How to give the yard a spring house cleaning
"Growing Together" columnist Don Kinzler shares tips for caring for your lawn, perennial garden, shrubs and trees this spring.
Did you hear about the two ferns that were close companions? They became fronds forever.
April is when our yards and landscapes come to life after their winter hibernation. Spring is always uplifting, but the disappearing snow often reveals matted grass, rabbit damage, and an assortment of other tasks needing our attention.
- Snow mold is widespread this spring. The long winter and continuous snow cover on ground that hadn’t frozen deeply last fall favored the buildup of the fungus that appears as gray or pinkish webbing on the surface of matted grass.
- To remedy snow mold, fluff up the affected lawn areas with a leaf rake. Raking aerates and untangles matted grass, improving the lawn almost immediately. Snow mold usually doesn’t cause long-term problems, unless left unattended.
- Voles were active in lawns once again, creating their surface channels through the turf while working under the protective snow cover. Raking the areas to remove the chewed-up grass is usually all that’s needed, and most lawn areas regrow from vole damage without further repair measures.
- Power-raking, also called dethatching, can be destructive to a lawn if done too soon in spring while the turf is moist and tender. To reduce the risk of tearing up grass plants, delay power-raking until grass is actively growing and mowed several times. Many lawns never need power-raking, which is an operation intended to remove excess thatch. To assess thatch content, cut a wedge-shaped plug from the turf profile and measure the undecomposed layer between grass blades and soil. One-half to one inch of thatch is considered a beneficial amount, conserving moisture, shading the roots, and suppressing weeds.
- Spring lawn fertilizing recommendations have changed over the years, based on turf research. The old way of thinking was to apply fertilizer as early as possible to “get the grass to green up.” Research showed much of the fertilizer was wasted in spring rain runoff before the grass was ready or able to use it. For a more effective approach, wait to fertilize the lawn until it’s green and actively growing, with Memorial Day and Labor Day being the two most beneficial and easy-to-remember yearly target dates. Fertilizing in May provides nutrition for lawns recovering from vole damage, last year’s drought, and snow mold.
- Most perennials survive winter best with above-ground parts left intact. Cut them back in April after the coldest weather is likely past, and before new growth emerging at ground level reaches an inch.
- Many native pollinators survive winter by nesting in the hollow stems of perennial flowers, and they don’t emerge until weather is reliably warmer. Because the stems we remove in April might still contain these beneficial pollinating insects, it’s best to pile the stems discreetly at the rear of the perennial garden, or another out-of-the-way place, until late May, when the insects will have emerged.
- Nearly all perennials thrive in soil that’s high in organic matter. Incorporate several inches of peatmoss or compost into the soil surface.
- Adding a layer of mulch over the soil of a perennial bed will conserve moisture, keep the soil cooler, and diminish weeds. Shredded wood mulch is more plant-friendly than rock mulch, which becomes hot in summer and weighs heavily on plant roots, compacting the soil.
- April is the preferred month to prune deciduous (leafy) shrubs. Evergreens can wait until May and June. Pruning of spring-flowering shrubs, like lilac and forsythia, can wait until after blooming if this spring’s flowers are desired.
- Rabbit damage was severe this winter and many landscape shrubs offered fine dining. Deciduous shrubs can be pruned down to a point below the rabbit injury and they usually regenerate fine, sometimes growing better than before.
- Evergreen shrubs, such as arborvitae, don’t have the ability to recover from rabbit or deer injury the way deciduous shrubs do. If branches are gnawed and foliage is stripped back to older inner branches, new foliage rarely regenerates in that area. That’s why past rabbit or deer injury is often evident for the remainder of an arborvitae’s life, and unfortunately there’s little remedy once damage is done.
- Most tree types are best pruned in April before new leaves emerge. Exceptions are birch and maple, which bleed sap when pruned in spring, so pruning can be delayed until leaves are fully expanded to minimize sap oozing.
Don Kinzler, a lifelong gardener, is the horticulturist with North Dakota State University Extension for Cass County. Readers can reach him at firstname.lastname@example.org.