Reasons Why Your Lilac Is Not Flowering or Blooming

Last Updated on November 9, 2022 by Stephanie

The reason why lilacs arent blooming is typically because they have been cut too much or in the wrong season. Lilacs bloom best when theyre not pruned. The buds grow on old wood, therefore when lilacs are pruned in the winter months of Summer, Fall, or Winter the buds of flowers are removed and the lilac will not flower until Spring.

8 reasons why lilacs arent blooming:

  1. Pruning too hard or early in the growing season, which can cause flower buds to fall off.
  2. There isnt enough sunshine for the lilacs to bloom.
  3. Warm or humid climates that have mild winters (lilacs require an extended period of cold dormant during winter).
  4. The acidic soils hinder flowering.
  5. A lot of fertilizer (often discharged of lawn fertiliser) encourages growth of foliage which is detrimental to flowers.
  6. Stress from drought.
  7. The Lilac plant isnt mature enough to flower.
  8. The late frosts could stop lilacs from blooming.

Read on to find out why your Lilac ( Syringa) isnt blooming and the best way to fix the problem to ensure that your will be able to bloom next year…

(Note that nearly all varieties of lilacs should flower in late Spring.).

1. Pruning Lilac Reduces Flowering

Lilacs show their blooms from old trees rather than the new growth and will bloom best when allowed to grow on their own instead of undergoing regular annual pruning.

If you have to trim your lilacs, the ideal time to do it is right after the flowering stage or else you could stop the lilac from flowering next year.

The flower buds begin growing in the summer months to be displayed in the next year. If you cut too late during the time of year (Summer winter, fall or summer) you take the flower buds off and stop the lilac from blooming throughout the year.

Lilacs bloom more when they are not cut. Pruning encourages an increase in leaves to replace the loss of growth, but not the creation of new flowers, so you get a lush Lilac plant without flowers.

If youve cut your lilac , it is still blooming however it will require patience, as it could take a year or more for the lilac to grow additional growth, which is what the flowers will bloom the next year.

While pruning lilacs is not recommended when you are looking to bloom regular deadheading of the flowers that have been disposed of is a good practice and will increase the quantity of blooms as Lilacs energy is diverted from producing seeds and generating more flowers in the season.

lilac flowers

2. Hot Climates or Humid Conditions Prevent Lilac Flowering

Lilacs can be adapted to environments with low humidity, and the seasonal cycle of temperature fluctuations all through the season.

This pattern of continual changes in temperature, particularly the winter cold snap is crucial for the lilacs production of flowers.

A time of dormancy that is cold-initiated is essential for the production of blooms and buds of the lilacs. Lilacs are often unable to bloom in climates that has mild winters.

Lilacs are extremely hardy to cold however they are not tolerant of humid winters or mild temperatures because this is contrast to the conditions in which they have adapted to their natural habitat.

Lilacs thrive in USDA zones 3-7 that have the right climate that allows the lilacs to more consistently bloom.

3. Not Enough Sunlight for Lilacs to Flower

Lilacs need the full sunshine (6 or more hours in sunshine or more) to bloom the best flowers. However, they can bloom in light shade, but there will likely be significantly fewer flowers.

In a shaded area, the lilac will not bloom, but the growth will be sluggish.

The native lilac plant is their native Balkan region located in Southern Europe where they are found in hills of sand with generally full sunshine.

If your lilac is an extremely small plant, I suggest that you transplant it (in the early spring or fall) into an area with more sunlight to encourage blooming and to ensure better health.

Established, mature Lilacs trim any branches or trees that could be putting shade over your lilac, so that it will bloom more during the next spring/summer.

4. Acidic Soils can Prevent Flowering

If your lilac isnt blooming, it could be due to overly acidic soils. Lilacs thrive in chalky soils that drain well which are usually alkaline or pH neutral. When the soil becomes acidic, then the lilac will be to be stressed and flower, and the growth will be likely to be poor.

Lilacs can tolerate slightly acidic soils and bloom very well. If the soil in your garden is extremely acidic (lower than pH 6) the acidity could hinder the lilacs ability to absorb certain nutrients, which could hinder flowering.

If your lilac is doing poor and isnt flowering, I would suggest asking your gardening-savvy neighbors about the soils pH since they will be able to be able to tell whether the soil is especially acidic.

You can test your soils pH yourself using an instrument for testing soil or send an e-mail with a soil sample away to be tested to find out the pH of your soil and if this is the reason for the lilacs not blooming.

(Read my article on the reason why my Lilac is dying).

