Bougainvillea plants are covered with color over spring, summer and fall with beautiful green shiny leaves. If bougainvillea leaves are turning yellow in summer this could be a sign that the plant is lacking water, nitrogen, magnesium or damaged roots. Leaves should be a deep green over summer but if they are not there could be a problem.
Bougainvillea that develop yellow leaves in summer can be saved if the problem is addressed. This article will explore the top causes of bougainvillea leaves turning yellow in summer and how to solve each one.
Why bougainvillea leaves turn yellow in summer
Here are the top causes of yellow leaves developing in bougainvillea plants and how to solve each one.
1. Cold weather
Bougainville leaves can turn yellow in summer if there is a sudden cold snap of weather. These plants love warm summers so if you live in a cold southern or northern region they can struggle to grow.
Bougainvillea plants need protection from any cold changes as their leaves can rapidly curl or turn yellow. Temperatures below 40 degrees Fahrenheit can stress the plant and it can head into hibernation.
In very cold winters, bougainvillea will actually drop their leaves until the weather warms in spring.
If you live in an area that experiences cooler summers it is best to plant bougainvillea in a position that gets protection from cold winds. Plant them next to other shrubs or near a garden screen to break up the cold wind.
If the plant loses its leaves, don’t panic. With regular water they can grow these leaves back and recover. Cut back any dead wood and the plant will regrow when the weather warms up.
2. Hot winds
While cold winds can stress bougainvillea hot winds are equally troublesome. Hot summer winds can cause bougainvillea leaves to curl, drop or turn yellow. While these plants love warm, humid summers, hot winds can dry out their leaves and they can lose color.
Protecting bougainvillea from hot winds is easily achieved by surrounding them with other summer hardy shrubs. Anything that protects them from strong winds is an ideal companion to the bougainvillea. Bottlebrush is a great choice because they can tolerate hot summers well.
3. Too much water washing away nitrogen
Overwatering bougainvillea in the summer can cause nitrogen to wash out of the soil. A nitrogen deficiency can cause bougainvillea leaves to turn yellow in summer as the chlorophyll is lost from the leaves.
Too much water from rain or irrigation can wash this water soluble vitamin out of the soil and cause the leaves to lose color.
To fix this problem add a few handfuls of pelleted chicken manure around the bougainvillea. Water it in well and the nitrogen will be slowly released to the plant. Bougainvillea plants usually only need fertilizer once per year.
I like to use a natural option which will slowly release the nitrogen as too much can reduce flowering.
4. Not enough water causing the plant to dry out
Bougainvillea plants are drought hardy but if they get too dry they can develop yellow leaves in the summer. If they are planted in sandy soil that does not hold water well they can get dry out even faster.
Bougainvillea plants need watering once or twice per week in warm weather. It is better to deep water the plant around the root system rather than watering a small amount more often.
Potted bougainvillea plants will benefit from regular water but check the soil before adding more. Water the plant when the top soil has dried out 2 inches below the surface. Avoid letting the plant sit in pot trays full of water as this can rot the roots.
5. Lack of iron or magnesium
Micronutrient deficiencies such as iron and magnesium can both cause the bougainvillea leaves to lose their color and turn yellow over summer. Magnesium deficiency will cause the leaves to turn yellow while leaving the veins green.
Magnesium deficiency will look similar to iron deficiency, however it will usually start at the leaf tip, leaving the rest of the leaf and veins a darker green.
Both iron deficiency and magnesium deficiency can be solved easily by the addition of liquid chelates. Iron and magnesium chelates can be bought from garden centers, diluted and watered onto the root system.
Over the next 1-2 months the leaves can regain their green color. These are easy to apply and simple way to solve this nutritional problem.
6. Damaged root systems
Bougainvillea have sensitive root systems and can suffer from damage easily. Raking or digging near the surface of the soil around the root system can damage the brittle, surface roots. Root damage can stop the plant getting the water and nutrients it needs to grow well and can cause yellowing leaves.
Bougainvillea roost grow like a tight mat near the surface of the soil and can be easily torn or broken.
Repotting bougainvillea also risks damaging their roots. They hate any root disturbance so being too harsh with their roots when handling can cause transplant shock.
7. Old leaves
Bougainvillea plants will naturally replace old leaves with new over time. Before the old leaves drop off, they can turn yellow or brown. This is a completely natural process and can happen throughout the year, including summer.
This is not a problem to worry about unless the plant is losing excessive leaves during summer. The plant will replace the old leaves with new and keep its bushy habit.
Bougainvillea Leaves Turning Yellow in Summer | Summary
Bougainvillea plants can develop yellow leaves over summer if they are not getting enough water, if they are exposed to hot winds or if they are overwatered. A lack of essential nutrients like iron, magnesium and nitrogen can all cause the leaves to turn yellow.
Feeding bougainvillea with a nitrogen rich fertilizer like chicken manure pellets and treating any deficiencies with chelates will quickly turn the leaves back to green.