Happy Hydrangeas, Part 2: Blue or Pink?

One of the most curious things about Bigleaf Hydrangeas (Hydrangea macrophylla) is their chameleon-like ability to change color.  That striking pink-flowered hydrangea you just planted from your local garden center may have blue flowers by the time next year rolls around.  Likewise, that stunning blue-flowered hydrangea you just transplanted from your mother’s house may have pink flowers next growing season.  But how can this be?!  What makes a hydrangea change color, and how can you be sure that it will stay a certain color?

Photo: Bigleaf Hydrangeas (H. macrophylla) come in a rainbow of pinks and blues

The answer to this perplexing plant phenomenon has to do with aluminum in the soil.  Aluminum is the most abundant metal in the Earth’s crust, but it is toxic to almost all plants.  There are very few plants that can actually accumulate aluminum internally without any ill effects.  One of these rare aluminum-tolerant plants is Bigleaf Hydrangea.  Hydrangea uses organic acids to detoxify aluminum, forming aluminum-citrate.  While inside the plant, aluminum also reacts with the plant pigment anthocyanin, producing a blue hue in the flowers.  As the concentration of aluminum in a hydrangea increases, the intensity of the blue color also increases. 

Thankfully for all the non-aluminum-tolerant plants, this metal cannot typically be absorbed by plant roots in its normal form.  Only when the soil is very acidic and the pH drops below 5.5, does aluminum change and become the soluble ion Al3+ which can be absorbed by plant roots.  So even if aluminum is present in the soil (which it almost always is), it may not be available to your hydrangea because the soil is not acidic enough. 

If you want to change the color of a Hydrangea that is planted outside, focus on adjusting the soil pH.  Always take a soil pH test before doing anything.  Based upon the results of your pH test, you can add elemental sulfur to the soil which will slowly lower the pH over time, eventually resulting in bluer hydrangeas.  Or you can add lime to the soil which will more quickly increase the pH, resulting in pinker hydrangeas.  Still, changes in soil pH typically take several months, so patience is key.  Also, be aware that soils near concrete walkways and house foundations as well as turf areas that have been heavily limed will be more alkaline, and work better for growing pink hydrangeas.   

Photo: Pink flowered hydrangeas show their colors in more alkaline or basic soils - those with a higher soil pH

On the other hand, if you are growing a hydrangea in a container and have used potting mix rather than mineral soil, there is a good chance that aluminum is missing.  If you’re looking to grow a potted hydrangea with bright blue flowers, you might need to add some aluminum sulfate.  This specialty soil amendment supplies aluminum while lowering the pH.   The tricky part though, is knowing how much aluminum sulfate to apply.  At too high aluminum concentrations, even aluminum-tolerant Hydrangea can be dwarfed and killed.  Even the great plant-God, Michael Dirr has admitted to killing Hydrangeas with too much aluminum sulfate.  For potting mix that has no soil in it (and therefore no existing aluminum), Dirr recommends that 0.75 – 1.5 ounces (21 – 42 grams) of aluminum sulfate be applied to the surface of a 3 gallon container.  Multiple applications at this rate may be needed if the pH remains higher than 5.6.  Make sure to read all label directions carefully and follow application rates carefully!  Some hydrangea growers will apply aluminum sulfate at the end of the season in August or September, and then again during the forcing stage the following spring.  It is important to water thoroughly after application to ensure movement into the root zone and to not apply when the potting mix is dry. 

Photo: Before adding any soil amendments, be sure to always take a soil test.

Lastly, the type of fertilizer you use can also affect hydrangea flower color.  Nitrate nitrogen fertilizers increase the pH, and ammonium nitrogen fertilizers lower the pH.  High levels of phosphorus can decrease the uptake of aluminum, while high levels of potassium can increase the uptake of aluminum.

In summary, if you want blue or pink Hydrangeas:

·         Blue:  high Al, pH 5.0 – 5.5, very low P, high K, and moderate ammonium N

·         Pink:  low Al, pH 6.0 – 6.5, high P, low K, and high nitrate N

Hopefully that clears up some of the mystery behind Hydrangea coloring, a topic that is almost as confusing as Hydrangea pruning!  If you’d like to learn more about hydrangeas, a great resource is Hydrangeas for American Gardens by Michael Dirr from 2004, published by Timber Press.

