My lilacs are not blooming: 7 reasons and measures

The Syringa Vulgaris is mainly found in German gardens. This flowers from May to June. If there are no flowers from May, it may be a lilac variety that flowers later. In principle, a distinction is made between early, summer and autumn lilacs. A special feature are summer and autumn lilacs, which depending on the variety bloom in spring/early summer and autumn or can have continuous blooms from summer to October. If the flowering time for the respective specimen in the garden or on the balcony has not yet come, you simply have to wait until then.

Here are some examples of varieties:

• Hyacinth lilac (Syringa hyacinthiflora): March/April depending on region and weather
• Autumn lilac (Syringa microphylla ‘Superba’) – June and again in October
• Butterfly bush/summer lilac (Buddleja davidii): July through October

location

The lilac (Syringa) is a sun-loving plant. If there is a lack of sun and light intensity, flowering will falter and, in the worst case, will not occur at all. Moving to a very sunny and bright location is then a must. But that’s not always possible, because early-blooming varieties in particular have a hard time with an often very rainy spring with gray skies. In this case, it is all the more important that affected plants are given every chance to catch sunlight as soon as the first rays appear. If the lilac has been too dark for too long, it will usually not bloom for the year.

soil condition

The Syringa is mainly supplied via the soil/the substrate. If disturbances occur here due to suboptimal soil conditions, it is not uncommon for flowering to fail. To remedy this, the following measures are required:

• Measure the pH value and correct it with lime fertilization if necessary – the ideal pH value is between 5.5 and 7.5
• Loosen up compacted soil
• Enrich soil with, for example, perlite (supports the looseness of the soil)
• Work in coarse sand in heavy loamy soils (ensures cavities for better water permeability)

planting distance

The Syringa is one of the shallow and deep rooters. Depending on the growth height, the roots can reach up to a few meters in width and depth. If they are placed too close to neighboring plants, there will quickly be insufficient space in the soil, so growth will be inhibited and flowering may not occur. It is therefore essential to observe the ideal planting distance according to the respective growth size when planting.

pruning

One of the reasons for the lack of (abundant) flowering can be due to pruning. It is important to know that lilacs already plant their new buds in autumn for the flowering season in the following year. If you cut back between autumn and spring, you run the risk of cutting off bud shoots. Buds only form on shoots that are at least one year old or older. If these are cut off, the result is a lack of buds and, in the worst case, a gardening season without a sea of ​​flowers.

Therefore, the following applies: pruning is carried out at most immediately after flowering and ideally only shoots on which no buds have formed yet.

nutrient supply

How extensive flowers form and how well they develop depends primarily on the nutrient supply. Before bud formation and just before the beginning of the flowering period, the nutrient requirements of lilacs increase significantly. If this is not covered, there is a deficiency/undersupply and there will be no flowering or the buds and/or flowers will wither away.

But an oversupply is also one of the possible reasons for the lack of flowers. This can have the same effect as with undersupply. Only the right fertilizer measures can help here:

• Only apply low-nitrogen fertilizers in autumn and before the start of flowering (nitrogen promotes green growth and inhibits flowering)
• Use fertilizers high in potassium and phosphorus
• Support with flowering plant fertilizer every two weeks from April to September
• Alternatively: Long-term fertilizer in spring
• For older lilac bushes, add slow-release fertilizer in June
• Do not fertilize for at least six weeks after transplanting/repotting into fresh soil/fresh substrate
• Organic fertilizer distributes nutrients slowly – over-fertilization is almost impossible
• Mineral fertilizer ideal as “first aid” because it quickly delivers larger quantities (increased risk of over-fertilization)
• Only dose mineral fertilizers very sparingly for potted plants
• Always strictly follow the manufacturer’s dosage specifications
• Home remedies for fertilizing: coffee grounds or egg shells – (keep an eye on the pH of the soil)

fungal disease

The lilac is considered to be very susceptible to fungal diseases, such as the dreaded lilac disease. If the lilac is ill, it consumes a lot of energy for the immune system, so that there is a lack of supply for the bud/flower formation and the lilac does not bloom. The following are the most common diseases plus measures to combat them:

Fliederseuche (Pseudomonas syringae)

Typical identification features:

• Small brown spots on the leaves
• Shoots wilt
• Shoot coloring from brown to black
• Shoot rot and/or desiccation
• buckling of the shoots
• Dark brown stripes on young shoots in May/June

Measure: Cut off and dispose of all affected parts of the plant down to the healthy plant area (lilac will recover by itself – flowering only possible after two years)

Leaf spot disease (Ascochyta syringae)

Typical identification features:

• Light gray spots with brown borders on leaves
• weakened plant
• Torn branches
• shoots wither

Measure: Cut off and discard all affected parts of the plant down to the healthy plant area

Chrysanthemum disease (Chondrostereum purpureum)

Typical identification features:

• Silver to lead-grey leaf coloration
• In the advanced stage, purple-colored fruiting bodies are formed on the wood
• Increasing growth disturbances due to plant weakening
• Spreads incessantly over entire plant until it dies

Measure: Cut off and discard all affected parts of the plant down to the healthy part of the plant (depending on the severity of the infestation, it may take years for it to bloom again)

Alter

Young lilac

One of the simplest reasons a lilac doesn’t flower is that certain varieties are too young. Wild lilac in particular sometimes needs up to three or four years of age before it flowers for the first time – in some cases even longer. It is much faster with the formation of flowers, for example in the case of lilac. Once planted, the buds usually sprout from young plants.

old plants

Old lilac bushes and those that have not been pruned for years also tend to have fewer or even no flowers at all. Metabolism slows down over the years and “signs of aging” show up. Cutting stimulates growth and keeps the metabolism going, so that flowering increases again. Because one-year-old and older shoots are “victims” of the cutting, an improvement can usually only be expected after two years.