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.”

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?

The 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.

Garden events in Middle Tennessee

Feb. 8 – 10: Antiques and Garden Show of Nashville. Six beautiful gardens plus dozens of booths featuring fine antiques and horticulture dealers at the NashvilleConvention   Center. Hours are 10 a.m. – 7 p.m. Feb. 8 and 9, 11 a.m. – 5 p.m. Feb. 10. This year’s theme is “Be Inspired – A Tribute to Albert Hadley.” General admission tickets are $20; special prices for lectures and workshop. Learn more here.

Feb. 19: Perennial Plant Society meets at Cheekwood, beginning with plant swap and refreshments at 6:30, program at 7 p.m. Guest speaker is Marshall Allen, founder and owner of Allen Landscape Management; the topic is “Design using hardscape, various types of plants and other features of interest.” No charge for admission, and the public is invited.

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.

Feb. 28 – March 3:Nashville Lawn & Garden Show at the TennesseeState Fairgrounds. More than 20 live gardens (all indoors!) by local landscape professionals; a series of free lectures by expert horticulturists and garden designers, and 250 booths of horticultural products, services and equipment for show and sale. Hours are 10 a.m. – 8 p.m. Feb. 28, March 1 and 2, and 10 a.m. – 5 p.m. March 3. This annual event is produced by the Horticultural Association of Tennessee. Learn more here.

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.

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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Bring bay indoors

I bought a bay laurel seedling this past spring that was about six inches tall and set it out in a pot in the herb garden because I heard you may have to bring it indoors in the winter. It’s now about a foot tall. Could it survive outdoors? How do you harvest and use the leaves?

Bay laurel, or sweet bay (Laurus nobilis) is generally considered hardy to Zone 8 (well to the south of us here in Middle Tennessee), so it will need to come indoors before it gets too cold.

Place the plant where it gets as much sun as you can give it, in a south or west-facing window, if possible, and don’t let it get too dry (keep the soil evenly moist but not overly wet, the experts at the Herb Society of America suggest). It may also appreciate occasional misting if the air in your house is very dry. Take it back outdoors when the weather is consistently above freezing in the spring.

Bay leaves can be used dried or fresh; they’re usually added to long-cooking soups and stews. Snip them from the plant and use them as needed, or dry them to save for later. Use them whole (crumbled leaves have very sharp edges, which could be an unpleasant surprise to diners), and be sure to remove them before you serve. A bay leaf is a key ingredient in a bouquet garni (tied in a bundle along with thyme, parsley and other herbs), which would be added to a dish while it’s cooking and removed before serving.

By the way, there have been reports of bay laurel surviving the winter in colder climates, provided it is in a protected area. But to be on the safe side, find a sunny spot for it indoors.

Garden events in Middle Tennessee

Sept. 18:  Perennial Plant Society’s monthly meeting at Cheekwood’s Botanic Hall begins with refreshments at 6:30 p.m., meeting at 7 p.m. Speaker is Terry White.

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. 27: Middle Tennessee Hosta Society meets at 6:30 p.m. at Cheekwood. Speaker is Susan Webb of Hurricane Valley Ornamentals in Gurley, Ala. Topic is “Growing Miniature Hostas in Hypertufa Containers.”

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.

October 6: The Nashville Rose Society and Chattanooga Tri-State Rose Society host the annual Tenarky District Fall Convention and Rose Show Oct. 5 – 7. Events open to the public on Oct. 6 include Rose Garden Tours, 9 – 11 a.m.; a rose show, 11 a.m. – 4 p.m.; and a public seminar: Basics of Growing Roses,” 2:30 p.m. Learn more here.

Oct. 16: Perennial Plant Society’s monthly meeting at Cheekwood’s Botanic Hall begins with refreshments and plant swap at 6:30 p.m.; program at 7 p.m. Speaker is landscaper Tina Ramsey  on the topic, “Winter Gardening.” Open to the public.

Transplant azaleas in early fall

I have an azalea I’d like to move to a different location in the yard. Can I dig it up and move it now?

Now is not the best time to transplant azaleas, but start planning to make the move, because you can do it soon. The U.S. National Arboretum Web site and the Azalea Society of America both suggest early fall, after the weather has cooled a bit, as a good time to transplant an azalea.

When the time comes, start by preparing the new planting site (azaleas need good drainage, partial sun, and slightly acid soil). Dig a wide hole, but not a deep one because azaleas have fairly shallow roots. Dig the azalea with as big a root ball as you can manage, then lift the plant by the root ball, not by the trunk, and move it to its new location. If it’s a very large plant, you may want to work a tarp or a big square of burlap under the root ball, then tie it up and lift it using the tarp (probably not a one-person job).

