When Bad Things happen to Good Plants

Another lavender suffers an August fungal fate

Let’s say you’re a gardener. And let’s say you built some new garden beds last fall, and you added a bunch of juicy compost to the soil. You shoveled that compost into your native soil, watered it, then planted a very smart mix of dry loving shrubs and perennials. All winter you kept a tight eye on things, making sure the new plants never went without. Spring arrived, and you threw out some mild organic fertilizer just to give everything a leg up for the growing season ahead. Your lavender exploded. Your blackfoot daisies set records. Your Texas sage, well, let’s just say it was embarrassingly beautiful, which is probably why Bob across the street was giving you the stinkeye from behind his sad, sad nandina hedge. April rocked. May was amazing. June was fine. July, uh…July was not great, but that’s life in Texas, and nothing died, so victory.
Now it’s August, and things have changed. It’s stupid hot. And dry. The armadillo has found your priceless stockpile of earthworms, and has proceeded to blindly, thoughtlessly vandalize everything. The only flowers you see are from the wild morning glory vines that have taken over your texas sage and the giant weedy daisy looking things you’ve been meaning to pull. Things are bad, and you’re beginning to consider not only a new hobby, but a new region of the country in which to practice it. But alas, out of the heavens a dark cloud blows in, and for the next day and a half your parched paradise gets soaked in sweet, sweet summer rain, pregnant with nitrogen and magical microbes, and your heart sings. Before the last drop of rain hits the roof, you’re sprinting out to the garden to give it a great big horticultural hug. After a few days of crawling around in a post-rain steam cloud, pulling weeds and deadheading spent blooms, your celebration is interrupted by the discovery of a dead lavender plant. Whole thing, dead. Yesterday it was fine. You scan the bed, and see a few more dead lavenders. A half dead blackfoot daisy withers in the shade of a wilting Texas sage. Over the next couple of weeks, half of everything you planted in your dry bed last fall wilts, then dies. You water, but it doesn’t seem to help.
August and September are crucial and difficult months in the Austin garden for many reasons, mostly because it’s all kinds of hot. But the answer is often more involved than that, especially regarding drought tolerant xeric perennials and desert shrubs. The hard truth is, Austin suffers from a sort of multiple personality disorder when it comes to climate. Temperature and moisture can shift dramatically and quickly, taking a semi-arid August dunescape straight into equatorial jungle terrarium literally overnight. Heat plus moisture plus nutrient rich, organic soil is like kryptonite to many of our toughest desert plants. Many harmful soil fungi are at their best under these conditions, and waste no time turning vulnerable plant roots into a fungal buffet. Plants like lavender, culinary sage, silver germander, and blackfoot daisies, that have spent thousands of years living and evolving in dry climates, have traded their fungus fighting skills for other adaptations like waxy or succulent leaves, and other physiological and chemical mechanisms to combat heat and drought. This means they’re sitting ducks when opportunistic soil fungi that normally occur in wet, tropical or subtropical climates are enjoying their day in the sun.
We can’t control when rain happens, and there’s nothing better than an August storm in Central Texas. But if you want to keep your dry plants happy and floriferous through summer, there are a few preventative measures you can take.
1. Location, location, location. Pick a site for your xeric plants that is sunny and breezy. Sloped areas are better than flat, as they allow moisture to drain from the soil faster.
2. Poor soil is best for xeric plants. Don’t baby your blackfoot daisies with rich, composted soil. Good old fashioned sandy loam with little to no amendments and no mulch will give harmful fungi no safe harbor. Once plants are established, keep soil on the dry side and nutrient poor, and your plants will live for many years.
3. Be patient. If you follow steps 1 and 2, you will likely notice your plants growing slowly, and in the summer not growing much at all. This is what is supposed to happen. Be the tortoise, not the hare, and win the race. Patience is both free and priceless in the garden.