Preventing Seedling Stretch
Posted: March 20, 2015
Many of us like to get a head start with the growing season by starting seeds for our garden, especially our vegetables. If you are a beginner gardener or never learned proper seed starting technique, there is a good chance you have seen tall, lanky, and frail plants as a result from your indoor seed starting efforts. I applaud your enthusiasm in growing your own plants, because it is enjoyable and self-rewarding. However, it can also be disappointing when you consistently grow weak, spindly plants that seem under par compared to commercial transplants. Seed starting under unfavorable conditions can create plant “stretch” and less hardy roots and stems.
Seeds that are directly sowed in the natural environment will always look like hardy plants, but when you want to get a head start in the spring with plants such as tomatoes, peppers, and many annuals; trying to replicate natural conditions requires a few variables.
The first condition is sunlight. Without sufficient light, the plant stems will grow high too quickly in search of the sun. Greenhouses or Hot Houses work best for letting in the natural sun, but many of us do not have these facilities. Instead, grow lights can be effective in garages, basements or other indoor rooms. There are many grow lights on the market, and you do not necessarily need the most expensive. Many are now LED bulbs, and are a great investment. If you plan to start a large amount of plants each year, it would benefit you to spend a little more on a grow light system. Some systems have bulbs for specific color wavelengths that plants prefer for photosynthesis. You will see red and blue colored bulbs, which are the most absorbed light waves by the chlorophyll. Your grow light system should always move up and down, so you may have to create your own pulley lift. One of the common mistakes people make when starting their own seeds is not having the light close enough to the plant. As soon as the seedlings open leaves, the light should be 2-4 inches away, and remain that distance as the plants grow; hence the pulley system. This is also why grow lights have cool bulbs. Your lights should be kept on for 14- 16 hours a day.
The second condition is movement. Plants build stem strength to the wind in our natural environment. With no wind, the stems will remain thin and weak. When starting seeds in an enclosed space, we have to mechanically mock wind movement to the plants. An oscillating fan turned on for 30 minutes twice a day is the preferred method. You can also brush through the tray of plants with a wand or hand a few times a day, but there is more risk of injury, especially to peppers, so take caution; the bending and vibrating in the stem causes ethylene, a stem growth hormone, to be released in the plant, which results in a thicker, more durable plant.
The third condition is water. When seedlings are young, you should keep the soil moist at all times, but as plants grow taller, you should cut back. The goal is to stress the plants as they would normally be between rain events. If they remain under perfect watering conditions, the plants will begin to grow fast and be less hardy. When 3-4 leaves are showing, allow the plants to reach wilting point between watering. The soil media will look dry and the leaves will just start to show drooping. You will need to pay attention so not to overstress the plant into injury.
The fourth condition is temperature. Since the reason for starting indoors is because it is too cold outside, this condition is already understood. The growing space should be 60-70 degrees F for adequate growth. If you are able to regulate temperature, you should drop it to 50-55 degrees each day for the first 3 hours after turning on the lights. This is a hardening process called “temperature differential” and certain plants, like tomatoes, ar especially responsive to this method. You may also purchase a heated mat for under your plant trays. This promotes faster germination.
The last condition is nutrients. If you are using a seed starting soil media, take a look at the packaging. You will see a nutrient analysis. The starter soils come with a 2-4 week nutrient charge, so do not add any fertilizer to your water. In many cases, you will be ready to transplant before you will need to add nutrients. Too much ammonium and phosphorous fertilizers will promote the stretching and elongation of the plants.
The purpose of these seed starting conditions is to come as close as possible to the natural environment, so we can begin gardening early and lengthen the growing season. Of course, nothing can be as good as the real thing, so take advantage of any sunny day that is above 55 degrees and get those planted trays outside to harden off, but don’t forget to bring them back in when the temperature drops! With proper conditioning of your growing space, your plants will be hardy, healthy, and ready to transplant in the garden.