Starting your own seedlings can be a great way to improve your garden. It gives you access to a wider range of varieties and helps you save a bit of money. It can also help ensure that you start the season with healthy plants, as long as you avoid a few common mistakes. Here are some of the common issues with seedlings we see and how to avoid them. 

Leggy or spindly seedlings

Seedlings that grow tall or “leggy” with long, spindly stems are a clear sign your plants aren’t getting enough light. Your plants are literally reaching for the sun.

Plants have evolved to grow quickly towards the sun until their leaves are receiving adequate levels of light. In the wild, this helps newly germinated plants clear the soil, plant debris, and the leaves of other plants until they reach a level where they will receive adequate sunlight.

While this adaptation serves them well in the wild, it also means that if your vegetable crops don’t get enough light, they will develop long, weak stems. To prevent this, use supplement lights like grow lights or LED shop lights and keep them about 2 to 4 inches above the tops of your plants.

Burned leaves with brown or white spots

While tall, skinny seedlings mean your seedlings aren’t getting enough light, it’s also possible for them to get too much light. Leaving high-intensity or hot lights too close to your seedlings can burn the leaves, resulting in brown edges, brown tips, brown or white spots on the leaves, or a combination of these symptoms.

Seedlings may also burn while you try to transition them outdoors. True sunlight is much harsher than any grow lights or indoor lighting. To avoid burning your seedlings, you need to slowly acclimate them in a process called hardening off. 

Visit our blog How to Harden Off Seedlings to learn more.

Dampening off

Another common issue is “dampening off,” which is when your seedlings develop a soft, discolored stem near the soil line and suddenly fall over and die. Fungi and molds that thrive in damp, cool conditions cause this disease. 

Unfortunately, these molds and fungi will spread and may survive in soil and on equipment like pots, tools, and trays. If you spot dampening off in your seedlings, remove that tray from the others and carefully monitor the others. To clean your tools, trays, and equipment, soak them in a solution of water and 10% household bleach for 30 minutes.

There are also several ways to prevent dampening off:

• Select containers with drainage holes or use soil blocks. 
• Use seed starting mix or potting soil that drains well.
• Avoid overwatering. 
• Provide 12 to 16 hours of supplemental light for seedlings.
• If possible, use heating pads to maintain a soil temperature of 70-75°F.
• Use a low fan so improve air circulation. 

Stunted plants with discolored purple, yellow, or discolored leaves

If your seedlings are growing particularly slowly and appear stunted with leaf discoloration, they may have a nutrient deficiency. Different deficiencies present with different symptoms. 

Seed starting mix rarely contains high levels of nutrients, as it’s just designed to get plants started. Older seedlings may need to be fertilized and potted up. However, seedlings may often present with nutrient deficiencies when the soil is perfectly adequate. Conditions like waterlogged soil, dry soil, or cold temperatures prevent the plants from taking up nutrients.

Nitrogen deficiency

Nitrogen deficiency causes seedlings to turn yellow, beginning with the older, lower leaves before spreading to the younger leaves. Seedlings will also put on poor growth and may develop thin, spindly stems. 

Cool soil, below 60°F, can affect your seedlings’ ability to take up nitrogen.

Phosphorus deficiency

Seedlings with phosphorus deficiency may have a purple appearance, particularly on the undersides of the leaves. 

Even if there is plenty of phosphorus available, seedlings can present with phosphorus deficiency if they’re too cold or wet. Soil temperatures below 60°F or waterlogged soil can prevent seedlings from taking up phosphorus, even if plenty is available.

Potassium deficiency

Potassium deficiency can cause stunted growth, leading to stocky seedlings with weak stems. The older leaves often feature yellowing or purple-red coloration with browning or burned edges. 

Seedlings may fail to take up adequate levels of potassium in waterlogged or cool soil below 60°F.

Visit our blog on Common Nutrient Deficiencies to learn more about identifying other deficiencies. 

Correcting nutrient deficiencies

To correct nutrient deficiencies, ensure that your seedlings are at an adequate temperature and receiving an appropriate amount of water. If those needs are met, you can supplement them with a liquid fertilizer like liquid kelp or fish emulsion. Typically, you dilute these fertilizers in your watering can. Check the specific product instructions before applying. 

Starting your own seedlings is an easy and fun way to start the season, but there are a few common snags growers run into. Avoiding these common seedling mistakes will ensure you start the season with healthy, vigorous transplants. 

Having trouble with seeds germinating slowly? Check out our  Five Quick Tips for Good Germination. 

