Cucumber leaves turning yellow: 10 main reasons. How to fix the cucumber plant problems?

The health of cucumbers is easy to judge by the leaves. Sometimes people, seeing that the cucumber leaves are affected by a disease or pests and think that all plants need to be removed from the garden. Many newcomers have panic and just one question, why are my cucumber leaves yellowing? Don’t worry, try to determine the cause and fix the yellow cucumber leaves.

cucumber leaves turning yellow

Table of Contents

Cause according to which cucumber leaves turning yellow No. 1: lack of lighting

If the old lower leaves of cucumber plants turn yellow, do not worry – for the cucumber “jungle” this is rather the norm.

Cucumber plants grow a large green mass and light almost does not penetrate inside.

What to do if cucumber leaves are turning? Should I cut off yellow cucumber leaves?

In general, you don’t have to worry.

But for good development and fruiting, do not thicken the planting of cucumbers, tie up and form whips, and regularly remove old yellowed leaves.

Cause according to which cucumber leaves turning yellow No. 2: insufficient watering or waterlogging. How do you tell if you are overwatering cucumbers?

What to do: focus on weather conditions and phases of plant development.

Water for irrigation should be warm – 73-75°F.

Before flowering and fruiting, the cucumber plant requires moderate humidity, and therefore the plants are watered 1-2 times a week (after 3-4 days).

With the beginning of the fruiting period, it is necessary to water the cucumbers more often, after 2-3 days.

In the heat – daily, deeply wetting the ground, and in cool weather, the frequency and volume of watering should be reduced.

What do overwatered cucumber leaves look like? Mulching helps keep moisture in the soil. In rainy weather or excessive watering, cucumbers can be affected by rot.

Cause according to which cucumber leaves turning yellow No.3: nutrient deficiency

  • If the edges of the cucumber leaves turn yellow, a yellow border (marginal burn) appears, and the leaf plates themselves are wrinkled, and deformed, which means that the cucumbers have a potassium deficiency (the pear-shaped fruit indicates the same).
  • If at the same time the flowers are weakly tied or the ovaries dry out, the shoots are brittle, they grow poorly – the cucumber plant lack boron.
  • Young cucumber leaves turn yellow but they have dark green veins (interveinal chlorosis) – cucumber plant lack manganese or iron deficiency.
  • Yellow-green spots (mosaic) appear on old cucumber leaves between green veins – the cucumber plant lack magnesium. The cucumber leaves (including the veins) evenly turning yellow (from light green to yellowish green), and become smaller and thinner – a lack of nitrogen.

What to do if the leaves turn yellow?

Spray cucumbers on the leaf with fertilizers containing the missing nutrient element, or appropriate mineral solutions.

If the leaves turn yellow, organic fertilizers also can help.

For example, with a potassium deficiency, cucumbers are saved by an infusion of ash – 1 cup per 10 liters of water – spraying or watering under the root or a weak pink solution of potassium permanganate (spraying).

Cause according to which cucumber leaves turning yellow No. 4 and the most dangerous: cucumber diseases

Peronosporosis (downy mildew) in cucumbers

The downy mildew is determined by small numerous pale yellow, yellow-brown spots, which gradually increase in size, turn brown and dry out, as well as by the “islands” of white mealy plaque.

The downy mildew develops with temperature changes, and high humidity (more often in spring and in August-September).

What to do if cucumber plants are sick with downy mildew?

As in the previous case, it is necessary to follow agricultural practices, and if a downy mildew is detected, spray with fungicides.

Root rot in cucumber plants

If the cucumber plant leaves gradually wither and dry out, check the roots of the infected plants.

You can see that the root neck turns brown, and the roots rot.

What to do if cucumbers have root rot?

As a preventive measure, steam the soil, pickle the seeds before sowing, do not thicken the plantings, and water the cucumber plants with warm water.

Sick cucumber plants “rejuvenate”: the stem is bent to the ground, and a little fertile soil is poured on top and rooted for 10-15 days.

Fusarium in cucumber plants

The disease is common in greenhouses, especially with large temperature fluctuations in spring.

It affects seedlings and adult cucumber plants.

Before flowering, cucumber plants look healthy, and then, when the ovary appears, they begin to wither.

You can see yellow cucumber leaves, the stems become thinner and dry out, then the roots die off and the whole plant dies.

What to do if the cucumbers are sick with fusarium?

