April Garden Calendar – Colorado

Trees and Shrubs

– Plant trees, shrubs, and bare-root stock. Consider the design of your yard when choosing plants. Group plants with similar soil, light and water requirements.

– Remove mulch around roses and prune dead or damaged canes.

– Water shrubs and trees if the weather is warm and dry.

Flowers, Ground Covers, Perennials, and Ornamental Grasses

– Continue flowerbed cleanup and weed control as needed.

– Plant bare root perennials and transplant or divide summer and fall-blooming perennials like daylilies, asters, and fall anemones as they start to emerge.

– Selectively prune or pinch late blooming perennials so they are full bodied later in the season.

– Fertilize flowerbeds while plants are still dormant. A slow release 5-10-5 fertilizer is generally recommended. Apply fertilizer in bands 3-4” away from the crowns of plants and scratch fertilizer into the soil with a rake or cultivator. Keep fertilizer granules off of foliage. A soil test will determine the level of organic matter levels of your soil. This will determine if you need fertilizer and if so what type.

– “Stake” or “cage” taller perennials, like peonies and delphiniums, as they emerge. Doing this before they start to flop avoids damaging them during staking. Many nurseries and garden centers have special cages for these perennials designed specifically to maintain their natural appearance.


– Control weeds as needed.

– Core-aerate lawn.

– Check mower blades for sharpness and sharpen/replace as needed.

– Depending on growth, begin regular mowing.

– Re-seed or re-sod bare spots in the lawn.

– If cool season turf is in poor condition fertilize at 0.5 – 1 pounds. Nitrogen/1,000 sq. ft and sod or over-seed thin areas. Water as needed based on current local watering guidelines and restrictions.

– Precipitation is often at its highest in April and lawns need only about ¼” of water per week under normal circumstances. Delaying the start-up of your sprinkler system may save you money and conserve our most precious natural resource – water. Daily watering is only necessary with new seed or sod to help it establish. In all other circumstances daily watering only encourages shallow root growth and reduces the turf’s drought tolerance.

– As soon as your lawn reaches 3.5” high begin mowing; keep in mind ideal lawn height is 2.5” – 3”. To encourage lawn health and strength, try not to remove more than 1/3 of the leaf blade at each mowing. In April and May this my mean mowing every 4-5 days.


– Control weeds as needed; pulling is a great option while they are small.

– If you didn’t get this done in late March, plant cool-season vegetable crops, such as spinach, peas, carrots, lettuce, broccoli, cabbage, Swiss chard, kale, beets, carrots, radishes, radicchio, turnips and onion sets outdoors.

– If you wish to start vegetables early, warm the soil with a Wall of Water, Kozy Cone, Hot Caps or Season Extenders for one week before planting warm season vegetables.


– When you start your sprinkler system this spring consider upgrading your time clock to one with water saving features or installing a rain sensor or soil moisture sensors to help conserve water. Watch for runoff and avoid watering streets and sidewalks. Reducing your irrigation to just what the plant needs will save you money and helps prevent diseases.

– Celebrate Earth Day and Arbor Day by planting a tree or donating your time to an environmental event in your community.

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