Keeping them healthy

So let’s see where we are. Planting materials sanitized and seeds planted? Check. Damping off avoided? Double check. So the next step in our quest for the perfect vegetable is keeping those seedlings healthy. There are many factors that go into keeping seedlings healthy. Fertilization and proper light are the likely most important, and easiest to remedy.

Fertilization

Your average seed starting mix or potting soil has no fertilizer in it. When seeds first germinate they have nutrient reserves in their cotyledons (see ‘What happens while you wait’ post). Those nutrient reserves are enough to help the seedling germinate and develop roots, but not much more. To help those seedlings grow, you should plan on adding a dilute (1/2 or less of the recommended rate) fertilizer as soon as the cotyledons are opened. I would plan on fertilizing them with the dilute mix every 1 to 2 weeks. Once the first true leaves are fully developed, fertilize with a regular dose of fertilizer every two weeks until you transplant. Foliage should be a nice rich green color, not a lime green or yellowish color (check the varieties that you’re growing though. Some cultivars have been bred to have a lime green foliage). Sickly seedlings will be a pale green/yellow color and are more likely to succumb to disease or environmental stress. The objective is to keep your seedlings a healthy, but manageable size, until they can be transplanted. Healthy foliage is good, but a healthy root system is better.  Consistent watering, and fertilization will help promote the development of a nice vigorous root system. Even if the upper part of your plant is a little small, once they are transplanted they can catch up in growth if their roots are well developed.

Notice the healthy white roots on the plant on the left compared to that on the right

 Light

The two most common symptoms of light deficiency (not enough light) are pale leaves and leggy seedlings. Leggy seedlings are skinny and tall and look like they are reaching for any stray sunshine they can find. If you don’t have a nice sunny south facing window with 8-10 hours of sun to keep your seeds in then you probably need artificial light. Even if you have a window, artificial light may still be needed. Standard fluorescent bulbs work just fine. You can get a 4’ two-light fixture (T12 or T8) from Home Depot for about $15 and two fluorescent bulbs for another $10. Using 1 cool white and 1 warm white is best. Bulbs should be placed about 2-3 inches from seedlings. If the seedlings are still getting leggy try replacing the bulbs – bulb life is typically two years and light quality goes down as they age. As the plants grow, you will need to raise the fixture to keep from burning the leaves. When using artificial light sources, you’ll need to provide them with 14-16 hours of light each day. For ease of use, consider putting the lights on a timer. If you decided to turn them on and off manually, be sure to turn the lights off for 8-10 hours each day. Plants, like people, have internal clocks and the dark helps plants set their clock.

Nice dark vigorous green foliage of tomatoes after 3 weeks of growth

To give credit, where credit is due, these sources contributed information to this post:

http://extension.umass.edu/floriculture/fact-sheets/fertilizing-bedding-plant-seedlings

http://extension.missouri.edu/p/G6570

http://www.hort.purdue.edu/ext/ho-14.pdf

http://www.extension.umn.edu/distribution/horticulture/M1245.html

Preventing Seedling Diseases

Diseases are, unfortunately, a part of most gardens. Every year I wait to see the tell-tale spots of powdery mildew on my zucchini. The best way to manage disease in the garden is by preventing it and seedling diseases are no different. A common seedling disease many urban gardeners will see is damping off. Damping off is a general term used to describe wilting and subsequent death of seedlings by root rot microbes. While it is not the only disease a seedling can have, it is one of the most common. For disease prevention in general, you should focus on four things: sanitation, watering, temperature and scouting (checking) your plants.

Sanitation is the first step. This means using clean materials when you plant: clean seed trays, clean soil and disease-free seeds. If you choose to reuse seed trays, tools, and tags, be sure to bleach (1 cup bleach to 9 cups water) for at least 10 minutes before you use them. Many microbes, good and bad, produce structures similar to seeds called spores to reproduce and survive when conditions are bad. These spores will germinate when conditions are favorable. The active ingredient in bleach can penetrate the surface of these spores and kill them after soaking for approximately 10-30 minutes. Even if you sanitize everything, potting mixes can contain soil or compost that have their own microbes that might take advantage of your seedlings.

Pepper seedlings with early damping off symptoms (wilting plants and losing leaves)

Starting off with clean materials is a great way to begin, but there is more. Watering is another point of prevention. Too much or too little water can stress your seedlings. Remember how your immune system is lowered when you are stressed? Plants don't have immune systems like ours, but stressed seedlings are also far more susceptible to infections. In general, it is good to have moist, but not saturated/water-logged soil. Water plants through the bottom of the tray, allowing the water to be absorbed up into the soil. Watering from the top can increase the humidity in the leaf canopy. Root diseases, like damping off, are more common when the soil is saturated, but leaf diseases, like leaf spots, often need warm humid leaf canopies. If you have to water seedlings from the top, try to promote good air flow by using a fan.

Temperature is an often-overlooked component of disease prevention. Microbes, like plants, have minimum growing temperatures, maximum growing temperatures and optimum temperatures. Many (not all) seedling diseases like cooler temperatures. Keeping your soil warm (but not too warm) will help your seeds germinate faster and reduce the chance of disease occurring. When you plant, keep the temperature above 65 degrees. 

Tomato seedling suffering from damping off (brown squishy stem near soil) and adventitious roots (white roots on stem) right above the diseased tissue.