When you place the root ball in its new hole, make sure it’s at the same level as it had been growing. Fill the hole with soil and water thoroughly, and add a couple of inches of pine straw mulch. Water it again the next day, and at least once a week for several weeks, the Azalea Society suggests. Water deeply if the plant begins to look wilted.

Garden events in Middle Tennessee

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. 18:  Perennial Plant Society’s monthly meeting at Cheekwood’s Botanic Hall begins with refreshments at 6:30 p.m., meeting at 7 p.m. Speaker is Terry White.

Sept. 18: Orchid Society of Middle Tennessee meets at 7 p.m. at Cheekwood. Member Alice Jensen will present information and photos of her trip to Costa Rica. The evening begins with a social at 6:30, open to all.

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. 27: Middle Tennessee Hosta Society meets at 6:30 p.m. at Cheekwood. Speaker is Susan Webb of Hurricane Valley Ornamentals in Gurley, Ala. Topic is “Growing Miniature Hostas in Hypertufa Containers.”

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.

Grow the best blueberry bushes

QUESTION: I have had blueberry bushes for 2 years and they still look awful. I’ve been told to put coffee grounds around them but they don’t grow or produce fruit.  We have them in a bed with some calla lilies which are doing very well. The plants were healthy plants from the co-op.  I have a friend in Clarksville that has lush bushes with lots of fruit.  I asked if they did anything special and she said “no”.  Any tips to help us would be appreciated. — Karen in Donelson

Blueberries need sun, water and the proper soil pH to produce a good crop.

Blueberries are pretty finicky about what they need to grow well and produce, so I’ll let you know what those needs are, and you can decide if they’re getting what they require.

Do you know what the variety of your plants? Different types are adapted for different regions, and in Middle Tennessee, the varieties called rabbiteye and southern highbush blueberries are the most reliable choices.

Furthermore, they are not always self-fertile, which means you need more than one variety for cross-pollination to take place (and the insects buzzing around to pollinate them at the right time).

Now, the soil. Blueberries require acid soil, with a pH level of 4.5 to 5.6, so if you don’t have that information, have the soil tested. Coffee grounds are acidic, and that’s why the addition of coffee grounds may have been suggested. The fact that the calla lilies are doing well suggests that the pH might be part of the problem; they grow better in soil that is more alkaline. Blueberries also require soil that is well-drained, so make sure they’re planted in a place that doesn’t stay wet.

They need full sun, and they don’t like to compete with grass and weeds, so mulch around them with shredded bark or compost to keep weeds under control. They also suffer during times of drought because of their shallow roots, so make sure they get sufficient water (about once a week in dry weather, suggests garden expert Felder Rushing in his book, Guide to Tennessee Vegetable Gardening).

Blueberry bushes benefit from the same type of fertilizer as azaleas (which also need acid soil to grow well). Apply fertilizer, following label directions, in the spring.

Your friend who has lush bushes and lots of fruit may not be doing anything special, but it sounds like her plants are the right type for the area, in soil they like, and are getting plenty of sun and enough water. With a little more care and attention, yours may also re-gain their health.

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.

Boxwood pruning, and May fairs, sales & tours

If boxwoods need trimming, try to get the job done in late winter or early spring, before new growth begins.

QUESTION: Our boxwoods have a few limbs at the bottom that have lost their leaves and appear dead. Is it safe to trim boxwoods at this time of year?

If the limbs are dead, cut them off. No matter what time of year it is, dead limbs serve no useful purpose. If the rest of the shrub seems healthy, those lower limbs may have died because they haven’t received enough sun, or from mower damage. “But boxwoods are pretty good about repairing themselves,” says Randall Lantz, a horticulturist who has a lot of experience with these popular landscape shrubs.

The ideal time to trim boxwood is late winter or early spring, before new growth begins. It’s not a good idea to trim late in the summer. New growth that may follow the trim will not have a chance to harden before winter, and tender new leaves could be killed. Pruning out dead limbs now shouldn’t be a problem, thought. “They’re very forgiving shrubs,” Lantz says.

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Garden events

Take a break from digging to enjoy these garden-related events this month:

May 12

* First Unitarian Universalist Churchof Nashville’s Herb & Craft Fair. Shop for herb seedlings, heirloom tomatoes, native wildflowers, handmade aprons, sachets, soaps and totes, pressed flower cards, homemade breads, spice mixes, vinegars and more. 9 a.m. – 3 p.m.1808 Woodmont Blvd. www.firstuunashville.org.

