Gardening in Colorado can be a challenge, partly because of our short growing season. If you don't have a home greenhouse, there are still a few things you can do to get a jump on the season and have that early crop of vegetables or flowers. You can also use the same things to extend the season, once the frost begins in the fall, to lengthen the season on that end as well.
Start by becoming familar with your yard. While this sounds strange, several microclimates can exist within the same yard. I know that at Four Seasons we have some things which will survive on one part of the property but will die in another location. Get a good feel for what will grow best where, before you plant. One of my favorite tricks is to put tomatoes and other heat loving herbs and veggies near the south facing stucco wall at my house. The stucco will hold the heat of the day and help keep the plants warm in the evenings.
Early in the spring, when possible, start seeds indoors about 6-8 weeks before it is time to put them into the ground. This will give you an established seedling to begin with, rather than starting your plants by directly sowing. Of course you can't do this with root crops that don't transplant well, but tomatoes, peppers, squash, flowers, and other above ground crops can be done in this way. That will give you a month or so's jump on the season.
If you are dying for some spring color, choose pansies, sweet peas, snapdragons, dianthus, violas and other cold tolerant annuals. If you planted fall pansies, they should be in full bloom. Mine are hearty and vigorous this year. All of the snow cover provided insulation for them and they are fabulous right now and full of blooms.
I always get a chuckle watching the men in the vegetable department on the weekends. They want the first ripe tomato of the neighborhood and often end up comparing plants. If you want to cheat, start with the largest plants that you can get. Fo example, our tomato plants already have tomatoes on them and some are even beginning to blush and turn to red when they go home. These large plants often have 30-60 or more days of growth already on them and will give you a significant jump on the season.
Explore alternatives to traditional gardens or flower beds to get started earlier and have better results. Consider Earth Boxes, or if you have a small space in which to garden, consider going vertical! The popular Topsy Turvy tomato or strawberry planters can be used to start plants earlier, hung out during the day, and brought under cover in the evenings. Or consider container gardening. The pots can be brought in and out as the temperatures dictate. This will also give you a jump on the season and provide some early spring color in your yard.
If you just can't wait to have a yard that's full and beautiful, and for instant color, purchase one of our premium hanging baskets, then transplant that into your flower beds or containers. It's a giant burst of color for your yard.
Use Walls O' Water to protect young plants when you first set them out. They will not only protect the plants from frost, but also from the winds that we have been experiencing. The ground surrounding the plant, but inside of the Wall O' Water, will also be protected and the temperature raised by the solar energy created during the day.
FreezePruf is a new product we added to our arsenal last year. A topical spray as well as a systemic, this product works to protect your plants during temperatures up to 9.4 degrees colder than they would normally survive. You must use FreezePruf in advance of a frost or freeze however, in order to give it time to work through the system of the plant. Think of it as a natural anti-freeze for your plants. While it isn't a magic bullet, it may save your fruit tree blossoms! Those folks that used it in the fall, if applied in advance, had some pretty good results.
Cloches will do the same thing and a simple version can be made at home by cutting the bottoms out of milk jugs to place over young plants. Hot Kaps, little waxed paper domes that you place over plants, are also helpful not only in retaining heat and encouraging growth, but may also help in keeping rodents and insects at bay.

Mulch film and tomato trays, new products for us last year, have seemed not only to aid in increasing yield and harvest, but also provide some protection from the wind early in the season, as well as helping to retain moisture and raise the soil temperature. The red color attracts and holds the heat from the sun. I used both in my garden last year and was fairly pleased with the results.
Row cover is another tool to have in your arsenal. If you get a cool night, use it to cover on cool or frosty evenings. Use newspaper, a sheet or blanket, or an overturned basket to protect your plants. Stay away from plastic as it will conduct the cold rather than protect. Think about what you would wrap up in to keep warm and use that. I'll bet it wouldn't be plastic!
Finally, remember to keep after the weeds. They compete with the desirable plants for water and nutrients and by keeping them at bay, you'll improve the health and longevity of your flowers and vegetable plants.