Hydrangeas are beautiful plants known for their bright clusters of flowers. When these flowers fail to appear, their absence can cause great concern for careful gardeners. A hydrangea failing to flower is more common than you might think, and one that has multiple causes. Someone interested in their garden’s health should first and foremost figure out why the hydrangea is struggling in its current environment, as deficiencies and poor access to resources are the main reasons for a failure to flower. Some other potential causes are a lack of old wood, overzealous pruning, an early frost, and even disease.

Nutrient Deficiencies – Phosphorous

The most common nutrient deficiency in hydrangeas is phosphorous. Most gardeners know that plants require a certain amount of nutrients in their soil, including nitrogen, potassium, and phosphorous. Phosphorous is one of the primary ingredients plants like hydrangeas absorb and need to produce beautiful blooms. If the soil in which the hydrangea is planted is stripped or deficient, very few flowers can emerge. The easiest way to tell if the soil is the problem is to complete a soil test. Most hardware and garden stores sell soil testing kits that provide quick results at home. People who want something more professional can also take a sample and mail it to a lab, which will analyze the sample and send back the results. Usually, a soil testing kit is all you need to know and can come in handy for another testing you might do in your garden such as trying to change the colour of the flowers.

If phosphorous or another nutrient deficiency is the problem, there are a couple of solutions. The most obvious one is to apply a high-quality fertilizer to the garden. The fertilizer should have a high phosphorous content but low nitrogen. Why? Nitrogen is beneficial, but it mainly affects the growth and health of the rest of the hydrangea, mainly the foliage. So, a hydrangea with healthy stems and leaves but no flowers already has all the nitrogen it needs. Gardeners should instead focus on adding phosphorous so the hydrangea flowers and blooms. The best fertilizers will include bone meal, which has a high phosphorous content.

Old Wood or New Wood?

Some people might be confused by what a lack of old wood means when it comes to hydrangeas. The old wood on a hydrangea is stems that are at least one year old. Usually gardeners prune away the old wood each year to facilitate growth. However, this isn’t always the best idea.

Why? Because, depending on the type of hydrangea planted, the plant might actually need the old wood to bloom. The Bigleaf Hydrangea is the most common victim of the question, “Why Is My Hydrangea Not Flowering?” This is because the bigleaf needs old wood on which to bloom, but the hydrangea frequently suffers from the old wood dying back into the ground during the winter or from its old wood being cut away. When this happens, there simply are not the resources necessary for the Big-Leaf to produc it’s signature blue and pink flowers. Some other common hydrangea types with this issue are the lacecap and oakleaf.

If hydrangeas aren’t flowering, see if they are one of these old wood varieties. If they are, do not prune them back during the summer too much. In fact, sometimes it’s best not to prune at all until the fall and only take a little off. Otherwise, it’s possible to remove all of the old wood and leave nothing for the hydrangeas to flower upon. If the old wood is already gone, there is no reason to worry. Flowers might not bloom this year, but will have enough old wood to appear next year.

If a hydrangea blossoms on new wood and still isn’t flowering, there still might be a pruning problem. Sometimes gardeners get zealous with the shears and strip off too much material when trying to cut plants back. When this happens, there is literally no space for flowers to appear. Someone who is obsessed with getting their hydrangea to be the right shape or simply has little experience working with the plant might struggle to prune correctly.

Pruning

How can one prune a new wood hydrangea without restricting flowering?

The best time to prune a new wood hydrangea is in late winter or early spring. This is right before the shrub starts to grow during the spring and can help eliminate dead ends and facilitate growth. Gardeners can prune all the way down to the bottom of the stem at this point in time, which will encourage the development of bright flowers on brand new stems. However, this can create flopping. To avoid this problem, many gardeners leave behind a framework of old stems to help support the new and keep flowers big and popping. Pruning for new wood should never be done in the spring or summer because the gardener is likely to clip off the hydrangea blossoms before they have a chance to bloom.

Disease and Insects

If, after testing the soil, checking the type of hydrangea, and changing pruning patterns, the hydrangea still refuses to flower, there could be another, more dangerous issue with the shrub. Sometimes, a hydrangea failing to flower is the result of a disease or insect activity that is killing the plant. Gardeners who think this might be the case needs to look for other signs of damage, such as leaves dying in the spring and summer, a lack of growth, and brittleness. Holes eaten away by aphids or spider mites are common, and grey or white powdery growths on leaves and flowers can indicate major problems.

If there still doesn’t seem to be a problem, the hydrangeas might have just suffered from bad luck. Sometimes a freak late spring freeze will stop flowers from blooming. When this happens, gardeners will need to wait until next year to enjoy the fruits of their labour.

Conclusion

If someone asks themselves, “Why is my hydrangea not flowering?” there are five potential answers. Test each one to get the best results for the next year.

1. Make sure there is enough phosphorous in the soil.
2. Determine whether the hydrangea blooms on old wood and adjust pruning.
3. Determine whether the hydrangea blooms on new wood and adjust pruning.
4. Check for diseases like Botrytis blight or insect activity from aphids and spider mites.
5. Determine whether a late spring frost killed the blooms.

Last update on 2024-04-20 / Affiliate links / Images from Amazon Product Advertising API