How to water plants through a heat wave

How to water plants through a heat wave

Heat waves make me a worried gardener. What can I do to help my plants? Should I water again? How much?

This summer of 2017 has started off with a blast of multiple heat waves for Southern California’s valleys (the beach has been spared by the presence of a marine layer). In my yard, twenty miles from the ocean in San Diego County, it was over 95 for six days June 16 through 21, and then again for three days June 25 through 27. A couple days reached over 100.

But my vegetables and fruit trees came through pretty well, save some sunburned apricots:

sunburned apricots

I believe it’s because I’ve settled on a two-part watering routine that helps the plants cope with heat waves. Here’s what I do:



First, I make a pre-emptive attack. I’m convinced that this is the most important thing to do. When a heat wave is predicted, I pre-irrigate, heavily. I learned this from Reuben Hofshi, an avocado farmer. The day before a heat wave is forecast to start, I water with enough to give all plants full moisture in the soil of their root zone, and then I add about 50% or more. So, for example, I gave my avocado and citrus trees a normal round of irrigation of three hours and 18 minutes, and then I applied an extra 50% of one hour and 39 minutes.

The idea is to make sure the trees have access to all the moisture their roots can touch. They’re totally prepared to pull up maximum amounts of water to supply their transpiring leaves in the stressful heat.


Daily replenishment

Second, I replenish the water used by some plants each day during the heat wave. I feel the need to do this for avocados and vegetables. I’ve noticed that they stress if I don’t. On the other hand, citrus and deciduous fruit trees (apricot, peach, pomegranate, plum, apple, etc.) don’t need such coddling. I don’t water them daily through a heat wave.

But for avocados and vegetables, I estimate how much water they’re using each day and replace it each day. For example, I gave my avocados 42 minutes each afternoon.

Meanwhile, for my vegetables, before the heat waves I had been watering my vegetables for 25 minutes every three days, which had been working well, and which is equal to about eight minutes per day. During the heat wave, I ran the drip lines on my vegetables for 12 minutes each day; that was my estimate of how much they needed. I came up with that time by taking the daily eight minutes and adding 50% (four minutes) since it was hotter than usual, which gave me 12 minutes.

To sum up, I pre-irrigate with at least 150% of what I think the plants need the day before the heat hits in order to be fully saturated, and then I irrigate every day during the heat with about 150% of what avocados and vegetables normally need each day in the summer. 


Nota bene:

Let me mention some factors about my specific situation and why they might make things work differently for you. My soil is sandy loam. If yours is clay, you shouldn’t need to water anything daily even in a heat wave. Also, I irrigate my vegetables with drip lines. When I used to irrigate with overhead sprinklers, I could get through heat waves without watering my vegetables daily. The sprinklers gave them larger root zones and therefore made for tougher plants.

I have always watered my deciduous fruit trees every ten days to two weeks in the summer. It is when a heat wave occurs that I’ll water every ten days; otherwise, during normal summer temperatures, it’s every two weeks. Deciduous fruit trees (and grapes) never stop surprising me by how little and infrequently they need water — while still producing oodles of great fruit. That’s why I keep planting more of them!

grapes on chainlink fence


P.S. Apologies for the pretentious “nota bene,” but whatever, I’ll leave it in there.


You might also like to read:

Gardening benefits of a hot-summer climate

Heat tolerance of avocado varieties

Rain makes dreams come true

Rain makes dreams come true

This morning I awoke to the sound of rain. It’s the most pleasant sound, a muffled pecking on the roof. This is the first storm in a series of four that the National Weather Service says will give us three to six inches by Tuesday, an event with more potential to flood than anything we’ve seen since 2010, before the drought started. (Will this be the first year since then that we have above average rainfall too?)

I am possessive of my rain. See, I just did it — “my” rain. If I’m home while it’s coming down, then I’m outside running around checking levels on the tanks, adjusting hoses, observing the mulched basins I’ve built, getting soaked. My goal is that every raindrop sinks into the soil on my property — that not a single drop runs off my property.

I’m not there yet. I still lose some from the driveway, whose curb I need to make more cuts in. But elsewhere I capture it all. I refuse to treat rain like sewage.

How can we lament the drought and demand watering restrictions only to discard rain into the streets?

