The best time of day to plant your new vegetable starts, or any other container-grown plants, is after sundown, when the temperature has decreased a bit and the sunlight is not direct. Avoid planting in windy conditions, which can desiccate the fragile plant. If you plant in the evening, plants will have all night and early morning to make some adjustment to their new homes.
We have found that applying mycorrhizae to the roots while planting vastly improves a plant’s ability to adapt successfully. You can use either a granular or water-soluble form.
Be sure to give your new plants a deep watering and check on their water needs every day for the first week, then every 2-3 days in the second week. Watering with Compost Tea will activate the soil biology to help new plants access nutrients more quickly. And, a foliar spray application of liquid kelp solution will strengthen the cuticle (‘skin’) of the leaves and stems and reduce transpiration. Another wonderful product (with an unfortunate name) is Sledgehammer, which is a Yucca concentrate. It acts as a surfactant, breaking down the surface tension of water and allowing plant tissues, both roots and foliage, to absorb your spray or drench. In addition, yucca contains trace minerals and plant enzymes that benefit plants!
In very hot, sunny conditions, it can also help a lot to erect some kind of temporary shade that can be left in place until the transplant has had time to establish its root system (about 2 weeks). An example are the below frames with screen material stretched over them and lashed to tomato cages at the corners, do the job of shading pepper plants and protecting the crops from hail, too. It’s also easy to construct wire frames at any scale and cover them with row-cover fabric or shade cloth. Use your creativity to come up with attractive and functional temporary ways to protect your new plantings!
Applying a thick mulch will help keep plant roots cooler, and placing a landscape flag next to a new plant also helps you to keep an eye on it and remember to water.
Happy Planting!