* Robertson County Master Gardeners plant sale. Locally grown perennials, herbs, annuals, shrubs and small trees, 8:30 a.m. – 2:30 p.m.at the UT Extension Office pavilion on the square inSpringfield.

* The Middle Tennessee Hosta Society sale. More than 200 varieties of hostas for sale at the parking lot of Maryland Farms YMCA in Brentwood, 8:30 a.m. – 2 p.m.For a list of plants, visit www.mths-hosta.com.

May 19

* Gardening A to Z, a gardening workshop presented by the Davidson County Master Gardeners. The day includes four gardening lectures (including Jeff Poppen, the Barefoot Gardener), question-and-answer booth, plant sale, and Jr. Master Gardener White Elephant Sale, 9 a.m. – 2 p.m.at the DCMG Demonstration Garden at Ellington Agricultural Center. Admission is free; lectures are $2 each or all four for $5. Information: http://dcmggardeningatoz.weebly.com.

*The Mid-South Chapter of the Lupus Foundation’s Down the Garden Path garden tour and plant sale May 19 and 20. Visit nine gardens in Belle Meade, Green Hills and Franklin. 10 a.m. – 5 p.m.Saturday, noon– 6 p.m.Sunday. Tickets are $20 prior to the event, $25 on tour days, and proceeds benefit the Lupus Foundation of America, Mid-South chapter. www.lupusmidsouth.org.

Looking ahead

Plan a road trip on June 9 to Rugby, Tenn., for an all-day event at Historic Rugby Cumberland   Plateau Gardens. The day begins at 9 a.m. (Eastern Daylight Time) with “Rugby Landscape Gardening From 1880 to 2012” by Rick Murphy, followed by “Garden Design Sun to Shade” a workshop by Bob Washburn of Wolf River Valley Growers. Lunch, garden tours and a British Cream Tea round out the schedule. The cost is $40, and advance reservations are required. Proceeds benefit Historic Rugby. Information, 888-214-3400.

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It was a roller-coaster spring, weather-wise. But now it’s suddenly summer, and time for serious gardening. Check out the May Landscape & Garden Calendar in today’s Tennessean and at Tennessean.com here and here.

Best time to tame a rose

Question: When is the best time to prune roses? I have a bush that needs trimming, but don’t want to damage it by pruning at the wrong time.

If the rose is out of control, it won’t hurt to get out the clippers now. This advice comes from Annie Owen, a Master Rosarian and member of the Nashville Rose Society: “If the bush is overgrown, this is an okay time to prune it back, as long as it gets plenty of water.” In fact, if you reduce the size of the bush, you reduce its need for water, she said.

This goes for most types of roses, even those with finicky personalities and special fertilizing and spraying needs, as long as they’re healthy. If it’s a Knockout rose, no worries at all. “If it’s a Knockout, you can’t kill those things,” Owen said.

The Nashville Rose Society offers these pruning guidelines: Use sharp bypass pruning shears, which will make a clean cut without crushing the stem. Start by taking out older wood, along with any dead or dying canes. Remove any canes that rub or cross each other, or any twiggy, unnecessary growth. Make each pruning cut about ¼-inch above an outward-facing bud eye, where the leaf is attached to the stem.

Rose enthusiasts who winterize their prized roses will do more severe pruning in the fall. To begin the winterizing process, stop fertilizing roses now to allow the plant to slow down production of new growth. Early in October, stop cutting the dead flowers and leave the rose hips in place. In late November or early in December, cut the canes back to 2 to 3 feet, and place a mound of mulch around
the bush. This will hold them until spring, when you should prune lightly again to get new growth.

For general good advice on pruning and anything else that has to do with roses, visit the Nashville Rose Society’s Web site, www.nashvillerosesociety.com.

Meeting: The Nashville African Violet Club meets at 1:45  p.m. at the Green Hill Women’s Center, 10905  Lebanon Road in Mt.  Juliet. To learn more about this organization or specifics on this meeting, contact Julie at Julie.mavity@gmail.com or call 615-364-8459.

Calendar: It’s August, and time to start thinking about fall – specifically, about what to plant in a fall garden. Find suggestions in the August Landscape & Garden Calendar in today’s Tennessean and at Tennessean.com.

It’s too hot to garden, but all is not lost over at Turning Toward the Sun.

Stem cuttings: A good way to share your garden

I have a hibiscus plant growing in my yard. I don’t remember planting it, but one neighbor is fascinated by the blooms and has asked me to give her a cutting from the plant. What’s the best way to do that? – A.J.

