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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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Best time to transplant hydrangeas

We have hydrangeas we’d like to move to another location in the yard, where they can get more sun in the morning. When is the best time to move them?
Hydrangea vertHydrangea experts say that the best time to transplant the shrubs is when they are dormant (after most of the leaves have fallen off). Information at the Web site Hydrangeas! Hydrangeas! suggests waiting until November or December, but anytime after the weather cools should be fine.
Prepare the new site before you dig up the shrub. Hydrangeas are generally happy in a site that gets morning sun and afternoon shade, and in soil that drains well. When you begin the move, dig up as much of the root ball as possible and move it to the new site, setting it at the same depth it had been growing. Fill the hole with soil and water deeply. Be extra attentive to the newly transplanted shrub during the first growing season, making sure it gets enough moisture as it adjusts to its new site.

‘Annabelle’ hydrangea stands up to summer

QUESTION: What is the best way to secure Annabelle hydrangeas to keep the beautiful blooms from breaking in the wind and rain?

AnnabelleThis is a question many gardeners ask, especially since one of our favorite varieties, ‘Annabelle,’ is at its best right now, and the big, heavy bloom heads can get quite heavy and messy when they’re hit by soaking rains. Here’s an answer from The Garden Bench a few years ago that bears repeating:

The best way to keep them standing is to prop them up. Judith King, who writes a Web site devoted to hydrangeas, has several suggestions. She says you can plant them next to a decorative fence, plant three Annabelle shrubs together so they prop each other up, or, early in the spring, surround each plant with a short wire cage. As they leaf out and grow, the foliage hides the cage, and all you see is your tall, lovely hydrangeas, happily standing.

One cultural practice to consider: Some gardeners cut the stems of Annabelles close to the ground in the fall. Since these hydrangeas bloom on new growth, they’ll grow and bloom just fine next summer, but the stems will not have had a chance to grow as thick and sturdy. If you leave the stems 18 to 24 inches tall, those stouter stems will help support the newer branches and blooms next year.

 

Why lilacs don’t bloom

Question: Our lilac bush receives sunlight for about half the day and bloomed in the past, but not much. Now it does not bloom at all, though the foliage is healthy. It is planted in well-drained soil, and other lilacs in the neighborhood are doing well.

Lilac

Lilac (Syringa vulgaris) ‘Albert F. Holden’

Lilacs are deciduous shrubs that produce clusters of flowers in mid-spring. There are several factors that could keep the plant from flowering, but the most common is the lack of sufficient sunlight. Garden experts who favor lilacs insist that they really need full sun – six or more hours of direct sunlight – to bloom.

As gardens grow and change over the years, the nature of the sunlight the garden receives may also change – trees grow taller and wider and filter more of the sunlight that gets to your garden. Could that be a factor in your landscape?

Lilacs also need adequate water in summer – not just a sprinkling around the roots, but the entire ground, says gardener Anne Owen, who has several years’ experience with growing lilacs in Middle Tennessee.

One other thing to consider is whether the plant needs pruning, which could encourage the setting of new buds and flowers next year (lilacs bloom on the previous year’s growth).

And as always, consider testing the soil. If a soil sample from your garden bed test low in phosphorous, the lilac may respond to an application of fertilizer.

In general, here is what lilacs need to grow well and bloom each spring: Full sun, well-drained soil that is lightly alkaline or neutral pH, regular water. Be aware that they are prone to developing powdery mildew. Also note that lilacs bloom best where winters are consistently cold, and they suffer in long, hot summer nights. If you live in the Southern U.S., garden expert Felder Rushing suggests planting lilacs in well-drained soil on the north side of a building, where it might be colder in winter, and hope for cool August nights.

Azaleas thrive when conditions are right

Question: Our azaleas on the eastern side of the house have never been very showy. The flowers are always puny and short-lived. This year one plant’s leaves are quite yellow. Is this is sign of disease or need for fertilizer? Any advice on helping the plants do better?

AzaleaFirst, consider what azaleas need to grow well, and you may find that one or more of these conditions (outlined by the Azalea Society of America) is not being met:

-Slightly acid soil (pH 5.5 – 6; a soil test can provide that information about the soil in your azalea bed).

-Enough sunlight. Less than 3 hours of sun reduces the number of buds.

-Adequate moisture. Like many other shrubs and perennials in the garden, azaleas need about an inch of water (rainfall or watering) per week. Mulch around the shrubs can help the soil retain moisture.

There are several factors that affect the number of blooms — including the fact that some are just “shy bloomers,” according to the Azalea Society. Lack of moisture during late spring and summer also affect bud formation, or there may be a phosphorous deficiency (again, the soil test can determine if that’s the case).

As for those yellow leaves: If the yellowing is between dark green veins, the condition is called chlorosis, which is usually caused by an iron deficiency, alkalinity of the soil, potassium, calcium or magnesium deficiency, or too much phosphorous. Iron sulfate or sulfur can acidify the soil.

Leaves that are uniformly a yellow – green color may just need more nitrogen. That soil test should be your first step to determine what the problem may be.

