In the Ornamental Garden
The key words for the month of July are watering and weeding. This is not the time for planting or transplanting, and if either becomes necessary, be vigilant about watering and mulching to keep soil temperatures down as much as possible. It’s best to postpone new plantings until the cooler days of September. Cutting back and deadheading perennials for re-bloom are definitely on the agenda.
- Water new plantings to be sure they stay moist. The root systems of recently-planted perennials, shrubs, and trees are too small to cope with drought conditions initially. Even drought-tolerant plants require ample moisture during their first year or two in the garden.
- Water plants in the cooler, early morning hours so that the water will soak into the ground rather than evaporate into the air.
- Water plants deeply, giving them about an inch of water per week.
- Avoid sprinkling plants from overhead. That just moistens the top of the soil but it doesn’t put water down at the root level where it’s needed.
- Use drip irrigation or soaker hoses under the mulch to water slowly and deeply at the base of each plant. If you don’t have drip irrigation, use a hose with an adjustable nozzle or a watering can to deliver water only at the base of each plant.
- Don’t water foliage; that can encourage diseases.
- In the absence of sufficient rainfall, even established plants may need water.
- Check containerized plantings daily for sufficient moisture levels. Potting soil dries out at the surface but it may be wet deeper in the pot. Stick your finger about two inches into the soil. If the soil at the tip of your finger feels dry, then add water. Water the soil – not the leaves. Bear in mind that plants have different moisture needs. Succulents and cactus, for example, prefer to be kept on the drier side whereas many annuals prefer evenly moist soil. How often you need to water will depend on the planting medium used, the type of container, the amount of sunlight, and the plants themselves.
- Be efficient in your use of water. To learn more about how we gardeners can conserve this essential resource, read Creating a Water-Wise Landscape, Va.Coop.Ext. Pub. 426-713. As this publication makes clear, sprinkler systems and other kinds of overhead watering are not nearly as efficient as drip or trickle irrigation systems:
“Avoid watering by hand. It often wastes water as there is excess runoff, and water does not penetrate beyond the top 1 inch of soil. This irrigation practice harms plants by forcing root growth too close to the surface. If you must water by hand, place a 5-gallon bucket with a few holes in the bottom next to the plant and fill it with water; when it is has drained, move it to the next plant and refill.
If you’re using rain barrels or stock tanks to store rainwater — an earth-friendly practice — be sure to treat that standing water to prevent mosquitos. The larvicide in mosquito dunks or rings is a naturally-occurring bacteria from the soil and does no harm to wildlife, except to mosquito larvae. Read more about backyard mosquito control in “Battling Mosquitos,” N.C.Ext.,https://chatham.ces.ncsu.edu/2014/08/battling-mosquitoes-2/.
Weeding is the last thing you’d choose to do on a hot summer day, but it’s truly important. Try attacking the weeds in the cool of the morning or evening. You want to get them before those weeds set seed and before they steal nutrients and moisture from your desirable plants. And keep in mind that weeds may spread disease.
Pruning, Cutting Back and Deadheading
- Deadheading and pruning can yield more flowers on certain perennials and annuals. Shear or pinch back the spent blossoms of zinnia, lavender, scabiosa, snapdragons, garden phlox, purple coneflower, and thread-leaf coreopsis so that the plant will develop more blooms later on. If you want to know more about how to employ deadheading and pruning for reblooming or staggering blooms through the season, I highly recommend the book The Well-Tended Perennial Garden by Tracy DiSabato-Aust, whose studies in her own garden have made her an expert.
- Deadleafing — the removal of dead leaves from perennials — can improve the appearance of a plant, especially one that has already bloomed. It can also prevent or reduce the spread of disease or pests.
- Pinch back chrysanthemums and asters one last time no later than mid-July. Do not pinch them back after that. Otherwise, the plant will not have time to set buds for this growing season. Pinching these plants back helps keep them from splaying open in the middle and also delays bloom time until later in the growing season.
- Pruning shrubs: July has traditionally been the final opportunity to prune azaleas and rhododendrons before they begin to set buds for next spring. This is true for a number of other shrubs as well, including quince, mountain laurel, deutzia, forsythia, winter jasmine, lilac, and deciduous viburnums, as well as several others. Before you start, consult the Cooperative Extension’s Shrub Pruning Calendar. And hone your pruning techniques with help from A Pruning Primer: Tools, Techniques and Timing in The Garden Shed, Feb. 2020. If you see signs of earlier bud set due to our changing climate, please comment below.
Monitor for pests and diseases
Mid-summer is when many problems with pests and diseases become noticeable. Watch for powdery mildew, black spot, rust, root rot, and for pests like aphids, Japanese beetles, and stinkbugs. Prompt removal of diseased foliage can help prevent the spread of disease, as can picking off insect pests. Review the recent Garden Shed articles on “Integrated Pest Management,” The Garden Shed, May 2020, and “Natural Pest Control: Attracting Beneficial Insects,” The Garden Shed, June 2020.
Bearded Iris: To Divide or Not? And How?
Unlike most perennials, daylillies and iris are usually divided in late summer. Very few of my irises — and I have both Siberian and Bearded types — bloomed this year, so I suspect they need dividing, which needs to be done between July and the end of summer. The most frequent causes of failure to bloom are (1) rhizomes are planted too deep instead of near the surface where they need to be, (2) too much shade, (3) too much fertilizer, or (4) plants have become overcrowded and need division. Mo.Botanical Garden/ Iris Germanica. Typically, iris need to be divided every three years. For instructions on how to do this task properly, look at Dividing Iris/Univ.Md.Ext. and Dividing Iris/Penn.St.Extension. And you can watch a video: Dividing Iris, Kansas St. Univ.Extension.
Be sure to take a look at the additional tasks and tips at Monthly Gardening Tips, July.
July is often the peak month of bloom in many gardens, so be sure to stop and enjoy those flowers. This is a good time to take some pictures and to take a hard look at your design and spacing, making note of plants to move or remove or divide or add in autumn or next spring.
The Well-Tended Perennial Garden (Tracy DiSabato-Aust, expanded ed. 2006)
Featured Photo: courtesy of Gail Clark