Pruning at the wrong time of year and Winter damage to the flower buds are the most common reasons for hydrangeas not blooming. Hydrangeas flower buds develop on old wood. Pruning last years growth removes the developing flower buds and stops your hydrangeas from blooming.
Most common reasons for hydrangeas not blooming:
- Pruning hydrangeas in the Spring removes last years growth and the developing flower buds.
- Late Spring frosts can damage the emerging blooms in Spring and prevent flowering.
- Too much nitrogen in the soil causes lots of foliage to grow but with fewer flowers.
- Hydrangeas require partial sun or dappled light to flower and too much shade can prevent flowering.
- Hydrangea is not yet mature enough for flowering.
- Drought stress in Fall and Spring can harm the development of flower buds.
Keep reading to learn why your hydrangea is not blooming and to solve the problem…
1. Pruning Can Prevent Flowering- Hydrangeas Bloom on Old Wood
Hydrangeas only flower from shoots that come from last years growth. If you prune hydrangea too heavily or at the wrong time of year then you cut back into the growth from which the flowers emerge and prevent the hydrangea from blooming until the following year.
Hydrangeas do not need regular annual pruning in the same way other shrubs (like roses) do and often flower best when you leave the plant alone to bloom.
If you have pruned your hydrangea back significantly then it tends to grow lots of lush green foliage in the Spring without any flowers.
Hydrangeas are very resilient once established and a heavy pruning only tends to delay blooms until the following year.
When pruning hydrangeas, focus on cutting back any stems that are straggly or dying back to the base to encourage new growth that can support more flowers, rather then reducing the shape of your hydrangea as pruning hydrangeas should generally be limited to deadheading.
It is best practice to cut away any dead growth back and spent flower heads to new healthy growth or the next flower buds in the Spring as this encourage more airflow and allows more light on the developing blooms.
I must emphasize that heavy annual pruning is not necessary and is likely to prevent your hydrangea from flowering as hydrangeas flower from old wood.
If it is necessary to prune your hydrangea because it is too large for your garden then cut back your hydrangea straight after flowering as this can give the hydrangea enough time for new growth to develop and be next years mature growth which can support flowers the following year.
For a great visual guide on pruning and deadheading to encourage flowers watch this YouTube video:
2. Winter Damage to Flower Buds
The reason for hydrangeas not blooming is often because of frost damage to the flower buds in Spring. The emerging flower buds are particularly sensitive to a sudden drop in temperature, and late Spring frosts damages the buds and prevents the hydrangea from blooming.
Whilst hydrangeas are hardy in freezing temperatures during Winter, it is the new emerging growth that is vulnerable in the Spring so if the hydrangea flower buds and new growth appear brown or black, this is the clearest sign of frost damage.
Hydrangeas are adapted to living in woodlands where the shelter of the forest canopy provides some protection from the affects of frost and adverse weather conditions, so always avoid planting hydrangeas in open and windy areas which can decimate tender new growth.
A good way to protect the emerging flower buds is to resist the urge to deadhead and actually leave the old flower heads from the previous year on the plant.
The old flower heads act as an effective form of protection against frost and insulate the new buds from cold temperatures similar to horticultural fleece.
This increases the chance of the buds surviving any late frost to ensure your hydrangea flowers well.
As for this years flowers, it is best practices to trim back any frost damaged growth with pruners as it does not revive.
By trimming back the damaged growth you allow more light to flower buds that have formed further down the stem which are more likely to survive a frost as they are often afforded some protection from the foliage.
The damage to hydrangeas tends to be limited to the outer most growth after a frost so with some patience the buds can often still flower that are further down the stems rather then at the outer most points of the hydrangea and you should still see some blooms later in the Summer.
(Read my article, how to revive a dying hydrangea).
3. Too Much Nitrogen Fertilizer (Reduce Fertilizer use)
If you apply fertilizer too often or in too high concentration this can cause the hydrangea to grow lots of foliage at the expense of flowers. Hydrangeas only require a well balanced fertilizer applied at the start of Spring to encourage flowers.
