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?

The 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.”

Give mums a trim now … or later

Question: In your opinion should chrysanthemums be cut back in the late fall or spring?

Different sources say different things about what to do with mums after they are browned by frost. One source advises to cut them back in the spring; another says to cut them back to about 8 inches after they finish blooming in the fall.

In my experience, either way seems to work. I usually leave them until spring in my garden beds, which tend to be informal (some might call them “messy”), and often the new leaves start to come up from the roots very early — as early as February, if we have a mild winter. At that time, I cut back all the dead stems and divide and move clumps where necessary, and they grow happily and vigorously through the spring and summer. I cut them back a couple of times during the summer to delay flowering, and they start to bloom in the fall.

If you prefer a tidier look throughout the winter, cut off the blooms after they turn brown. They will rest during winter and be ready to pop up again early next spring.

Garden events in Middle Tennessee

Nov. 17: The Nashville Tree Foundation hosts ReLeafing Day. Volunteers meet at 8 a.m. at Coleman Park, near Thompson Lane and Nolensville Road, to plant trees in the Woodbine area. Find more details and sign up to volunteer at www.nashvilletreefoundation.org or call 292-5175.

Nov. 20: The Perennial Plant Society meets at Cheekwood’s Botanic Hall, with the program “Winter Landscape Maintenance for Woody Ornamentals” presented by UT Extension agent David Cook. Refreshments and plant swap at 6:30 p.m., meeting and program at 7 p.m. Open to the public.

Dec. 14: All About Gardening, 9 – 10:30 am. at Warner Park Nature Center. Learn when and how to grow an organic garden from naturalist Deb Beazley. Class is limited to 15 adults; call to register, 352-6299.

Jan. 6: The Nashville African Violet Club meets at the Green Hill meets at the Green Hill Women’s Center, 10905 Lebanon Road in Mt. Juliet. For more information, contact Julie at Julie.mavity@gmail.com or 615-364-8459.

Jan. 15: Orchid Society of Middle Tennessee meets at Cheekwood with a program on Paphiopedilums. Refreshments at 6:30, and the program begins at 7 p.m. There is no admission, and the meeting is open to the public.

Feb. 20: Orchid Society of Middle Tennessee meets at CheekwoodBotanical Garden. The program is on Phalaenopsis orchids. Refreshments at 6:30, and the program begins at 7 p.m. There is no admission, and the meeting is open to the public. No admission to Cheekwood and the meeting is open to the public.

Poppies next spring

I saw beautiful poppies in gardens this spring and summer and would like to grow some of my own. When and how do you plant them?

There are several types of poppies; some are perennials, some are cool-season annuals. A few of them can be grown from seed sown in the fall, so start planning now to have a garden of poppies next year. Here’s a short list of the possibilities, according to the editors of the Southern Living Garden Book:

Iceland poppy (Papaver nudicaule) is a short-lived perennial with cup-shaped blooms of yellow, orange, salmon, pink, white or cream. Sow seeds or set out transplants in the fall.

Oriental poppy (P. orientale) has large, crinkled blooms in scarlet, orange, pink, salmon or white that grow from bushy clumps of foliage. The blooms may be black at the base. Plant dormant roots in the fall.

Shirley poppy, or Flanders Field poppy (P. rhoeas) is an annual poppy with single or double flowers in white, pink, salmon, red, scarlet, lilac or blue. Sow in the fall by mixing seeds with an equal amount of sand and broadcast it where you want them to grow. Note: The Southern Living Garden Book says this is a “notorious self-sower,” which is usually a gentle way to say it could take over your garden whether you want it to or not.

Alpine poppy (P. alpinum) is a perennial that grows better in fast-draining, gritty soil. It has smaller flowers (1 ½ to 2 inches in white, yellow, orange or salmon. It, too, self-sows freely. Sow seeds in fall or early spring.

To plant poppy seeds, prepare the soil in a bed in full sun and simply scatter the seeds on top, or barely cover the seeds. Water the ground carefully, and kept the area moist throughout the fall.

Garden events in Middle Tennessee

Sept. 5:WarnerParkNatureCenter hosts Hummingbird Happy Hour, 4 – 6 p.m. at the WarnerParkNatureCenter. Bird banding demonstrations and other kid-friendly activities are on the agenda. Free admission, but registration is required; call 352-6299. While you’re there, visit the NatureCenter’s vegetable, herb and flower garden. Info: http://www.nashville.gov/parks/nature/wpnc.