5. A lot of fertilizer can stop Lilacs flowering (Run away of Lawn Fertilizer)

A lot of fertilizer can cause the lilac to produce lots of leaves, but at the cost of flowers. If youve applied fertilizer frequently or in a high amount the lilac will not be able to show a lot of flowers.

The main reason is the that lawn fertilizers runoff is a major factor because lawn fertilizer usually has an extremely high amount of Nitrogen which is the nutrient that causes the lilacs to develop leaves at the expense of flowers.

Nitrogen is water-soluble and, therefore, when it rains , it will dissolve and then run across the lawn to nearby garden boards which is where your lilac plant could be planted.

If the lilac has been given too much fertilizer, theres nothing that you could do in order to encourage blooms this year, but when you reduce the fertilizer, the lilac will be able to bloom next year.

If the lilac is cultivated in a good soil and the specific plant is mature, then lilacs generally dont require the most, or even any fertilizer. The older an lilac is, the better it develops its roots system and thus the better availability of nutrients in the soil.

A general, all-purpose fertiliser that is balanced can aid less mature lilacs to become established within the first couple of years of development.

6. The stress of drought can prevent Lilac from Blooming

Lilacs dont bloom when the soil is too wet or dry. They require balance of soil that is moist and well draining in order to show their blooms.

When theres a dry spell during the spring, this is likely to impact the flowers, however a prolonged drought in the summer can impact buds that grow for the flower next year.

Most often, drought stress doesnt cause problems for older, more established lilac plants, but the younger or newly planted plants can be affected and show less flowers.

The best way to reduce the effects of drought on blooming of the plant is by giving it a extensive watering, and then apply two inches of mulch at the bottom of the plant (ensure that the mulch isnt touching the wood, as this could cause the wood to rot).

Materials for mulching like compost leaf mold, leaf mold, or composted manure are great because they aid in conserving water and improve soils structure so that its more favourable for lilacs to flourish and show off their blooms in the spring.

7. Lilac isn’t Mature Enough to Flower

Lilacs can be considered to be long-lived plants, with certain varieties capable of surviving 100 years or more.

If a lilac is unripe or was recently transplanted, it could take between 2 and 3 years to bloom correctly.

This is due to the fact that in the initial 2 years of growth, the Lilac puts its energy into the establishment of its root system because it is essential to its the immediate survival of the plant and for long-term prosperity.

Once the roots have established, there is more mature development (and the weather is favorable with plenty of sun, and full sun.) The lilac will shift its focus from its immediate survival following the planting process to produce a beautiful display of blooms.

8. Late Frosts can Prevent Flowering

Lilacs bloom in late spring and they attempt to predict when they will emerge their blooms after the last frost.

In the event of a heavy, late frost, and the flowers are still emerging it can make the flowers brown and hinder an attractive display of flowers.

Lilacs are extremely cold-hardy however the blossoms that are emerging are more sensitive to the frigid temperatures and frost, which can affect the ability of the plant to show its blooms.

Key Takeaways:

  • The most common reason for lilacs not blooming is that it was cut too hard or is not at the right season. Lilacs bloom on old wood. If lilacs are cut back in the spring, this will remove the buds that are developing and the lilac is unable to show its flowers in the Spring.
  • Lilacs need at least six hours of sunshine to encourage blooming. If the lilac is located in shade, this could hinder the blooming of the lilac.
  • Lilacs require a time of dormancy in cold temperatures to begin flowering. If winter is too warm, the lilac will not bloom.
  • Lilacs thrive in acidic soils, neutral or alkaline. When the soil becomes too acidic, it prevents the roots from absorbing certain nutrients, which leads to slow growth and the lilac not blooming.
  • A high concentration of nitrogen in soil due to excessive fertilizer or run-off from lawn fertilizer causes an abundant lilac but there are no flowers.
  • Lilacs need the soil to be equally humid. If the soil is dry as the flower buds begin to emerge or when buds of the flowers are growing in the summer, this could hinder the blooming of the lilac.
  • Lilac plants do not bloom when they are young (less than 3 years old) or have been planted recently. The lilac shifts its focus away from flowering to growing its roots in the initial few years, as it focuses on its long-term survival. Lilacs typically bloom within 3 years, when their roots have become more established.
  • The late frosts of spring can make the blooms of lilacs brown, preventing the flowering process from taking place properly.
Stephanie

Stephanie

Went from an inexperienced gardener to a half-decent one over 10+ years. I cover anything from general indoor plant guides and lawn care, to succulents and flowers. Super happy to share my tips and tricks with you :)