Very small gardens, balconies, decks and rooftops are ideal places for growing lilacs in containers. The smallest varieties of container lilacs are basically bonsai.
Select any small or dwarf lilac for growing in containers. Some of the lilacs that are most suited for growing in containers include S. oblata subsp. dilatata, S. meyeri, S. pubescens, S. patula as well as the dwarf varieties of Syringa vulgaris like the “Little Miss Muffet” bearing ping-magenta hued flowers, “Pixie” producing single, white flowers, “Minuet” that bear purple blooms, “Purple Gem” producing only single flowers and “Prairie Petite” that produces purple blooms. Like their other cousins, the dwarf lilacs are also flowering varieties and some of them bear aromatic blooms. S. pubescens subsp. microphylla is among the dwarf lilacs that produces most aromatic blooms. This dwarf lilac grows excellently in chilly greenhouses, where it comes to bloom at least six weeks before compared to the plants that are grown outdoors. If you are thinking about growing a much smaller dwarf lilac, you may opt for the “Dwarf Pixie” that grows up to a height of about 4 feet to 5 feet.
Go for a container that is strong, eye-catching and comes with drainage holes. Remember, larger containers mean better insulation of the roots from extreme heat and cold. At the same time, when the container is large, it ensures that the roots are protected from being exposed to excessive heat or being frozen. Larger containers also mean that the plants need to be watered less frequently. Avoid using containers made from black plastic, as they absorb too much heat, and this may scorch the roots. Position the container prior to filling, planting the lilacs and watering them, because the container will become heavy later. Ideally, you should position the container in a place that receives direct sunlight for no less than six hours daily. Use good quality topsoil and water the plants whenever the soil becomes arid to a depth of about an inch (2.5 cm) from the surface. Never water the plants until the surface becomes dry because the dwarf lilac varieties cannot endure continuous dampness at all.
When grown in relatively warm climatic zones, you can keep the lilacs grown in containers outdoors throughout the year. However, if the winters are very harsh in your region, the severe cold may harm the roots of these lilacs. Hence, you should take the lilac out of the container and plant it in the garden for the duration of the winter months. Alternatively, you may also bury the plant along with the container in the soil; in straw or leaves. Never bring the lilacs indoors during this time of the year, as cold is necessary to help the flowering buds mature.
If the roots of lilacs are restricted, they will generally not flower or even have a proper growth. Therefore, it is really a challenge to successfully grow a majority of lilac varieties in containers. However, this does not mean that lilacs cannot be grown in containers. A number of lilac varieties, for instance, the smaller plants, dwarf varieties and the plants that are cultivated as trees, can flourish when grown in containers. However, this is only possible when you take appropriate care of the plants and also cut back their roots when they grow beyond what can be sustained in containers.
Lilacs in containers grow well when they are able to stretch their roots and also develop into large plants. Therefore, it is advisable that you opt for a very strong and large container that you can get. In fact, the container should be at least 15 inches deep and 24 inches across. Irrespective of the container you select, make sure that it comes with drainage holes at the base to drain out excess water. Select a suitable place to grow your lilacs in containers – the place should receive full sunlight for no less than six hours daily as was said before. Position the container in the place prior to packing it with soil and planting the lilac.
Lilacs or Syringa cannot endure acidic soils. Therefore, prior to growing lilacs in containers, you need to look for alkaline or a base potting soil. Majority of the potting mixes available commercially have peat moss, which actually makes the soil acidic – however, only to some degree. When you add one cup (250 ml) dolomite lime for every bag containing 2 cubic foot of commercial potting mix, it will help to augment the pH of the soil. At the same time, calcium and magnesium in dolomite lime also help the plant’s growth. In addition, you should add a small amount of lime to the soil every spring.
When you are growing lilacs in containers, water is the most important aspect for the proper growth of the plants. As the soil in the container becomes dry very fast, it is vital for you to monitor the soil condition every day and water the plants whenever the soil becomes dry to a depth of 1 inch (2.5 cm) from the surface. Also, ensure that you provide fertilizers to the lilacs in containers every year at the beginning of spring. Ideally, you should use 10-10-10 fertilizer and feed the plants after their blooming season is over. In case you find the lilac roots emerging from the drainage holes of the pot, you should know that the plant is in some kind of trouble. Therefore, it may be time to take the plant out of the container and cut back its roots. Using a very sharp knife, sever about 1 inch (2.5 cm) of the roots around the entire root ball. Subsequently, employ pruning shears to trim all the lilac roots that are considerably thick compared to the other normal roots and replant the lilac.