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6 Mistakes That Cause Hydrangea Leaves to Turn Yellow (And How to Fix Them)

Hydrangeas stand out in any garden with their big, beautiful flowers. But sometimes, they face issues, and that’s what we’re diving into today.

Ever noticed your hydrangea leaves turning yellow? This usually happens when they’re not making enough chlorophyll, often due to not having enough iron. This condition is called chlorosis. Iron is super important for making chlorophyll, which plants need for photosynthesis.

Let’s explore all the reasons why hydrangea leaves might turn yellow and how you can fix it.

1. Deficiency

hydrangea leaves turning yellow

Hydrangea leaves turning yellow because of nutrient deficiency.

The most common reason hydrangea leaves turn yellow is due to missing trace elements in the soil, messing up photosynthesis and changing leaf colors. Let’s check out a few key elements and their impact.

Iron Deficiency

Iron’s super important for the growth of leaves and stems. Without enough iron, chlorophyll can’t do its job in photosynthesis, leading to a condition called chlorosis.

When hydrangeas lack iron, you’ll see the leaves turning yellow between the veins. The veins stay green, but the surrounding areas start pale and then turn yellow.

Fixing It:

  1. You can use iron chelate, a form of iron that hydrangeas can easily take up. You can find this at garden centers or online.
  2. Follow the instructions on the label for how much to use, and don’t go overboard.

But remember, it won’t be an instant fix. And the yellow leaves won’t turn green again. Only the new leaves will be healthy and green.

Nitrogen Deficiency

Another issue for hydrangeas is not getting enough nitrogen. They need nitrogen for big, green leaves. Often, this happens when the soil isn’t rich enough.

You’ll notice this problem when the leaf tips start turning yellow, and then it spreads towards the center of the leaf.

Fixing It:

  1. One way is to add organic matter to the soil around your hydrangea. Using high-quality compost is a great choice.
  2. Alternatively, you can use a nitrogen-rich fertilizer. This will give your hydrangeas the nitrogen boost they need.

Magnesium Deficiency

Magnesium plays a crucial role in photosynthesis. While hydrangeas don’t need a lot of it, they often lack this element.

Just like with iron deficiency, a magnesium shortage also leads to chlorosis. You’ll notice the leaves turning yellow between the veins.

Fixing It:

  1. To tackle this, magnesium sulfate is your go-to solution. You can easily find it at plant stores.
  2. Also, for the future, make sure the fertilizer you choose for your hydrangeas contains magnesium. This helps prevent the issue from cropping up again.

2. Watering Issues

Watering problems, both too much and too little, can cause hydrangea leaves to turn yellow.

Overwatering

Overwatering

Hydrangea leaves turning yellow because of overwatering.

It’s a common issue for many plants, hydrangeas included. They do like moisture, but too much water can lead to root rot.

When roots rot, they can’t take up nutrients or water well, which often turns the leaves yellow. Overwatering happens from watering too often, poor soil drainage, long periods of rain, or planting in a very wet spot.

Signs of an overwatered hydrangea include stunted growth and leaves turning yellow at the tips or edges, eventually falling off.

Fixing Overwatering:

  1. Only water your hydrangeas when the top 2 inches of soil feel dry.
  2. In winter, when the plant is dormant, cut back on watering.
  3. Ensure your hydrangea has good drainage.
  4. Try not to plant it in an area that’s always soggy.

Underwatering

Not giving hydrangeas enough water can also lead to yellow leaves. If they don’t get enough, they’ll usually wilt and change color.

Fixing Underwatering:

  1. Water your hydrangeas when the top 2 inches of soil are dry, but don’t wait any longer than that.
  2. Pay extra attention to the soil moisture during hot summers.
  3. Each plant typically needs about 1 gallon of water, maybe more.
  4. Also, it’s a good idea to mulch around the root zone with 2 inches of organic matter. This helps retain moisture.

3. Too Much Sun

hydrangea leaves turning yellow

Hydrangea leaves turning yellow because of too much sun.

Excessive sun exposure can make hydrangea leaves turn yellow. For Hydrangea paniculata, which tolerates sun well, a bit of shade is only needed in hotter zones, like zone 7.

