilac stem either in summer or in fall and spreading the mulch right away. Alternatively, you may use an environmentally friendly method for your home garden. This entails spreading multiple layers of newspaper on top of the sod and subsequently covering the newspapers with mulch. The newspaper will convert into compost soon, eliminating the sod lying below. There is also a substitute for bark mulch and that is using a ground cover – which is, in fact, living mulch.

After planting the lilac, water it thoroughly for the first month. If the weather conditions are dry, water the plant once every week. Water the lilac once in two weeks for the remaining part of the first summer of the plant if the weather is dry. While lilac roots are generally shallow, they can be stimulated to grow further downward by watering them deeply. You need not water the lilac in the subsequent seasons, provided your region suffers from extended periods of drought.

Grafted vs. Own-Root

In case you are growing a grafted lilac, you will notice a small swelling, some kind of a knee joint, just a little above the roots. The bark of the shrub or tree may have a different appearance below and above the swollen joint. Precisely speaking, grafting is a process wherein your favorite lilac cultivar (known as scion) is joined to a different lilac variety that is solely used for its roots (known as the rootstock). When you are planting the grafted lilac, you need to ensure that the graft portion lies under the ground so that the scion is encouraged to grow its own roots. Although grafting lilac plants was quite widespread at one time, these days growers do not prefer this method due to quite a few reasons.

One of these reasons is that since the rootstock is taken from a lilac variety that is different from the scion, it may not be as winter-hardy or even be incompatible to some extent. In addition, if the rootstock also gives rise to new shoots, your lilac plant may be of an altogether different type – not the one you had selected. You can easily detect whether the lilac growing in your garden was actually grafted. If the shoots emerging from under the ground produce the same flowers as those on the older branches, you can rest assured that the plant was not grafted. Or it may also be possible that the roots of the plant have developed from above the joint where the lilac was grafted. One more problem with grafted lilac plants is that the joint of the graft offers entry points for borers. In addition, the joint where the plant was grafted may also allow the development of a fungal disease that may result in deterioration of the plant’s health and eventually cause it to die.


Lilacs possess the aptitude to survive even without fertilizers. In fact, the majority of the garden lilacs, as well as those growing in the wild, can do without any fertilizing. Lilacs are very self-reliant and use of fertilizers is more likely to harm them than doing any good. If you still want to fertilize your favorite lilacs, you should abstain from doing so in the year of their planting and wait until spring next year. People who are using commercial fertilizers should apply them in measures of 1 lb to 2 lbs for every 100 square feet (0.5 kg to 1 kg/ 10 m2) for lilac shrubs that are grown in groups in beds. The rate for each specimen plant is 0.5 lb to 1.0 lb (0.25 kg to 0.5 kg). If you are growing lilacs in colder regions, it is advisable that you use the lower figures. The fertilizer should be applied lightly in the region of the drip line – the ground that is directly below the farthest periphery of the branch ends. It is important to note that lilacs should only be fertilized in spring. If you are using a dry fertilizer, water the plants adequately after fertilizing.

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