Disinfect the soil in the greenhouse, maintain optimal conditions (temperature, air humidity), and water the cucumber plants only with warm water.

If leaves are turning yellow, infected plants should be destroyed.

Anthracnose in cucumbers

Numerous rounded yellowish (brownish) spots appear on the edges of the cucumber leaves and the stems. On the fruits – sunken spots, light brown, wet ulcers.

What to do if cucumbers get sick with anthracnose?

Carry out the whole range of preventive and therapeutic measures, including pre-sowing seed treatment with fungicides, high-quality balanced top dressing, and removal of plant residues and diseased cucumber plants.

Spray diseased cucumber plants with a 1% solution of Bordeaux mix or 0.5% solution of copper sulfate.

Cucumber mosaic virus

The cucumber mosaic virus is caused by a virus that is activated in hot weather (about 86 °F) or during alternating heat and cold snaps.

The first signs of the disease are yellowish or reduction of green leaf pigment that forms a mosaic pattern on young leaves.

As the disease progresses, the spots merge and only the standard color remains on the veins. Later, the yellow leaves become lethargic and deformed.

The disease of cucumber leaves gradually passes to the fruits: they stop growing, lose their taste, and die.

Ground cucumbers are more likely to suffer from cucumber mosaics, but they can also appear in a greenhouse. Pathogens overwinter in the soil and plant debris and can remain there for up to several years.

What to do if THE entire plant gets sick with anthracnose?

There are no agrochemical remedies for cucumber mosaics since viral diseases are practically untreatable.

If diseased plants are found, they are immediately removed and burned.

Prevention of cucumber mosaic – seed dressing before sowing, greenhouse disinfection, crop rotation.

It is important to regularly inspect the bushes for the presence of aphids and, if insects are found, immediately apply control methods.

In the case of the cucumber mosaic virus, aphids become its carriers.

It is important to prevent the appearance of aphids, as viruses easily penetrate through the damage left by pests on the plant.

The reason you have yellow cucumber leaves No. 5: pests of cucumbers

Spider mites on cucumbers

Spider mites predominantly live on the underside of leaves. Spider mites braid the cucumber leaves with a thin web and suck out the sap.

First, whitish dots form on the leaves, then they become larger, turning into spots. Eventually, yellow cucumber leaves dry up.

What to do if the spider mites appear on cucumbers?

You must spray each cucumber plant with acaricides, paying particular attention to the underside of the foliage.

It is necessary to ventilate the greenhouse, periodically spray the leaves, and adjust the irrigation regime.

Cucumber beetles

Small insects can cause light yellow spots to appear on the leaves. With the development of the lesion, the foliage turns brown and dries.

What to do if cucumber beetles ARE found on cucumbers?

You must spray the cucumber plants with insecticides. Preventive measures from cucumber beetles – regularly dig and loosen the soil, and destroy weeds.

Whitefly on cucumber plants

The whitefly infects cucumber plants primarily in greenhouses, but some species can also live in open ground.

Fuzzy yellow spots appear on damaged cucumber leaves. They are gradually increasing. Cucumber yellow leaves may curl slightly.

What to do if a whitefly is found in the greenhouse?

You must use preventive measures, and insecticide treatment.

The reason you have yellow cucumber leaves No. 6: cucumber plants are overloaded with ovaries

In greenhouses and when growing cucumbers outdoors on a trellis, the leaves may turn yellow and the ovaries dry out if you do not form a plant.

In greenhouses, cucumbers must be pinched, removing and pinching lateral shoots, and leaving no more than 20-25 ovaries at the same time on the entire plant.

Standard scheme for the formation of cucumbers

The lower 4-6 nodes of the main shoot are blinding. In the next 3 nodes, all side shoots are removed, leaving the ovaries. Further, the remaining shoot is visually divided into three parts: the nodes of the lower-lateral shoots are pinched into 1-2 sheets, the middle – by 2, and the top – by 3. Then the shoot is wrapped around the trellis 1-2 times and pinched.

The reason you have yellow cucumber leaves No. 7: cucumbers are poorly pollinated

What to do: when growing bee-pollinated varieties, provide good conditions for bees and bumblebees. In warm weather, keep the greenhouse open or ventilate it periodically. To attract pollinators, plant honey plants, and dill near cucumbers.

Spraying with honey or sugar solution also helps (half a tablespoon of sugar or honey per liter of water). Among the preparations are boric acid (5 g per 10 l), and boron-magnesium fertilizers.