Rose of Sharon (Hibiscus syriacus) photo by David Wagner.

There are many types of hibiscus, ranging from the tropical Hibiscus rosa-sinensis, which can grow  to the size of a small tree but must be kept indoors in winter in this zone, to H. syriacus, the old-fashioned rose of Sharon or shrub althaea, which is unfussy about soil and weather and is easy  to grow, and often pops up unexpectedly from dropped seeds.

It looks like any of them can be propagated from stem cuttings, so here are general guidelines for taking cuttings of woody ornamentals (such as hibiscus) and growing them into new plants:

Cut lengths of softwood (soft, succulent new growth) or semi-hardwood (partially mature wood of the current season’s growth) about six inches long from a healthy host plant. Remove the bottom leaves, and dip the cut ends in rooting hormone powder. Stick the cut ends about one-third their length into a rooting medium that drains well, such as perlite or vermiculite. Cover the cuttings with some sort of plastic covering to maintain a humid environment, and place them in indirect light.

Keep the rooting medium moist until roots develop. It will likely take several weeks, but you’ll know the cuttings have grown roots when you tug gently on the cuttings and feel resistance. Transplant them into containers to allow them to grow to a larger size before you plant them in the garden.

 Aloe: Easy on the water

QUESTION: I have an aloe plant that seems to be dying, even though I water it once a week. Does it need to be watered more often?

No. Absolutely not. In fact, if you are watering your aloe plant every week, you are watering it too much. While the soil shouldn’t stay bone dry for many weeks at a time, it’s enough to water an aloe plant every two or three weeks in summer, and even less in winter.

Aloe barbadensis (or A. vera) is a succulent, easy to grow and readily available, and it’s true what they say about the ability of the sap to relieve minor burns. Split open a leaf and place it on the burn to alleviate the pain.

Besides a little water every now and then, here’s what else aloe needs to stay healthy: loose soil (add a little sand to potting soil for better drainage), bright light in a sunny window, especially in winter. In
summer, aloe can stay outdoors, but be sure to bring it in before temperatures fall. It appreciates a light dose of balanced houseplant fertilizer every month or so in spring and summer, but don’t fertilize at all in winter.

An update on something awesome: Click over to Turning Toward the Sun to see pictures of the abundant raised beds at a school’s new outdoor classroom.

All leaves, no flowers

QUESTION: I have five plants that I’ve been told are ‘Mini Penny’ hydrangeas. Last year they had lots of white blooms. This year they are growing very well with lots of green leaves etc, but only very few (3) blooms. I have fertilized with an acid balanced Miracle Grow fertilizer as well as a root stimulator. Can you suggest any reason for the lack of blooms this year? – George Carr

First, let’s consider the hydrangea variety that goes by the name ‘Mini Penny.’ A Web search shows that it’s one of the French hydrangeas, a compact, slow-growing mophead variety that blooms pink if the soil is alkaline, or powder blue in acid soil. You say yours had white blooms, so perhaps it’s something else.

Still, we can talk in general about why hydrangeas don’t bloom. The hydrangea expert Judith King, who runs the Web site hydrangeashydrangeas.com (I referred to this site a couple of weeks ago, writing about ‘Annabelle’ hydrangeas), says there are three common reasons why mopheads fail to bloom. 1) If a late spring freeze kills the developing buds, which grow on last year’s stems; 2) If you pruned the shrub too late last year, cutting off the stems that held this year’s buds; 3) If you have a variety that is not suited for this area.

This year, a late spring freeze is probably not the problem. It was cool in late spring, but we didn’t get a freeze, and I’ve seen some gorgeous hydrangeas blooming in gardens around town.

Did you prune? Buds for the following year start forming on French hydrangeas in the summer, so if you pruned the shrub in late summer or fall, you may have cut off all but a few (3) buds.

The third reason – the plant is not suited for the area – can’t be considered until you know what variety you have.

One more note about fertilizer: King advises using a balanced product such as10-10-10, applying it once or twice during the summer. Use caution and follow the package directions, because too much fertilizer can damage the shrubs. It’s also best to fertilize before August, she says, so that any new growth has a chance to harden before winter. Remember, too, that too much nitrogen can cause a plant to grow lots of greenery, but does little to aid in flowering.

Today’s garden event: The Middle Tennessee Iris Society’s iris rhizome sale is going on today from8 a.m. – 3:30 p.m. at the Ed Jones Auditorium atEllingtonAgriculturalCenter. They have a large selection of varieties and colors, priced from $1 to $6. Admission to the sale is free.