10 October 2022 – Today I learned:
How to water the garden in a drought, thanks to the amazing Rebecca McMackin, for the last decade Director of Horticulture of Brooklyn Bridge Park and now living in Cambridge, Mass. after having been awarded the Harvard Loeb Fellowship to study ecological design and science communication. She’s just published a blog post with some really good information about watering plants.
The key things: Make sure water reaches at least 6 inches deep (check by digging a little hole and putting your finger in it to feel the moisture); and, just like it’s hard to mop up water with a totally dry sponge, dry soils can’t soak up water efficiently either, and in fact it’s worse for soils, “given that some soils have waxes that can further inhibit water infiltration. This can be dangerous, as water will bead up on and sheet off of hydrophobic soil, preventing percolation, increasing runoff, and killing even dry-adapted plants.”
To avoid that and to get the water where the plants need it (deep), here are her tips:
- Water deep and long, using drip systems, gators, and soaker hoses to prevent water from evaporating. If you have only a hose or a sprinkler, water for hours at slow trickle, and if you’re in a rush, make a little moat with mulch and fill it a few times.
I’m usually in a bit of a rush when watering the whole dry garden, as it takes about an hour to get some water to everything* when hand watering — but my watering is probably counterproductive since I’m obviously not watering for an hour in one spot like I should be. / *When I say everything, I don’t mean all the plants; I actually I water only the new and newly transplanted plants (I had about 50 this year), the annuals (seeds, vegetables, and a few flowers), and some other plants that I know tend to be thirsty. Lately I’ve been planting more natives, which I hope can handle some drought by themselves.
- Her next suggestion is the hardest one for me, a night owl. She advises to “water early in the morning, even before the sun is out. The cool earth and lack of direct sun will minimize evaporation.” Sadly, and unusual among gardeners, I think, I am typically doing garden tasks at the worst time, from noon to 2 p.m., though I try to wait to water until between 5 and 7 p.m. in high summer, if I’m really on the ball, but then there’s the risk of fungus and mildew on leaves, though I try to avoid them.
- Next, she says to “water when it rains. I know, it’s counterintuitive but it’s absolutely the smartest thing to do.” Remember the dry sponge analogy. Also, watering the top few inches, where it can dry out, doesn’t get the water where it needs to be, six inches down; adding your water to the rain “can help chase the rain water down deeper.”
- If you can’t do it all, then focus on watering the trees. All the trees. “Keeping trees alive is, frankly, more important than other plants. Their roots are mostly in the top foot of soil and a prolonged drought can damage a tree for life.” The is the most counter-intuitive for me, since established trees seem like they’d have the necessary root structure and depth to survive without my help.
- And, at the opposite end of the scale from trees, she says to “keep lawn grasses as long as you can manage,” about 3-1/2 inches tall, to help shade the soil. Or just let them go dormant to save water. We already mow the lawn (monthly, this season) about 4 inches high.
- She also reminds us not to prune trees during a drought because it can stimulate new growth, which is unsustainable without enough water. In general, I don’t prune in summer anyway, except dead branches (and often not even those), because I don’t want to disturb caterpillars, chrysalises, and other insects using the plants.
My notes for next year, if there’s not enough rain, are to instead of trying to water everything a little every day for an hour, use that same amount of time to water one section of the garden each day for longer, so that in a week I’ll have given a good soaking to the whole. And focus on trees. I always focus on the veggies and any new plants or transplants from that spring or the prior fall, and I’ll keep doing that, but I’ll add established trees if we are in more than a mild drought. And I’ll sincerely try to get out to water before 10 a.m. some days, though it won’t be easy.
As I type, it’s raining lightly outside. As of about a week ago, my part of New Hampshire was still abnormally dry, though not actually in a drought as it was in the summer. Since the U.S. Drought monitor began in 2000 (only then?), “the longest duration of drought (moderate to exceptional) in New Hampshire lasted 90 weeks beginning on June 23, 2020, and ending on March 8, 2022. The most intense period of drought occurred the week of October 6, 2020, where extreme drought affected 22.0% of New Hampshire land.” Only time will tell what the future holds.
Featured image: how I often water, with watering can (and vegetable in hand)