April in the garden: Taking time to select right plants will pay dividends

As the weather warms, gardening fever sets in. But use some discipline and restraint as you peruse plant catalogs and visit garden centers. Take the time to select plants that are suited to your garden’s growing conditions and fulfill your design criteria rather than buying on impulse (although there is nothing wrong with some experimenting). Putting the right plant in the right location will result in a better-looking garden that requires less maintenance. There are many plants to choose from, so explore the options.

Bulbs

Daffodils are easy to grow and wildlife-resistant. They need plenty of sunlight for six weeks after they bloom so the leaves can make food for next year’s flower show. Dividing them is normally not necessary. But if an old clump produces lots of leaves and no flowers, wait until they finish flowering. Dig under the whole clump with a spading fork, shake off the loose soil and carefully separate the roots of the large bulbs from each another. Replant the bulbs at the same depth in a new sunny location. You may remove spent daffodil flowers for aesthetic reasons, but most hybrid varieties produce few real seeds that would drain energy from the next year’s bloom if you don’t deadhead.

Take photographs of your bulb displays now and make notes as to where new bulbs can be added in the fall to improve the display. Observe your garden over the course of spring and early summer and make a plan to add bulbs that bloom at different times to extend the color. This will make it much easier when you are ordering and planting bulbs later this year.

Trees and shrubs

It is time to begin spraying crab apples that are susceptible to apple scab (typically this disease affects older varieties of crabs). If your tree’s leaves typically become covered with black spots and fall off in late summer, it needs a protective spray program or should be replaced with a new disease-resistant cultivar. Begin spraying after the buds open and treat once every seven to 10 days until the leaves are fully open (generally three treatments suffice). Call the Chicago Botanic Garden Plant Information Service at (847) 835-0972 for recommended fungicides and timing for applications.

Prune out winter damage. If your evergreen shrubs, such as boxwood or yews, have brown tips from winter damage, prune out the damaged twigs. New spring growth will fill in where pruning was done.

General garden care

If you have digging to do in your garden, it’s important to know where utility lines are buried first. In the suburbs, call JULIE, a free utility locating service, at (800) 892-0123. Their website is illinois1call.com. In Chicago, call DIGGER at (312) 744-7000. It generally takes two working days for these services to come out and mark the locations of your utility lines, so allow plenty of time before digging. These locating services will not mark any lines you have installed yourself, such as a gas line to a grill. Dig carefully by hand if you are working within 18 inches of either side of any marked underground utilities. Also take care when digging in gardens with underground sprinklers.

Many garden beds have irregular edges. Beds will look better and be easier to mow along if they have smooth flowing curves. Use a pliable garden hose or rope to lay out your new bed line. All clumps of grass should be removed from the bed and any clods of soil should be broken up and spread around. A sharp, flat spade works best to edge beds.

Mulching is always a good garden practice. But avoid the “volcano effect” around trees caused by piling soil and mulch up around the trunk. Keep the layer of mulch even and an inch or so away from the bark.

Good soil is extremely important for the success of a garden. If you are undertaking any major construction, work with your contractor to ensure that your site is restored with adequate topsoil. Planting beds for trees and shrubs should have 12 to 18 inches of topsoil. Remove any small amounts of clay left on top of the soil.

It is best to use rough black topsoil to regrade your planting beds. Pulverized soil may be easier to work with, but its structure has been damaged in the pulverizing process. It is important for soil to have large particles and spaces where air and water can flow through it. If you only have access to pulverized soil, amend it with compost to begin rebuilding the soil structure.

Before adding compost or tilling garden beds, grade your bed roughly as needed. Hand-spading the bed to loosen the soil makes tilling easier and allows you to incorporate compost more deeply into the soil. The goal is to uniformly work the compost into the soil throughout the entire bed.

Gardeners who are not working in a construction zone can add compost to their gardens too.

If a soil test shows that your soil is too alkaline, elemental or granulated sulfur can be added to lower the pH. Add 3 pounds of sulfur per 100 square feet of garden area per year. It is best to apply in the spring and again in fall, applying at half the recommended rate each time. Work the sulfur into the soil and water it in. Sulfur is slow-acting. Wear plastic gloves and be careful to keep the dust out of your eyes when applying it.

Lawn care

Use a slit seeder to overseed sections of your lawn that need renovation. A slit seeder is a machine that cuts slits in the soil and drops in grass seed. This allows you to seed evenly over a lawn with minimal work. A slit seeder also can be used to seed new lawns once the site has been tilled and graded.

Choose the proper grass seed for your site. Seed mixtures are combinations of two or more species of grass, and seed blends are combinations of two or more cultivars of a species. Combining different grass species and cultivars helps create a diverse stand of grass better able to withstand stress and problems. Mixtures and blends of Kentucky bluegrass, perennial ryegrass and fine fescues are good for Chicago-area lawns. Choose a mix that is appropriate for the amount of sun your lawn receives.

Growing a lush lawn in the shade is a challenge. Select a seed mix especially for shaded conditions. But keep in mind that even shade-tolerant grasses can tolerate only so much shade. In heavily shaded situations, you will need to overseed bare or thinning spots once a year. To help grow grass in shade, prune up trees and shrubs to increase light and minimize foot and machinery traffic on shady areas.

Apply crab grass control to lawns, if needed, in early to mid-April before weeds germinate. Complete this work before lilacs begin to flower. Do not apply crab grass control if you are planning to overseed your lawn; products used to prevent crab grass seeds from germinating also will prevent grass seed from germinating.

ŸTim Johnson is director of horticulture at the Chicago Botanic Garden (chicagobotanic.org).