All plants require Nitrogen, Phosphorous and Potassium (NPK) to grow and flower, but if there is a high amount of nitrogen in the soil then this causes the stems, leaves and flower heads of the hydrangea to become sappy, weak and droop with far fewer flowers on display.
Sappy weak growth from using too much fertilizer also leaves your hydrangea at greater risk of pests and diseases.
It is imperative that you get the balance of fertilizer right for hydrangea to display flowers.
Personally I recommend a using a well balanced fertilizer such as miracle-gro all purpose granular fertilizer for hydrangeas which contains all the nutrients a hydrangea requires for growth and blooming, at the right concentration.
The granular formulation releases the nutrients slowly which helps to mitigate any risk from using too much fertilizer or applying the fertilizer in too high concentration which is a common problem with other types of fertilizers.
If your hydrangea has lots of sappy foliage growth with few flowers then scale back the use of your current fertilizer and monitor for insect infestations or disease.
If the hydrangea is establish they are usually very hardy plants that withstand a lot of mistreatment, so it is likely the hydrangea can recover and display flowers the following year, if you use the right sort of fertilizer and follow the manufacturers instructions.
Once the fertilizer has been applied there is not much you can do to promote blooms in the mean time so some patience is required.
It is important to note that lawn fertilizer can often dilute in heavy rainfall and run off into garden boarders where your hydrangea and other plants are planted.
Lawn fertilizer is particularly high in nitrogen which is often a cause of plants in the surrounding boarders not flowering if there has been significant run off after rainfall.
(Too much fertilizer often causes hydrangeas to have a drooping appearance, however there can be a few different reasons for this. Read my article, why is my hydrangea drooping for the solution).
4. Not Enough Sunlight for Flowering
Hydrangeas flower best in morning sun followed by afternoon shade or in dappled light. If hydrangeas are in full shade all day then they grow lots of foliage but without any flowers. Sunlight helps to stimulate more flowers and afternoon shade protects the hydrangea from leaf scorch.
Hydrangeas flower best in 4 to 6 hours of morning sun or dappled light under a tree canopy to provide them with the energy for flowering.
Shading the hydrangea in the afternoon is best as intense sun and high temperatures often causes drought stress and can scorch the leaves, so either find a location of morning sun and afternoon shade or an area of dappled light under a tree canopy that allows some light in throughout the day for the optimal balance of sun.
If your hydrangea is not blooming then consider whether the surrounding tree canopy has and is casting too much shade on your hydrangea depriving it of the sun that is require for blooming.
In which case you may consider cutting back some of the overhanging branches which helps to create the dappled light conditions for the balance of sun and shade to help stimulate blooms and protect the delicate leaves from scorch.
If cutting back tree limbs or creating more light is impractical the it consider whether you could transplant the hydrangea to a sunnier location in the garden.
The best time for transplanting hydrangeas is in the Fall when the soil is still warm enough for the roots to establish and hydrangeas do not have to contend with the stress of high temperatures, blazing sunshine and transplant shock in Summer.
5. Hydrangea not Mature Enough To Flower
Hydrangeas often do not flower in the first year after planting as they invest their energy into developing the root system and adjusting to their new conditions rather then displaying flowers. Hydrangeas tend to bloom more the year after planting or once they have matured for a few years in the soil.
When you purchase a hydrangea from a garden center or nursery, it is likely to have been cultivated in a green house with optimal conditions (such as controlled temperature, light, soil, fertilizer and airflow) before sale.
This means that the hydrangea has adapted to growing in a very specific and controlled set of conditions that are in contrast to the conditions of your garden.
Therefore after planting hydrangea can suffer an element of transplant shock as it adjusts to its new conditions.
This transplant shock can prevent the hydrangea from blooming in the first year after planting and the hydrangea is more likely to redirect its energy from displaying flowers to establishing its root system in the new garden soil.