Recently, I cut a downspout pipe that channeled rain from one section of my roof directly to the street. It used to be that the rainwater gushed out of that pipe and eroded the soil at the edge of my yard and then carved a gully out of our dirt road and then flowed downhill to add to our neighbors’ flooding problems. So I unearthed that pipe and chopped it.

For one, that rain is mine. I’m going to keep it. For two, that erosion and flooding is my fault and I need to knock it off.

When my wife and I were looking for a house to buy we dreamed of having a yard large enough that would allow me to grow much of our food, and we also dreamed of having a creek running through the property. But creeks are extremely rare in Southern California, and alas we moved into this house and left our dreams of a creek behind.

Below our house the yard slopes down at about 5 degrees. One day after chopping the downspout pipe, I put our two sons in a wagon and told them we needed to collect rocks to make a river bed. Cass liked the idea of “making a river.” The boys and I tossed rocks into the wagon and then I towed them back to the place where I’d chopped off the downspout pipe. At the opening of the pipe they eagerly helped me lay a path of rocks — some yard work is meant for young boys, and carrying and tossing rocks is one of them.

“We made a river!” I said.

Well, we had made a bed for a tiny creek. Cass didn’t call me out on it.

Our creek is very short and it is not perennial; it only runs during a rain. But an ephemeral creek is better than none, and it’s better than erosion, and it’s better than flooding our neighbors, and it helps sink “our” rain into our yard. Better yet, it sinks the rainwater between some of our fruit trees, and I imagine the trees’ roots will eventually tap our creek’s flow.

Our creek is flowing this morning. And it looks like it will continue for the next week straight. Rain is making our little dream come true.

Cactus among cedars

What’s this? It’s a garden on the campus of Willamette University in Salem, Oregon where lush squash, tomatoes and peppers are growing behind these pads of cactus. Huge cedars and healthy Japanese maples partly shade the garden. I find the scene hilarious because it reminds me of a way in which we gardeners are all the same. We can’t help but try to grow plants that don’t belong.

This cactus would be at home on some of the south-facing hills near my home in Southern California (where such prickly pear cactus is native), but it must feel out of place in the Willamette Valley in January when it’s 40 degrees and 30 inches of rain has already fallen that winter.

I can’t stick to what grows easily in my particular climate either. I’ve got blueberries, for example. They hate our intense sun, our alkaline water, and of course our lack of rainfall. I can’t help but try to grow them, however. We’re all the same.

Gardening benefits of a hot-summer climate

Every August, I curse the summer. I grow tired of the heat and I wish I lived at the beach again. Last week, I wrote an email to the host of my favorite garden show asking for encouragement in this season of discomfort.

Don Shor hosts the Davis Garden Show alongside Lois Richter on KDRT in Davis, California. Davis gets even slightly hotter than we do here in the inland valleys of Southern California, having an average high of 93 degrees in August compared to my 91. But like me, Don has also gardened near the ocean. He grew up in La Jolla.

So I asked Don about the gardening benefits he has found in the hot summer climate of Davis compared to the mild maritime climate of La Jolla. I was hoping he could make me feel better about tolerating these toasty August afternoons, and he did.

For starters, he said that his tomato yields are much higher compared to La Jolla. The majority of the nation’s canning tomatoes are grown in the hot Central Valley, he noted. Also, his chile peppers are more flavorful, intense, pungent, and his plants have far fewer disease problems, such as powdery mildew, due to the very low humidity in Davis.

These poblanos have been both fruitful and flavorful.

These poblanos have been both fruitful and flavorful for me this summer.

Along with increased summer heat often comes increased winter chill, as is the case of Davis compared to La Jolla. Because of this, Don also mentioned that he can now grow superior deciduous fruit trees. His dad planted an apple tree in his La Jolla yard — Beverly Hills variety. “Yeah, it was an apple,” said Don. “That’s about the best you can say about it.”

This reminded me of the apple trees I had when I lived close to the beach — Anna and Dorsett Golden varieties. They were apples. I can’t say that they had any taste to write home about though. Same with the plums I grew in that yard. They were plums.

But now in my hotter-summer (and cooler-winter) climate of inland San Diego County, my plums (Burgundy variety) taste amazing, far superior.

Finally, Don said that a lot of the Mediterranean plants love the heat, plants like rosemary and lavender. I’ve found that to be true in my yard as well. Coincidentally, just yesterday I removed rosemary and lavender plants because they outgrew the space I had allotted to them. I was tired of trimming them back despite the fact that I never gave them a drop of water!

