The Ornamental Garden in June

  • By Pat Chadwick
  • /
  • June 2017 - Vol. 3 No.6
  • /

Now that it’s June, the temperatures and humidity levels are cranking up and the ornamental garden is growing at a phenomenal rate.  To keep your garden looking its best, monitor moisture levels and keep weeds, pests, and diseases under control.

The Ornamental Garden in June


Timing is critical to keeping your ornamental garden looking interesting, particularly during the summer months.   Plant annuals and perennials that offer color all season long.  As one plant finishes blooming, time it so that another plant will take up the baton and keep the color display going.  If that seems overwhelming or even expensive to you, then try plants with interesting foliage. Here are a few ideas:

  • Glossy Foliage — Plants with glossy foliage, such as New Jersey Tea (Ceanothus americanus), Leucothoe, or glossy abelia always look fresh and inviting regardless of the heat and humidity.
  • Contrasting colors

    Contrasting Purple and Chartreuse colors (‘Homestead Purple’ Verbena and ‘Firepower’ Nandina

    Plants with silver, burgundy, purple, or chartreuse foliage liven up the landscape, adding a touch of drama and excitement. Coral bells (Heuchera), purple-leaved ninebark (Physocarpus), and purple smokebush (Cotinus coggygria) are just a few examples.

  • Variegated Foliage – Incorporate plants that have variegated foliage, such as hostas, brunnera, dogwoods, and weigela.
  • Tropical plants – For a real change of pace, try using plants with large or unusual foliage such as Musa (hardy banana), Canna, or Colocasia (elephant ear).


  • Add deadheading and pinching to your list of routine gardening chores this month. Pinch back annuals, such as petunias and coleus, to keep them bushy and prevent them from becoming leggy. Annuals with large flower heads, such as geraniums (pelargonium) or zinnias, should be deadheaded (pinched back to just above the first leaf below the flower) to keep them looking tidy.  TIP:  Many of the newer varieties of annuals are self-cleaning and don’t need to be deadheaded.
  • Deadhead rhododendrons in June, about three weeks after the shrubs finish blooming. While deadheading really isn’t necessary, it improves the appearance of the shrub. It also helps to divert the plant’s energy into developing flower buds for next year’s blossoms.  Just snap off the spent blooms, being careful not to damage the emerging buds for next year’s blooms.    The idea is to divert the energy from the old flower heads to buds for next year.  June is also the best time to prune rhododendrons (See Virginia Cooperative Extension Publication 430-462, Shrub Pruning Calendar).  Don’t wait too long to do this.  Rhododendrons bloom on new wood.  If you wait too long to prune, the plant will not have time to develop buds for next year’s flowers.
  • Clean up dead foliage from daffodils and other spring bulbs that have long since finished blooming. If any foliage resists when you tug it, leave it alone for the time being.  It’s still absorbing sunlight for next year’s floral display.  Plant some annuals to fill in the space if you now have holes in the landscape where the spring bubs grew.


Now that Irises have finished blooming, don’t neglect them.

  • Flower Stalks — Cut off the spent flower stalks at the base of the plant. That will divert the plant’s energy from forming seeds to storing energy in the rhizome for next year’s flowers.
  • Weeds — Pull weeds and grass from around the rhizomes.
  • Nutrients — Apply a light application of a low-nitrogen fertilizer, such as 6-10-10. Work it into the soil and water it in.   Avoid piling fertilizer on top of the exposed rhizomes. That can burn them as well as encourage problems with rot.
  • Water – Avoid overwatering irises. Too much water can lead to issues with rot. Established irises are drought tolerant and don’t require much water during the remainder of the growing season.  Re-blooming irises are an exception to this rule.  They should be watered periodically to encourage a healthy second round of blooms late in the summer.
  • Foliar Diseases — Remove any leaves that turn brown, leaving healthy green leaves only.

Garden Phlox (Phlox paniculata) is one of the classic mainstays of the sunny perennial border.  But powdery mildew can devastate the foliage of this plant and turn it into an ugly, unsightly mess.  To combat this disease, plant garden phlox in full sun.  Allow plenty of spacing between plants for good air circulation.  In general, they should be spaced about 18 to 24 inches apart.   Thin out clumps by snipping out the weakest stems, leaving only 5 or 6 sturdy stems.   Give phlox plenty of water, particularly during dry weather.   Water the clumps with a soaker hose at soil level and avoid wetting the foliage.  A layer of mulch around the roots will help retain moisture in the soil.

For the best looking roses in the neighborhood, pay attention to their specific needs.  To prolong the bloom time, remove the spent blossoms to just above a fresh set of five leaves.  For repeat-blooming hybrid tea roses and floribundas, apply a general-purpose, balanced fertilizer after the first display of blooms has passed.  In the absence of adequate rainfall, give your roses about an inch of water per week to keep them vigorous and happy.  A deep watering periodically is more effective than a shallow watering. Always water at the soil level and avoid getting the foliage wet.  Overly wet foliage can set the stage for fungal diseases such as black spot or powdery mildew.  If you detect either of these problems, treat the foliage with a fungicide as necessary.  Also, monitor for pests such as aphids, spider mites, and Japanese beetles.

Vines, climbing roses, and other twining or climbing plants normally go through a growth spurt in early summer.  Monitor them as they grow and train them onto supports as needed before they become unmanageable.  As you tie up the vines, spread them out to the extent possible to cover trellises better and to provide better air circulation.


