Plant the Seeds of Your Success

The proper time to sow seeds for transplants depends on when plants may safely be moved out-of-doors in your area.  This period may range from 2-3 weeks (lettuce) to 8 weeks (pepper, eggplant) before transplanting, depending on the speed of germination and rate of growth (see “Germination Information for Selected Vegetable Crops” below). A common mistake is to sow seeds too early and then attempt to hold the seedlings back under poor light or improper temperature ranges. This can result in tall, weak, spindly plants that do not perform well in the garden.

What should I plant?

  • Typical vegetable transplants found in garden centers in the spring include cabbage, broccoli, and cauliflower; followed by tomato, pepper, eggplant, squash, cucumber, melon, and lots of different herbs.
  • You can grow all of these under your fluorescent lights PLUS the following: beets, spinach, Swiss chard, kale, mustard, broccoli raab, arugula, Asian greens, onion, leek, bean, and sweet corn!
  • And don’t forget about your need for mid-summer, late summer and early fall transplants to keep you garden productive. It’s difficult to find vegetable transplants in stores beyond mid-June.
  • Use fresh seed or seed that has been stored properly from last year. Surplus seeds should be stored in a cool, dry location, like your freezer.
Lightstand

You can grow two standard size (10.5 in. X 21 in.) trays under one 4 ft. long fluorescent fixture with two tubes. You can grow four trays under two fixtures. Each tray can hold about 12-18 large transplants and 50-120 small1transplants.


Moisten your dry growing medium ahead of time

  • Place the amount you estimate you’ll be using in a bucket or tub. Pour lukewarm tap water in slowly and mix it into the growing medium. It should be as moist as a wrung-out sponge, not soppy wet. Water sprinkled on top of dry soilless media will bead up and fail to soak in.
dry media wet media
Dry media in wheelbarrow Add water
mix water media soil ball
Mix thoroughly Moist soil ball

Fill containers

  • After selecting a container, fill it to within ¾ of an inch from the top with the moistened medium you have chosen. 
add media filled flat
Add media to container Black flat filled with potting media
  • Firm the medium very lightly at the corners and edges with your fingers or a block of wood to provide a uniform, flat surface.

Mark your rows

furrows
Mark rows in flat with straight edge

 

  • Good light and air movement results from sowing in rows, as compared to broadcasting the seed randomly across the surface. If “damping-off” disease appears (see “Transplant Care” below for details), there is less chance it will spread.  Seedlings grown in rows are easier to label and handle at transplanting time. 
  • For small-to-medium size seeds (all crops except cucumber, squash, melons, corn, bean) make rows about 1- to 2-inches apart and 1/8”-1/4”  of an inch deep across the surface of the container, using a narrow board or pot label. 

Plant

hand seed index card
Planting seeds by hand Planting seeds using folded index card
cover seed  
Lightly cover seeds with media  

 

  • Sow the seeds thinly and uniformly in the rows by gently tapping the packet of seed as it is moved along the row.  Lightly cover the seeds (lettuce seeds can be left on the surface un-covered or very lightly covered) and press down gently to ensure good contact between the seed and the soilless growing medium. 
  • A suitable planting depth is usually about twice the diameter of the seed.
  • Sow large seeds (cucumber, squash, melons, corn, bean) directly into small containers or cell packs, eliminating the need for potting up latter. Sow two or three seeds per unit and later thin to allow the strongest seedling to grow. 
spacing thinning
Top 2 rows correctly spaced Hand pull seedlings to correct spacing

Tips for quick germination

  • The seeds and growing medium need to be moist and warm to germinate. Generally, 65°-75°F is best for germinating seeds of most plants.  This should be the temperature of the growing medium, not the air. 
  • Seed germination begins with the absorption of water. An adequate and continuous supply is essential. Once the process has begun, a dry period will cause the death of the embryo. Spray some water from a plastic mister on the growing medium as needed, to keep it moist.
  • Cover the container with a piece of clear plastic or insert the container in a plastic bag. This will increase the humidity and temperature. The plastic should not be in contact with the growing medium. Remove the plastic as soon as sprouts appear.
  • You can buy heating pads to set your containers on to warm the growing medium and speed-up germination. A cheaper and easier approach is to drape clear plastic over your light fixture. The plastic should rest on the frame holding the fixture and not on the fixture itself. Leave the lights on and the heat from the ballast will be trapped inside the plastic tent and keep the temperature at 70º-75º F.
  • The top of your refrigerator is another good warm place for quicker germination.
seed packet seedling in yogurt cup
Planting information on back of seed packet Arugula seedling in yogurt cup
broccoli rows of seedlings

Broccoli seedling in 4-cell pack

Lettuce seedlings planted in rows
 
Germination information for selected plants:
Plant Approximate
time to seed
before last frost
date (weeks)
Time seeds
need to
germinate
(days)
Temperature
(F)
Light/dark
requirement
Broccoli 8 5 to 10 70 Either
Cabbage 8 5 to 10 70 Either
Cauliflower 8 5 to 10 70 Either
Cucumber 4 or less 5 to 10 85 Either
Eggplant 8 5 to 10 70 Either
Lettuce 8 5 to 10 70 Light
Muskmelon 4 or less 5 to 10 85 Either
Pepper 8 5 to 10 80 Either
Squash 4 or less 5 to 10 85 Either
Tomato 6 5 to 10 80 Either
Watermelon 6 5 to 10 70 Either
Section: 
Maintained by the IET Department of the College of Agriculture and Natural Resources. © 2017.