At Southern Exposure, our goal is to preserve and share open-pollinated and heirloom varieties that thrive in the Southeast and Mid-Atlantic. Naturally, this means that many of our varieties tolerate some heat and humidity. However, if you’re a grower in the Deep South, you know that summers there can bring intense conditions. Many regions in the southeastern states deal with high temperatures, high humidity, increased disease and pest pressure, and some drought. To grow in these conditions, you’ll need to select varieties that can withstand them. 

Look for the Especially Well-Suited to the Southeast Symbol

The sun symbol in our catalog and website listings indicates that a variety will thrive in conditions particular to the Southeast. While all our varieties are well-adapted to the mid-Atlantic, those varieties with the sun symbol are particularly well-suited to hot, humid summers. 

Crops that earn the sun symbol are those that reliably produce with good flavor in the Southeast’s unique conditions. Their exact characteristics vary with crop type. For example, Anuenue Batavian Lettuce earned the sun symbol because it germinates well at soil temperatures above 80°F and is bolt resistant while our Arkansas Traveler tomatoes earned the sun symbol because they are disease resistant and produced delicious tomatoes under high heat and drought when other varieties failed. 

On the website you can sort for crops that are especially well-suited to the southeast.

Cool-Weather Crops

For cool-season crops, we look for varieties that display more heat resistance than standard varieties. Note that they still won’t perform well during the height of summer in the south. You’ll need to get these varieties in early or late.

Folks in warm climates can also grow cool-weather crops during the off season. In the Deep South, try fall planting crops like cabbage, lettuce, kale, and radishes for winter production. In areas with some cold temperatures, you can use row cover to plant about two weeks early in the spring or keep plants going about two weeks longer in late fall.

Shade cloth can also help you grow cool-season crops later into the spring by offering them a respite from the intense sun. 

Brassicas

When labeling brassicas for the southeast, we choose heat resistant varieties that are slow to bolt and maintain good color, texture, and flavor in hot conditions. 

Greens & Lettuce

Varieties of greens and lettuce that thrive in the Southeast generally have a few specific characteristics. These varieties germinate well even in warm soil, are bolt-resistant, and resistant to tip burn. They may also be drought-tolerant.

Root Vegetables

Root vegetables that are ideal for the Southeast maintain their solid, crisp texture even in hot dry conditions, rather than becoming large and woody.

Warm-Weather Crops

When we select warm-weather crops, we’re looking at a few key factors like disease resistance, especially to fungal diseases, pest resistance, drought tolerance, and the ability to set fruit and maintain good flavor in high heat. 

Tomatoes

High heat and fungal diseases often affect tomato production in the Southeast. At high temperatures, tomatoes may abort their flowers and fail to set fruit. In high humidity, they are more likely to succumb to common fungal diseases like late blight, alternaria, and fusarium wilt.

When selecting tomatoes for the Southeast, we look for disease-resistant and heat-resistant varieties that maintain good production in challenging conditions.

Cucumbers  

Cucumbers are a warm-weather crop, but at high temperatures, they tend to drop their flowers and fail to set fruit. For the Southeast, we select varieties that hold their flowers at higher temperatures and produce reliably. 

Squash

Vine borers are the enemy of all southern squash lovers. When selecting varieties for the Southeast, we look for good resistance to vine borers, fungal diseases, and tolerance of high heat and humidity. 

Peppers

Peppers generally perform well in hot weather, but many fall prey to a common pest in the Southeast: root knot nematodes. Peppers that receive the sun symbol show good disease and pest resistance. 

Beans 

Beans are another warm-season crop that can fall prey to high heat, diseases, and nematodes in the Southeast. Our recommended bean varieties for the Southeast display resistance to these common issues. 

Many other traditional southern crops like okra, southern peas, and dent corn are also well-suited to the Southeast.

A Few of Our Favorite Heat Tolerant Crops

Malabar Spinach: This tropical vining plant is a great alternative to traditional spinach and will produce all summer even in high heat.

Seminole Pumpkins: A small butternut-like winter squash variety that thrives in hot, humid areas thanks to its excellent resistance to vine borers and Downey mildew. 

Whaley’s Favorite Cabbage Collards: This old-time variety forms loose heads with mild flavor. It’s a great cabbage alternative and makes excellent collard kraut. 

Carolina Wonder Bell Peppers: This is the best nematode-resistant bell pepper for home gardeners. It’s also less prone to developing fungus in the seed cavity than the classic California Wonder. 

Neptune Tomato: Developed at the University of Florida, this hardy variety is ideal for gardeners and market growers in hot, humid, rainy growing regions where it is difficult to grow tomatoes. It has excellent heat tolerance and is resistant to bacterial wilt that’s common in the Southeast and Florida.