Shrubs for a good foundation

Question: I plan to replant the bed at the front foundation of the house with new shrubs. I will need about 5 shrubs, evergreen and low maintenance. The front of our house gets morning sun and afternoon shade. What type of shrubs can you suggest?

boxwood shrubs

Boxwoods are a favorite choice of shrubs for foundation plantings.

I talked with Mark Kerske at Gardens of Babylon garden center in Nashville, and he has several good recommendations:

Boxwood is a tried-and-true choice. “It’s one of my favorite plants,” Kerske says. Boxwoods can grow quite large over time, but there are smaller varieties available that grow to more suitable size for foundation plantings. They take full sun but also do well with some shade.

Cryptomeria is a fast-growing conifer with dark green needles that can grow very tall and wide, but there are dwarf varieties (‘Lobii Nana’ and ‘Pygmaea’ are two that are mentioned in the Southern Living Garden Book) that grow only to about 3 – 4 feet tall.

The cherry laurel ‘Otto Luyken’ is also a favorite. It’s a compact shrub with deep green, glossy leaves that grows to about 4 feet tall and 4 to 6 feet wide.

Whichever shrubs you choose, good soil preparation will ensure that they get off to a good start. Work good compost into the soil to improve the drainage, and use mulch in the planting bed after you plant the shrubs to keep the soil moisture consistent. “You don’t want to keep the soil wet, but just moist,” Kerske says. “That’s the key, maintaining constant moisture.”

Time to plant a rose

Question: We want to add roses to our landscape this year. When is the best time to plant them? Is it better to buy bare root plants, or plants in containers?

Rose WebRoses purchased as bare-root plants can be planted in late winter, whenever the soil can be worked. In this area (USDA Hardiness Zone 7a), roses in containers should be planted after mid-April, say the experts at the Nashville Rose Society. Either should grow well and bloom if they’re given the right conditions: lots of sun – six or more hours a day – and good drainage.

Here’s how to plant roses to get them off to a good start:

Before you plant a bare root rose, soak it for 8 – 24 hours in a large bucket of water with root stimulator added. This rehydrates the plant. Dig a hole 18 inches wide and deep. Place ½ cup of superphosphate in the bottom of the hole, and cover it with a mound of soil made up of 1/3 top soil, 1/3 compost and 1/3 sand or perlite. Prune any broken or dead branches or old canes smaller in diameter than a pencil, and prune back any broken or unusually long roots.

Place the roots over the soil mound in the hole and spread them out and downward over the mound. Place the soil mix around the roots to fill the hole about halfway, and pour a gallon of water with root stimulant over the soil and let it drain. After this has soaked in, finish filling the hole up to ground level with soil mix. Cover the soil with mulch to help keep the bush hydrated until the feeder roots begin to grow; remove the mulch gradually as the weather begins to get warmer.

To plant a potted rose (after the last frost date in your area), dig a hole slightly larger than the diameter of the pot and about 18 inches deep. Place ½ cup of superphosphate or bone meal in the bottom of the hole and cover it with 2 inches of soil. Remove the bush from the pot without breaking the root ball (you may have to cut the sides of the pot away) and place the root ball in the hole so that bud union – the knot where the rose was grafted onto the root stock — is just above ground level.

Fill in around the root ball with soil, and water thoroughly with a bit of root stimulator added to the water.

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The Garden Calendar returns in The Tennessean and at Tennessean.com

In March, hope springs eternal in the garden

Winter shrub damage: They may be down, but not out

Winter burn 1Question: Some of my shrubs look like they’ve been damaged by the extremely cold weather. Should I cut them back or cut off the dead parts?

It’s true, the landscape may be looking a little ragged right now. In Middle Tennessee (where The Garden Bench calls home) long days and nights of cold and wind seem to have smacked down a lot of shrubs that usually breeze through mild winters. It looks like this winter has been particulary cruel to marginally hardy and semi-evergreen plants.

You may be tempted to get out the loppers and pruners, ready to cut off the winter-burned branches and limbs, but don’t be in such a hurry. “Wait until the flush of growth in spring, so you can know where to cut back to, to know what’s really dead,” says Nashville horticulturist Carl Pitchford.

winter burn 2Leafy semi-evergreens, such as nandina, and some of the more finicky tender perennial herbs, such as rosemary, seem to have been especially hard hit. “A lot of those will show winter burn after those cold temperatures,” Carl says. “You just have to wait and see.” With nandinas, for example, you may have just lost the foliage. The cold would not have damaged the root systems, and new leaves should sprout in the spring.

Book giveway: Here’s our winner!

Last week I interviewed Judy Lowe, the author of Month-By-Month Gardening in Middle Tennessee & Kentucky, about gardening in winter. Then I asked readers to leave a comment about their must-do winter garden tasks for the chance to enter a drawing to win a copy of the book (determined by a number generated at random by Random.org)

And the winner is… Judy Lee: “I am ready for spring when winter loses its grip. Let’s go! Let’s garden!

