I'm including the link of my last year's May Planting Tips (which has links to prior years - extra good information).
This time of year we are in one of those transition times, where going from mild to hot can occur in one felled swoop of heat.
Transplanting vs sowing can be a challenge as transplanting can stress the plants.
1) Harden them off by placing in the sun 1 hour then moving to shade, next day in sun 2 hours, move to shade - repeat until the plants have been in the sun for 4 hours and you can transplant then with a whole less stress and shock to the plant. If the temps are already in the 90+ range double the days for each hardening, e.g., 2 days for 1 hour, then shade, 2 days for 2 hours then shade. Your plants will thank you!
2) Use my "flower mulching" technique for transplant in warm/hot weather. Get a six pack of flowers at the nursery and either plant your target plant (basil for example) and surround the basil with the flowers (about 5 inches apart), OR plant all at the same time -- imagine a 12 inch circle and plant the basil in the center and 4-6 flower plants around. Flower mulching canopies the soil and shades the sides of the basil, while allowing the basil to get all the sun it needs.
3) Sow seeds under existing plants, just under the edge of the plant/flower canopy.
Both the "flower mulching" and the "edge sowing" are variations of the "nurse plant" concept seen in the desert where the cactus seed settles at the base of a Mesquite tree. Shielded from birds and other critters, the seed, is held in place, watered with the rain and grows up with the mesquite protecting it.
Fruit Trees (With Care)
SEED IN: Basil, Chive (Garlic or Onion), Epazote, Perilla, or Catnip-- making use of the canopy of flowering or vegetable plants.
EDIBLE FLOWERS TO PLANT:
Marigolds, including Tangerine Scented (Tagetes Lemonii), Citrus Scented (Tagetes Nelsonii)
Have a great day in the garden!