How to Treat Turnip Greens That Are Turning Purple

Co-authored by JoAnna Minneci and Madeleine Flamiano

Last Updated: July 11, 2022 References

Turnip greens, the leafy tops of turnips, are eye-catching and edible—but what does it mean when they turn purple? In this article, we'll explain why that happens and tell you what to feed your turnips to keep their leaves green. We'll also share ways to treat turnip greens that have turned purple and prevent discoloration in future crops. Read on to keep your crop in good health so you can enjoy a harvest of luscious turnip greens.

Section 1 of 3:

Why do turnip greens turn purple?

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Damaged roots can cause turnip greens to turn purple. Extremely warm weather can make the turnip’s soil too dry, while excessive moisture or too much mulch will make the turnips' soil too wet. Soil that’s too dry or too wet will put stress on turnips' roots and injure them.^{[1]
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Research source} The roots won’t be able to absorb oxygen easily, so turnip greens will start to develop purplish spots, which are signs of an oxygen deficiency.^{[2]
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Turnip greens turn purple when they don't get enough phosphorus.^{[3]
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Research source} Phosphorus is an important nutrient for many crops—when plants, like turnips, don’t get enough of it from their soil, they’ll have a phosphorus deficiency and their roots won't grow normally.^{[4]
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Trustworthy Source
PubMed Central
Journal archive from the U.S. National Institutes of Health
Go to source} Healthy roots are essential for delivering oxygen to plants, like turnips.^{[5]
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Research source} When the roots of turnips are underdeveloped, their leafy tops, or "turnip greens," will become purple because they haven't received enough oxygen and have dried out.

Section 2 of 3:

Options for Treating Nutrient Deficiency in Turnip Greens

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Give your turnips 1 inch (2.5 cm) of water a week to repair their roots. Try this option if your turnips are growing in conditions that might make their soil too dry or too wet. Use a watering can and soak the soil thoroughly. Test the soil's moisture with a trowel to see if the water is at least 2 inches (5.1 cm) deep. If your soil is dry and sandy, or if you're in a drought, water your turnips more than once a week.^{[6]
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- Keep your turnips' soil moist so their roots will develop properly and extract oxygen from the soil—it's more likely that their leaves will become green again.
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Feed turnip greens bone meal to boost levels of phosphorus. This is one way to fix a phosphorus deficiency. First, test your soil’s PH level and make sure it’s below 7.^{[7]
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Research source} If the soil for your turnips has a pH below 7, then add bone meal to it—it will act as a rapid release fertilizer.^{[8]
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Research source} Till in 10 pounds (4.5 kg) of bone meal fertilizer per 100 sq. ft.^{[9]
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- A soil that has a pH level between 6-7 has maximum phosphorus availability. When the soil’s pH is below 7 so that it's alkaline, phosphorus can be converted into a nutrient for turnip greens.
- If the soil’s pH is above 7, then it’ll be too acidic to fully absorb phosphorus.^{[10]
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- Bone meal has a 15% concentration of phosphorus, so it’ll be great for treating a phosphorus deficiency in your turnips.
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Give turnip greens plenty of nutrients with a superphosphate fertilizer. As a possible treatment for giving your turnips enough phosphorus, use a fertilizer that’s a 0-46-0 high phosphorus formula, also known as a “triple super phosphate” blend. ^{[11]
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Research source} Apply it to soil that has a pH level below 7 so the phosphorus will be available to your turnips. Till in ¹⁄₄–¹⁄₂ pound (0.11–0.23 kg) per 100 sq. ft.^{[12]
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Apply rabbit manure to turnip green crops to feed them phosphorus. Rabbit manure is a great option to really enhance phosphorus levels because it’s higher in phosphorus than other manures. Add it to soil with a pH level below 7 so the soil can access the phosphorus in the rabbit manure. Topdress your turnip green crops with pellets of fresh rabbit manure.^{[13]
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- Rabbit manure has 4 times more nutrients than horse or cow manure.
- Pellets of rabbit manure don't need to be composed and can be used as a fertilizer right away.
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Use compost to give turnip greens phosphorus and support growth. Compost is another alternative for boosting phosphorus levels in turnips. Apply composts with biosolids or manure—they have the highest nutrient levels. If your soil has a pH level below 7 that's ideal for making phosphorus available to your turnips, blend in compost to the top 4–6 inches (10–15 cm) of soil.^{[14]
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- The organic matter in compost also restores the soil structure of your turnip greens. When the soil structure is healthy, the ecosystem inside—including worms, fungi, and mites—releases phosphorus.^{[15]
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Section 3 of 3:

