The Ornamental Garden in May

  • By Pat Chadwick
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  • May 2016-Vol.2 No.5
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When it comes to gardening chores, April is just a dress rehearsal for May.  With the arrival of warmer weather, gardening evolves into a competitive sport among us gardeners.  So we design, plant, sow, weed, mulch, and fuss over each emerging plant.  Once we’re satisfied that the garden is at its most glorious –admit it – we can’t wait to show it off, right?  I can’t think of a better excuse to throw a barbecue or picnic and invite friends and neighbors over.   After all, gardens are meant for sharing.

Author's Ornamental Garden in May

Author’s Ornamental Garden in May


This is the time of year when gardeners are most likely to indulge in impulse buying sprees at the garden centers.  With so many plant choices, it’s easy to see why.  Don’t buy more plants than your available garden space can accommodate.   That’s how yours truly ended up with a 5-foot wide hardy hibiscus in a space meant for a plant half that size. If the ultimate size of the plant you ABSOLUTELY MUST HAVE exceeds the dimensions of your planting space, quietly put the plant back on the display at the garden center and walk away.    

Replace pansies and violas with colorful warm weather annuals this month.  Pansies normally last into May but start to look tired as summer temperatures heat up.  Rip them out now so that their replacements will have time to get established before the onset of hot weather.  TIP:  Consider heat- and drought-tolerant annuals such as petunias, verbena, lantana, madagascar vinca, portulaca, or perhaps fan flower (scaevola).  Depending on the spreading tendencies of your selection, a few plants can cover a large area.

Scaevola (Fan Flower) Used As a Ground Cover

Scaevola (Fan Flower) Used As a Ground Cover


Direct sow seeds of annuals such as cosmos, marigolds, cleome, gomphrena, or zinnias in the early part of May.   Later, when the plants reach 4 to 6 inches in height, pinch them back to promote bushier growth.  This will ultimately produce more flowers.

Transplant bedding plants on a cool, calm, cloudy day.  The cooler temperatures and cloud cover will cause less stress to the plants and will help them settle in sooner.  Also, pinch off any buds or open blooms so that the plant will concentrate its energy into root development.  A little delayed gratification now will mean a healthier, more floriferous plant later.

Plant a container garden this spring.  If you’ve never planted one before, container gardens are a great way to experiment with colors, textures, and new plant combinations.  For best results, choose a large pot that has a hole for drainage.  TIP:  A plastic pot holds moisture better than a terra cotta pot and is not as heavy.  Choose plants that have similar requirements for light, water, and soil and that are in scale with one another.  In other words, choose:  (1) a thriller — at least one plant that is as tall as the container to give the composition height and proportion, (2) spillers – vining or creeping plants that will drape over the edge of the pot and soften the composition, and (3) fillers – mid-size plants that will fill out the composition.

Plant tender summer-blooming bulbs, including dahlias, tuberous begonias, caladiums, elephant’s ears, Colocasia (taro), oxalis, gloriosa lilies, calla lilies, canna lilies, gladioli and tuberoses, among others.  Summer bulbs must be planted after the danger of frost and in soil that has warmed up to about 60°F.  To prevent the bulbs from molding or rotting before they can become established, plant them in a well-drained site. Unless package directions instruct otherwise, plant the bulbs about three times the depth of the bulb circumference.  In other words, a bulb with a circumference of 2 inches should be planted about 6 inches deep.

Plant a vine to add architectural interest to the ornamental garden or to add a vertical dimension to a smaller garden where space is limited. If you’re not ready to commit to a perennial vine, experiment with annual vines, such as:

Black-Eyed Susan Vine

Black-Eyed Susan Vine

1. Black-eyed Susan Vine (Thunbergia alata) — This 6- to 7-ft. long vine sports perky orange, yellow, or white blossoms with dark centers.  Pinch back the spent blossoms to keep it blooming.

2. Cardinal Climber (Ipomoea x multifidi) – The bright red, trumpet-shaped flowers are nectar rich.  Expect lots of hummingbird activity in the vicinity of this climber, which grows from 6 to 12 ft. tall.  This twining vine can self-sow aggressively but seedlings are easy to remove from the garden.

3. Moonflower (Ipomoea alba) – Large heart-shaped leaves are very attractive along the 20-ft. long stems.  The large, fragrant, white flowers open in late afternoon and close by late morning the next day.

Morning Glory 'Heavenly Blue'

Morning Glory ‘Heavenly Blue’

4. Morning glory (Ipomoea purpurea) – As its name suggests, it blooms in the mornings and closes during the heat of the day.  As fall approaches, the flowers stay open most of the day and put on a spectacular show.  Tip:  This 15-ft. long vining plant readily re-seeds.  To prevent re-seeding, either remove spent flowers as they fade or pull up all the dead vines after the first killing frost.


