Question: I sometimes have difficulty locating plants of some of my favorite flowers and vegetables. Would you please explain how I can start some of my own plants from seeds?
Answer: I start flower and vegetable seeds in my home using a dual head LED grow lamp, which I bought online for about $25. It has flexible arms which allow me to position lights various distances above the seeds and plants. I also use a 10 by 20 inch electrically heated mat that raises the soil temperature to about 70 degrees. This mat stimulates rapid seed sprouting and costs about $12 online.
I plant fine seeds like petunia, salvia, tomato, pepper and broccoli in 4-inch pots filled with potting soil. I scatter six to 12 seeds on top and push them gently into the soil. Then I place the pots on the heating mat and place a piece of clear plastic over them to reduce evaporation.
After seeds have sprouted and developed about two leaves each, I remove the plastic. I transplant individual plants into 2-inch pots or cell packs with 2-inch cells when they have about four leaves per plant. As they grow larger, I move some of them into 4 inch or larger pots.
I plant larger seeds, like marigold, zinnia, sunflower, squash and melon, two or three seeds per 4-inch pot. They grow more quickly and do not need to be transplanted. I use new pots or used pots sterilized with Clorox solution to avoid disease.
As soon as outside daytime temperatures reach the mid-50s, I begin placing plants outside and bring them back inside at night. This alternating cool day and warm night temperature causes plants to grow more compactly. Plants should be placed in the shade or covered with newspaper for the first few days until they become hardened to the drier outside air. Then they can be placed in full sun. Plants dry quickly outside and may need to be watered more than once per day.
Petunias need about 12 to 16 weeks to develop plants large enough to transplant in the ground. Tomatoes and peppers require six to 12 weeks, depending on how large a plant you want to plant outside. Small, 2-inch plants require about six weeks, and gallon pots need about 12 weeks. Broccoli, cabbage, marigolds and zinnias take about six weeks. Squash and melons need about four weeks. Sunflowers only need two to three weeks.
Count backward from when you want to plant into the ground. Frost tolerant plants like petunias, cabbage and broccoli can be planted outside in late April. Tender plants like marigold, zinnia, sunflower, squash, melon, tomato and pepper should wait until late May. Check seed company web sites and catalogs for how long and when to plant other flowers and vegetables.