Sept. 15: Urban Chicken Appreciation Day at Shelby Bottoms Nature Center, 10 – 11 a.m., celebrates feathered backyard friends. Learn how to get started in backyard chicken keeping in a session led by Bonnie Bowles. Call (862-8539) or email (shelbybottomsnature@nashville.gov) to register.

Sept. 22 & 23: Many rare and unusual houseplants will be available at the Tennessee Gesneriad Society’s annual Flower Show and plant sale, which will be held at Cheekwood’s Botanic Hall. The event is open to the public 9:30 a.m. – 4:30 p.m. Saturday, and 11 a.m. – 4:30 p.m. Sunday. To learn more contact Julie Mavity-Hudson at Julie.mavity@gmail.com.

Sept. 29: Herb Society of Nashville’s Herb Day at Cheekwood’s Botanic Hall: “Cooking & Gardening with Native Plants.” 9 a.m. – 4 p.m.; admission is $40 plus Cheekwood gate fee. To register: www.herbsocietynashville.org.

The squash and the bees

I planted squash plants among my flowers. They look great and are blooming, but they’re not setting any squash. The blossom falls off before the squash begins to grow. Any help?

Squash grows after it has been pollinated by insects or by hand.

When squash plants bloom without producing squash, it probably means they need help with pollination. Squash plants produce male flowers at first, followed by female flowers a few days later. (You can tell the difference this way: male flowers have a single stamen in the center; female flowers have a four-part pistil, and appear swollen just beneath the blossom.)

According to information at GardenGuides.com, if the female flowers drop off without growing a squash, it means that it didn’t get pollinated by the bees or other pollinators that visit the garden.

Squash flowers are big, so if the bees aren’t doing an adequate job, you can do it yourself.  Use a cotton swab or a small, soft brush to gather the pollen from inside the male flower, and transfer it to the female flower. Or pick a male flower, remove the petals and swirl it around inside the female flower. (Look here for pictures of how this is done). With luck, a squash is born!

Hot news! The August Garden Calendar in Saturday’s Tennessean and at Tennessean.com.

Events

Aug. 4 (and every Saturday this month): Guided garden tours at Cheekwood, 11 a.m. – noon.Tours are free with Cheekwood admission, and no reservation is required. Garden Tours meet at Botanic Hall.

Aug. 5: The Nashville African Violet Club will meet at 1:45 at the Green Hill Women’s Center, 10905 Lebanon Road in Mt. Juliet. To learn more, contact Julie at Julie.mavity@gmail.com

Aug. 11: Celebrate the tomato at the annual Tomato Art Fest in East Nashville’s Five Points area, hosted by Art and Invention Gallery. Events include a Tomato 5K, a Fun Run, costumes, parades, games, art, entertainment, contests, competitions and more family fun. Look here to learn more.

Aug. 12: The Tennessee Gesneriad Society will meet at Cheekwood at the Frist Learning Center at 2 p.m. The program will be a pollinaton/hybridization workshop. For more info contact Julie at Julie.mavity@gmail.com (or 615-364-8459).

Aug. 16: Lunch and Lecture: New & Unique Plants for your Garden, noon – 1 p.m. at Cheekwood. Learn how to add color throughout the season and other helpful tips from Cheekwood’s garden staff. $15 for members, $25 for non-members (includes lunch). Call 615-353-9827 to register.

Aug. 21: Two meetings at Cheekwood’s Botanic Hall:

- The Perennial Plant Society meets at 6:30, beginning with refreshments and plant swap. Program begins at 7 p.m., and the speaker is Audubon naturalist Sherra Owens, presenting “Gardenening On The Wild Side With Nature’s Most Important Plant.”

- The Orchid Society of Middle Tennessee meets at 7 p.m. Michael Wenzel of the AtlanticBotanical Garden will speak on Phalaenopsis species.

Both meetings are open to the public.

Aug. 23: The Middle Tennessee Hosta Society meets at Cheekwood, 6:30 p.m., in the Potter Room. Guest speaker is landscape designer, photographer and writer Troy Marden; his topic: In a Southern Garden: Lessons from 20 Years of Gardening in the South.” To learn more about MTHS, visit http://www.mths-hosta.com.

Prevent powdery mildew

QUESTION: How do I keep my beautiful zinnias from getting powdery mildew? It may be too late for this year, but what should I do different next year?