So, while all’s not perfect here — it’s often too hot in summer for personal comfort — this climate is clearly heavenly for some plants, as Don Shor points out. Next August, I’m hoping to remember that and complain about the heat less. In the near future, I’m also going to take advantage of the hot-summer climate gardening benefits and plant more peppers, more tomatoes, and more deciduous fruit trees.

Just move!

Walking around the San Diego neighborhood of South Park yesterday, I noticed that most yards had ornamental plants (giant bird of paradise, bougainvillea, lawn, Mexican sage, ficus, magnolia), but I came upon one that made me reminisce. It had peach and apricot trees, fava beans, broccoli, tomatoes, pole beans, hop vines, grape vines, avocado, citrus trees, pepper seedlings — all crammed into patches between the house and the street, including the strip between the street and the sidewalk, and also including another strip beside the neighbor’s driveway. These houses have tiny yards, but this person was using every square inch to grow food. I remember those days.


Tomatoes in my old Hillcrest canyon scream for sun.

I used to live in the nearby neighborhood of Hillcrest, where by hand I terraced the steep slope that was our yard. I cut back trees to allow for more sunlight, I asked the neighbor if I could grow a corn patch on his slope, and I grew boysenberries and tomatoes in the public right-of-way at the bottom of the canyon. Eventually, I even bought a series of pots and hauled them onto our roof to take advantage of that space. As I look back on it I see myself as desperate — as must be this person in South Park.

Hillcrest and South Park are places for people who like restaurants; they’re not for people who like to grow food. Living there only produces frustration for weirdos like us; living where I do now feels like paradise. To my South Park comrade: Move!

You won’t regret it. I’ve now got even more sunlight than I want. I actually have to plant my peppers to the east of tall tomatoes, or corn, or the house, so they don’t get burned by the afternoon sun. And to think that I was once cursing the neighbor’s eucalyptus and secretly lopping branches off another neighbor’s ficus to give peppers in Hillcrest a fighting chance.

I’ve got more land than I would ever plant. It’s actually not that much land, not much over an acre, but it is capable of being so productive since there are no neighbors’ trees casting shade. And we can let our trees grow as big as they naturally desire. The avocado tree at the house in South Park was struggling to be happy in its 20 square feet of allotted space. An avocado in such confines, and in less than full sun, simply can’t make much fruit for you.

There are costs to moving out of the city to be sure, but to a person like this one in South Park filling his yard with stunted apricot trees and claustrophobic hop vines, the pleasures of never again seeing botrytis on your boysenberries, of eating honeydew melon from your yard that is the sweetest and crispest you’ve ever tasted, of being able to grow more broccoli than your broccoli-loving wife can eat, of having a Reed avocado tree laden with softball-sized fruit right outside your door, of seeing any fruit tree at the nursery and knowing you could buy it and plant it in your yard if you felt like it, and five more if you felt like it — these feelings of freedom and success are invaluable.

El Nino is not rain, and it doesn’t “come” to California

There seems to be a lot of misunderstanding about El Nino among us non-meteorologists. Here are two examples from Sunset magazine’s November 2015 issue:

“Before El Nino rears up this winter as predicted, here are easy ways to ready your garden for rainfall.”

And, “Because no matter how impatient we Westerners are for El Nino to arrive, the ensuing gray, gloomy weather might eventually feel a bit, well, gloomy.”

El Nino is not something that might “rear up,” and it is not going to “arrive” here in the American West, ever.

Why? What is El Nino?

I guess an official definition would be one given by the National Weather Service. They say, “El Nino refers to the above-average sea-surface temperatures that periodically develop across the east-central equatorial Pacific.”

That’s all El Nino is: relatively warm ocean water down near Peru.

That warm ocean water ends up affecting the nearby atmosphere and weather patterns, and then weather patterns around the globe, but those related effects are related effects and not El Nino itself.

So, El Nino is not rain, and more than that, El Nino is already “here.” That is, the condition of that certain part of the Pacific Ocean being warmer than normal has already been met.

What may or may not arrive in Southern California are the heavy rains that are sometimes related to that warm equatorial ocean water. And if they do arrive, then we will be having heavy rain that is possibly, partially caused by El Nino; we will not be experiencing the “arrival” of El Nino.