MARCH 2020
Once crocuses, daffodils, tulips, and other bulbs have bloomed, cut off faded flowers, but do not trim off the leaves until they have wilted and died.  The leaves produce food that the bulb will store and use for next year's growth and bloom.
Plant bare-root roses and transplant rose bushes this month as soon as the soil becomes workable.
It is best to prune many trees in late winter or early spring while they are dormant; therefore, if you have trees that need pruning, do it now.  One advantage to pruning now is you can more easily see how to shape the tree when it has no leaves.  Also, insects and disease organisms that penetrate trees through pruning wounds are less prevalent in cold weather.  Birch, maple and walnut trees may ooze sap when pruned now.  Therefore, some gardeners prefer to prune these in mid-summer. 
Roses and other tender shrubs should not be pruned at this time.  Pruning stimulates new growth that could be killed by frost or heavy snow.
  In order to get good-sized onion bulbs, plant onion seed during March.
  Toward the end of March and in early April, residents along the Front Range may plant peas, potatoes, broccoli, cabbage, radishes, spinach, turnips and lettuce.
Continue to water your yard periodically ("winter water") if it doesn't rain or snow.  March's winds and sunny days can be very drying.  
  In Colorado, March can be the snowiest month of the year.  Heavy, wet snow can break the branches of evergreen trees and deciduous trees that have leafed out early.  If heavy snowfall endangers tree branches, you may wish to knock off excess snow by gently lifting branches upward with a broom or rake.  Be careful not to add to the weight already on the branches by pressing down! 
If you didn't fertilize your lawn in the fall, then you might want to fertilize it with a good nitrogen fertilizer in mid-March or early April to promote spring green-up and growth.  (This recommendation does not apply to Buffalo grass or Bermuda grass.)