Are Your Cucumber Leaves Turning Yellow? (5 Possible Causes)

Cucumber Leaves Turning Yellow

Growing your own personal garden can be one of the most rewarding hobbies you take on in your household.  When all of your fruits and vegetables are doing well, you and your family can enjoy your bountiful harvest. However, when your plants start dying, it can be frustrating trying to figure out exactly what has gone wrong.

If your cucumber leaves are turning yellow, this is a clear indication that your plant is unwell and near death.  This could be for a variety of reasons ranging from not enough sun, water, phosphorus, or nitrogen, to too much. There could be extreme weather conditions, pests eating your plant, or your plant could not be properly trained.

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Five Common Reasons Your Cucumber Leaves Are Turning Yellow

Caring for plants is a big responsibility, and just like pets or babies, they cannot tell us what’s wrong. Fortunately, just like humans and pets get a fever, plants turn different colors to tell us they are unwell. Chlorosis is the scientific name for leaves turning yellow, caused by a lack of chlorophyll.

Yellow cucumber leaves indicate your plant is out of balance chemically or that something is causing it to be sick. Without chlorophyll, your plant cannot convert sunlight into energy and is sure to die unless you take these steps.

1. A Lack of Nitrogen or Phosphorus

Most plants need nitrogen in large amounts to drive plant growth.  It plays a crucial role in the composition of proteins in plants. Nitrogen is also a significant component in the production of chlorophyll, which is vital for photosynthesis. This is the process when plants use sunlight to produce energy.

Without nitrogen, the plant could die, but even if it lives, it may not produce or flower.  To adjust nitrogen levels, you can add composting manure or coffee grinds to the soil.  You can also find a nitrate-rich fertilizer or one specifically made for cucumber plants.

Just like with nitrogen, a lack of phosphorus can also cause your cucumber leaves to become the color of bananas.  To rectify the lack of phosphorus, you can try adding bone meal, manure, rock phosphate, and phosphate-fertilizers.

2. Too Little or Too Much Water

All plants need food and water, and just like humans, if you deprive them of water, they die.  The main requirement of cucumber plants is water, and they require at least an inch of water per week. If you live in an extra dry or warm climate, it’s best to water daily or several times a week.

A good test to check to see if the soil is damp enough is to put your finger in it.  If the soil is dry down past the first joint of your finger, your soil lacks water.  It’s essential to water your cucumbers on a schedule as inconsistency can lead to a bitter taste.

However, you definitely want to be careful not to overwater your cucumber, as this can also drown it.  Yellow leaves can be a clear sign of leaf overwatering.  It’s also bad if there’s standing water, so you’ll want to make sure your cucumber plant has adequate drainage.

3. Too Little or Too Much Sun

It’s hard for cucumbers to get too much sun as they are a full sun plant. This is different from extreme weather conditions, which we’ll talk about below.  Ideally, your cucumber should receive at least 5 to 8 hours of full sun per day.

If you plant your cucumber in the wrong spot, like in a home shadow, you may need to move it.  You should pay careful attention to where the sun rises and sets each day. This will allow you to determine the sun’s path and where you should place your cucumber plant.

You’ll also need to monitor the weather in a freeze or extreme storm conditions.  Cucumbers thrive under temperatures of around 65° to about 75°F.   While many varieties can tolerate the heat, it’s best that they not stay that way for long.  

Your cucumbers can experience stunted fruiting and growth at temperatures above 85°F.  Conversely, cucumbers will die if the temperature gets below 32°F.  You should definitely cover your cucumbers with a tarp if you’re in for a freeze.

4. Bugs Are Eating Your Cucumbers!

Cucumbers are tasty, and humans aren’t the only ones who think so!  There can be lots of little critters eating your cucumbers, including aphids, slugs, snails, spider mites, and wireworms.  There’s even a yellow and black bug nicknamed the cucumber beetle, which has a spotted and a striped variety. 

