Gardening tips for April

Consider planting a butterfly garden this month. Butterflies add beauty and help pollinate flowering plants. Milkweed is a popular nectar and host plant for the Monarch butterfly.

“Spring will come and so will happiness. Hold on. Life will get warmer.” — Anita Krizzan

It is officially spring and it is time to dig out of the wet winter weather and get outside.

Here are some helpful tips to get your garden started this season.

Cedar-apple rust disease forms its galls on Virginia cedar (Juniperus virginiana) in April. The odd-looking galls are at first bright orange gelatinous balls with long “horns” or projections; they later turn brown and become hard. They are the alternate host structure for a disease that does very little harm to the junipers but can be quite destructive to apple trees, hawthorns and quince.

Continue planting and transplanting trees and shrubs this month. Choose quality trees: shade trees should have a single, straight trunk. Planting and transplanting should be completed before the end of June.

The viburnum leaf beetle is a serious pest of native arrowhead viburnum, cranberry bush and many others. Look for feeding damage on viburnum and yellow larvae. Control them promptly since they can defoliate plants. Repeated defoliation can result in the death of native viburnums.

Spotted lantern-fly eggs will start hatching late April or early May depending on the weather.

Eastern box turtles and various species of snakes are coming out of hibernation and may visit your yard. Box turtles are becoming scarce through much of Maryland because of road mortality and habitat destruction. Observe, but leave them it in the wild.

Many spring bulbs have fully emerged and are flowering. Remove spent flowers but leave the green bulb foliage alone until it yellows and dies back naturally.

Lawn mowing season begins in April.

The height and how frequently you mow your lawn is very important. Cool season grasses such as tall fescue and bluegrass should be maintained between 3 and 4 inches for most of the growing season and no more than one-third of the leaf blade should be removed at each mowing.

Always make sure to sharpen your mower blades at the beginning of the season.

For vegetable gardens, continue to sow lettuce, spinach, Swiss chard, beets and other favorite salad vegetables.

Thin out seedlings of leafy greens to a few inches apart and eat the ones you pull. Check a planting chart for final spacing between mature plants.

Plant seeds of carrots, turnips and parsnips in deeply worked, well-draining soil.

Don’t jump the gun with warm season crops; plant outside only after all danger of frost is past. Night temperatures below 45º F can damage plants and later fruiting.

One option: lay down black plastic mulch to warm the soil two to three weeks before planting warm season crops like tomato, pepper, eggplant and melon. Plastic mulch also keeps down weeds.

Biodegradable non-plastic mulch, made out of corn, is now available; is one source.

Sow beans and corn outdoors late this month or early May, when soil temperatures are above 50º F or pre-start them indoors to get them off to a faster start.

Start squash, melon and cucumbers indoors to be transplanted in the garden in two to three weeks. These plants also benefit from black plastic or biodegradable mulch. Or, plant them directly in the garden, in late May through mid-June.

Start seeds of herbs, including rosemary, thyme, lavender, sage, basil and tarragon. Make cuttings of fresh mint, tarragon and rosemary from potted plants or from stems purchased in food markets. Root the cuttings in soil-less mix, under lights.

When it comes to indoor plants, groom houseplants by removing dead and diseased foliage or spent flowers; this reduces insect and disease problems and improves their appearance.

Gently dust the leaves with a soft rag.

If possible, periodically place your plants in the shower to remove dust and to give them a good drink of water. This can revive a tired houseplant and helps to leach soluble salts from fertilizers out of the soil.

Fungus gnats are small, harmless black flies that hover around, breed in and feed on moist growing media. Be careful not to over-water houseplants. Growing media should be allowed to dry out before watering again.

Different types of foraging ants may appear in your home. Try using bait stations to control minor infestations. Liquid and gel formulations are usually quite effective.

Rachel J. Rhodes,, is the horticulture educator and Master Gardener coordinator for the University of Maryland Extension in Queen Anne’s County. She is one third of “The Garden Thyme Podcast.” “The Garden Thyme Podcast” is a monthly podcast with University of Maryland Extension Educators, helping you get down and dirty in your garden with timely gardening tips, information about native plants and more.

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