Seed starting: It is seed starting time! 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 the rotted roots below.
Some seeds especially flowers may need to be started early — in February, but most vegetable seeds for plants with a long growing season that should be started indoors are best planted in March. Usually we start peppers around the second or third week of March as they take a little while to germinate. Tomato seeds, which germinate and grow relatively quickly, can be started later, around the March 20 through 25 (or a little later) so all 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 — guidance on how many weeks before that date the seed should be planted is typically on the seed packet. For other areas of the state, such as Milwaukee or Janesville, the date is a little earlier, and up north the date is quite a bit later.
Once your seedlings have reached about an inch in height, you can start fertilizing them with a dilute water-soluble fertilizer about every other week. 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), because that much light simulates the long days of summer, when bolting usually happens. When spinach bolts, it becomes tough and bitter tasting. When it gets close to the time you can plant outside, (whenever your last frost date is for your area) start to acclimate the plants by putting them outside for a while each day, starting in a semi-shaded place and gradually moving them to more sun. This process should take one to two weeks.
Keep in mind that by the “last frost date” there is still a 50 percent chance of a freeze after that date, so you may want to wait until May 20 in Madison, 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 you can stunt your plants due to cold. Daytime temperatures should be in the 60s, preferably, or higher. 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.