Happy Hydrangeas, Part 1: Pruning

Warm weather is finally here and the excitement and relaxation of summer is just around the corner.  One of the simple pleasures I look forward to every summer is the blooming of my mophead hydrangeas.  I have two ‘Nikko Blue’s stuffed and crammed into my very small, overcrowded, front garden.  Their thick stems and toothed leaves are already claiming the walkway, and I have to be careful not to knock them as I make the short walk from door to driveway.  But they are totally worthy of such prized garden space.  Already, I can see the tiny green flower buds forming in the leaf axils, which in the coming six weeks will yield heaping mounds of sky blue flowers. 

Photo: Bigleaf Hydrangea with Day Lilies in my summer garden, Commack

If you’re a hydrangea aficionado (like so many gardeners are these days), I’m sure you also feel excitement when you see their tiny green flower buds forming.  Or, frustration when you don’t.  If you have a mass of hydrangea leaves and no flowers, you might be wondering, what the heck did I do wrong THIS time?!  Most likely, the answer is that they were pruned incorrectly (or that the cold killed the tops of them.)

Let me start by saying that hydrangeas are tricky in both pruning and cultural requirements.  There have been a handful of times when landscape professionals have called me up asking what the heck they did wrong THIS time to Mrs. Smith’s hydrangeas.  The trickiness of pruning hydrangeas begins with the fact that there are so many different types of hydrangeas.  You need to know which is which, sometimes down to the cultivar level, in order to prune them correctly… 

The four main species of shrub hydrangeas are Smooth Hydrangea (Hydrangea arborescens), Panicle Hydrangea (H. paniculata), Oakleaf Hydrangea (H. quercifolia), and Bigleaf Hydrangea (H. macrophylla).  Smooth Hydrangea is actually native to New York, and grows along forested streambanks in its natural habitat.  Common cultivars include ‘Annabelle’ and Incrediball™.   

Photo: White Dome® Smooth Hydrangea - H. arbroescens, Ithaca 

Panicle Hydrangea can be seen on many old homesteads, flowering in late summer.  The white flowers fade to a dull mauve as the season wanes.  Common cultivars include the old standby PeeGee (‘Grandiflora’), and the newer, quite popular Limelight® and ‘Tardiva.’  Oakleaf Hydrangea, in addition to their big, bright white flower panicles, has oak leaf-shaped leaves which turn a lovely burgundy in the fall.  Cultivars include ‘Alice’ and Snow Queen ™. 

Photo: Oakleaf Hydrangea - H. quercifolia, Old Westbury Gardens

Bigleaf Hydrangea is by far the most popular hydrangea today.  The innumerable cultivars of H. macrophylla are divided into two groups – mopheads and lacecaps.  Bigleaf Hydrangea does admirably on Long Island.  It is fairly salt-tolerant and can be planted in sandy, acidic soil.  It does needs plenty of water though, and some cultivars are not quite cold-hardy during severe winters.

While removing dead flowerheads and dead branches can be done anytime of the year to any species of hydrangea, removal of live branches should be done only at certain times if you want your hydrangea to flower.  Both Smooth Hydrangea and Panicle Hydrangea bloom on the current season’s growth.  This means that the optimal time to prune live branches without impacting flower production is late winter/ early spring before new growth starts.  On the other hand, both Oakleaf Hydrangea and Bigleaf Hydrangea bloom on last season’s wood, which means that flower buds have already been formed in the fall to flower the following spring.  Because of this, pruning in late winter/ early spring (the optimal pruning time for many plants) would remove those existing flower buds.  New ones would not be formed.  Therefore, for Oakleaf and Bigleaf Hydrangeas, pruning live branches should only be done after flowering in August or by mid-September at the very latest.

Now that I’ve made that perfectly clear, let me backtrack and say that there’s one exception.  (There’s always an exception in horticulture!)  There are a few cultivars of Bigleaf Hydrangea which flower on both old and new wood.  This means that if you accidentally prune off the flower buds in late winter/ early spring, no big deal - new ones will form on the new growth.  These reblooming hydrangeas are “remontant,” meaning that they flower on both old and new wood.  Most outstanding is the Endless Summer® Collection by Bailey Nurseries, Inc. of St. Paul, Minnesota. 

Photo: Endless Summer® Mophead Hydrangea - H. macrophylla, Hicks Nurseries

World-renowned plantsman, horticulture ‘God,’ and living plant legand, Michael Dirr, helped discover the original Endless Summer® plant, and led tests of it in his University of Georgia lab, which confirmed its remarkable reblooming ability.  In 2004, Endless Summer®, the first tested, truly reliable remontant Bigleaf Hydrangea, exploded on the market.  Now seven years later, a couple other reblooming hydrangeas have popped up, and the hydrangea-craze seems to be at an all-time high.  These reblooming hydrangeas have simplified the pruning requirements for Bigleaf Hydrangeas.  Now, if only we could all figure out how to keep our hydrangeas blue!  To be continued!

