Creating a Drought Tolerant garden
much more than simply choosing drought tolerant plants. Our
well-intentioned habit of watering the garden too often should be corrected to create a healthier
garden that simply doesn't need our watering help to thrive.
Here's an article I wrote a few years ago that will help you
work towards a healthier and more Drought Tolerant Garden.
THIS SUMMER WE'LL BE READY
by Evelyn Wolf, 2002
Sneaking out at midnight with a watering can to your perennial beds during a water ban is not the time or way to
protect your garden from drought. Spring and early summer is when to prepare your plants for the inevitable heat and drought of high summer by training them to send their roots deep
through smart watering habits. Early in their life, all plants benefit
from being taught an important life lesson - they must stretch their muscles and work for their meal. In these days of a heightened consciousness about water conservation, there can be no more express room service
delivering water at the first sign of a dry warm summer!
In our hurried lives, we often take a bit of time every few days and give the garden a quick sprinkle with the idea that plants, like children, need our constant nurturing. But plants past their first few months are not children - they are fully mature adults that know how to look after themselves. This constant moisture at the soil surface is actually harmful since it promotes mildew and fungus diseases like black spot and powdery mildew, and worse - it promotes an unnaturally shallow root system which makes them vulnerable to drought.
Plants aren't stupid - they know that water is essential to life, and they will work hard to find it. All plants naturally reach for wherever the water is, which should be downwards. When we water frequently and shallowly, roots don't have to reach at all and instead stay within the top 6 inches of the soil rather than establishing a deep root system. Quite simply, we promote a false sense of security and make them lazy with our pampering. Under these conditions, it would take just one rainless weekend away from your garden for these plants to show signs of drought stress. It is far better to not water at all, and make your plants stretch down for their water. They will be much stronger having developed a larger root system and fully able to glide through the long hot days of July and
August unscathed. Their roots will be down a good 12 - 18" or
more where it is usually still cool and moist.
When drought is severe, such as we experienced last year, some plants may be stressed to the point of withholding bloom or may even enter early dormancy as they try to cope with the lack of water. However, as with all forms of life, the instinct for survival is strong and long term survival skills are built into the genes. Rather than expend energy on blooming and risk death in a drought, perennial plants will hunker down and conserve energy by not blooming or growing. They may even drop or fold up their leaves, with the goal of simply surviving until they can go dormant for the winter and come back in spring when conditions are better. If they have been trained to have a strong, deep root system, they will come back with flying colours. If they have shallow root systems because of
frequent shallow watering, some may not make it through the winter having been stressed too severely in the drought. (If you had roses and shrubs that died over the past winter, they didn't die because of the harsh winter alone, they probably died because they entered a tough winter with a drought weakened root system.)
Here's some general guidelines for watering your perennial beds -
ever water until at least the top 3" of soil is fully dry.
2) If you feel watering is needed
but only have time for a quicky, don't water at all.
Instead, spend those
few minutes you have giving any
new plants a good
3) When you do water your garden, a slow steady trickle right at the soil level is best. Overhead sprinklers waste a tremendous amount of water through evaporation (up to 1/3) before it ever has a chance to get to the roots, and the constant moisture on the leaves promotes disease
and rot problems. Soaker hoses are a great choice if installed properly just at or under the soil surface so they don't spray up. I used to devote an afternoon to moving around a
little fountain type sprinkler at a very low pressure setting to really soak any area
that needed it for about an hour. Visualize the root zone of your plants, not
just the soil surface. Your goal is to have moist soil at the bottom of the root system and beyond to encourage roots
downward - that means about 12" - 18" down. If your watering efforts only went 4-5" deep, then that's where the plant's roots will stay
and you've actually done more harm than good.
4) If you have conditions such as a slope or hard clay which tries your patience, try
taking a plastic jug with the bottom cut out and burying it upside down beside your moisture lovers to deliver water directly to the root area. Most of your plants will still need to fend for themselves, but at least you can cater to those
few that need your help.