Purple Hyacinth Bean

Purple Hyacinth Bean


5.  Purple Hyacinth Bean (Lablab purpureus) – You get a bonus with this 6- to 15-ft. long vine.  In addition to rich lavender flower spikes, this vine produces deep reddish-purple seed pods that are every bit as attractive as the flowers.

6. Sweet peas (Lathyrus odoratus) – An old-fashioned favorite, this vine grows 6 to 8 feet tall.  The more you cut the sweet-smelling flowers for bouquets, the more the plant will produce.

Provide adequate water to newly-planted seedlings and transplants and protect them from drying wind and hot sun until they establish good root structures. This is particularly important during the first few weeks for healthy root development. Lack of moisture is one of the key reasons young plants die before they become established.  If the root ball dries out, the plant may not recover from the stress.  Too much water is just as bad for seedlings and transplants because soggy soil may cause their roots to rot.

Monitor moisture requirements of newly planted trees.  In general, it takes 2 to 3 years for a tree to become established in the landscape.  Adequate moisture is particularly critical during this period to encourage healthy root development beyond the original root ball.  Don’t take it for granted that light spring rains will provide enough moisture at the root level.  In the absence of good soaking rains, provide supplemental water, particularly as daytime temperatures grow hotter.   Cover the entire area under the tree canopy to keep the soil evenly moist but not soggy around the root ball and surrounding soil.  Too much water can be as detrimental to the health of a tree as too little.

If you want to attract bees and other pollinators to your ornamental garden, flowers with single petals rather than double petals are generally a better choice.  Plant developers have put a great deal of effort into producing double flowering varieties.  Echinacea (cone flower) is a good example of a plant that has undergone significant breeding for fuller, showier flowers. While that gives the average home gardener more variety and pizzazz for the garden, the downside is that it affects the flower’s ability to produce pollen. In order to produce double flowers, the stamens (male portion of the flower) are bred to transform into extra petals. Because of this alteration to the basic anatomy of the flower, the blossom may not produce as much pollen as a flower having single-petals.  So, if you’re looking to attract pollinators, go with the old-fashioned species.

Snip off the seed heads of daffodils and other spring-flowering bulbs after the flowers are finished but leave the foliage alone so that it continues to photosynthesize. Just let it die back naturally.  TIP:  Plant some fast-growing annuals nearby so that they can camouflage the dying bulb foliage.   Petunias, lantana or verbena are good choices for this purpose.

Pinch back chrysanthemums as soon as the new shoots are 4 to 6 inches long.  This will encourage lateral branching and a sturdier, more compact shape.  Just grasp the growing tip and pinch about ½ to 1 inch of the stem back to a leaf node.  The plant will push out new branches from these nodes.  Those branches in turn will need to be pinched back by the early part of July. Also, apply slow release granular fertilizer scratched into the soil.

Prune spring-flowering shrubs after they finish blooming.   If you put off doing this until later, you run the risk of cutting off buds for next year’s blooms.  Virginia Cooperative Extension (Va. Coop. Ext) Publication 430-462, “Shrub Pruning Calendar” ( provides guidance on the best time of year to prune a variety of shrubs.

Lightly fertilize azaleas and rhododendrons after they finish blooming if a soil test indicates that nutrients in the soil are low.  Use a fertilizer that is specially formulated for acid-loving plants and follow the directions carefully.  Lightly scatter the fertilizer at the edge of the root zone.  Azaleas have delicate roots that are close to the soil surface and can be easily burned by excess fertilizer.  Too much fertilizer may also cause scorched leaf margins.

Now that it’s spring, it’s time to start monitoring your prized plantings for insect pests of all kinds – creeping, crawling, flying, etc.  If you need to do some sleuthing to figure out what pest has invaded your garden, take a look at Va. Coop. Ext. Publication 2909-1414 ( It contains a slide show of insect pests common to ornamental plants in Virginia, including shade trees, shrubs, flowers and houseplants. The slide show is grouped by insects that (1) feed on plant juices, (2) eat leaves, (3) bore into wood, and (4) produce galls.  You will also find information on beneficial insects.  Click on each image to learn more about the insect displayed in the photo.

It’s time to move potted houseplants outdoors now that night-time temperatures are stabilizing above 50° F.  To get the plants ready for their summer home, water each one thoroughly.   Rinse off the foliage with room-temperature water to remove dust and dirt that may have accumulated over winter. Groom each plant by removing any dead or dying leaves.  Re-pot any plants that have outgrown their pots.   For plants that don’t need to be re-potted, top off the soil with an inch or two of fresh potting soil.  Gradually acclimate the plants by placing them in a shady location initially while they adjust to brighter light.

Introduce your children to gardening by giving them a small plot of their own to manage.  Show them how to sow seeds.  For small children, you might want to start with nasturtium seeds, which are large and easy for little hands to handle. Let the kids help you transplant a few bedding plants, such as petunias, marigolds, geraniums, or begonias.  With a little guidance from you, gardening will be a rewarding experience for them and for the whole family.  Just don’t visibly cringe if your little guy or gal pulls up the petunias to see what the roots look like.



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