Powdery mildew is a fungus that thrives when nights are moderately cool and foliage stays damp. It travels by airborne spores, and appears as gray or white splotches on leaves, stems and flowers of susceptible plants, such as zinnias. A mild case is merely unattractive; a severe case of powdery mildew can cause distorted shoots and leaves, misshapen flowers or can prevent flowering altogether.

The best defense is to give zinnias room to grow without crowding, which allows air to circulate better around the plants, and water only in the morning, so the foliage has time to dry before nightfall. Cut back on the use of high-nitrogen fertilizer, which produces succulent new growth that is a major powdery mildew magnet. Grow them in full sun; hot temperatures (above 90 degrees) inhibit the growth of mildew.

There are fungicides available that should be applied as soon as you begin to spot the mildew (so yes, probably too late for this year), but I always suggest trying the good-cultural-practices method first. The University of Tennessee Extension has a short list in a publication about powdery mildew here. If you decide to go that route, be sure to read and follow directions on the product label.

Zinnias are not the only things plagued by powdery mildew. Lilacs, roses, crepe myrtles and other woody ornamentals, and many herbaceous ornamentals and bedding plants are also targets when weather conditions favor the fungus.

Coming up

July 17: Middle Tennessee Orchid Society meets at 7 p.m at Cheekwood. On the agenda: an orchid auction and discussion on Cattleya Orchids. To learn more, visit www.tnorchid.com.

July 17: Perennial Plant Society meets at Cheekwood in Botanic Hall. Refreshments and plant swap at 6:30; meeting and program at 7. Guest is Kelly Norris, horticulturist, plant breeder and manager of Rainbow Iris Farm in Bedford, Iowa will present “The Modern Plant Explorer.” The meeting is open to the public.

July 26: Farmer Jason performs at Family Night Out at Cheekwood, 6:30 p.m. The event is free with regular Cheekwood admission. www.cheekwood.org.

Iris time in Tennessee

QUESTION: When is the right time to divide irises?

Bearded irises can be divided after they finish blooming.

Bearded irises, the large, showy flowers that have fuzzy patches on the outer petals, are putting on a pretty nice show across the region right now, and they’ll continue to bloom for several weeks.

After they have finished blooming, the rhizomes can be thinned out and divided if needed. But if you don’t get to it right away, you can wait until later. Irises are resilient and can survive being moved as long as they are re-planted properly.

Garden expert Judy Lowe recommends this method in her book, Month by Month Gardening in Tennessee & Kentucky:

Cut the leaves into a 6-inch high fan shape, then lift the clump with a spading fork and gently wash the dirt from the tubers. Cut off any soft, mushy or damaged parts, then cut the rhizome into smaller pieces, each with an eye or bud, using a sharp knife.

Lowe recommends dipping each rhizome into a fungicide solution to reduce the chance of fungal problems; one part liquid bleach to nine parts water is one suggestion to use.

Replant the rhizome sections close to the soil surface and water them well. Rhizomes of bearded irises should be planted so that their tops are visible above the soil. Iris beds should not be mulched.

In general, you may need to think iris beds every three to five years.

What else can you do in the garden? Pull on your gardening gloves and check today’s Tennessean, where you’ll find information about upcoming garden events and the April Landscape & Gardening calendar.

News & Events

Nashville garden specialist Barbara Wise has a passion for pots – that is, planting and growing container gardens. She now has a new book out: Container Gardening For All Seasons.

“I wrote it for new gardeners and for those who like simple (easy) steps to follow that will help them succeed as gardeners,” she says.

The book features 101 container “recipes” that any novice gardener can follow – she tells what plants to buy, what size container to use, how to place the plants, and substitutions to consider if you can’t find (or don’t like) the suggested “ingredients.” But it’s also nice for experienced gardeners who are looking for new ideas. It’s published by Cool Springs Press; retails for $19.99 and you can order it through Parnassus Books and Amazon.

*

Bloom ‘n’ Garden Expo is next weekend, April 13 – 15 at the Ag Expo Center in Franklin, Tenn. Plants, gardening products from hundreds of vendors, speakers and educational workshops are on the schedule throughout the weekend. Details, http://bloomngarden.com.

The Perennial Plant Society’s annual sale is coming back to the Tennessee State Fairgrounds April 14, 9 a.m. – 2 p.m. There will be thousands of perennials for sale for sun and shade, all from Tennessee growers, so they’re adapted to our growing conditions. Admission is free, but PPSMT notes that the Fairgrounds has a $5 parking fee. To learn more, visit the PPSMT’s website www.ppsmt.org.

