A few readers recently reached out to me, asking if I knew why their grapevines are getting yellow leaves. I had an idea, but I wanted to do more research to learn more and give them my best answer. Here’s what I found.
Grapevine leaves normally yellow and drop in the fall and winter as the plant enters dormancy. However, if its leaves are yellowing in the spring or summer, the plant is most likely stressed from over-watering, extreme heat, improper nutrients, a lack of sunlight, or pests and diseases.
So, while grapevines get yellow leaves for several reasons, how can we tell which issue it is, and from there—how can we fix it? Let’s take a closer look.
Grapevines are deciduous plants, so their leaves naturally yellow, brown, and drop in the fall and winter. This is a survival strategy many plants picked up to successfully live in cooler, more temperate climates. By shedding their leaves, the plants enter a dormant state—similar to a bear hibernating.
Typically, deciduous plants require chill hours to stay in dormancy (under 45ºF). Warmer grapevine varieties require around 500 chill hours, while colder varieties prefer up to 2000 chill hours. Depending on the variety, the plant can become damaged or die if temperatures drop below 0ºF.
Different grape species and cultivars have varying chilling requirements (from 500–2000 hours) that must be met before bud break can successfully occur.
Hans Walter-Peterson, Viticulture Extension Specialist at Cornell Cooperative Extension
On the other hand, evergreen plants keep their leaves year-round. These plants either developed other ways to survive the cold, or live in tropical climates (with little to no frost).
So, if your grapevine has yellow, red, or brown leaves in the fall or winter, know that this is normal. Leaves with discolored spots are different and can indicate disease (more on this later).
If this is the case for you—you shouldn’t need to fix anything. Just ensure it doesn’t get too cold for your grapevines (0ºF or below for most grapevines) and wait for spring!
However, what happens if your grapevine has yellow leaves in the spring or summer?
The most common reason why grapevines get yellow and dropping leaves is stress from over-watering. This is especially common in soils with poor drainage.
Over time, waterlogged soil can develop mold and lead to root rot (also called Phytophthora root and crown root). Root rot slowly decays the grapevine’s roots, causing drooping, curling, and yellowing leaves. Over several days to a few weeks, it can kill the plant.
So, what’s the optimal way to water grapevines?
The best way to water grapevines is to only water when the top 2-4 inches of soil is dry. You can check this by pushing a finger into the soil. Water until the soil is saturated down to 2 feet deep. Additionally, provide 2 inches of compost and 4 inches of mulch such as leaves, bark, straw, or pine needles.
By watering the soil down to 2 feet, you’re providing 90% of the grapevine’s roots with water.
Also, by only watering when the soil is dry, you’re preventing both under-watering and over-watering. This helps the plant establish water independence.
Grapevines that are watered with frequent and light watering typically only grow extremely shallow roots. After all, why would they grow deeper roots if the water and nutrients are only on the surface?
This keeps the plant at a disadvantage as their shallow roots mean they’re poorly prepared for windy weather and droughts.
So, if you want your grapevine to be more self-sufficient and have a better chance of surviving the occasional drought, water it only when the soil is dry and down to 2 feet deep.
However, soils that have poor drainage (common with clay soils) can complicate this process.
Generally, planted grapevines are hard to amend as there are large volumes of soil (needing large amounts of amendments). Because of this, the best way to amend garden soil for better drainage is to apply 2 inches of compost on top of the soil every 1-2 months. Over time, the smaller particles will work their way into the deeper soil. Avoid excessive mulching at this time it can further lock in the moisture.
On the other hand, potted grapevines with poor drainage can be amended fairly quickly by repotting them with fresh potting soil. Since the roots are limited to the pot, they generally don’t get as much transplant shock as digging up planted grapevines with spread-out and established roots.
But, what if we’re watering our grapevines correctly? What do we check next?
3. Improper Nutrients
Excess nutrients are typically caused by over-fertilizing grapevines. This can lead to the potential burning of the grapevine’s roots, causing the plant stress and developing drooping, curling, and yellow leaves. Normally, fast-release fertilizers are the cause of over-fertilization as compost isn’t potent enough.
Lack of Nutrients
|Entire leaf is pale or yellow
|Dark green veins, rest of the leaf is yellowing
|Broadly pale leaves, foliage color looks mottled or smeared
A lack of nutrients also causes stress to the grapevine, which then develops yellow leaves. Insufficient nutrients are commonly caused by poor soils, leaching, and other stressors. Nutrient leaching is when soils have too much drainage or are over-watered and the nutrients seep too far down into the soil, out of reach of the plant’s roots.
