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Schmidt: Seed starting

By Staff | Mar 31, 2017

Recent warm snaps we’ve had let us know that spring isn’t too far away. Seed catalogs also are out, which gives the avid gardener an itch this time of year. Many gardeners like to start their own seeds for the greater variety of vegetables, flowers, and herbs seed starting offers compared to nursery-raised starts (transplants) and some gardeners like myself do it for fun. February and March is the typical time to order seeds and begin the seed starting process. However, there is still plenty of time to start some seeds even tomatoes or peppers.

Transplants can be started indoors at home, or they can be purchased. In many cases, it is easier and cheaper to buy transplants. Be sure to buy stocky, well-grown plants, not tall, spindly ones. If you grow transplants yourself, (1) you can grow the variety you want and (2) they will be on hand when you want them.

You can grow transplants at home if you know what the plants need. If not started properly home-grown transplants often end up tall, spindly, and weak. This can happen when they are started too early, grown too warm, over-watered, or given too little light. Lighting is probably the most common problem gardeners’ face when startingseed. Without adequate light, seedwill end up leggy, pale, and weak. Natural light is great, but seedshould have up to 16 hours of light a day, so supplemental light usually is necessary.

While seeds can be started on a sunny windowsill, growing seedlings under florescent tubes often produces the best results. Special grow-light tubes are not needed. A pair of standard 4 to 6 foot fluorescent “shop” tubes will do fine, but combining a warm-white tube with a cool-white tube will create the best spectrum of light. Having the light fixture on chains also is beneficial because the light should be very close to the seed(no more than an inch away). If the seedare grown in a windowsill, try to avoid drafty areas. Seedgrow well in air temperatures between 65 and 75 degrees.

Soil is another important factor that may be overlooked. Use a high quality planting mix or make your own by mixing equal amounts of vermiculite, milled sphagnum moss, and perlite. Some gardeners may be tempted to use soil from the garden but garden soil can get rock hard after a few waterings preventing germinating seeds from breaking through the surface. Garden soil can also harbor insect and disease problems.

Fertilization is not necessary for seeds because they carry their own food and have enough food energy to germinate on their own. Shortly after germination young seedlings will need a weak fertilizer to grow successfully. As the seedlings get bigger and have several sets of true leaves, the dose can be increased to full strength being sure to follow product label directions.

Seed starting containers can be anything from milk cartons cut off lengthwise, deep sided aluminum pans, cardboard tubes from empty toilet paper or paper towel rolls, to special seed-starting systems. Whatever seed starting containers you choose to use should be at least 3 inches deep to provide adequate space for roots to grow and have small holes in the bottom for drainage. Adequate drainage is important to prevent root rot and dampening off.

Most seeds don’t need light to germinate, just warmth, moisture, and darkness. After the seedling appears above the soil light is a necessity. Generally, seeds germinate better if their soiltemperature is kept constantly 70oor above. This is because many seeds are native to tropical or subtropical regions and are genetically programmed to grow only in warm soil temperatures. To provide constant warm soil temperatures home gardeners may wish to purchase a bottom-heating seed propagation mat available from most garden supply catalogs.

Seeds also need to be kept constantly moist to germinate. The consistency of a just wrung-out sponge is a good standard to use. Once the seedare up, begin watering them slightly less often. When they are at least a few inches tall, it is OK to let the top 1/2 inch or so of soil have a chance to dry out between waterings. Check the soil with your finger on a daily basis. Too much moisture can cause root rot and damping-off problems.

Thinning seedlings is another critically important step. It usually is hard for first-time gardeners to discard seedthat they have so carefully nurtured, but it is a necessary step. Overcrowded seedalways develop into inferior plants. Their roots become intertwined and crowded and the plants are weaker, more disease prone, leggy, and chlorotic (pale and yellowed). Thinning should begin as soon as the seedhave their first set of true leaves. A small scissors is recommended to be used for thinning. Yanking seedlings out disturbs the roots and soil of the remaining plants.

Tender seedlings grown indoors under constant conditions need to be acclimated gradually to the harsher outdoor environment so they can withstand the exposure to direct sun, wind, and changing temperatures. This process is called hardening off. When the weather is warm and settled both day and night, set seedling containers outdoors in a lightly shaded, sheltered spot. Gradually increase the time the plants spend outdoors until the seedlings spend a half day outside and then increase the time to a full 24 hours.

Next is the transition into sunlight. Begin with just a few hours of full sun. Gradually increase the time in the sun to a half day and then several full days in the sun before transplanting the seedlings to a permanent spot in the garden.

Some vegetable and flower seeds need be started as early as 10 weeks in advance of permanent placing in the garden. An NDSU publication, “How to Succeed at Seed Starting (H-1139) contains a chart listing sowing and transplanting dates for many common plants. Seed packets also contain this information. As an example, the average last spring frost date in Pierce County falls around May 21. This would require a March 12 seeding date. No need to panic, though, as most seed starting dates range from two to eight weeks in advance of permanent placement in the garden.

A general garden planting timeline followed by seasoned gardeners is to plant “hardy” vegetables in the early spring, typically in late April early May as they will tolerate freezing temps and cold, wet soil. “Half hardy” vegetables may be direct seeded or transplanted mid-spring about 1-2 weeks before the last killing frost as they will tolerate light frosts. “Tender” vegetables can be transplanted after the average date of the last killing frost as they are easily damaged by frosts.

“Hardy” (Early Spring): Asparagus, broccoli, cabbage, onions, peas, radishes, rhubarb, rutabaga, spinach, turnips.

“Half-hardy” (Mid-Spring): Beets, carrots, cauliflower, lettuce, parsnip, potatoes, swiss chard.

“Tender” (Early Summer): Beans, cantalope, cucumbers, peppers, pumpkins, squash, tomatoes, watermelons.

An NDSU publication, “How to Succeed at Seed Starting (H-1139),” is available at www.ag.ndsu.edu/pubs/vegetable.html or a copy can be obtained from the Pierce County Extension Office.

Schmidt is the Pierce County agent of the NDSU Extension Service.

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