My SoCal Garden

Planting in the Heat of Summer

By Steve Thomas-Patel·
Daisies in Summer

Summer gardening is Southern California has limited options, but here are things you can do!

I don't know about you, but as our first heatwave of the year is quickly approaching, I'm having to accept that the planting season is over. Goodbye spring!

In California, the general rule is, this means no more planting Native plants. The good news is that rule isn't 100% true, there are some exceptions you can get away with. But for the most part it is time to back off.

What Not To Plant

The problem with trying to plant native plants this season has to do with their roots. When you transplant anything into the ground, you kill a large amount of the root system.

It's mainly the delicate hairs on the roots that do the work, and when they are transplanted, many of these root hairs are shed. So even if you don't tear out any roots you are damaging the root system. This is one of the main reasons plants experience "transplant shock".

"Transplant shock" is a defensive mechanism plants go through when they are repairing their roots. The plant needs to put all of it's energy into fixing it's roots, so it takes the energy from the leaves, or even sheds them off so they are no longer drawing water and energy. The best defense against transplant shock is to water the plant. You've damaged the roots, they are less efficient, so they need more available water.

This is a big problem for most California Native Plants in the summertime. In the summertime as the sun beats down on the soil for hours on end, it becomes very hot. When you mix that heat with water, some nasty bacteria suddenly receive exactly what they need to grow and multiply, and they want to feed on your vulnerable underdeveloped ceanothus or manzanita.

Those are two plants you definitely don't want to plant in the ground in summertime. Some plants are just known to be even more susceptible to "summer water" than others. An unwanted drenching in summer can quickly kill a even a healthy, well-established ceanothus.

Worse than that, some plants like ceanothus tend to go dormant in summer. They will look like they are dying and our natural instinct is to water them, essentially to poison them.

Plants to Definitely NOT Plant or Water in the Summer:

  • Fremontodendron (flannelbush)
  • Dendromecon (bush poppy)
  • Trichostema (woolly blue curls)
  • Arctostaphylos (manzanita)
  • Ceanothus (California lilac)

Almost as a rule, you should only plant these five plants in the fall. That way they get the most time before summer to really setup their root system. Think of it like a runner preparing for a marathon, summer is their marathon and you want to give them the most time to train beforehand.

What Can Be Planted in Summer

There are some exceptions to the "no planting in summer" rule. They fall into two categories:

  • Heat loving desert plants
  • Water loving plants

The first is because desert plants are used to the heat. They have natural defenses against the fungi and bacteria that also love the heat. So go ahead and plant your Indian Palmer's Mallow and create that Dudleya rock garden you've been wanting to put together. (Just do it in the early morning, or evening hours to avoid getting sunburn).

The second is because water loving plants expect water all year long. These are your riparian plants, like miner's lettuce and seep monkeyflower. If summer water was going to kill them, they'd all be annuals.

What to do with Unplanted Plants?

I have a terrible habit of buying lots of plants that I don't know what to do with. I figure I will take them home and find a spot for them. But then I realize there is all of this prep I have to do before I put them in the grown.

Long story short, my porch is full of native plants sitting in the pots they came in. What am I going to do for summer?

The good news is, it's okay to pot container plants in summer. That is because the bacteria and fungi you have to worry about are not likely to be present in the nursery pots. Use good potting soil and be sure not to add dirt from the ground in your yard and you should be okay.

If you need to hold on to plants for the summer, the best thing you can do is repot them in larger pots and keep them in a somewhat shaded location, like I do on my porch and stick to a light watering regimen. The main thin is you don't want to encourage too much growth since that could cause them to become rootbound in their pots. You just want to keep them happy and healthy until fall comes around when you can plant them.

The corrollary to all of this is that, yes, you can absolutely plant your potted natives in the summertime. A lot of people don't know you can grow natives in pots. But many are ameanable to it!

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