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    Save the Date: Perennial Plant Society’s 30th Plant Sale is April 4, 2020, 9 a.m. – 1 p.m. at the new Expo 3 Building at The Fairgrounds Nashville. Here’s where you can find the newest varieties of perennials, shrubs, vines and annuals from local growers, along with long-time, never-fail favorites, ready for spring planting. Learn more at the PPS website.

     

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Hydrangeas’ color depends on the soil

My hydrangeas have pink flowers. Is it true I can make them change to blue? How do you do that? Can I also change my white hydrangeas to pink or blue?

Hydrangea-blueThe French hydrangea (Hydrangea macrophylla) is the one with the big, round, blue or pink clusters of flowers. The color of the flowers depends on the pH level of the soil – how acid or alkaline it is. French hydrangeas growing in alkaline soil have pink flowers; if the flowers are blue, that indicates that the soil is acid.

Continue reading

Gardenia is worth pampering

I received a gardenia plant in a 3-gallon plastic pot and a large, beautiful ceramic pot to plant it in for Mother’s Day. It’s outdoors in an area that receives part sun. Only one bloom has opened, but it’s full of buds and will be covered in white flowers soon, I hope. When should I repot it into the new pot? Are gardenias hardy in Middle Tennessee?

GardeniaIf buds have formed since you received this lovely gift, I’d wait to repot it until after it has finished blooming. Gardenias don’t always settle into a new environment easily, and a typical response to such a move is to stop flowering.

After the flowers fade, get ready to pamper this temperamental beauty. Continue reading

Winterize your roses

I’ve heard gardeners talk about “winterizing” roses. What does that mean? And how do you do that?

Rose

Winterize rose shrubs to prevent damage from cold and wind.

If you live in an area that experiences intense cold or cycles of freezing and thawing, you may have heard about the importance of winterizing your roses. While rose shrubs are generally hardy, some varieties may be vulnerable to extended cold weather and strong winter winds. “Winterizing” helps protect roses from winter damage.

The process begins in late summer. You should discontinue fertilizer applications about mid-August, to slow down new growth. Stop cutting off the dead blooms in early October, which signals the plant to stop producing new growth.

Now comes the important “winterizing” part: Between now (late November) and mid-December, cut the canes back to 2 to 3 feet tall to keep them from blowing around in the winter winds, loosening the soil around the roots. Rose experts at the Nashville Rose Society suggests placing a 12-inch high mound of soil or mulch around each bush. To minimize winter damage at the end of each cane, you can also erect a small cage of chicken wire around each bush and pile about two feet of hay or other loose organic material inside.

Miniature roses and others grown in containers can be moved to an unheated garage or other space where the temperature remains above 20 degrees. Plants should be watered just enough to keep them moist.

For advice on roses in Middle Tennessee (where The Garden Bench calls home), I usually turn to the rosarians at the Nashville Rose Society, who provide excellent information on growing roses at their website. We are in USDA Hardiness Zone 7a, and the schedule reflects normal conditions in our climate. Gardeners in colder areas may adjust accordingly.

Rose enthusiasts can also get information (and see photos of beautiful blooms) from Birmingham, Alabama-based rose expert Chris VanCleave aka “The Redneck Rosarian.” He writes about roses, hosts podcasts, and keeps the conversation going with #RoseChat on Twitter.

Pruning oakleaf hydrangea

Our oak leaf hydrangea bloomed beautifully this year, and the flowers have turned pink or brown but they’re still on the plant. The shrub is huge and needs to be cut back. Is it too late to prune it now? I want to make sure it blooms again next year.

oakleaf hydrangea Hydrangea quercifoliaLandscape designer and plantsman Troy Marden, in his book Southern Gardener’s Handbook, says that pruning oak leaf hydrangea can be “tricky.” It blooms on old wood, and next year’s buds may already have begun to develop. If you prune it now, mid-August, you likely will be cutting off some of next year’s flowers. Best to prune the plant shortly after the flowers have turned from white to beige, he suggests.

There’s no reason you can’t remove any dead branches or stems now, though. Use sharp pruning shears, and cut dead twigs and stems off close to the branches. In fact, hydrangea experts note that dead stems should be removed every year.

Shortly after the shrub blooms next spring, consider removing about a third of the older living stems at ground level, which should revitalize the plant.

Spider mites can ruin your roses

What could be stripping the leaves off the branches of my roses? I spray with a product that is supposed to protect roses from insects and diseases, but it hasn’t helped.

Knock Out roseKeep an eye on roses when it’s hot and dry. That’s when spider mites do their worst damage, say rosarians at the Nashville Rose Society, and they can turn a lovely rose bush into an ugly mess.

The tiny creatures get on the undersides of leaves and feed on the plant’s juices. The damaged leaves look speckled, turn yellow and fall off.

Spider mites are not insects; they are more closely related to spiders, so insecticides won’t have any effect. You can use a miticide, but it can be expensive. The best and cheapest way to control them is with a blast of water directed at the undersides of the leaves, rosarians say. If you do this every three days for a week or so, you break the mites’ gestation cycle.

Here’s a little more information about the tiny arachnids: Adult mites are less than 1/50 inch long. They use their mouthparts to pierce individual plant cells and remove the liquid. They produce webs that can coat the foliage with a fine silk that collects dust, making the leaves look dirty.

You can’t see them, but you can certainly see the damage. Heavily infested plants will be discolored, and if they are not controlled, the rose can be stunted, or even killed.

Prune to preserve the sweet scent of mock orange

Our two mock orange shrubs are full of blooms right now, but they haven’t been pruned in many years and they are very tall and lanky with a lot of dead wood, and look terrible the rest of the time. When can they be shaped up or pruned?

Philadelphus - mock orange

Mock Orange

The flowers of the mock orange shrub last only a week or two in late spring in USDA Hardiness Zone 7a (where The Garden Bench calls home), but they can provide a stunning show, and the fragrance, which is said to resemble orange blossoms, is delicate and sweet.

Those flowers bloom on the previous year’s growth, so you should prune the shrubs right after they finish blooming this year, which allows time for new growth to mature and bloom next spring.

If the shrub is in really bad shape but still vigorous, you can actually do a rejuvenation pruning, removing the oldest stems at ground level to encourage vigorous new growth. Information from the National Gardening Association suggests cutting out about a third of the stems. Pruning the shrub every year encourages it to grow more densely.

In general, mock orange (Philadelphus is the botanical name) grows best in full sun but can tolerate a little shade. It does well in most types of soil, as long as it has good drainage. Mock orange is good to use as a background shrub or a specimen plant in the landscape. If you’re considering a new shrub, be sure to plant it where you can enjoy that sweet, though fleeting, fragrance.

Book giveaway – winners!

southern gardeners handbookLast week we announced a book giveaway – two copies of Southern Gardener’s Handbook by Middle Tennessee author Troy B. Marden. Commenters Rhonda and Amanda were picked in random drawings, and they’ll receive copies of the book from the publisher, Cool Springs Press. Thanks for your comments!