Checking or scouting your plants is the last step to managing seedling diseases. Check your plants daily to look for indicators that something is wrong. If you see a seedling that is wilting, even though it has plenty of water, it may have the seedling disease called damping off. I know your first reaction when you see a wilting plant is to give it more water, but don’t. Check to see if the soil is damp. If it still has plenty of water move the plant (and the surrounding plants) away from the rest of your seedlings. This will help reduce the microbes spreading to your other seedlings. If they continue wilting, go ahead and throw them away, you can’t heal a sick plant. Don’t bother composting your diseased plants; most microbes have survival structures that can persist through composting. Bag them up, say a few last words, and put them into the city trash.

Healthy pepper seedlings

If you garden, chances are you will end up with disease at some point. Taking steps early on to prevent disease can help minimize your losses during the growing season. Giving your plants proper light, temperatures, wind (using a fan), and maintaining appropriate moisture will give them a great start and reduce their chances of getting disease.

What happens under the soil while you wait?

It’s easy to be impatient while waiting for seeds to germinate, but it doesn’t help. Pepper seeds can take as little as 10 days and some varieties can take as long 120 days to germinate. Thankfully most common vegetables and flowers will germinate in 2 to 3 weeks. So what happens in the soil after you plant your seed? What goes on down there? Well, there are three phases of germination: the water uptake (hydration), the activation of processes and growth. To show how this process works we can follow a single chard seed from germination to seedling.

This is an MRI I took of a dormant chard seed. You can see the white C-shaped embryo with its cotyledon on the right

Before you put your seed into the ground it was most likely dormant, sort of like hibernation for seeds. This means that it was dehydrated and waiting for suitable environmental conditions before it would germinate. These conditions, warm air and soil temperatures, sunlight and rain, are provided by you when you plant. When you first plant your seed, it takes up water, loosening its seed coat (the outer hull around your seed) and allowing the tissues to swell and expand. This is the hydration phase. The seed coat protects the seed from microbes and other things that could potentially eat or destroy it. The expanding tissue will be the food source for your emerging plant. If the seed coat wasn’t loosened the tissues couldn’t take up water and expand, this is why some seeds need to have their seed coats nicked (like Lotus) to improve germination. 

The next phase of this process is the activation. This is when the seed’s metabolism starts. All that hydration starts moving nutrients and energy stored in the seed so the embryo can begin the final stage: growth. First the tiny root will emerge and start to grow, and the shoots will follow a couple days later. 

Germinating chard seed. You can see the brown seed coat and the white root

With most seeds it doesn’t matter which direction you orient the seed. The roots always grow down and the emerging leaves will grow up a phenomenon called gravitropism. In the roots, there are tiny granules that fall downward so the roots can always detect which direction is down. The seed only has the food that was stored in it to keep it going. If seeds are planted too deep the shoots might not have enough energy to break the surface, if seeds are too shallow they might dry out or be baked by the sun. Planting seeds to the recommended depth ensures that your seeds will have room to germinate, but still be safely nestled in the soil. Once your shoots break the soil surface, the first two (or one) leaves that emerge and extend are called cotyledons. These aren’t actually true leaves, those will come later. 

Chard seedlings with their cotyledons

Baby chards who now have their true leaves

And that’s what happens, while you wait!

Starting Transplants: The Basics

Spring is in the air and gardening season is right around the corner. My seed catalogues have all arrived, and I’m picking out varieties and getting ready to start my babies. Starting your own transplants is fun, easy and gives you access to almost any variety you could want (for more information on varieties check back for upcoming posts!)  

 Starting seeds requires four things: soil, seeds, pots and a bit of time.  The best plan is to figure out what you want in your garden and then pick out varieties that best fulfill that. On the back of your seed packets should be a plant date. Many seeds are started between 3 and 8 weeks before your final frost date. Here in Lansing the final frost date is generally between the middle of May and the middle of June. Once you have your brightly colored seed packets sitting on your counter it’s almost impossible not to dream about perfect rows of crisp lettuce and climbing beans curling around poles.
However, there is still a lot of work before these seeds even make it to the garden.

Seeds are like babies; they require time, love, attention and the proper nutrients to give them the best chance in life. For your seeds, that best chance starts with planting. You can buy seed trays from the local store or reuse old ones from previous years. If you want a biodegradable option you can try old cardboard egg cartons and toilet paper roll inserts for starting your seeds. If you are reusing old seed trays always sanitize them by washing out old dirt and debris and soaking them in 10% bleach (1 cup bleach to 9 cups water) for at least 10 minutes. That should be long enough to kill any bad microbes that survived from the previous year. So for sanitation just remember 10 for 10. 10% bleach for 10 minutes. Let the seed trays air dry before filling with soil and planting.  

Fill the seed trays about a ¼” from the top of the seed tray with potting mix, this leaves a little room for water to sit on each cell and filter through your media. Lightly press the potting mix down, but do not pack it. Water your seed trays before you plant the seeds. Plant seeds according to what it says on the back of the seed packet. Most seeds only like to be 1/8-1/2” deep. Label each variety with a plant tag written in black Sharpie. If you’re anything like me you’ll plant 15 varieties of squash and have no way of telling them apart until they fruit. Put your little seed babies into a nice warm location with 6-8 hours of sun daily. If you don’t have access to sun, you can use artificial light such as grow lights to compensate. Just like that you’re planted; so sit back and watch them germinate!