Yellowing or chlorosis is a condition where the plant leaves turns yellow due to lack of chlorophyll.
Should you be worried about this?
No, instead you must inspect your pumpkin plant leaves thoroughly. So, that you can determine the cause and revive the plant.
Yes, its heart wrenching to see the green foliage turn yellow, when the harvest time is around the corner.
You’d be happy to know that yellowing of pumpkin plant leaves can simple a normal part of their growth. (Source) But, you need to diagnose the plant soil, its fertilizers and watering frequency to determine this.
Excess exposure to sunlight, lack of nutrients, light, inadequate watering, diseases and pests can be held responsible for pumpkin plant leaves are turning yellow.
Pumpkin Plant Leaves Turning Yellow – Decoding
Initially, you must analyze pumpkin plant and inspect which leaves are yellow and where they are discolored.
Case -1: If you notice the older leaves of your plant are turning yellow, while the new foliage is green and healthy, then you don’t have to worry much.
Probably, stress related issues like inadequate sunlight or overwatering can be held responsible.
Case – 2: Check which part of leaves are yellow. If only the edges of the leaf are getting yellow while the interior stays green, then it can be a common aging process.
Older plant leaves turns yellow when the nutrients supply are shifted to other new leaves.
Even environmental stress which I’ll discuss later in this article can turn edges of new leaves yellow.
Case – 3: In third case, when most leaves are turning yellow in contrast to case-1, then may be underwatering, overwatering, long exposure to sunlight, disease or pests can be reason behind this discoloration. (Source)
Note: In a nutshell, if only few older leaves are turning yellow, then its common and you don’t have to worry much. You must be concerned, if new leaves are turning yellow.
Before dwelling into its causes, if you’re an amateur gardener it is very essential to know growing needs of pumpkin.
Also, later in this article you’ll know about possible solutions to revive yellowing of leaves.
Pumpkin Plant Needs – Soil, Sunlight and Water
While diagnosing yellow pumpkin leaves, gardeners found sandy soil that fail to hold moisture for longer time can result in yellowing of leaves.
Soil should be well drained and at the same time hold moisture for longer time. In above case it’s unfair to held soil as culprit; it can be underwatering that caused chlorosis.
Am going to list essential growing needs for this plant, you can skip this and jump to core topic.
Soil – well drained filled with organic matter
- Ideal soil pH for growing pumpkin is 6.0 to 6.8.
- Sandy soil that includes lots of organic matter is ideal to grow this winter squash.
- While planting pumpkin soil temperature must range between 65F to 95F.
Prepare the potting soil by mixing soil, sand and vermicompost. Or you can buy potting soil from local garden store.
Check this: How Far Apart to Plant Sweet Potatoes?
Sunlight – 8 hours of full sunlight
Choose a spot that gets full sun for at-least 8 hours.
Low exposure or too much exposure can result in yellowing of leaves.
Watering – avoid overwatering and underwatering
Check the soil moisture with your index finger. Water the plant if it’s dry.
Water generously till you see the excess water is drained out of the hole. In hot days, water twice if needed.
Mulching your plant with hay grass can reduce water evaporation in summer.
Fertilizing – organic matter while planting
- Apart from adding organic matter while planting, you should fertilize your pumpkin plant twice in growing season.
- As mentioned this winter squash plants are heavy feeders.
- Low levels of nutrients will impact the harvest and result in discolored foliage.
Why Are My Pumpkin Leaves Turning Yellow – Causes?
To make it easy, I’ll classify causes of chlorosis in two categories. One environmental stress and other disease & pests related.
#1 Water Related Issue (Overwatering and Underwatering)
We all know the importance of water for plant’s survival. Out of curiosity, most amateur gardeners overwater their pumpkin plants. With this water gets accumulated in the soil resulting in root rot.
Overwatering pumpkin plant often results in yellow leaves, stunt growth and eventually killing the plant.
Similarly underwatering the plant may result in drooping and yellow leaves.
Choosing the wrong potting soil that fail to drain excess water, results in overwatering issue.
How to revive:
First make sure the soil is well-drained. Next, check the soil surface. If the soil is dry and plant has drooping leaves, then water regularly.
In case of overwatering, you’ll find too much moisture and in some cases green algae layer on surface of the soil.