 

Hydrangeas’ color codes

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 garden benchThe 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.

There’s a lot of science surrounding the explanation of soil’s pH that involves discussion of hydrogen ions in the soil – way beyond the scope of this column. One simple thing to remember is that pH is measured on a scale from 0 to 14; pH 7 is neutral, below 7 is acid, above 7 is alkaline. You can learn your soil’s pH level by having the soil tested at your county’s extension service.

You can change the soil’s pH level (and therefore, the color of the French hydrangea flowers) by adding lime to the soil, to make it more alkaline (pink). Add aluminum sulfate, to make it more acidic (blue). How much of either amendment to use depends on the soil type and current soil pH – a good reason to have the soil tested before you proceed.

The change doesn’t take place right away. Changing the pH of the soil this year will mean changing the color of next year’s blooms.

Soil pH doesn’t affect the color of white hydrangeas such as Annabelle or oakleaf. Their flowers are always white, though as they age, Annabelle flowers take on a green tint.  Oakleaf hydrangea flowers mellow to a rosy pink shade

Garden events in Middle Tennessee

May 18: Gardening with chickens with Megan Lightell, 10 a.m., Gardens of Babylon (at the Farmer’s Market) Click here to sign up.

May 21: Perennial Plant Society of Middle Tennessee meets at Cheekwood’s Botanic Hall. Speaker is Jimmy Williams from Paris, Tenn, on “The Perennial Border from February through December.” Refreshments at 6:30, meeting at 7 p.m.
May 23: Middle Tennessee Hosta Society meets at Cheekwood’s Potter Room, 7 p.m. Featured speaker is Jason Rives, owner of Petals From the Past in Jemison. Ala.; topic is “Incorporating Antique Roses into the Hosta garden.”

Moving a camellia

QUESTION: I planted a camellia more than ten years ago. Apparently it’s in the wrong place because it has never bloomed; it hasn’t even grown much, though it hasn’t died. It’s in a spot that I now realize is in shade most of the time, and maybe it doesn’t get enough water, so I’m considering moving it. When is the best time to do that? And what’s the best way to do it?

CamelliaThe general consensus among camellia experts seems to be that camellias don’t take well to being moved. That said, it sounds like your shrub is already unhappy, so why not try moving it to a better spot? Now, while the plant is dormant, is a good time to do the job.

First, a short lesson on what camellias need:  well-drained, slightly acidic soil rich with organic matter, light shade, and regular water (as long as it drains well). It should be protected from strong sun and punishing winds.

The challenge in moving the camellia will be in preserving as much of the root structure as possible.  For large, established camellias, experts suggest root-pruning a year in advance of the move, but for a shrub that’s still small, that probably won’t be necessary.

Begin by carefully digging a trench around the plant at the drip line, working your way around and down and under to lift as much of the soil and roots as possible. Camellias have a shallow root system, but it’s still best to try to keep as much of it intact as you can. Transfer the root ball to a tarp or a sheet and move it to the new location, where you will have dug a hole about twice as wide but not as deep as the root ball you lifted out.

When you transfer the root ball to the new hole, make sure it is not planted deeper than it had been in the original location. Cover the exposed roots, but don’t pile soil up around the trunk. Water it thoroughly, and keep it well watered (but not soggy) during the first growing season. Consider providing protection from very cold weather; camellias can be sensitive to extreme temperatures, and in this climate (Zone 7a) some varieties tolerate cold better than others.

 

For trees and shrubs, prime planting time

QUESTION: I have a hydrangea that I bought at a nursery last spring, and it’s still in the pot it came in. Is it too late to plant it?

Fall is a good time to plant hydrangeas and other woody ornamentals.

Fall is a good time to plant hydrangeas and other woody ornamentals.

I’m sure every gardener has, at some point, bought sturdy plants in the spring, but somehow never got around to putting them in the ground (I know I have!). You can be sure that your hydrangea will be happier in the ground than it will be if it has to struggle through the winter in a plastic pot.

In fact, fall and winter are good times to plant woody ornamentals, when they are dormant and have fewer energy requirements. They still need water, but require less than they would in spring going into the hot summer. In fall, new trees and shrubs can begin to establish a strong root system and be ready to begin new growth next spring.

Here are general guidelines from UT/TSU Extension for planting container-grown trees and shrubs:

-Choose your location and begin by digging a wide hole, two or three times the width, but no deeper than the height of the root ball in the container.

-Water the plant before you take it out of the pot. After you remove the plant, cut any roots that circle the ball of soil (if the roots and soil don’t come out easily, cut the plastic away from the root ball. Don’t pull the plant out by its trunk). Use a sharp knife to make two or three vertical cuts, and gently loosen the ball to expose more roots to the soil.

-Place the plant in the hole to that the top of the root ball is even with the soil line or an inch or two above it, and backfill the hole with soil and water again. Rake over the soil to even it out with the ground, and cover the area with 2 or 3 inches of mulch (keeping the mulch away from the shrub’s trunk.

-Don’t forget to provide water to newly planted shrubs and trees if the weather is dry.
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