Let me just say that this year has been amazing for my garden. Everything has been green and fruitful. It is sunshine, rainbows and miniature men in white suits listening me tell them awful jokes in my garden this year. Then I walked through the other day and realized that it was not all fun and haberdashery in the garden. There were some concerning signs in the garden of problems, disease problems. Today, let dig into plant disease and how I am going to fix it.

Plant Disease 1: My Sweet Potatoes Are Turning Purple

So my plants are packed together tight. I mean my cucamelons are using corn and ground cherries as a trellis tight. My sweet potatoes are in my fennel bed. It also contains chocolate mint, some weird French peppers, the last vestiges of my fennel and an infant watermelon vine. There is a bunch going on in this small bed.

When I saw my sweet potato vines, I saw them starting to turn purple. To my knowledge, there is no disease or pest in Oklahoma that makes leaves purple. Also, look at the leaves, they are healthy looking other than their pigment. I checked and Beauregard Sweet Potatoes are not a purple variety so it is not genetics. The temps have been in 70-90F range in the night & days so this is not likely due to cold weather. The last option is nutrition. If a plant is turning purple, that is a sign of needing Phosphorus. At least in most circumstances.

I am going to give this a healthy dose of Bone Meal. It will take a bit of time since the bone meal will have to breakdown but I expect to nip this problem in the bud and have pretty green leaves trying to take over everything in no time.

Plant Disease 2: Yellow Corn Leaves

Anytime I see yellow leaves, I get nervous. When I saw my corn, I got concerned.

Now the tops of the plants look green and healthy.

First, this is not going from cold weather to warm. This is not likely a result of rapid growth. I don’t think this is diseased as the plant looks otherwise very healthy.

There are no holes in the leaves so I am betting it is not a pest.

It is likely a nutrient deficiency but which one? Corn is susceptible to Nitrogen and Potassium deficiencies.

It is possible it is a potassium deficiency but I think not. We have has so much rain that I doubt we are having an uptake issue with the plant. In drought corn will decrease uptake of potassium. I don’t think it has really been that dry. Especially in the mulched bed where this picture was taken.

More likely with corn, it is a nitrogen deficiency. It manifests as strong and healthy at the top and yellowing leaves at the bottom. Also my first bed is more effected by this than my second bed. My first bed housed bok choy and cucamelons. The cucas are still there and the corn was planted after the bok choy. The second bed had ground cherries, sweet peas, cilantro and bok choy in it. When they went away, the corn came into the garden in place of the bok choy. Beans replaced my sweet peas. But here is the thing. I did not rip out my peas roots, I cut them out so the roots mostly remained.

Since peas will nitrogen fix in the soil, I suspect the remaining roots released nitrogen into the soil meaning that my corn got more.

My corn is getting to about 5-6 feet in size so they are nearing their max size. Normally, you want a little bit of leaf yellowing at the bottom of the plant at harvest 3 or 4 leaves. The plant pulls nitrogen out of the lower leaves and feeds it up. If you are pulling your corn ears off and the plant is completely green, you are over fertilizing. Make sure to note that for whatever you succession plant and make sure that you won’t get reduced yields from that high nitrogen.

With all that said, this is too early for some corn leaves to be yellow. I need to do something. I will add a healthy dose of blood meal and give it a kelp meal chaser, just in case of a potassium shortage is present. This is the second crop grown in this bed this year so the soil is probably a bit used up.

Plant Disease 3: Cucumber Leaves Turning White

This one is easy. My cucumbers have the beginning stages of Powdery Mildew. I will get after them with a 3T/.5 gallon H2O2 mixture every other day to help try and control it. The reality is that the heat is here and these plants don’t like the mid 90’s F. Their under leaves are already starting to die off and it is fruiting aggressively. I hate to see it happen but we are several weeks behind normal years as this summer has been so temperate. I can only delay the inevitable for so long.

It is going to be tragic to lose these plants. They have been my most healthy cucumbers in my gardening career and seeing them go away makes me a bit teary eyed.

Plant Disease 4: Pak Choy Leaves Turning Yellow

So, I am way past when I should be growing cabbage. This is also the 3rd set of pak choy I have grown in this container this year. I am suffering a nitrogen deficiency. I rode this soil hard and put it up wet and it is giving me some expected results. A healthy dose of blood meal is in this pots future.

Conditions in My Garden Specifically

Even in the healthiest of gardens there is a bit of disease and death going on. Some plants like my cucumbers are coming to their end while others just need a bit of tender love and care to get the soil back to where it needs to be. I have been amazed at how good this garden has been. I have struggled with nitrogen deficiencies all year. My Martian soil was just not completed-enough compost to prevent that from happening. That unfinished compost has been sucking the nitrogen out all year. It is sad but large quantities of blood meal have fixes this issue.