Hydrangeas are renowned for being relatively low maintenance, and having the ability to fill out garden spaces with vibrant blues, pinks, reds, and purples, as well as pearly whites. So, when your hydrangeas start changing color, or even worse, fading, it’s easy to think there’s something wrong with your plant.
The bad news is that it’s normal for many hydrangea varieties to change or lose some of their color. The good news is that in most cases it’s not a sign of a serious problem.
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Why Are My Hydrangeas Changing Color?
If your hydrangeas are changing color from blue to pink or vice versa, that is due to a change in soil pH. Hydrangeas will change color depending on whether they’re grown in acidic or alkaline soil, and this color can change throughout the growing season.
Acidic soil (below 6.5 pH) will produce blue hydrangeas, while alkaline soil (above 7 pH) will produce pink hydrangea flowers. Somewhere in the middle at a neutral pH, you’ll get a mix of purplish blue and pink. If your soil is relatively neutral, a slight pH change can easily change the color of your hydrangeas.
The change in color is most apparent in bigleaf/French hydrangea (Hydrangea macrophylla), while other types of hydrangea are less affected by pH.
Another factor to consider is how late in the season you are, as hydrangeas will naturally lose some of their color over time. If your vibrant blues and pinks are turning more pale, that’s the likely reason.
Why Are My White Hydrangeas Turning Green?
Many white hydrangeas, especially smooth hydrangeas (Hydrangea arborescens) will naturally turn green as they age. The reason for this is that the white “petals” are actually sepals, which are naturally green. Sepals are the green leaf-like parts right behind many flowers. In the case of hydrangea, those sepals come in a variety of colors. Usually, after a few weeks of blooming, the blooms will start to get a lime green tinge.
This process happens in all hydrangeas, but it’s mostly noticeable in white ones, which is why they tend to look light green as they age. There are a few white varieties, however, that turn pale pink when they age, such as Pinky Winky.
If your white hydrangeas are always green and never turned white, it’s likely that you planted them in a place with too much shade. Hydrangeas tolerate partial shade, but thrive in full sun and will produce pearly white blooms. However, the more sun a hydrangea gets, the faster its color will become less vibrant, so be mindful of that if planting blue or pink varieties.
Why Are My Hydrangeas Turning Brown?
If your hydrangeas are turning brown, there are two common causes: too much heat or drought. While hydrangeas love the sun, if they are battered by scorching heat, this can stress the plant and turn your flowers brown. Similarly, if your hydrangea is struggling to get enough water and is wilting a lot in the summer, this can stress the plant too much and lead to brown flowers and leaves.
To keep your hydrangeas safe from the heat, plant somewhere they can get full sun all morning and then some partial shade in the early afternoon when it’s hottest. If you live in a hot climate, mulch is your friend. Mulch is not only beneficial for protecting your hydrangeas in winter, but also protects them from drought, working to both shade the soil from extreme heat and also act as a moisture buffer to reduce evaporation.
Also, when you’re expecting a string of days with extreme heat, give your hydrangeas a deep watering to reduce the chance of wilting.
Hydrangeas grown in containers are more likely to experience drought stress, as a fully grown hydrangea can quickly soak up all the water in a pot. Water container hydrangeas more often, especially during the summer.
Why Are My Hydrangea Leaves Turning Yellow?
A few yellow hydrangea leaves are often not something to be concerned about, but if you notice a lot of your hydrangeas turning yellow or a pattern to the yellowing (like only the older leaves turning yellow while the new leaves are light green) then that could be the sign of a problem.
Nutrient Deficiency
If there is no sign of disease or pest damage on your hydrangeas, nutrient deficiencies could be the reason for yellowing leaves.
Nitrogen deficiencies are characterized by an overall yellowing of older leaves, while new leaves stay vibrant (but lighter) green. Nitrogen is a mobile nutrient, so when soil is nitrogen poor, a growing plant will pull nitrogen out of older leaves to the new growth.
If your leaves are turning yellow but the veins are staying green, it’s possible you have either a magnesium or iron deficiency. Both of these are micronutrients and plants don’t need much fertilizer to recover. One thing to note is that plants in very alkaline soils are more likely to have iron deficiencies and those grown in very acidic soils are more likely to have magnesium deficiencies, due to the way pH affects nutrient availability (and therefore absorption).
If you suspect you have a magnesium deficiency, epsom salt is a cheap and widely available fertilizer. You can even apply it as a foliar spray (1 to 2 tablespoons dissolved per gallon of water), applied to the leaves in the early morning or late evening, once a week for a few weeks and see if it fixes the problem. The most easily available organic iron fertilizer is blood meal, which is also one of the best organic nitrogen fertilizers. For non-animal sources of iron, try a good balanced compost or greensand.
Read more general information about important plant nutrients here.
Your Soil Is Too Alkaline or Too Acidic
If you think you have a nutrient deficiency, before you add more fertilizer, check your soil pH. While hydrangeas are usually grown in more acidic or alkaline soil to promote vibrant blue or pink blooms, soil that is too acidic or too alkaline can harm plant growth and development by affecting nutrient availability.
The main issue is that certain nutrients are best taken up at certain pH levels. So, while iron has a high absorption rate in very acidic soils, those same soils will have less available magnesium your plants can absorb, and vice versa.
See the chart below; the light green shaded area is the optimal range for growing plants, although hydrangeas typically can tolerate slightly more acidic and alkaline pH levels.
Leaf Scorch
If your leaves are turning crispy and yellow or brown, and the yellow color is pale (almost like the leaf was bleached) then it’s possible your hydrangea is suffering from leaf scorch, also known as sun scorch. This is due to high sun exposure, and can be worsened by other factors like transplant shock, overfertilization, or drought. This can happen with established plants, but it’s most common with new transplants or if you’re moving a hydrangea from a shaded area or indoors to full sun for the first time without gradually hardening off the plants over a few days to weeks.
Too Much or Too Little Water
A lack of water not only causes hydrangea flowers to turn brown, but stresses the whole plant, causing it to shed yellow leaves. However, too much water is also a problem as it can drown some of the roots and reduce nutrient uptake. In severe cases where roots are constantly submerged in muddy soil, the roots can die off and begin to rot, severely weakening or killing the whole plant.