Our grapevine’s leaves were turning brown this past season and we were a bit concerned if the plant would make it. To find out more, I did some research. Here’s what I found about grapevine leaves turning brown.
Grapevine leaves turn normally turn yellow and brown in the autumn. However, if they’re turning brown in the spring or summer, it’s likely due to under-watering, extreme heat, improper nutrients, or pests and diseases. For best results, only water grapevines when the soil is dry and provide compost and mulch.
So, while grapevines get brown leaves for several reasons, how can we tell which issue is causing it, and what can we do to fix it? Let’s take a closer look.
1. Seasonal
This past winter, I went to a local winery with some friends and one of them said, “Why would I go to that vineyard? All of their grapevines are dead!”.
I understood why they thought this way. They’re from southern California, where there’s little to no frost and many plants are evergreen. Growing up in Florida, I was also unfamiliar with deciduous plants before I started gardening.
I replied, “They’re not dead—they’re just dormant.”
Grapevines are deciduous plants, so they naturally drop their leaves in the fall and winter. This is a survival strategy many plants picked up to successfully live in more temperate climates. By shedding their leaves, the plants enter a dormant state—similar to a bear hibernating.
Typically, these 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’s leaves are drooping or turning yellow, red, or brown in the fall or winter, know that this is normal. Leaves with discolored spots are different and can indicate disease (more on this later).
However, what happens your grapevine is has brown leaves in the spring or summer?
2. Under-Watering
Aside from seasonality, the most common cause of brown leaves on grapevines is under-watering. When grapevines don’t get enough water, their leaves begin to dry, curl, and brown in the process. Eventually, without sufficient water, the grapevine will die.
So, what’s the best way to water grapevines?
Ideally, only water grapevines when their soil is dry. You can check this by pushing a finger 2-4 inches into the soil. By watering in this way, you’re preventing both under-watering and over-watering. Additionally, provide 2 inches of compost and 4 inches of mulch to retain moisture and protect the soil.
When watering, aim to soak the ground down to 2 feet as 90% of grapevine roots are found within this depth. Many vineyards have found success using drip irrigation to water their grapevines as much of the water gets absorbed into the ground (as opposed to excess evaporation from sprinklers shooting water into the air).
Also, providing compost and mulch are essential practices that go a long way.
Compost provides valuable nutrients for the grapevine (as well as beneficial soil life) and increases the richness of the soil. For every 1% increase in the soil’s richness, 1 acre of soil can hold an additional 20,000 gallons of water (source).
Mulch is equally as important as compost as it protects the soil from drying out and eroding in the sun and wind, which also keeps the beneficial soil life alive. It also significantly reduces evaporation.
When applying compost and mulch, make sure to keep them at least 3 inches away from the stem of the grapevine as the moisture can encourage mold on the stem. Reapply compost every 1-2 months and mulch every 3-6 months.
Use mulches such as leaves, bark, and straw. However, pine needles and pine bark are some of the best mulches since grapevines prefer slightly acidic soil (more on this later).
However, if your grapevine’s soil has poor drainage, make sure to address this first as compost and mulch can make the drainage worse in this case.
Generally, with poorly draining soils, potted grapevines can be repotted with fresh potting soil, while planted grapevines are a bit trickier. Typically, the best way is to provide lots of compost on top of the soil and let it naturally work its way into the soil over time.
If you’re working with heavy clay soil, the poor drainage and alkalinity will likely lead to growth issues for the grapevine. In this case, it can be better to plant on mounds of soil instead of digging into it.
For more information about clay soil and planting in mounds, check out my other post: Can Fruit Trees Grow in Clay Soil (& How To Plant Them)?.
3. Extreme Heat
The common grapevine, Vitis vinifera, makes up most of the wine grapes we have, including Cabernet Sauvignon, Chardonnay, Pinot noir, and Merlot (source). Vitis vinifera is generally hardy down to USDA zones 6-7. However, there are some exceptions.
