Success with lavender

02/19/2008
Success with lavender

The lavender was always bluer on the other side of the fence--or the world, as the case may be.  At least that's the way it seemed to me when I was gardening back in Indiana.  Now that I live (part of the time) in the region of the world where lavender grows wild, I can only look back on that period with a mixture of rue (at the countless hours I spent getting lavender through midwestern winters for myself and my landscape clients) and amazement (on where I find myself now).

I'm not sure if it's lavender's color, its elegant, ever-gray-green foliage, or its fragrance--clean, floral, spicy--that seduces us most.  Maybe it's that lavender wraps it all into one plant--a plant that is a handsome companion to just about anything and which seems to clash with nothing.  Dreaming up beautiful planting combinations is a no-brainer.  But growing the plant successfully in a cold, humid continental climate is anything but.



Just as with people, to get along with lavender you have to understand where it is coming from.  That is, you have to understand the elements of its native habitat in the Mediterranean basin.  True lavender (Lavandula angustifolia), which is the species most of us try to grow, is native to the rocky hills of Provence and other parts of France above 600 meters (about 1800 feet) in altitude.  Lavender grows like a weed, in fact, in the very driest parts of France.  But, note, not in the hottest parts.  In fact, if grown under the correct conditions, true lavender is hardy to -5 F with little or no dieback.  It can go colder and still come back from the roots.

Okay, so just what are those "correct" conditions?  Well, there are three:  drainage, drainage, and drainage.  Look at the spaces between the rows in any lavender field, and what do you see?  Rocks!  Nothing but calcareous rocks.  Lavender grows without irrigation in full blistering sun  where there is often little or no rain from mid-June until September or later.  And where even winter rains drain away instantly.

Now, think about the soil environment and the rainfall patterns in most of the U.S., and you begin to understand why lavender often struggles.  In much of the U.S., it rains year-round, often copiously.  Our soils are often as not heavy, poorly drained clay.  And to make matters worse, we pile wood mulch around our plants (keeping them even wetter) and often have overhead irrigation systems pelting them with water on a daily basis.

Growing lavender successfully requires mimicking its native environment as much as possible.  First and foremost, locate your lavender in full sun, thoroughly out of reach of overhead irrigation.  Give it room to breathe; other plants crowding in on lavender will quickly kill it. 

Next, make sure the drainage in your bed is perfect.  Don't choose a low spot!  Amend the soil with plenty of river sand and some compost to a depth of 2 feet.  If drainage is really abysmal, you may even want to install a perforated drain beneath the bed.


When planting your lavender, make sure the plant's roots are thoroughly moist in the container before planting.  (That's right.  Just because it likes good drainage doesn't mean it wants to be dehydrated.)  Scarify the surface of the rootball to stimulate growth outward into the soil.  Should the roots be growing around the pot in a tight circle (what the French call a chignon), literally comb them out with your fingers and spread them evenly in the planting hole.  Fill in with the sandy-humusy mix your soil should now be, leaving about an inch of space around the crown of the plant, and water in thoroughly.

Now, the most important part.  Fill in the rest of the way around your plants with river sand or gravel, so that the crown is in this highly porous mixture,and not down in the soil itself.  Why?  Because the crown is the part of the lavender plant that is most sensitive to rotting under humid conditions.  Keeping it surrounded by sand or gravel ensures that water will always drain away from the crown quickly.

Were you ready to reach for your bark mulch pile?  STOP!  No bark or other organic mulch allowed!  If you feel it necessary to protect your plants from extreme cold, use some dry oak leaves, if necessary pinned down with floating row cover or netting.  Remember to thoroughly remove this material the following spring.

Lavender is actually a tiny shrub, or subshrub in the coldest zones.  So what about pruning it?  Most of us have found out the hard way that most of the pruning we do on lavender is cutting back the parts that winterkilled.  But now that you're growing this dryland plant correctly, you're going to have less of that.  Nevertheless, in spring, watch for new,bright green growth poking out of the blackish stems.  Cut back to just above the uppermost of that new growth. 

Right after the flowers fade is the second time to prune lavender.  Cut back the flowering stems just above the vegetative (leafy) part of the plant.  If you do this promptly, then water circumspectly (by hand), you may get a second bloom on your plants in late summer or early fall.




Up to know I've been talking about "lavender" as if all lavenders were created equal.  Of course they're not.  When discussing lavender species and varieties, however, it's best to avoid common names.  Here's why.  "English lavender" (L. angustifolia) is not from England (too humid!) at all but from southern France.  "French lavender" (L. dentata) is native to Spain and Portugal.  And in France, this species is called English lavender!  Spike lavender (L. latifolia) is also native to Provence, but in zones below 600 meters. 

Numerous named hybrids exist, as well, especially between L. angustifolia and L. latifolia.  In France, these are collectively known as "lavandin".  As a group, they are characterized by longer stems and better resistance to humidity than L. angustifolia.  Lavandin cultivars ('Provence,' 'Grosso,' for example) are good choices if you live where summers are hot and humid in Zones 7 and southward.  However, lavandins are notably less cold-hardy than L. angustifolia.  Other species--such as L. stoechas, right--abound, but most of them are much more tender and best handled as container plants.







Many cultivars of L. angustifolia are available, including lavender, deep blue, gray, white, and even pink-flowered strains.  Curiously, while the French know and use all the "anglo" cultivars such as 'Hidcote Blue' etc., the anglophone gardening world continues to largely ignore the many French cultivars.  I come close to calling this lavender chauvinism, were it not for the fact that lavender really is a French plant.

If you do your groundwork, you really can grow lavender successfully from Zone 5 southward.  Just remember:  In the North, grow L. angustifolia, in the humid south, try lavandins, and everywhere this mantra:  perfect drainage, no mulch, no overhead irrigation.  Voilà tout!