There’s nothing better than a crisp snack and a cool beverage during summer. Perhaps you want fresh slices of cucumber to snack on or a refreshing lemonade drink to battle the heat of the sun. It’s always more satisfying if the vegetable came straight from your garden and onto your plate or glass.
Summary
The most common reasons cucumber plant leaves often turn yellow or brown are because of nutritional deficiencies or disease. Viral and fungal infections are common types of diseases that turn cucumber leaves yellow or brown. Overwatering is the most common problem that can turn cucumber leaves yellow or brown.
Here are our favorite products for each cause.
Invalid table id.Cucumbers (Cucumis sativus) are sun- and water-loving plants since these are native to sub-tropical regions. They are fairly easy to take care of and can grow quickly, giving you a bountiful harvest.
However, there are times when things go wrong. Your plant may be wilting. Cucumber leaves can turn yellow, white, or brown. Leaves can develop black or white spots. It all leads to ruining the chances of it setting fruit.
To help you have a bountiful harvest, we’ll enumerate some of the most common reasons behind these issues. We’ll also include their respective treatment and precautions.
Why are the cucumber leaves turning yellow/brown?
Abnormal yellowing is called chlorosis, which happens when they lack chlorophyll. It’s an essential green pigment for survival. This can be caused by a range of things. Some of the most common causes are damaged roots and poor drainage.
Nutrient deficiency or high soil pH are also common causes. Other symptoms that accompany yellowing and browning (scorched leaf) wilting may be caused by diseases or pests. Things to look out for include lesions or unusual spots.
wilting and yellowing
Image source: Guan, W., Egel, D., & Ingwell, L.
Diseases, Pests, and Problems
There are a lot of diseases and pests that can cause a loss of yield in cucumbers. Suppose you noticed it wilting and developing spots or different leaf colors.
You’ve even given them enough amount of sun and other important things they need. In that case, you might need to check for diseases and pests.
It’s important to quickly determine the cause behind the symptoms your plants are experiencing. A pathogen or pest infestation may quickly spread and destroy your crop.
Image source: Garden
Overwatering
The most common sign of overwatering is leaf yellowing or appearing limp. Roots become damaged and unable to absorb nutrients when the soil around them is too moist or submerged in water.
Overwatering can cause root rot because moist areas promote the growth of molds. Since overwatering leads to the inability of roots to absorb nutrients, they will also suffer from nutrient deficiency. It eventually leads to chlorosis.
To solve this, all you need to do is reduce watering to only when it truly needs it and make sure to get rid of any standing water around the base. Ensure that your garden bed or pot has good drainage.
overwatered cucumber plant
Image source: Stack Exchange
Nutrient deficiency
The appearance of chlorosis (yellowing) will be different in terms of where it manifests in the leaves, depending on the type of nutrient deficiency.
This is the most common reason for chlorosis in most plants since nitrogen is involved in producing an important pigment, chlorophyll.
- SYMPTOMS – Chlorosis develops in older leaves first, then progresses towards younger ones.
- REASON – Nitrogen is required in chlorophyll production, the green pigment that traps the energy from sunlight. As a consequence, a shortage of nitrogen reduces the capacity to get energy during photosynthesis.
- A nitrogen-deficient vegetative growth (stunted growth) and fruit production are both severely restricted. If it is nitrogen-deficient during the flowering stage, the fruiting potential will be affected negatively. Yield will be low with distorted and discolored fruit, or fruits may not develop at all.
How to treat nitrogen deficiency
Fertilize with nitrogen fertilizer (N fertilizer) with a proper dilution rate and form of nitrogen. Fertilize it weekly with a low-nitrogen & high-potassium fertilizer with an N-P-K ratio of 2-3-6 for container-grown. For soil-grown ones, apply a 20-50 kg/ha of N via side-dressing. Put the fertilizers in a shallow furrow along the side of the crops.
Check your potassium fertilizer to see if your nitrogen is being sufficiently supplied to your plant. You still see symptoms of N deficiency. Excessive potassium can also cause nitrogen deficiency.
Here are some great fertilizers to consider to treat yellow leaves when a lack of nutrients arises.
| Name | Organic Tomato & Vegetable Plant Food Fertilizer |
| Item Form | Granular |
| Item Weight | 2.25 Pounds |
| Manufacturer | The Old Farmer’s Almanac |
| Product Dimensions | 2 x 7 x 10 inches |
Pros
- We love that it’s organic.
- It is a great fertilizer for vegetables.
- It’s done wonders for our vegetables.
Cons
- Some people have had issues with the delivery. However, we didn’t.
minimal (B), intermediate (C), and severe (D) nitrogen deficiency
Image source: Little, C.R.
Nitrogen-deficient plant
Image source: Haifa
Excessive nitrogen can also cause chlorosis
If the leaves turn yellow despite giving it nitrogen fertilizer, it may be caused by excessive nitrogen. Unlike most plants, they require lower amounts of nitrogen. Overfertilizing it with a high-nitrogen fertilizer will cause more damage than good.
- SYMPTOMS – Chlorosis will be accompanied by wilting and downward cupping of older parts. Lower ones will exhibit chlorosis next, with brown burnt areas or scorching.