To rid yourself of these pesky pests, you can pick them off by hand when you notice them.  You can also use kaolin clay to mask the plant or plant other plants nearby that have smell deterrents.  Finally, you can set a sticky trap near your cucumbers to catch them. 

Some bugs don’t like cucumbers: sugar ants can’t stand them.  So, cucumbers would be an excellent repellent to keep ants out of your garden.

5. Not Enough Space to Grow

Cucumbers are known for taking over gardens with their rapidly growing tendrils that like to attach to everything in sight.  Because cucumbers require so much space, a common mistake is that people misunderestimate how much room they need to grow.

If you can, try to grow your cucumbers vertically.

How to Train Your Cucumbers to Grow Vertically

To grow your cucumbers vertically, you’ll need to train them, and you’ll need the following items.

Tools You Need for the Job:

  • A wooden stake or fence post (or a trellis)
  • A drill
  • Some wooden dowels or string
  • A drill bit the size of your wooden dowels
  • Some zip ties or bread ties 

Perform the following steps to train your cucumbers:

Step 1:  Set up the Wooden Structure

If you have an existing trellis, you can use that to train your cucumbers.  You may need to use a zip tie at first while the cucumbers get used to where you’ve put them.  Over time they will learn where you’d like them to grow quickly.

Step 2: Insert Stakes or Poles

If you don’t have a trellis, you can stick wooden stakes or poles into the ground with just a few inches between them. Your cucumber plant will have separate vines, and each should get its own stick.  

Step 3: Attach Cucumbers to Dowels or String

If you have a roll of string, you can run the string horizontally between the stakes.  If you don’t, you can use your drill to drill holes. Attach wooden dowels inside each hole by pressing firmly.  Wrap your cucumber tendrils around the wooden dowels or string to show it where to attach.  

You can also use chicken wire.

Step 4:  Check Your Cucumbers Frequently

Check your cucumbers daily to ensure they continue to grow in a spiral around the strings or sticks.  Over time, they’ll eventually grow in the direction you wanted and will do that naturally from then on.

Because cucumber tendrils like to attach to everything in sight, you should be careful what you put near your cucumbers. If you place a cucumber plant next to a more fragile plant, it could break it after the added weight.

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Related Questions

Is there an app that can help with my cucumbers?

Sometimes it may be difficult to tell why your cucumber leaves are yellow, or even if they are yellow.  Fortunately, like everything else, there’s an app for that.  Several apps on the market allow you to take pictures of your plant and upload them.

Once you upload the picture, the app will identify the plant, genus, and current health status of the plant.  It will even give you suggested remedies based on your plant’s specific ailment.  PictureThis, PlantSnap, Seek, and Plantyx are all available for free in the App Store.

Should I dig up and replant my cucumbers?

If your cucumbers aren’t doing well and you’d like to try again, you may want to dig them up.  This is also helpful if they are in a pot or need more space.  You may also need to relocate them to train them to grow vertically.

A cucumber is a cucurbit, and it does not like to be uprooted, especially because it grows so rapidly.  There is a lot of risk to moving your cucumber so just be sure it’s worth it.  It’s helpful to move it as early in its process as you can.

Can I grow a cucumber plant from a cucumber?

You can grow cucumber plants from a cucumber, but it is a lengthy process. You’ll have to cut a cucumber in half lengthwise and extract the seeds.  

Place the seeds and pulp into a small jar and fill with water.  The mixture needs to ferment for up to 3 days, and then you have to remove the pulp from the seeds. As with any plant, it’s better to start your seeds inside in a pot until it’s a healthy seedling. Then you’ll be able to transfer it into the proper garden.

Because this process is complicated, you may just want to buy a cucumber plant if you’re new to growing cucumbers.  You can also purchase seedlings at your local nursery, Home Depot, Lowe’s, or even your local grocery store.

Stacy Randall

Stacy Randall is a wife, mother, and freelance writer from NOLA that has always had a love for DIY projects, home organization, and making spaces beautiful. Together with her husband, she has been spending the last several years lovingly renovating her grandparent’s former home, making it their own and learning a lot about life along the way.

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