The Best Way to Fertilize Grapevines
You can choose to fertilize your grapevine’s plant’s soil with fertilizer or compost. If you choose store-bought fertilizer, aim for a balanced NPK (nitrogen, phosphorus, and potassium).
Generally, while chemical fertilizers have nutrients in quantity, they typically don’t have nutrients in quality. So, chemical fertilizers might be sufficient over the short term, but over the long term, they often cause damage by short-circuiting the nutrient exchange between the plant and its beneficial soil life. This leads to dry and dead soil (dirt) and overall decreased plant health.
On the other hand, compost provides more than sufficient nutrients, increases water retention, and promotes healthy soils. For example, every 1% increase in the soil’s richness (organic matter) leads to 20,000 more gallons of water absorbed per acre (source).
Many gardeners are even finding that compost is successfully replacing their fertilizers.
If you’d like to see my recommendations for both compost and fertilizer, check out my recommend fertilizer page.
Aside from nutrients, keep in mind that grapevines need a balanced soil pH between 5.5 to 6.5 (source).
The reason why grapevines prefer soil with a slightly acidic pH is that it’s ideal to dissolve nutrients in the soil.
Fourteen of the seventeen essential plant nutrients are obtained from the soil. Before a nutrient can be used by plants it must be dissolved in the soil solution. Most minerals and nutrients are more soluble or available in acid soils than in neutral or slightly alkaline soils.Donald Bickelhaupt, Instructional Support Specialist, Department of Forest and Natural Resources Management
Two good ways to check your soil’s pH are either by using a pH strip or a pH meter. I prefer using a pH meter since they’re affordable and easy to use. To see which pH meter I use and recommend, check out my recommended tools page.
If you find that your grapevine’s soil is too alkaline (above 6.5) you can add acidic amendments such as coffee grounds, sand, and peat moss. On the other hand, if your grapevine’s soil is too acidic (below 5.5), add alkaline materials such as wood ash, charcoal, or lime.
Additionally, cold and/or wet soils are not good at promoting nutrient uptake as the grapevine will either be slightly dormant during the cold or too stressed in wet soils.
If you’re growing your grapevine in a container, aim to have at least a 15-gallon pot as the grapevine’s roots need a bit of room to spread.
4. Lack of Sunlight
Grapevines generally require at least 6 hours of sunlight to photosynthesize properly. Without it, their leaves turn yellow and they’re unable to develop sugars for the plant. Over time, this low energy leads to the plant’s declining health, and eventually, the plant can die.
Tips to Increase Sunlight
- Plant the grapevine in a south-facing direction for maximum sunlight (north-facing if you live in the southern hemisphere)
- Plant the grapevine along a south-facing wall to reflect more sunlight and heat onto the tree (some heat even persists into the night).
- Prune some overstory trees that are blocking the grapevine’s canopy from the sun. You can also prune the grapevine itself to allow more light to reach the mid and lower branches. This new space also increases aeration from the sun and wind—discouraging disease from spreading.
5. Pests and Diseases
|Common Pests for Grapevines
|Common Diseases for Grapevines
|Grape Berry Moths
|Armillaria Root Rot
Grapevine leaves can turn yellow and fall off due to pests and diseases such as Grape phylloxera, Japanese beetles, leaf spot, and root rot. Treat pests by using organic insecticides or companion plants, and diseases with organic fungicides.
You can generally tell if a grapevine has pests by inspecting the leaves and the fruit. You should be able to see the pests themselves or signs of the pest such as holes in the leaves or fruits.
On the other hand, diseases are typically shown as yellow, red, or brown spots or blotches on the leaves and other parts of the vine.
To see a full list of the diseases grapevines get and how to treat them, check out this resource by Michigan State University.
A Note on Pesticides and Fungicides
We recently had an issue with caterpillars eating our basil plants and we were about FED UP. Every time we’d plant basil plants, the caterpillars ate it.
Fortunately, we found an organic spray at our local nursery that’s made from fermented rum. The day after spraying, we’d find dead caterpillars on the soil.
If you’d like to find out more about this organic spray, you can find it here on Amazon.
So, what’s my point here?
Before using chemical sprays, weigh the pros and cons and consider trying organic or permaculture-based treatments first. Even though chemical sprays and fertilizers are an easy way out, like all easy and convenient things, there are usually long-term costs!
To give you a head start, Stefan Sobkowiak – The Permaculture Orchard has a great video on a safe, homemade, and more importantly—effective fungicide (hint: the secret ingredient is whey).
Also, check out how Mark Shepard uses a method called STUN (Sheer-Total-Utter-Neglect) to help his berries, fruit, and nut trees THRIVE.