Stop watering and transplant the plant if needed.
Also Read: How Often to Water Cabbage – Avoid Overwatering?
#2 Too much sunlight
Like water, your plant needs sunlight for photosynthesis process. But, hot days can break chlorophyll present in the leaves, thus resulting in yellow sunburned foliage. (Source)
How to revive:
This edible plant need 8 hours of sunlight. In hotter days you need to protect your plant from harsh sunlight by using a shade cloth and mulch around its base.
Mulching will control the soil temperature and also reduce water evaporation.
#3 Lack of Sunlight
If you’re growing your plant in such a location that gets inadequate sunlight, then you may see leaves turning pale yellow.
This is because, your plant need sunlight to produce chlorophyll – the pigment responsible for green color of your leaves. Absence of this pigment makes your plant leaves turn yellow.
How to revive:
Shift the plant to a spot that gets enough sunlight. It isn’t possible if you’re growing pumpkin in ground. You must remove the plants that are shade on pumpkin plant.
In simple words: Ensure the plant gets 8 hours of direct sunlight.
Also Read: How Much Sunlight Does Asparagus Need?
#4 Natural Processes
As the plant grow and start to fruit, older leaves of pumpkin plant turns yellow and this is natural process. You don’t have to worry.
Yes, you can cut older yellow leaves off pumpkin plant to avoid rotting and improve air circulation. (Read this: Why Should I Cut Off Yellow Leaves on Tomato Plants?)
Also, pumpkin is an annual plant. When the fruits are ready to be harvested, the plant eventually stops growing and its leaves turn yellow.
#5 Lack of Fertilizer
As mentioned earlier, this edible plant is a heavy feeder. Low levels of nutrients will not just turn leaves into yellow but it will eventually impact the overall growth of the plant.
How to revive:
Use 18-18-21 NPK ratio fertilizer to feed your pumpkin plant. Follow the product manufacturer’s instruction on the dosage.
Apart from this, you can also use natural fertilizers that are high in nitrogen.
Downy mildew, verticillium wilt and sudden wilt are few common disease suffered by pumpkin plant. All these diseases turn pumpkin leaves into yellow.
Verticillium wilt and sudden wilt both if left untreated can kill your pumpkin plant. Initially, leaves turn yellow and then eventually collapse.
Roots and stems of pumpkin plant infected by verticillium wilt turn light brown. While plant roots affected by sudden wilt turn darker in color. (Also Read: How Deep Do Potato Roots Grow?)
Signs of downy mildew are yellow spots will appear on upper leaves and yellowish brown spots on older leaves.
How to revive:
These diseases can easily spread to your next crop if you aren’t planning to rotate the crop.
Removing plant debris, growing different crops in your garden, avoid overwatering and sufficient sunlight can help to prevent these diseases.
Squash bugs, spider mites, white flies and aphids are common pests that attack your pumpkin plant and feed on sap of pumpkin plant.
When you plant gets infected by these pests leaves turn yellow.
Some of these pests also feed on pumpkin fruit, thus decreasing the yield.
How to revive:
Check your plant every week for white tiny flies, aphids or spider webs under leaves. Use insecticidal soap or neem oil to get rid of these pests.
Can yellow leaves turn green again?
It is impossible to undo yellow leaves. However, after diagnosis with the problem and reviving, you can expect new green foliage.
Should I cut/remove pumpkin yellow leaves?
If the leaves are turning yellow as a natural process, then it’s recommended to remove yellow leaves.
Else, just removing leaves won’t help the plant.
Yellowing of leaves can be due to overwatering, underwatering, excess exposure to harsh sun, low nutrient level, disease or pests related issue.
It is important to inspect the plant thoroughly to determine the cause. Only then you can revive accordingly.
Choosing wrong soil often result in overwatering or underwatering issue.
Potting soil should drain excess water but retain the moisture.
Water the plant when the soil is dry up to 1 inch.
The plant needs at-least 8 hours of sunlight to thrive. While sowing, make sure the spot gets required amount of light.
Edible plant like pumpkin is a heavy feeder, supply required amount of nutrients by applying the natural and liquid fertilizers. Disease and pests related issues also result in pumpkin leaves turning yellow. Check the plant every week to avoid such infestation in initial stage.