Wait! Isn’t nightshade a poison?!?
Well, yes. if we were talking “nightshade” the plant, that is a poison. But today, we’re talking “nightshade” the family of plants. And they are probably among your favorite veggies. Vegetables in the nightshade or solanaceous family include:
- peppers (both sweet and spicy varieties)
You can tell that these are all in the same family because their seeds are almost indistinguishable from each other and when they first sprout, their first leaves all look almost identical. Tomatoes typically have leaves that are serrated, but some tomato varieties have a type of leaf called a “potato leaf” that is not serrated and definitely looks, well, like a potato leaf. That’s another clue that the two plants are cousins.
Also, lesser known plants in this family include:
- salpiglossis–one of my favorite flowers for cutting!
- Wonderberry–developed by Luther Burbank, it makes a delicious jelly. It grows almost like a weed. You may even have some growing in your yard right now!
It’s important to know that these plants all belong to the same family because they have similar nutrient needs and share many of the same diseases. First thing to know: nightshades are heavy feeders. That means that they demand (and take up) a lot of nutrients from the soil. That’s why it’s always a good idea to add a top dressing of compost to your tomato and pepper plants when you plant them in the spring and apply foliar feedings throughout the summer.
They are also heavy users of potassium. That’s why a lot of gardeners recommend adding Epsom salt around tomato and pepper plants–it helps the plant in its uptake of potassium. Lack of nutrients, especially the minerals potassium and calcium, means that the plants will not do well under stress (such as extreme weather, lack of water or uneven watering) and that is the most common cause of blossom end rot.
The best way to ensure that your nightshade plants are getting the nutrition they need is to rotate your crops. The nightshades should be planted in the section that was planted in legumes (peas and beans) the year before. That’s because legumes “fix nitrogen”, which means they put more nutrients into the soil than they take up. This article explains more about the why and how of rotating crops.
The nightshades also share a lot of similar diseases. Some of the most common diseases that afflict the nightshade family include:
- Fusarium Wilt and Verticuillium Wilt. These related diseases are caused by a fungus that enters through the plants’ roots. The plants look wilted, like they aren’t getting enough water, which they aren’t, because the fungus is preventing water uptake.
- Early Blight and Late Blight. Leaves develop spots or brown edges and black spots on the fruit that eventually rot the entire fruit. All four of these diseases (F. Wilt, V. Wilt, Early and Late Blight) are all fatal to the plant and very contagious. Once you know a plant has one of these diseases you’ll want to keep it from spreading disease to other plants. So remove the plant from the garden and burn it. Do NOT compost it.
- Mosaic Virus. This disease does not kill the plant, but it does diminish the number and quality of fruits. Leaves will have a light green and yellow mottling on the leaves and and mottling on the fruits. Leaves may also grow in misshapen forms, sometimes resembling ferns.
There are hybrids that have been developed to be resistant to these diseases. But if you’re like me and you really, really want to plant heirloom varieties, by all means plant them. Just keep in mind that some heirloom varieties may be susceptible to these diseases.
But all is not lost
There are ways to prevent disease. The biggest, most important step to preventing disease is to rotate your crops. Most of these diseases can linger in the soil for a year or two, so never plant nightshades in the same part of the garden two years in a row.
Keep your plants healthy with regular watering and proper nutrition. Use a ground soaker hose or watering spikes to so that water does not stay on the leaves and harbor fungi. Add a side dressing of compost or balanced organic fertilizer when you first plant your seedlings.
Use clean equipment. Remember the bacteria can live in the soil for two or more years. So every fall, clean up all the tomato supports and trellises. Then wash shovels and hand tools that were used around your nightshades. Wash with soapy water, rinse and dip in a sanitizing solution of 1/2 cup of chlorine bleach to one gallon of water. Since I use a 5-gallon bucket for this job, that works out to 2.5 cups of bleach in a 5-gallon bucket. The 5-gallon bucket is the perfect size for dipping the ends of the tomato cages and shovel heads.
Do not add any diseased plants to your compost. That is a sure-fire way to guarantee that these diseases will plague your garden for years to come. Instead, you should burn any diseased plants.
Knowing the nutritional and disease-prevention needs of your nightshades will help ensure you always have a tasty crop every year.