Bagworm emerging from Cocoon

Inspect susceptible trees and shrubs, particularly junipers and arborvitae, for evidence of bagworm damage.  Bagworms are perennial insects that get their name from the spindle-shaped silken bag they weave around themselves.  According to Virginia Cooperative Extension Publication ENTO-83NP , these pests attack Juniper, arborvitae, other cedars, pine, hemlock, spruce, Chinese elm, honey locust, crabapple, maple, sycamore, box elder, willow, linden, and poplar trees, among others.  Bagworms produce one generation per year. The overwintering eggs begin hatching in early June and the larvae are capable of doing serious defoliation. Whereas small larvae are more susceptible to insecticides, larger larvae and molting larvae are not so easily killed.  Therefore, the optimum time to treat for bagworms is during mid-June.  A non-chemical method of control is to pick off and burn the bags from fall until spring.  

Common Garden Slug (Deroceras reticulatum)

Be alert to damage from slugs and snails.  These ground dwellers are capable of climbing plants and damaging them well about the ground.  Anyone who has grown hostas knows the heartbreak caused by these slimy mollusks.  They eat large, unsightly, ragged holes in foliage from spring until frost. They can also eat entire seedlings of other plants. Slugs and snails drink from puddles of water or absorb moisture directly through their skin. To keep cool and prevent dehydration, they hide during the day under leaves, rocks, loose flagstones, porches, flower pots, wood chip mulches, etc.   At night, they emerge from their hiding places to feed.

Frogs, toads, birds and some beetle species feed on slugs and snails.  These natural predators may help minimize damage to your plants.  If the damage is serious enough to require intervention, some non-chemical strategies to control these pests include the following:

  • Eliminate their hiding places.
  • Clear the soil of weeds, debris and decaying organic matter that might provide breeding and hiding places around your susceptible plants.
  • Keep shaded areas free of weeds and litter.
  • Pick the creatures off by hand, dropping them into soapy water. The best time to do this is about 2 hours after sunset when they are out and about feeding.  They may also be detected on overcast days.
  • Trap them under a board, inverted grapefruit half, or overturned flower pot and then physically remove them. For additional effectiveness, bait the trap with pieces of potato, apple, or lettuce.
  • Place a shallow container of beer in the garden. Position the container so that the mollusk can crawl into it to get to the beer and drown.  Beer is generally effective for about three days before you have to change it.


Extend the enjoyment of your ornamental garden by creating an evening or “moonlight” garden.  As the sun goes down, brightly colored flowers tend to fade into the landscape.  That’s when white flowers are at their best.  White reflects light and white flowers look particularly beguiling in moonlight.  Some white-flowering annuals and perennials include Angelonia, moonflower, clematis, impatiens, hydrangea, Nicotiana, petunias, verbena, snapdragons, bugbane, and alyssum.  Many of these plants add extra value to the landscape by perfuming the evening air. To add a little extra zip, combine some silvery-leaved plants such as lamb’s ear, Artemisia, or dusty miller with the white flowers. But keep the composition simple.  While a monochromatic palette may sound boring, it can actually be very serene and sophisticated, especially when the plants are grouped in a mass planting.

Variegated white and green foliage can have the same effect as an all-white planting.  Something as simple as variegated hostas planted beneath River birches or grouped along a meandering woodland path can transform the ordinary to the extraordinary in the moonlight.  The overall effect will dazzle the eye in the reflected light, bringing an otherworldly feel to the landscape.


To entice more pollinators to your ornamental garden, try some of the easy-to-grow plants listed below.  A wide range of plants blooming throughout the growing season will entice a variety of pollinators to your garden. Also, group plants of the same species together to form a mass of color or fragrance.  A mass planting makes it easier for the pollinators to spot your garden and will entice them to swoop in for a closer inspection.  If they like what they see, they’ll happily make your garden a regular stop on their daily food-foraging expeditions.

  • Achillea millefolium (Yarrow)
  • Agastache species (Anise hyssop)
  • Asclepias (Butterfly weed)
  • Aster species
  • Buddleja davidii (Butterfly bush)
  • Coreopsis species
  • Cosmos bipinnatus (Cosmos)
  • Echinacea (Purple Coneflower)
  • Eupatorium purpureum (Joe Pye Weed)
  • Helianthus annuus (Sunflower)
  • Herbs, such as dill, mint, fennel, borage, and oregano
  • Lantana
  • Liatris spicata (Liatris)
  • Lobelia cardinalis (Cardinal flower)
  • Monarda didyma (Beebalm)
  • Penstemon
  • Perovskia (Russian Sage)
  • Rudbeckia hirta (Black-Eyed Susan)
  • Salvia greggii (Salvia)
  • Sedum species (such as Autumn Joy)
  • Solidago species (Goldenrod)
  • Sweet Alyssum
  • Zinnia


Check the saucers under houseplants for standing water and empty any you find.  It only takes a tablespoon or so of water to provide a potential breeding place for mosquitos.

If you moved a tank-type Bromeliad outdoors for the summer, it is possible for mosquitos to lay their eggs in the plant’s reservoir.  To avoid a potential problem, spray the plant with fresh water every 2 or 3 days to flush out the old water and renew the reservoir.  Another strategy is to periodically add a few drops of cooking oil to the Bromeliad tank to smother mosquito larvae.

The move outdoors into brighter light and fresh air provides just the jump start that many houseplants need for a growth spurt.  It may be necessary to take preemptive steps to keep some of your plants from sprawling or becoming unwieldy.  Jade plant is one plant that tends to sprawl.  To keep it under control, pinch off the side shoots to keep the plant growing upright and looking fuller.  Don’t toss the side shoots that you pinched off.  Pot them and start new plants.

Houseplants tend to grow rapidly once they have adjusted to being outdoors.  To keep up with their summer growth spurt, give them sufficient water and feed them with a liquid fertilizer.


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