Hydrangea macrophylla (Bigleaf Hydrangea) is less sun-friendly. It does best with around 6 hours of direct sunlight daily, but not the harsh afternoon sun.

Fixing Sun Issues:

  1. Make sure your hydrangeas get about six hours of direct sunlight, but try to avoid the intense afternoon sun, especially for Bigleaf Hydrangeas.
  2. If your Bigleaf Hydrangea is getting too much afternoon sun, consider moving it to a spot with more suitable light conditions.

4. Diseases

Diseases are a common cause of yellowing hydrangea leaves. They can be viral, bacterial, or fungal, with fungal infections being the most frequent reason for leaf discoloration.

Fungal diseases

leaf disease

Hydrangea leaves turning yellow because of disease.

It usually starts in spring. Fungal spores land on young hydrangea leaves and start to grow. By summer, you might see brown spots on the leaves, followed by yellowing.

High humidity and poor air circulation in your garden can encourage these diseases.

Fixing Fungal Issues:

  1. First, remove any yellowed leaves to prevent the spread.
  2. Spray your hydrangea with a multi-purpose fungicide.
  3. After two weeks, give it another spray.
  4. Be careful not to overwater your hydrangeas.
  5. Make sure there’s good drainage and plenty of air flow around the bush.

Rot Root

Root rot

Hydrangea leaves turning yellow because of damaged roots.

Root rot is a disease that targets the roots of your plant. It often occurs from overwatering or when the soil doesn’t drain well. The first clue of root rot is usually leaves turning yellow.

The main culprits are usually overwatering or soil that doesn’t let water flow away properly.

Tackling Root Rot:

  1. To prevent it, be careful not to overwater. Only water your hydrangeas when the top 2 inches of soil are dry.
  2. Enhance soil drainage near the roots, or consider moving the hydrangea to a spot that’s not as damp.
  3. Also, be gentle with the roots when planting or moving your hydrangea to avoid damage.

5. Soil Issues

hydrangea leaves turning yellow

Hydrangea leaves turning yellow because of chlorosis.

If your soil doesn’t meet certain requirements, it can cause issues like changing leaf colors.

Soil pH is crucial. If it’s above 7.0, your hydrangea can struggle to absorb iron and other nutrients. This leads to chlorosis, where leaves turn yellow between the veins while veins stay green – just like with iron deficiency.

Fixing Soil pH:

  1. First, test the pH of your soil.
  2. If it’s higher than 7.0, you’ll need to lower it. You can do this by using a soil acidifier.

Poorly drained soil

Heavy, poorly drained soil often causes root rot, which, as you know, can turn hydrangea leaves yellow. Also, such soils are typically low in nutrients, leading to more problems.

Fixing Poorly Drained Soil:

  1. If you’re just planting your hydrangea, mix a few buckets of compost into the planting hole along with the native soil.
  2. For already planted hydrangeas, spread compost around the root area and blend it with the topsoil.
  3. Fertilize twice a year – once in early spring and again just after it flowers. Opt for a slow-release, multi-purpose fertilizer for best results.

6. Transplant Shock

newly planted hydrangea leaves turning yellow

Newly planted hydrangeas often go through transplant shock, affecting their leaves. This happens because the root system gets disturbed, impacting the entire plant.

Additionally, these hydrangeas are prone to underwatering. A new hydrangea hasn’t developed a large root system yet and can’t draw enough water from the surrounding soil. If not watered properly, the plant may turn yellow.

Fixing Transplant Shock:

  1. Provide extra shade for the newly planted hydrangea for a few months. It’s best to avoid direct sunlight during this period.
  2. Water the plant when the soil about an inch deep near the roots is dry, but be careful not to overwater.
  3. To minimize transplant shock, transplant hydrangeas in early spring before they leaf out. Do it gently to avoid damaging the roots.

Should you cut off yellow hydrangea leaves?

Yes, you should trim off yellow leaves from your hydrangea. This helps prevent the spread of fungal diseases. Yellow leaves often carry fungal spores, which could infect healthy leaves.

When cutting, do it at the middle of the leaf stem (petiole) to avoid harming the branches. Dispose of the removed leaves in the trash, away from your garden. Remember to sterilize your pruning tools both before and after use to prevent spreading any disease.