Most Vitis vinifera cultivars are hardy in Zones 6 or 7, meaning healthy vines can survive temperatures from zero to minus 10°F. Most American (Vitis labruscana) and hybrid varieties, including recent releases from the Cornell grape breeding program, are hardy to Zone 5 (hardy to -10°F to -20°F), and some of the newer “super hardy” cultivars developed in the Upper Midwest are hardy in Zones 3 or 4 (the hardiest of these varieties are hardy to about -40°F).
Rick Dunst, Viticulturist, Double A Vineyards, Inc.
So, while most grapevines are great at handling cool temperatures, how do they perform with hot temperatures?
When grapevines get too hot (above 85ºF), their leaves dry out quicker than their roots can transport moisture—cooling the leaves. As a result, the leaves begin to dry, curl, brown, and drop.
Most vineyards have their grapevines planted in fields, completely exposed to the elements, so there’s not much they can do in terms of protecting them from extreme weather. However, there are some ways you can get inventive and take care of your grapevine.
- Provide compost to improve the water retention ability of the soil. This goes a long way in regulating the soil temperature and cooling the plant.
- Apply mulch to further regulate the soil temperature and keep more water in the soil.
- Provide shade for the grapevines by using large umbrellas, shade sails, or other trees. A good way to do this is by planting grapevine companion plants that are overstories such as pine and oak trees.
Keep in mind that grapevines are also a great way to provide shade for your garden and house. In the photo below, we’ve trained our grapevine to grow up a wooden overhang and shade our patio.
For best results, consider using your grapevines and other plants to shade the western side of your property (as the western, afternoon sun gets the hottest).
4. Improper Nutrients
Grapevines that are over or under-fertilized become stressed, leading to browning and dropping leaves. A lack of nutrients causes deficiencies while nutrient potency from excess fertilizer causes the grapevine’s roots to burn.
For best results, use a quality fertilizer once a year or 2 inches of compost every 1-2 months.
Chemical Fertilizers vs Compost
While chemical fertilizers have nutrients in quantity, they typically lack nutrients in quality. This can cause stress for the grapevines as they’re unable to absorb sufficient nutrients. Additionally, much of the nutrients from chemical fertilizers are often leached from the soil when watering.
Chemical fertilizers can also have other, unintended consequences, such as killing beneficial soil life and drying out the soil.
Fortunately, compost and manure have been found to contain more than sufficient nutrients for plants (including grapevines), potentially replacing fertilizers.
Approximately 70-80% of nitrogen (N), 60-85% of phosphorus (P), and 80-90% of potassium (K) found in feeds is excreted in the manure. These nutrients can replace fertilizer needed for pasture or crop growth, eliminating the need to purchase fertilizers.
University of Massachusetts Amherst
Compost also feeds beneficial soil life such as earthworms and mycorrhizal fungi, leading to benefits such as improved soil aeration, nutrient availability, and disease resistance.
Mycorrhizal fungi promote many aspects of plant life, in particular improved nutrition, better growth, stress tolerance, and disease resistance.
Department of Biology, University of Fribourg, Switzerland
However, if you’re not big on compost, you can find out more about the grapevine fertilizers that I do recommend on my recommended fertilizer page.
Soil pH
Keep in mind that nutrients aren’t everything—grapevines also need a specific soil pH to properly absorb nutrients and thrive.
Grapevines prefer a soil pH of 5.5 to 6.5 (source).
This is important because an acidic soil pH dissolves the solid nutrients in the soil, and makes them available to be absorbed by the plant’s finer roots.
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, SUNY College of Environmental Science and Forestry
Two good ways to check the soil’s pH are with pH strips or a pH meter. I prefer using a meter since they’re affordable and easy to use. To see which pH meter I use and recommend, check out my recommended tools page.
5. Pests and Diseases
| Common Pests for Grapevines | Common Diseases for Grapevines |
|---|---|
| Grape Phylloxera | Leaf Spot |
| Japanese Beetles | Tar Spot |
| Grape Berry Moths | Armillaria Root Rot |
| Mealybugs | Mildew |
| Hoppers | Fruit Rot |
Grapevine leaves can turn brown 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.
To see more about pests and how to treat grapevines, check out this resource by the University of Minnesota. You can also reference this resource by napagrowers.org.
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.