Preventing Turnip Greens from Turning Purple

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Start with clean seeds to limit bacterial infections. Find high-quality seeds from a seed company that is certified as disease-free. Look for seed varieties that have been tested and that are proven to not contain the black rot bacterium. Ask for seeds that come from certified black-rot fee lots.^{[16]
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- As an extra precaution, sanitize your seeds by soaking them in water that’s 122 °F (50 °C) Wait 20 minutes before taking them out and planting them.^{[17]
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Feed turnips fertilizer with plenty of phosphorus to keep them green. Before you plant your turnips, scatter 2–3 pounds (0.91–1.36 kg) of a complete garden fertilizer high in phosphorus, like one that has a ratio of 10-20-10, per 100 sq. ft.^{[18]
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Trustworthy Source
University of Georgia Cooperative Extension
Division of the University of Georgia focused on research and community education
Go to source} After you've planted your turnips and they're 4–5 inches (10–13 cm) tall, use a fertilizer with a nutrient ratio of 1-3-0 or 2-3-1 and apply 1/2 cup (64 grams) of it every 10 feet (3.0 m).^{[19]
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Research source} Use a phosphorus-rich blend, like Neptune's Harvest Organic Fish/Seaweed Blend Fertilizer.
- Phosphorus and potassium help your turnips develop healthy roots. That way, turnip greens will get all the nutrients they need and won’t become discolored.
3
Keep turnips away from excessive moisture to avoid bacteria. While you should water them regularly, avoid overhead irrigation so your seedlings don't become too damp and develop harmful bacteria or a plant disease that will discolor turnip greens. Instead, use a watering can to apply 1–2 inches (2.5–5.1 cm) of water to the topsoil. Water your turnips on a weekly basis.^{[20]
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- If possible, use drip irrigation to provide your turnips just enough moisture without overwatering them and preventing their growth.^{[21]
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- It's okay to water your turnips more than once a week if the weather's hot and the soil is very dry.
4
Purge wild cruciferous weeds so bacteria won’t contaminate turnips. Since harmful bacteria and plant diseases are common in cruciferous weeds like wild radish and wild mustards, uproot and dispose of any that grow near your turnips. Throw them in a yard waste bin so their contaminants can't spread and infect turnip greens.^{[22]
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- Avoid growing crucifer crops, like cabbage, kale, or cauliflower, near your turnips. That way, these crucifer crops won't attract cruciferous weeds.^{[23]
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Spray fungicides on turnips susceptible to infection. Use a copper-based fungicide. If your turnips are growing in cold or humid environments that can damage their roots and lead to discoloration, spritz protective fungicide on the turnips as soon as they sprout leaves. Apply the fungicide on a weekly basis.^{[24]
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- Sulfur sprays or copper-based fungicides are highly effective at preventing the spread of fungal spores. They'll also stop the growth of plant diseases, like white leaf spots.^{[25]
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Use crop rotation so bacteria doesn’t grow in the turnips’ soil. When you plant a new batch of turnips, avoid planting them in the soil where you've recently grown similar plants. Instead, plant turnip seeds in soil that's been used for crops that aren't susceptible to the types of bacteria or diseases that discolor turnips.^{[26]
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- Plants that are related to turnips are broccoli, bok choy, Brussels sprouts, cabbage, cauliflower, collards, kale, kohlrabi, and mustard.