By Brad Shannon

Tired of snow? Happy for spring? April is a great month to get started on this season’s yard work. Here’s some expert advice to get your lawns ready to show off.

Get Those Lawns Green and Vibrant
First up: your lawn and flower beds. Time to trim, clean and aerate.

“Cut perennials to the ground as they start to push new growth. Some may need dividing. Summer bloomers can be dug up, separated and replanted. Divide spring bloomers after flowering. Cut ornamental grasses to 3 to 5 inches tall,” advises Alison O’Connor, Ph.D., horticulture agent at CSU Extension in Larimer County.

“Aeration is key,” says Mike Verde of Fort Collins Lawn Doctor. “It allows air, water and fertilizer to penetrate dense soil and for roots to spread.”

For mold and matted brown patches, a leaf rake, air and sun will help grass recover. Dog spots may fill themselves in. Adding seed is probably unnecessary. “Seeding is only required in areas bigger than the size of a dinner plate with no green growth. People scatter seed without proper soil preparation resulting in little or no germination. To germinate, the seed needs water 2 to 3 times a day for two weeks and proper soil preparation, which requires tilling, heavy raking or aerating,” says Verde.

Apply a balanced fertilizer and be careful with crabgrass control, he also advises. Over-application can cause problems. Only apply weed and feed products to your lawn, not ornamental plants and gardens.

Furthermore, power raking damages tender new growth. “Light raking and regular mowing will remove dead blades of grass. You can leave short, evenly distributed clippings. Don’t mow too short, it stresses the grass by exposing its crowns,” says Verde.
O’Connor recommends: “Water with ½- to 1-inch of water or time watering with precipitation. The best method to control weeds is a healthy lawn—proper water, mowing at the right height and fertilizer. Mow frequently. Instead of a schedule, remove a third or less of total plant height with mower height 2.5 to 3.5 inches tall. This keeps grass healthy, tidier (no clumps) and promotes good roots. You may have to mow twice a week or more.”

Time to Plant Trees
April is a great time to plant (and Arbor Day is April 24). Trees need holes three times as wide as the root ball with sloped sides. The top of the root ball should sit slightly above the soil surface. The bottom of the hole should be packed firmly to prevent sinking. Use mulch 3 to 4 inches thick and off the top of the root ball. Extend the mulch ring at least 3 to 4 feet across.

Hunter Higdon, Lawn Doctor’s tree expert, notes that the biggest mistake he sees is “planting trees too deep. The trunk flare at the base of the tree must be above ground. Burying it ensures either a quick or slow death.”

It’s best to avoid most pruning in April and May since trees and shrubs are flowering, leafing-out, setting fruit and putting on new growth. Focus instead on removals, planting, irrigation, treating for insects and disease, and fertilizing, says Higdon.

Photo courtesy of CSU Extention in Larimer County.

More Rules Around Watering
Some prefer to turn on sprinklers in early April; others wait until Mother’s Day, says Verde.

O’Connor emphasizes inspecting your system. “Look for tilted heads or those not popping up fully. Adjust to ensure proper coverage and swap in more efficient ones—some local water districts offer rebates. Manually turning them on (don’t set it and forget it) and adjusting run times and frequency will be better for your lawn and wallet.”

“Make sure trees and shrubs are receiving regular irrigation. Ten gallons of water per inch of trunk diameter or per foot of shrub height every 2 to 4 weeks depending on species and location,” Higdon recommends. “And yes, water your trees in winter, at least every six weeks on warmer days November through March, five gallons minimum per inch of tree trunk diameter or foot of shrub height.”

For your lawn, the team at Belmire Sprinkler & Landscaping advise knowing what type of turf you have and watering it appropriately. Colorado is a high desert climate not friendly to turfgrass, so watering before and during the hottest months isn’t optional if you want to keep it green and lush. They often see overwatered or underwatered lawns and note that the grass should be a darker shade of green. Overwatering turns it yellow or lime green, while underwatering produces heat spots and burn outs.

“During many Aprils, rain means additional watering may not be needed, but if it’s dry, then it’s important to water the entire landscape. How much to water is impossible to recommend, given factors like temperature, soil type, plant material, age of the landscape, location, etc. Any water you can apply during dry periods is good,” says O’Connor.

When to Hire a Pro
O’Connor suggests, “Hire a landscape contractor, arborist or lawn care professional for any task you’re not comfortable doing or don’t have proper equipment to do. For homeowners pruning trees, it’s recommended you keep both feet on the ground, and have a pro handle anything above six feet.”
Verde adds, “If you don’t want to mess with fertilizers and other materials, calling a lawn care company might be a good solution. Be sure that the company is licensed and has insurance.”

Landscape Resources
CSU Extension in Larimer County is happy to help with any lawn and garden questions. Master Gardener volunteers assist homeowners to troubleshoot and offer advice. Stop in and talk to a Master Gardener at 1525 Blue Spruce Drive, Fort Collins, on Monday, Wednesday or Friday from 10 a.m. to 1 p.m., starting April 13, email, or call 970.498.6000. You can also schedule a lawn visit for $75 or a tree visit for $25. Visit the CSU Extension website at or


The CSU Horticulture blog:

The International Society for

The Emerald Ash Borer

Colorado is under attack by a tiny green invader, and some of your favorite trees are casualties. Emerald ash borers (EAB), Agrilus planipennis, appeared in Boulder in 2013. Despite a quarantine, the insect spread. Last summer, it was found in Westminster and Broomfield. Last fall, it showed up in Berthoud. The spread led to the quarantine being lifted.

An Asia native, EAB appeared in the Midwest in the ‘90s and has killed millions of ash trees in dozens of states and two Canadian provinces. Parasitic wasps from Asia that prey on EAB larvae has been used with some success in Boulder, and woodpeckers have learned the borers are a good food source. However, their spread is inevitable. Homeowners and municipalities are faced with the choice of treating or removing ash trees as a result. The damage is estimated to be 15 percent of all urban and community trees in the state, including 1.4 million in Denver alone.

Do You Have Ash Trees?
You can identify any ash on your property with some basic research, by consulting an expert or using the free EAB/Ash Tree ID app for Apple or Android by searching for “ash tree.” The Colorado State Forest Service website says that ash trees have:

• compound leaves with 5 to 9 leaflets
• leaflets, buds and branches growing directly opposite from one another
• diamond-shaped bark ridges on mature trees

Are They Infested?
Unfortunately, it’s hard to detect EAB when they first infest a tree. It can take three to five years for symptoms to show, and, once a tree’s canopy is thinned by 30 to 50 percent, it’s too late to save it. The Forest Service shared signs of infestation, including:

• thinning of leaves and upper branches and twigs
• serpentine tunnels produced by larvae under the bark
• D-shaped exit holes 1/8-inch wide
• new sprouts on the lower trunk or lower branches
• vertical splits in the bark
• increased woodpeckeractivity

Your Options: Treat or Replace
Since EAB is eventually expected to spread to any and all ash trees in the state, homeowners and municipalities must decide which trees to treat and which to remove. Both treatment, which must be repeated periodically for the life of the tree, and removal can be expensive. Dead ash become brittle, are at risk of falling and can be challenging to remove. Your best option may be to consult with a certified arborist and come up with a management plan.


Colorado State Forest Service:

Denver Parks & Recreation:

Emerald Ash Borer Information Network:

Colorado Department of Agriculture:

CSU Agricultural Biology: