When you are planning out your planting calendar for your outdoor flower garden, there are several things that you need to keep in mind. Two of the main factors are what type of plant you are planting and what type of climate that you live in, as these will both be very important factors in your planting schedule. Another thing to factor in is the current weather as every year can be different. If you have early spring plants, you may have to hold off on planting them until you are sure that the last frost is gone if it's a particular cold year. The best time to start your flower garden varies depending on the type of plant as well.
Annual plants are those that need to be planed again every year. These are more delicate plants and you need to make sure that they are planed after the last spring frost, otherwise there is a very good chance that they will freeze with the next cold snap. There are a couple of exceptions which include violas and pansies. These are sold as cold weather annuals and can last through harsher weather conditions.
Bare Root Perennials
Perennials are sold either as bare root plants or container grown. If you have purchased a dormant bare root plant, as soon as you can work the ground, you can plant it. This is when the soil is no longer frozen but not wet and muddy either. Dormant bare root plants need to wake up slowly with the season and this is the perfect way to do this. If you have to store the plant before planting it, you want to keep it in a cool, dark place, but only for a couple of days. Get it in the ground as soon as possible and keep it out of warm areas or else the root may start to grow before you have a chance to transplant.
Container Grown Perennial Plants
If the container grows perennial has been grown outdoors, you can transplant it as soon as you purchase it, assuming that the ground is workable. Those which have been grown in a greenhouse, however, need time to adapt to the outdoor conditions. These can be hardened by setting the pot out in the sun each morning and keeping it in a more protected area during the reminder of the day and night. Make sure that it also has protection from the wind and the frost if it has leafed out. Keep it watered enough so that the soil is as moist as a wrung out sponge. After leaving it in these conditions for a week, you can transplant the flowers into your garden.
If you are in doubt about when to plant flowers outdoors, talk to your local nursery. Workers there will know all about proper planting times or will have the means to find out. The tags that come with most flowers will also give you a good idea of when they should be placed in the ground.