The reason you have yellowing leaves on cucumber plant No. 8: transplant stress

After planting seedlings in a permanent place, cucumbers often turn yellow and wither leaves. The reason for this is stress from the transplant.

Cucumbers, like all pumpkins, have fragile roots, so they endure transplantation extremely painfully. Cucumber seedlings are best grown in individual containers with a volume of at least 1 l.

Cucumber seedlings are planted in a permanent place as soon as 3-4 leaves form on the plants. When planting overgrown seedlings that have already bloomed, the plants can get sick for a long time, and the yellowing leaves of the cucumbers dry out.

To reduce the stress of plants from transplanting, it is necessary to sow seeds no earlier than a month before planting seedlings in a permanent place.

So that the seedlings do not outgrow, the cucumbers are treated with plant growth regulators.

They stimulate the development of the root system and inhibit the pulling of seedlings. The drug improves the survival of seedlings and reduces stress from transplantation.

After planting seedlings, cucumbers need to be shaded for a week or two, while the plants take root in a new place.

During this period, the soil should be moderately moist, and the drying of the earth in the root zone is not allowed. Dense spunbond saves plants from the scorching rays of the sun.

The reason you have yellowing leaves on cucumber plant No. 9: cold stress

At the beginning of summer, the weather often brings unpleasant surprises in the form of return frosts, unexpected cold snaps, squally winds, or hail. Cucumber, this tropical vine, is difficult to perceive such cataclysms.

At temperatures below 46 °F, cucumbers fall into a state of shock, the roots stop working, and the plant “freezes” and waits for the heat to return.

If return frosts caught cucumbers in a greenhouse or open ground, then they need to be saved by all possible means.

In unheated greenhouses, cucumbers are additionally covered with a dense spunbond; in the open field, arcs are installed above the cucumbers and covered with plastic wrap.

After the end of the cold weather, the plants look bad for some time, the cucumbers have small shriveled leaves, and the plants do not burst into growth.

During this period, it makes no sense to do root dressing because cucumber roots are under stress and unable to absorb nutrients.

After a cold snap, frost, or hail, it is useful to treat the plants with an anti-stress preparation with vitamins and amino acids, this will help them regain strength and recover from the shock.

Cause according to which cucumber leaves turning yellow No. 10 heat stress

Even though the cucumber is a heat-loving plant, it can be too hot for it. The optimum temperature for cucumber growth is 72-77 °F during the day and 60-64 °F at night. However, such ideal conditions are rarely created.

At the height of summer, the daytime temperature goes off the scale and rises to 86-90 °F in the shade, while in the sun or a greenhouse it is 104-113 °F. In such conditions, cucumber leaves are turning yellow and wither, which is not surprising.

In the southern regions, it is better to grow the cucumber plant in partial shade, planting in places that are illuminated by the sun for only half a day.

To save cucumbers from the scorching sun helps a special mesh. It is stretched over the beds, and the plants are in a light, lacy shade.

Unlike dense spunbond, the mesh is well blown, so windage is not created, and the shelter does not fly away in strong gusts of wind.

To reduce the temperature in the greenhouse, it is covered on top with a dense white spunbond or stretched inside the greenhouse, under the ceiling.

In hot summers, you can whitewash the ceiling of the greenhouse with a solution of chalk, this will reduce heating because the sun’s rays will be partially reflected.

Single yellow spots on the leaves of cucumbers can form as a result of sunburn if water gets on the leaves during morning watering. In a glass greenhouse, plants can get burned from touching hot glass.


Whatever the reason cucumber leaves are yellow, it is necessary not only to eliminate them but also to help the plant recover and continue growing. After the transferred stress, plants need preparation with a “soft” effect.

Fertilizer with a complex of trace elements and low nitrogen content. Trace elements are absorbed quickly and give a visible effect after a few days, and nitrogen accelerates the growth of new leaves. Fertilizer will be useful after cold snaps, and with chlorosis, as well as for recovering from illness or pest infestation.

2 thoughts on “Cucumber leaves turning yellow: 10 main reasons. How to fix the cucumber plant problems?”

  1. Pingback: 5 basic tips on how to keep outdoor plants alive in winter

  2. Pingback: 11 Causes Snake Plant Yellow Leaf: Best Helpful Tips

Leave a Comment

Your email address will not be published. Required fields are marked *