Bamboozled

“I’ve been living this nightmare for sixteen years now!  I’m losing all my land.  I’ve already hired a lawyer and they better be prepared because I’m coming in My Cousin Vinny style!,”  the woman on the phone begged me to help her.  After patiently listening to her rant for over fifteen minutes, I curtly said, “I’ll see what I can do,” and hung up the phone.   No, this woman wasn’t hysterical because she had been accused of murder in rural Alabama.  No, the government wasn’t taking away all her land.  And no, hoards of locusts did not descend upon her yard.  Instead, this woman was hysterical because of a … plant.  Yes, a seemingly innocuous plant had made her loath her neighbors, spend thousands in lawyer fees, initiate a national campaign, join a support group, and call another state’s Extension Agent to plead for assistance.  All because of a plant.  No joke.

The only plant that could make someone act this fanatical is a plant called running bamboo.  In this woman’s trial, bamboo was the culprit, and she wanted the plant (and her neighbors who had planted it) to pay for their crimes against her and the rest of society.  I don’t know how the trial is going, since she hasn’t called back (yet), but the campaign against running bamboo wages on across the country.

Photo: Running Bamboo spreading along the Peconic River, Calverton

A type of grass, running bamboos in the genus Phyllostachys are highly invasive when planted in the garden.  Originally from Asia, running bamboos were brought into the United States in the 1800s as ornamentals.  You have to admit, they do make an eye-catching, living screen, (dense enough to block out those fanatical neighbors), and look stunning in Japanese-inspired gardens.  They grow amazingly fast with no fertilizer, aren’t picky about water, are evergreen, and have no major pest issues.  In warmer climates, certain species of running bamboo grow so thick that their canes are used for “eco-friendly” flooring and wood products.  There are even national plant societies like the American Bamboo Society dedicated to promoting the beauty and utility of bamboo.  Heck, even pandas love bamboo!

Photo: Yellow Groove Bamboo (Phyllostachys aureosulcata)

Photo: Golden Bamboo (Phyllostachys aurea)

But there are also a lot of reasons to hate bamboo.  Not all bamboo, just the running bamboos, most notably Golden Bamboo (Phyllostachys aurea) and Yellow Groove Bamboo (Phyllostachys aureosulcata).  Running bamboos spread by a dense system of rhizomes, or underground stems, and in no time at all, they can overtake your yard and as well as your neighbor’s yard.  Running bamboos grow rampantly and can send up new shoots 20-30 feet away.  An impenetrable stand of bamboo canes, known as culms, will prevent the growth of other plants and make maneuvering about your garden difficult.  Furthermore, running bamboos can be very destructive, having the ability to penetrate house foundations and pools.

Because of their dense system of rhizomes, removing, or even controlling, running bamboos is extremely difficult.  Cutting down all the culms will do you no good – new ones will spring up from the rhizomes almost as fast.  Instead, to control the spread of an existing running bamboo, you would need to install a commercial rhizome barrier approximately 36 inches deep into the ground.   These barriers are very costly to install and can degrade over time, making them ineffective.  If you wanted to eradicate a stand, you would need to hire a landscape professional who is certified to apply herbicides.  A combination of cutting and multiple herbicide applications will wear out the vigor of the rhizomes, eventually killing the stand.  

There are many other ornamental plants that can be installed instead of running bamboos.  If you want an evergreen screen, consider planting other evergreens like White Pine (Pinus strobus) or Western Arborvitae (Thuja plicata).  If you really do like the look of bamboo, you can plant noninvasive, clumping bamboos in the genus Fargesia.  Clumping bamboos have all the ornamental attributes of running bamboos, but do not spread aggressively.  They can reach 10-20 feet tall and are evergreen.  Clumping bamboos form a beautiful vase shape, growing moderately from the original base, 4-10 inches per year.  Unfortunately, clumping bamboos are not as available and may be more difficult to find in a garden center.  Before purchasing a bamboo, be sure to check the scientific name on the plant label.  You want the genus to read Fargesia and not Phyllostachys.  Ask the garden center staff if you need any further clarification.

