April can bring all sorts of weather. As it warms, your garden will start to grow. But beware of late April and early May weather mischief. Wait for mid-May to plant tender annuals and vegetables. It is unusual for us to get through April without at least a few hard frosts.
• Finish any cleanup of garden debris, if you haven’t done it yet, cut back ornamental grasses early in the month.
• Start weed control by digging up weeds as they emerge.
• Replace mulch if needed.
• Pay attention to the weather. Cover tender foliage with cloth, a box or bucket if the temperature drops below 25 degrees at night; remove covers the next morning
• Consider hanging some pheromone traps for yellowjacket wasps. Trapping them early reduces nesting. The traps are widely available and are specific to yellowjackets.
• Core aerate your lawn.
• Consider over-seeding, or application of a pre-emergent weed control/ Don’t do both as the weed control will prevent the seed from growing.
• Apply fertilizer to cool season lawns.
• Water as needed.
• Mow when grass exceeds 3 inches tall.
Trees and shrubs
• Plant trees and shrubs as early as you can work the ground; make sure they are well watered until established.
• If tree trunks are wrapped, remove wrapping early in April.
• Now is the time to plant bare root roses. Soak roots for 12 hours before planting.
• Deer and rabbits are hungry. Consider deer repellent for plants they occasionally browse.
• Roses, once new growth starts, late April to May:
1. Remove mulch from around the plants.
2. Prune dead or damaged canes first; prune remaining canes to 1 to 2 feet.
3. Fertilize with a rose food formulation of 9-14-9.
4. For climbing roses, do not prune live canes, but do cut back any dead or damaged ones.
• Plant cool season vegetables, lettuce, spinach, kale, peas, beets once soil temperature is up to 40 degrees. Thin plants when they emerge.
• Start tomatoes, peppers and basil from seed indoors.
• Start seeds indoors for annuals, like zinnias and celosia, that need four weeks before transplant.
• Transplant summer and autumn blooming perennials.
Go to www.ext.colostate.edu for in depth information about the following:
• Roses – fact sheet 7.404
• Vegetables-CMG GardenNotes #720 Vegetable Planting Guide
• Tomatoes – Colorado Garden Notes #1817
• The Science of Planting Trees – Colorado Garden Notes #633
• Care of Recently Planted Trees – Colorado Garden Notes #6