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March and April Garden Checklist for Northern Colorado

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Get ready for spring! The months of March and April bring much needed moisture, longer days and warmer overall temperatures to Northern Colorado. Like most gardeners, you may be itching to get outside and plant this time of year, but keep in mind that the average last date of frost for our area is May 15. This means that you can expect freezing temperatures right up to and around that date. Be prepared to protect any frost-tender plants when necessary .


  • As soon as your garden soil is workable, take advantage of the opportunity to begin amending it. If you are not sure exactly what your soil needs, pick up a soil test kit. This will help determine what the soil nutrients and pH levels currently are. For a small initial investment, the results of testing your soil will more than pay for itself.
  • Remove and dispose of leaves and debris from the areas beneath trees and shrubs. Many insects and diseases overwinter in this debris and begin their growth cycles again in the spring. Removing this debris will greatly reduce the chance of their rebirth.
  • Add approximately 1” of nutrient rich compost to the soil in your garden beds. Mix well with the top 8-10” of your existing soil while being careful not to disturb any spring blooming bulbs.


  • Spring is an excellent time to plant or relocate trees and shrubs. Planting at this time of year will allow for greater root development which is crucial in establishing tolerance for environmental extremes such as the dry heat of summer and the continually freezing temperatures of winter.
  • Prune any spring-blooming shrubs such as lilac and forsythia only after they have finished blooming. Flower buds for the following year are set immediately after blooming.


  • Once you see new leaf buds forming, it is a good time to prune your rose bushes. Pruning will activate new growth, so be careful not to prune too early, the tender new growth will be easily damaged by frost.
  • Many vines respond well to a hard pruning in the spring. Certain varieties of clematis respond better to heavy pruning while others require only light pruning. To determine the appropriate pruning level for your clematis or other vines, contact us!
  • Dig up and divide overgrown perennials. Remember to use Root Stimulator when transplanting.


  • Purchase seeds and seedstarting supplies for your herb and vegetable garden. Seeds for most varieties can be started indoors as early as mid-March. This will allow approximately 8 weeks of growth before planting outside after the last date of frost in our area - which is May 15.
  • Plant potatoes and onion sets in early to mid-April.


  • Now is the ideal time to apply pre-emergent to help prevent crabgrass, dandelion and other pesky lawn weeds.

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