Photo: Evergreens such as White Pine (Pinus strobus) make a nice privacy screen, Commack

Don’t let running bamboo turn your yard into a nightmare, or you self into a crazy woman.  Instead, choose clumping bamboos or other evergreens.  Your sanity and your neighbors will thank you.

What Does Organic Mean?

It seems like all the time these days we hear the term “organic” used to describe many different things – things as varied as milk, fertilizer, landscape maintenance, cotton t-shirts, and bamboo flooring.  Have you stopped to ask yourself, what does “organic” really mean?  Organic products and services are what we all want, but I think few of us are able to offer a definition of what it truly means for something to be organic.

Photo: Apple orchard in bloom, Riverhead.

In the original sense, “organic” meant that something contains carbon.  If you ever had to struggle through an organic chemistry class in college, you already know this.  You were taught that organic molecules are ones that have a carbon atom, and non-organic molecules are ones that don’t.  Water for instance, which is composed of only hydrogen and oxygen, does not have a carbon atom and is therefore, in chemistry terms, not organic. 

Today’s newer and more ambiguous definition of “organic” is different.  In today’s terms, organic means a food or product that has been grown or formed from things that are natural.  It has no synthetic inputs; it is not man-made; it was pre-existing on this earth, and was not manufactured in the labs of chemical engineers.  Compost and sunshine for example, are organic, while the synthetic pesticide DDT and bioengineered corn are not.

Photo: Farm in Aquebogue.

In our minds, “organic” has come to be associated with not only being all-natural, but also better, healthier, and more environmentally-friendly.  While this may be true in some instances, organic products are not necessarily better, healthier, or more environmentally-friendly.   Just because something is natural and came into existence on its own rather than synthesized by people, does not intrinsically mean that it is better or safer.  Take for instance, arsenic, a naturally-occurring element, and morphine, a compound manufactured by poppy plants.   Although arsenic and morphine are natural, both are also harmful and can be deadly if ingested in sufficient quantities.  Nicotine is also all-natural, as it is manufactured by tobacco plants.  Radioactive uranium isotopes are also all-natural, occurring in the earth’s rock, soil, and water.  Just because something is natural, doesn’t mean it’s safe.

Keeping this in mind is important when you consider pesticides.  I hesitate to even bring up pesticides as they have come to represent cancer, death, pollution, government lies, and everything else our society considers abominable.  It is amazing how many groups today believe that if we just eliminated and banned pesticides, we would rid the world of sickness and death and usher in a new utopian paradise where we would be one with all the world.  But we need pesticides, even organic farmers.  Contrary to popular belief, pesticides are allowable and are frequently used in organic agriculture.  The difference is that in organic production, only naturally-occurring pesticides are allowable (excluding a few natural ones, including nicotine thankfully).  All synthetic pesticides and synthetic fertilizers are forbidden in organic production.  If you eat an apple certified by the federal US Department of Agriculture as organic, you’ll be guaranteed that there won’t be any synthetic pesticide residue on it.  But there may be natural pesticide residue on it, so make sure to still thoroughly wash your produce.

Photo: Traditional, and organic, method of weed control employed at nursery in Jamesport.

  

Thankfully though, most organic growers are not simply substituting synthetic pesticides with natural pesticides and plowing on with business as usual (and yes, that pun was intended!).  By eliminating synthetic pesticides, the number of pest control options has been greatly reduced, and organic growers must therefore get creative and explore other solutions for combating the ever-present insect pests and disease.  By taking a step back and looking at the bigger picture, organic farmers must focus on overall plant health and how their farm is working as a whole.  Organic growers need to make sure that every part of their farm is conducive to plant growth and deters pests.  Solutions for combating pests that a successful organic grower might employ include: selecting the most pest-resistant varieties of plants, growing many different varieties of plants, building the health of the soil by incorporating compost, using cover crops, and employing crop rotation.  When a grower employs all these best management practices, only rarely will he or she need to use natural pesticides as a last resort.          

Photo: Organic growers especially must focus on maintaining the health of their soil.

Don’t choose organic foods simply because they are grown without synthetic pesticides or synthetic fertilizers.  Natural doesn’t necessarily mean safe.  Instead, my suggestion would be to choose organic foods and products because there is a greater likelihood that best management practices were employed, and that the farm was managed from a holistic viewpoint.  Until we have a national USDA best management practices certification program, we’ll have to rely on using their existing organic program as a gauge.  Just remember to wash your produce before eating, even if it’s organic.