"How long can I wait to plant these?" -Well, you should plant them as soon as possible because any plant that is in a pot or balled & burlapped needs a lot of attention and can dry out quickly. If you can't plant your new purchase right away, put it in the shade on the grass or soil (hot pavement is not the right place) and water atleast every other day. If you keep up with those requirements, you can leave a plant in a pot for the entire summer in all reality, but it takes a lot of care. The sooner you put it in the ground, the faster it will take root, which then leads to our next question:
"How big do I have to dig the hole?" -On average, about double the width of the pot and one and a half times as deep. The soil that you dig out should be mixed with about 1/3 compost and then put back in so that the surface of the potted plant is level with the surface of the ground. Pop it out of its container, (squishing the sides with your foot can loosen a rootbound plant) take a shovel/knife/your fingers and run it over the roots so that they are 'fluffy' and will now grow 'outwards' instead of in a tight knot (please note: on Asclepias, Baptisia and other tap-rooted plants..do not disturb the roots when you plant them!) . Place the plant in the hole, push the extra soil around the edges and push down to make sure there is no air holes. TIP: with the extra soil, make a moat or ring around the surface so that the water will drain onto the roots.
"How much should I water?" -This question is a little tricky. A lot of factors play into this like: what kind of plant are you planting and what is the sun and weather situation? Ok, you always water a plant right after you plant it. Water it well. Drag the hose over to it and turn it on a dribble for ten minutes. This will help the soil settle and prevent transplant shock. In full sun and with no rain over 75 degrees, most plants, water every other day for a week then twice a week or when you see the leaves look limp for a month after. Push your finger down 4 inches and feel for moisture. In the shade in cooler weather with a bit of rain, you can water once a week, just keep your eye out for wilted plants.