Irrigation systems may be great for lawns but they can mean death for a
perennial garden. They are often on timers set to run every couple of days
for 20 minutes or so. The shallow roots of lawn grass are grateful, but
after a few years your perennial gardens develop a surface mass of roots that is
completely vulnerable to the constant stress of temperature fluctuations and
this constant stress leaves them generally weak. The problem multiplies
upon itself once this happens since the thick mass of fine roots that ends up
blanketing the whole soil surface actually starts to hold water like a sponge,
preventing water from percolating down. Your perennials have, ironically,
adapted to desert-like conditions where there is never water held deep in the
soil and plants develop their roots in a wide reaching surface skirt to catch
and use every single drop of rain that falls before it evaporates.
If you have an irrigation system, aim the heads at the lawn only and use soaker
hoses (or nothing at all) in your perennial beds.
Perennials in their first year need some watering help, but an established perennial garden is actually
better off left to what comes naturally from the sky. If soil is prepared well with plenty of organic matter in the form of compost, chopped leaves, or peat moss, roots will have the food to grow strong, and have an easy run to grow downwards where they're safe. Mulching or
using ground cover plants also helps conserve moisture, but be careful not to
pile mulch on or near the crown. If a serious drought does come, unpampered plants with their roots trained deep, will
be fully able to cope. They'll do the smart thing by plunging even deeper for water. While we gripe and complain about the heat, they'll be just fine.
A few leaves may get a bit tip burned, but that's about all the damage I've ever
experienced even after weeks with no rain.
In my last home, I established a garden bed in an area dominated by mature cedars that sucked the ground dry in a blink. I was determined though, and with persistence, I grew hostas, bleeding heart, etc. with moderate success. The first year I made sure to water deeply once a week, which in this bed meant that it was already very dry. In the second year, I watered deeply only when 2 weeks had gone by with no rain. In the third year, I watered only during the really dry times in August. Astilbes and some of the hostas just couldn't thrive in this bed, but many other perennials did.
When I moved and dug up some of these plants to take with me, I had to go down 18" - 20" before I gave up and simply cut the roots. They had reached down much more than they naturally would have in their quest for water. This was a real lesson for me
that gave me the confidence to start trusting that perennial plants know how to fend for themselves
and survive. It was a real "Daahh" moment when I truly realized that
plants are dynamic living things just like us, and that like all healthy living
things they will struggle with all their power to adapt and survive - to go
to where the food and water is if it isn't near at hand. Now, only real moisture lovers like my Ligularia or the many new plants
I put in each year get any watering attention from me at all. Dryland lovers like Flax,
Yucca, Artemesia, Lavender and others now grow tight and strong rather than weak and floppy as would happen in a wet garden,
and come back reliably each year rather than succumb to crown rot. As I
visit other gardens through my consultation work, it's been my observation that
MANY more plants die from crown rot through overwatering than die because of
Perennials are generally as tough as nails, as long as there is at least an attempt to meet their sun/soil preferences. When basic needs are met, they quickly adapt to their surroundings and begin the struggle for survival. They will adapt to dry hot conditions by sending roots deep. They will adapt to crowding above ground by stretching their stems and leaves as tall and straight as they can to reach for their fair share of sunlight. They will adapt to nutritionally lean soil conditions by growing tight and compact instead of lush and large to conserve precious food energy for blooming. Bottom line, they know how to survive - sometimes in spite of the gardener rather than because of them!
My plants are better than ever for this lesson learned, but I have to confess that I feel a bit rejected now that I realize that they really don't need me at all once I've gotten them past their first few months. (Perhaps this is why I'm always compelled to buy new plants!). I miss that lazy hour at the end of the day when watering would give me an excuse to linger in the garden. To accommodate this little pleasure and sooth my bruised ego, I keep a small patch of moisture lovers in a naturally dry spot just so that I can still feel needed. It works!