Seed starting: It is seed-starting time! Usually we start seeds around the 20th of March (or a little later) for peppers and tomatoes so they will be ready to go outside by the 15th of May after the “last frost.” If you live in Madison, our last frost date is May 15, so count backward from that date from the timing on the seed packet to determine when to start the seed. Keep in mind that even though the date is May 15, there is still a 50 percent chance of a freeze after that date, so you may want to wait until May 20 or even a little later to put sensitive crops like tomatoes and peppers outside. If temperatures, especially overnight, are in the 40s and low 50s, the cold can stunt your plants. It might be best to keep plants inside a little longer or at least move them inside overnight (i.e., don’t plant them in-ground too early). However, it is best that the plants be warmer during the day, so if moving them inside and outside, don’t put them someplace where they will be excessively warm at night since it can affect their development. Seed-starting mix can be purchased at most local garden centers. Monitor your seedlings carefully as they sprout to make sure they don’t dry out. Conversely, also make sure they are not sitting in water, as this is a great environment for damping off diseases such as pythium or phytophthora to develop. Damping off symptoms include the seedling stem withering at the base so the seedling falls over and dies due to rotted roots below. Start fertilizing your seedlings with a dilute water-soluble fertilizer about every other week once they get to be about 1 inch in height. The roots should be established enough by then to be able to take up the fertilizer well. If you are growing seedlings under grow-lights, the tops of the seedlings should be about 1 inch from the fluorescent tubes. Don’t allow the seedlings to grow into the lights as the leaves may burn. Lights should be on for about 16 hours a day. If you are growing spinach under lights, however, don’t give them more than 10 or 11 hours of light because they will be stimulated to “bolt” (flower) under conditions that simulate the long days of summer. When spinach bolts, it becomes tough and bitter-tasting.
Lisa Johnson, Dane County UW-Extension horticulture educator