*

The Herb Society of Nashville’s annual plant sale is April 21 at the Tennessee State Fairgrounds. It’s 9 a.m. – 2 p.m., but get there early to browse through 15,000 herbs (including some of those hard-to-find varieties) and talk to the Answer Ladies and all the other herb fanciers who turn out for this annual event. Look for more info at the Society’s website, www.herbsocietynashville.org and Facebook page.

*

Cheekwood is celebrating its gardens all through April with a series of Cheekwood in Bloom events.

The 20^th annual Spring Art Hop is today — April 7. More than 20,000 candy-filled eggs will be hidden throughout the gardens for egg hunts every half-hour. There will also be music, arts and crafts and live entertainment.

Ka-Bloom! on April 14 includes at family art activity and scavenger hunt,10 a.m. – 2 p.m.; flower arranging demonstration at 10:30 a.m.; guided tour of the Robertson Ellis Color Garden at 11 a.m. Howard Pink and his Musical Garden Hoses at noon; guided tour of the Carell Dogwood Garden at 1 p.m.; and container garden demonstration at 2 p.m.

The grand opening of the Howe Garden at Cheekwood (after a million-dollar renovation) will be April 21, with activities, live music, guided tours and refreshments,10 a.m. – 2 p.m.

In honor of national Arbor Day, April 28, there will be several drop-in activities and demonstrations. By the way, Cheekwood is now a certified Level IV arboretum, with more than 120 identified species of trees.

Every Sunday in April there will be guided greenhouse tours atnoon; guided museum tours at1 p.m.; and a drawing room concert series featuring Blair School of Music at 2 p.m.

Complete details on Cheekwood in Bloom are at Cheekwood’s web site.

Banish the Bradford pear

QUESTION: When should Bradford pear trees be pruned? Is now a good time? How far back should you prune them?

 

Bradford pear trees are the first to flower in spring, but they are not a good choice for landscape trees.

I’ll answer the last question first, and echo the thoughts of many landscape and forestry experts who believe that these trees should get just one pruning cut – about an inch above the ground.

Seriously, Bradford pears (Pyrus calleryana ‘Bradford’) are not good landscape trees, no matter how lovely they are this time of year. They live fast and die young – a 25-year-old Bradford pear is probably near the end of its life. Because their heavy limbs grow at narrow angles, they tend to split apart. And because they shoot up so quickly and easily, this import from China has been placed on alert as a possible threat by the Tennessee Exotic Pest Plant Council. So, is it time to reconsider?

But back to the question: It’s good to prune trees in late winter, while they’re still dormant. As you are no doubt aware if you’re in Middle Tennessee, “late winter” now seems to mean the same as “spring,” and most things are no longer dormant. So if you need to prune, do it now, before the tree leafs out fully and you can still see the branch structure easily.

Really, though, wouldn’t you rather have something else? Landscape professionals suggest a couple of good native alternatives to the Bradford pear: downy serviceberry (Amelanchier arboria), which has white flowers in spring, dark green foliage in summer and red berries in the fall; and Fringe tree (Chionanthus virginicus), white flowers, green leaves, small blue-black fruit enjoyed by birds in the fall.

Either would be better than a Bradford pear, guaranteed.

Latin lessons

If your high school Latin has gotten rusty, maybe it’s time for a refresher course. The Orchid Society of Middle Tennessee will meet Tuesday (March 20), and the guest speaker is Bonnie Tinsley, a classicist / Latin teacher whose curriculum includes botanical Latin – the naming of plants — as a major component. She will present an explanation of the binomial system that was developed and standardized by Carl von Linne (Linnaeus) in the 17^th century. And because this is the Orchid Society, the focus will be on both species and hybrid orchids to show how the enduring power of Latin helps us name and identify plants.

The meeting is at Cheekwood’s Botanical Garden in the Potter Room. Refreshments an fellowship begin at6:30, the meeting and program begin at 7. For more information about the Orchid Society of Middle Tennessee, visit their web site here.

Celebrating friendships – and cherry blossoms

The Nashville Cherry Blossom Festival is planned for March 24, and this year calls for special celebration.

2012 marks the 100^th anniversary of the gift of 3,000 cherry trees from the people ofJapan to the people of theUnited States – the trees that famously grace the Tidal Basin in the Nation’s Capital. The trees have been a symbol of friendship between Japan and the U.S. for the past century, and several cities in the Southeast – including Nashville — have been chosen to receive 20 seedlings that are direct descendents of the D.C. trees.