How to treat excessive nitrogen or overfertilizing
To remove excess fertilizer, leach it using freshwater. Use a fertilizer with the proper NPK ratio to fertilize accordingly.
overfertilized (excessive nitrogen)
Image source: Haifa
Potassium deficiency
Unlike most plants that require nitrogen as the bulk of their nutritional requirement, they have high potassium requirements. They’re one of the few plants that need more potassium than nitrogen.
- SYMPTOMS – Cupping, yellowing, and scorching (appears burnt and brown) manifest in older parts first. Chlorosis starts to occur at the margin, then spreads inwards to the center.
- REASON – Potassium is an important nutrient for all plants since it plays a major role in a lot of their physiological functions. Some of the many processes that potassium is involved in are the transportation of sugars (food) and growth and metabolism. It also influences the regulation of water balance and protein synthesis. Fruit development and disease resistance are just two other things it helps with.
- A potassium deficient plant is stunted, with short internodes and small leaves. It exhibits low and abnormal fruit development, sporting brown spots and a spongy-like texture.
How to treat potassium deficiency
Fertilize it properly with the correct ratio of nutrients. Check if you’ve been overfeeding with nitrogen and calcium. Sodium can also be an issue.
These can cause potassium deficiency as well. Their potassium requirements tend to be higher during the flowering stage. Make sure to adjust your fertilizer and schedule according to the growth stage.
Since they need more potassium than nitrogen, the typical K:N ratios are around 1.8:1 and 2.1:1.[3] It will be better for those grown in medium or heavy soils to incorporate potassium nitrate in the soil before you plant. For sandy or well-drained soils, you should do side-dressing of water-soluble potassium fertilizers.[2]
yellowing & scorched leaves of a potassium deficient cucumber
Image source: Haifa
K-deficient cucumber plant with yellow scorched cupped older parts
Image source: Haifa
Magnesium deficiency
An excessive supply of other nutrients can cause deficiency or lack of uptake of another nutrient. Magnesium deficiency can be caused by excessive potassium, ammonium, or calcium. Like nitrogen, magnesium plays a key role in the production of chlorophyll and photosynthesis.
- SYMPTOMS – Yellowing of older parts is the main symptom of Mg deficiency. A light tan burn follows it if the deficiency becomes severe.
- REASON – Magnesium is a major component of chlorophyll. A lack of magnesium severely affects the production of this pigment. As a result, photosynthesis will be affected, and fruit yield will be affected.
How to treat magnesium deficiency
Before planting, use magnesium-rich minerals or water-soluble magnesium nitrate for crops. You can incorporate it as a foliar spray. Examples of magnesium-rich minerals are magnesite and dolomite. Use 300 kg/ha for the former and 800 kg/ha for the latter.[2]
Old leaves of cucumber exhibit chlorosis (left and right) and a light tan burn (right). A young leaf (center) that is not as affected by the magnesium deficiency.
Image source: Haifa
Iron deficiency
Just like nitrogen and magnesium, iron is important in chlorophyll production. Iron deficiencies can be caused by poor drainage, alkaline soil, or high amounts of metallic ions in the soil or water.
- SYMPTOMS – New/young leaves of magnesium-deficient cucumbers are pale green to yellow. It is followed by scorching or browning due to sunlight if the deficiency becomes severe.
- REASON – Iron is needed for chlorophyll production. Without enough iron, the production of this green pigment is negatively affected. Iron is also needed for other processes like respiration.
How to treat iron deficiency
Since iron becomes unavailable to plants when the soil is alkaline (above pH 7), you need to correct its pH by acidifying it. Good drainage and aeration in the soil will help your plant’s iron uptake. You can use foliar sprays of iron sulfate at 150 g/100 L [2] or apply iron fertilizers to the soil.
young terminal leaves (at the top) of iron-deficient cucumber showing chlorosis
Image source: Haifa
Phosphorus deficiency
Phosphorus is important in all stages of development, from early growth to developing reproductive organs.
The phosphorus requirement is higher during crop establishment right after transplanting when roots. It’s also important during early growth. Since they continuously produce both vegetative and fruiting parts, they need a steady phosphorus supply.
- SYMPTOMS – The oldest leaf at the base of the plant turns bright yellow. However, the ones directly above it remain dark green. Brown patches also appear in the old leaves; these will be scorched and spread.
- REASON – Phosphorus is vital for cellular division and energy transformation. A lack of phosphorus will negatively affect growth.
- A phosphorus-deficient plant has weak roots and stunted growth. You’ll often find dull gray-green young leaves and low fruit production.
How to treat phosphorus deficiency
You can solve phosphorus deficiency for crops by fertilizing with a balanced NPK fertilizer or using foliar sprays. You can introduce phosphorus by using a soluble phosphorus source like monopotassium phosphate for the soil.
The oldest part of phosphorus-deficient cucumber is bright yellow, while younger parts remain green in color.
Image source: Haifa
Image source: Haifa
Why are they turning the wrong color?
There are other reasons for chlorosis and leaf scorching besides nutrient deficiency. These color changes may be brought upon by pests or due to a disease caused by an infection. Nutrient deficiencies seldom cause a cucumber leaf to turn white. Still, such symptoms can appear if fungi or other pathogens infect your plant.
white-spotted/colored leaf
Image source: University of Minnesota Extension
