Is there Spring and Summer Sowing? (seed lists included)
Yes you can do this, most certainly.
What you need to do is first assure that the soil stays moist. You need a container that has some depth to it....like a cool whip tub. The increased depth of the soil in ratio to the soil surface will decrease the amount of moisture loss through evaporation. Plain and simply, the deeper soil will hold more moisture because less is exposed to the air.
Second, because of the warmer days the temperature inside the flat will heat up faster and higher so the flats need to be in part shade. More specifically, they should be in a location where they will not get midday sun which is just too intense.
Third and last, you will need to add some extra vents in the lid to allow for rapid transpiration of the warm air inside the flat.
*Don't forget*....in the Summer you have to keep a closer eye on the watering needs of all flats.
"What seeds can I start now?"
You can Spring and Summer Sow the seeds of any perennial or biennial that says on the back of the packet "sow after last Spring frost", or "sow after ground has warmed", or anything similar to that. That information might not be mentioned at all....as long as you read on the packet any wording that indicates NO COLD PERIOD is required for germination you'll make good choices. I would think that any of the seeds that they sell at the dollar store would qualify.....all of those are very easy to grow.
Here's a list of perennials and biennials you can try with Spring and Summer Sowing:
And here's some fast growing annuals to try with the method. The cheery blooms of Spring Sown annuals will help perk up the garden during midsummer when some flowers start to wane and fizzle out from the heat. Summer Sown annuals can provide a "punch" of colorful fresh blossoms to enliven the Autumn garden.
The two lists above are both very short lists, and I will add to them as suggestions are made....so if you have some suggestions for either list please do email me with the variety names that you recommend.
"When can I transplant my Spring and Summer Sown seedlings into the ground?"
You can put the seedlings into the ground while they're very small. Let the seeds germinate and when they have a couple of sets of leaves they can go right in. Keep them well watered for the first few weeks.
If you're planting the seedlings into an area of direct full sun you can help them along for a few days by placing a lawn chair over them during the midday to shield them from the brilliant noon sun. Midday sun can be very strong, the seedlings are already acclimatized to the temperatures but that brilliant sun can stress them and may even give them a bit of sunscald.
To learn about fertilizing your seedlings please read the Winter Sowing FAQ called:
"Fertilizing Seedlings and a Simple Explanation of N-P-K"
Good luck with your Spring and Summer Sowing!