“We are taking this occasion of the Centennial to expand our friendship in Nashville as well,” says Megumi Osugi Stepien, Consul in charge of Culture, Information and Educational Affairs at the Consulate General of Japan inNashville. During this year’s festival at the Metro Courthouse Public Square, the cherry trees will be planted by Mayor Karl Dean and Hon. Hiroshi Sato, the First Consul General of Japan in Nashville.

The Centennial tree-planting initiative is also a chance for the citizens of Japan to show their gratitude to the American people for their support during the earthquake and tsunami a year ago, planners say.   The Cherry Blossom Festival project is a joint undertaking of the nonprofit Japan-America Society of Tennessee, the Consulate-General of Japan in Nashville and the office of Mayor Dean. Check here to learn more about Festival activities.

 

Keep African violets blooming

QUESTION: My African violets were blooming beautifully when I got them a few months ago, but no longer. How can I get them to bloom again?

It’s easy to love those dainty clusters of blossoms rising from rosettes of downy leaves. African violets look like they’d be fussy plants, but quite the opposite: “They’re easy to grow if you know a few secrets,” says Julie Mavity-Hudson of the Nashville African Violet Club.

One of those secrets may surprise you: African violets tend to bloom better when they’re slightly root-bound, so don’t rush to move them to larger pots. They thrive in bright, indirect light and average room temperatures, in soil that is kept slightly moist. “The thing that kills more African violets than anything is overwatering,” Mavity-Hudson says.

Failure to bloom might be because the plant is not getting enough light. In winter, when the light is low, try moving it to a south or west window where the light is brighter, but move it away from the window when the light is more intense. Direct sun will burn the leaves of African violets.

A light feeding of high-phosphorous plant food every few weeks may also help. Houseplant expert Barbara Pleasant (The Complete Houseplant Survival Manual) suggests adding a light pinch of Epsom salts to water to push balky plants into bloom.

To get together with other African violet aficionados, check out the Nashville African Violet Club, which meets the first Sunday of most months,1:45, at the Green Hill Women’s Center,10905 Lebanon RoadinMt.Juliet. The meetings are open to the public.

Events coming up

– Professional Landscape Association of Nashville, Tennessee – P.L.A.N.T. – will hold its winter seminar Thursday (Jan. 12),8 a.m. – 4 p.m., in Massey Hall atCheekwoodBotanical   Garden. The day’s topics include “Right Plant Right Spot,” by Kerry Mendez; “Pruning Techniques & Best Management Practices” by Karla Kean; Perennial Plant Collector’s Corner by Kerry Mendez; and “Longwood Gardens’ Vision for Horticultural Excellence and Beauty,” by Rodney Eason. Registration at the door is $100 for P.L.A.N.T. members, $125 for non-members (includes lunch). To learn more, visit P.L.A.N.T.’s Web site here.

–Another reminder that the Nashville Lawn & Garden Show is March 1 – 4 at the Tennessee State Fairgrounds. This year’s theme is Gardens Past, Present & Future, and as always the show features beautiful live gardens, 250 exhibit booths, a floral design gallery and a roster of free lectures.

Peter J. Hatch. The Thomas Jefferson Foundation Inc. at Monticello, photo by Robert Llewellyn.

Peter J. Hatch, Director of Gardens and Grounds at Monticello, the home of Thomas Jefferson, is one of this year’s speakers. Hatch is scheduled to speak on Friday, March 2 about “Thomas Jefferson’s Revolutionary Garden,” which featured more than 330 varieties of vegetables. On Saturday, March 3, Hatch will discuss Jefferson’s use of native plants, the union of gardening and sociability, and his experimentation with useful plants as a means of social change in his talk, “Thomas Jefferson, Gardener.” Other popular speakers are returning: Jeff Poppen, The Barefoot Farmer from Long Hungry Creek Farm in Red   Boiling Springs,Tenn.; Rita Randolph of Randolph’s Greenhouses from Jackson, Tenn.; and Justin Stelter, historic gardener for Carnton Plantation in Franklin and The Hermitage, Home of Andrew Jackson. Information about these free lectures is at the Nashville Lawn & Garden Show Web site.

Admission will be $10 for adults ($9 if you’re 65 or older), and this year the Tennessee State Fairgrounds will charge $5 per vehicle to park during the show. The Web site promises group discount and coupon offers coming soon.