Contact Us

University of Illinois Extension serving DuPage, Kane and Kendall Counties

Main Office (Kane County)
535 South Randall Road
St. Charles, IL 60174-1591
Phone: 630-584-6166
FAX: 630-584-4610
Hours: Monday - Friday 8:30 am to 4:30 pm

Branch Office (DuPage County)
1100 E. Warrenville Road
Suite 170
Naperville, IL 60563
Phone: 630-955-1123
FAX: 630-955-1180
Hours: Monday 11am to 7pm; Tuesday - Friday 8:30am to 4:30pm

Branch Office (Kendall County)
7775-B Illinois Route 47
Yorkville, IL 60560
Phone: 630-553-5823
FAX: 630-553-5871
Hours: Monday - Friday 8:30 am to 4:30 pm

News Release

Ready, set, grow

By late winter, as both veteran and less experienced gardeners start to get the "growing itch," many find themselves tempted by colorful and interesting seed packets.

"This is all encouraged by the fact that almost daily, a new seed catalog arrives in the mailbox or seed displays start showing up in the store," said University of Illinois Extension horticulture educator Greg Stack.

However, before investing in seeds, it is important to know how to grow them into healthy transplants for next spring's garden. Make sure you have, and understand how to use, the proper tools for growing seedlings.

You can start seedlings in anything from last season's recycled trays and flats to Styrofoam cups and cottage cheese containers. Make sure that the containers are clean and have drainage holes in the bottom. Clean them by rinsing them in a solution of 1 part bleach to 10 parts water, and make sure they have holes in the bottom.

The next step is to fill the containers with any of the many available potting or seed starting mixes. These mixes are formulated to provide adequate drainage while retaining enough moisture for seed germination. They are also sterile and free from pathogens that can attack new seedlings.

"Many of the mixes are combinations of peat, perlite, coir, and vermiculite and are often dry," Stack said. "So, prior to sowing seeds, moisten the mix by filling the container and placing it in a shallow tray of water. Water will be absorbed from the bottom up, assuring a thoroughly moistened mix."

To keep the seeds uniformly moist and retain moisture after germination, cover the containers with plastic. Gardeners often allow the media to dry out between waterings, causing the seeds to germinate poorly or erratically. A propagation mat is a helpful tool, particularly for growing a large number of seedlings. These thermostatically regulated heating mats provide a constant, uniform temperature to the media, which encourages a uniform germination."

Once seedlings start to appear, remove the cover, take them off the heating mat, and move them to a cooler, well-lit area. These conditions slow growth and help reduce seedling elongation. A four-foot, two-bulb fluorescent shop light positioned two to three inches above the seedlings can be used to supply artificial light. Leave it on for 14 to 16 hours a day.

"This will help greatly in reducing seedling elongation due to insufficient light from natural sources," said Stack. "If you use windows to grow seedlings, turn the seed containers daily to prevent seedlings from leaning into the light."

When seedlings have developed the first set of "true leaves" (leaves that look like those on the mature plant), transplant them into individual containers or trays. Again, use containers with holes in the bottom and filled with a prepared growing mix. Put the containers back under the lights or in a very well-lit, cool area and water as needed to keep them moist. This will help to limit elongation. Use fertilizer at half strength to maintain healthy plants without encouraging a lot of extra growth.

"The last and most important thing to remember is to schedule or time your seed sowing indoors so that the plants you produce will be at their best when you need them for outdoor planting," Stack said. "Many first-time gardeners make the mistake of sowing whenever the spirit moves them. But there is a science to the art of horticulture." Stack stresses the importance of knowing how long it takes to produce a usable transplant and planning the seed sowing indoors to correspond with the proper planting time outdoors.

For example, it takes approximately four to five weeks of indoor growing to produce a suitable tomato transplant. Seeds sowed indoors at the end of April will be ready for a May 30 planting date outdoors. This growing time varies with the type of seeds being sown and can range from 4 to 15 weeks, so check references before sowing. Sowing too early often results in transplants that are too tall and not in very good condition for the garden."

While it is easy to get caught up in the excitement and anticipation of growing things, the time spent assembling the needed materials and knowing how to use them will result in better-looking transplants for the garden.

"So, before you start buying those seed packets, have everything in place for a successful growing experience," Stack said.