Fall Landscape and Irrigation Prep

Healthy plants = water efficiency

Coneflower with beeWhen cooler temperatures begin to set in, it is important to prepare irrigation systems and landscapes to help prevent costly repairs and ensure plants bounce back easily in the spring. The average first freeze in Castle Rock is Oct. 7, so it is a good rule of thumb to start prepping the landscape in September and winterize the irrigation system by mid-October.

Seasonal watering

  • Cut back irrigation
    Unless the weather is exceptionally hot and dry, cut back irrigation days by 30% in September and 60% in October. Reducing irrigation days, but keeping the length of time, allows water to continue to fill the root zone and encourage deeper root growth. Filling the root zone helps produce more resilient plants. 
  • Winter watering
    During excessive dry and warm periods, when there is less than 1 inch of precipitation per month, getting the hose from the garage and watering plants may be warranted. 


  • One final mow to mulch the leaves
    Rake leaves into the lawn, set the mower on the highest setting and mow without the bag. Make two passes for the best efficiency. Chopping these leaves into smaller pieces increases moisture for plant roots, provides food for earthworms and reduces weeds. Place extra leaf mulch in garden beds or compost. Never allow leaves or yard debris to go down the stormdrain, which can accumulate and overwhelm the system.
  • Aerate the lawn
    Aerate twice a year (or once in the fall) to reduce soil compaction. This allows water, air and nutrients to reach the roots, encouraging deeper root growth and a healthier plant. Aerate when temperatures are below 80 degrees. Moisten (but don't drench) the lawn before aeration, and ensure plugs are 2 to 4 inches in depth.
  • Prep the area for next year
    In the fall, especially after lawn aeration, add a dusting of organic compost to enrich the soil. If fertilizing, use a slow-release one.


  • Take care of trees
    Help the tree prepare for the winter by reducing water. Don’t fertilize and only prune dead or diseased limbs. Add four inches of mulch around the tree root base, but keep the mulch a full 6 inches from the trunk of the tree. This keeps the root ball warm but prevents trapping unwanted moisture next to the bark.
  • Wrap young and tender trees
    Protect young and thin-barked trees from sunscald and frost cracks by wrapping the trunk with a light-colored crepe paper tree wrap. Start from the bottom and wrap up all the way to the first branch. Remove the wrap in early spring. (Note: plastic wraps are for protection during transport and not weather.)
  • Winter watering
    When natural precipitation is less than 1 inch per month, and temperatures are above 40 degrees, water trees monthly. Water in the morning allows warmer daytime temperatures to aid in absorption.
  • Support posts
    For new trees, keep tree stakes in place during the winter to help support the tree when exposed to excessive snow, ice and wind. Generally, tree supports should be removed 1 to 1.5 years after planting. Keeping posts for longer periods can inhibit growth and weaken the tree.


  • Mulch new shrubs
    Reduce watering, don’t fertilize and apply 4 inches of mulch to newly planted shrubs, remembering to keep the mulch 6 inches away from the base of the plant.
  • Wait to prune
    Only prune dead or diseased branches at this time. Spring is generally the best time to prune since shrubs are actively growing.


  • Mulch rose bushes
    Reduce watering, don’t fertilize and apply a healthy amount of mulch. Mulch should be placed to resemble a volcano around the base of the plant.
  • Wait to prune
    Only prune dead or diseased branches in the spring, when shrubs are actively growing.


  • Weed
    Weeding is a year-round endeavor and necessary so there is no competition for resources. 
  • Deadhead
    Remove spent (old/dry) flowers, but, generally, wait until the spring to cut back perennials.
  • Mulch
    Apply 4 inches of mulch to the base of each perennial.

Gardening Equipment

  • Prep and store equipment
    Wash clippers, shovels and equipment with warm water and mild soap and dry thoroughly. Use steel wool to remove any rust spots. To prevent any potential diseases from spreading, use a 70% isopropyl alcohol or a 10% bleach solution. Dry thoroughly and apply a lubricant to prevent rusting.
  • Drain and prep the lawn mower
    For gas-powered lawn mowers and trimmers, add a fuel stabilizer, and run the mower to distribute through the system. Turn off the mower, and after the mower has cooled, siphon out excess gas. Restart the mower and run it until it stops and the fuel lines are empty. Remove the blade, clean and sharpen. Clean the undercarriage and replace the oil, spark plugs and air filters. Replace the blade.
  • Wash plant pots
    Discard potted annuals and wash pots with a mild bleach solution.
  • Keep hoses handy
    Remove garden hoses from spigots and drain. Store in the garage but keep handy in case winter watering is required.
  • Protect spigots
    Check spigots and faucets for leaks or drips which can freeze. Cover the exterior faucet with an insulated slip-on cover. Most modern spigots have an anti-freeze component.

Blowing out the irrigation system

Generally, modern sprinkler systems are not equipped with a drain valve system that can purge the system with gravity. Additionally, irrigation pipes can shift over time and allow water to become trapped in low areas. It is recommended to ‘blow out’ the irrigation system to prevent freezing damage. While not difficult, there are considerations to be made when winterizing the irrigation system, and a professional contractor may be warranted.

WINTERIZATION_Supply line at meter2 WINTERIZATION_draining supplyline WINTERIZAATION_drainplug


  1. Get the ‘right’ air compressor. While only 40 to 80 psi is required, the volume of air is more important than the pressure. If an insufficient volume of air is used, only a small portion of water will be forced out, and the air will ride over the top of the water. This will result in the remaining water draining into low spots and potentially freezing. Rule of thumb: If the sprinkler heads stay up after the water is blown out, you are using the right-sized compressor.
  2. Blow-out tees should be installed after the backflow prevention assembly. Compressed air should never be blown through the assembly as this may cause damage or premature failure of internal parts. If the backflow device does not have a blowout fitting on the downstream side, one will need to be added before the irrigation system can be blown out.
  3. Blow out each zone twice, using two short cycles. Do not blow out excessively as the compressed air can cause friction and heat which can cause damage.
  4. After purging the system of all water, leave all the valves on your backflow prevention assembly half open (45° angle). This allows any potentially present water a place to expand when freezing.
  5. Wrapping the irrigation pipes, back flow and/or reduced pressure devices helps prevent moisture from reentering the system during winter storms. Wrapping is not a replacement for blowing out the system.

Note: A valve in the ON position is in line / parallel with the line and the OFF position is perpendicular or across the pipe.