It is important to consider the size and maturity of the plant as smaller, young plants also invest their energy into growth, particularly of the roots as immediate survival is the main priority rather the displaying flowers.
When the hydrangea has had time to adapt to its new surroundings and as long as the hydrangea has good conditions for growing (partial sun, moist, yet well draining soil etc) then the hydrangea should establish after a year or so, and grow into a larger more mature plant, then it can afford to display flowers the following year.
It is important to note that larger hydrangeas are more likely to flower in their first year then smaller plants.
Wait a year or so for the plant to mature, and ensure the hydrangea has all the conditions it requires to thrive, then it should bloom well the following year.
(Read my article, why are my hydrangea flowers turning green?)
6. Not Enough Water Whilst the Flower Buds Develop
Hydrangeas require well draining, yet consistently moist soil. If the soil around the roots dries out this causes drought stress which can prevent the development of flower buds and ultimately be the cause of your hydrangea not blooming.
Hydrangeas are naturally woodland plants that grow in soil composed of lots of organic material, which holds onto moisture and has a porous, friable stricture, that allows excess water to drain away rather then become water logged around the roots.
The leaves of the woodland floor also act as a natural mulch for the hydrangea to help converse moisture around the roots and prevent the soil drying out.
If your hydrangea is in a smaller pot, in sandy soil that drains too quickly or there has been a lack of rainfall, particularly in the Spring when the flowers buds are developing, then this results in a hydrangea with poor growth and fewer flowers.
Hydrangeas should be planted in a large pot or containers as larger pots have a greater capacity for soil and therefore can hold more moisture then smaller pots which dry out too quickly for hydrangeas to tolerate.
Hydrangeas should always be planted in garden boarders that have been prepared with lots of organic matter (compost, leaf mold or well rotted manure) around the planting area to recreate the optimal soil conditions and the ideal balance of drainage and consistent moisture, that hydrangeas require for flowering.
If there are drought like conditions then give your hydrangea a really generous soak, preferable with a soaker hose so that the surrounding soil is evenly moist.
Apply a 2 inch layer of mulch (leaf mold, compost or well rotted manure all work great) to the surface of the soil surrounding your hydrangea to help conserve the moisture, improve the soil structure and prevent the sun shining directly on the soil which can dry out the soil and heat up the roots which causes the hydrangea stress.
Water your hydrangea as often as required to keep the soil evenly moist and water your hydrangeas generously as this encourages good root development which increases the hydrangeas resistance to dry conditions.
With good evenly moist soil, that has been amended with organic matter, partial sunlight and fertile soil, the hydrangea has the required conditions to display flowers the following year.
(Read my article, why is my hydrangea wilting?)
- Pruning last years growth from a hydrangea in the Spring removes the developing flower buds and is the most common reason for hydrangeas not blooming. Hydrangeas flower on old wood and bloom best when they are not pruned annually.
- Emerging hydrangea flower buds are very sensitive to cold temperatures and a late Spring frost or excessive cold winds can cause the new growth to turn brown and stop your hydrangea from flowering.
- Hydrangeas do not flower if there is too much nitrogen in the soil due to using a fertilizer too often or in too high concentration. Hydrangeas produce lots of lush green foliage growth with few flowers with too much nitrogen in the soil.
- Hydrangeas grow naturally in woodland in the dappled light of a tree canopy. If they hydrangea is in full shade the tend to not flower but still grow plentiful foliage. Hydrangeas flower most when in morning sun followed by afternoon shade or in areas of the garden with filtered light.
- Hydrangeas only flower to their full potential when they are a mature plant that has been establish for several years. If the hydrangea is small or been recently transplanted then it redirects energy to establishing its root system and does not display flowers for a year or so.
- The hydrangea’s developing flower buds require consistently moist soil to form properly. If there is a period of drought or dry soil in the Spring or Fall when the buds are developing then the hydrangeas will not display flowers until the following year and the soil conditions are favorably moist.