Dryland Plant Management in the Nursery and Landscape

So, to follow up on a recent post, we hear that the proposed Seattle green code provisions have been shelved for now. Apparently they are going start over next year and consult various horticulture/landscaping industry representatives this time to draft a provision that makes sense. I have mixed feelings. Partly I almost think it would be (dare I say) funny to see the rule go forward more or less as originally proposed, just to see how nurseries and people would respond. Imagine Swanson’s selling 75% native plants… heh heh heh. Anyway, I read that there is going to be some big meeting about it on September 5th. I am really bummed that I did not get invitated, especially since all the ideas I sent them were so well-received by my readers (including many who didn’t comment on my blog). But I’m actually not that bummed, since we have a lot of things to do out here that are funner than sitting in meetings; and Seattle is far away, with lots of traffic, and politics, and people who sit in meetings. At least that is our perspective from the far away land of Sequim.

I wrote (more or less) against the rule, but (in part) not for the same reasons other people wrote against it. I really like this post about it by Mark Turner, a respected authority about native plants, who presents a very well-thought out and balanced view. On the other hand, I note that many of these letters make two major points which I believe are false: one, that native plants pose special problems when it comes to producing them in the nursery and/or growing them in your garden; two, that native plants offer such a limited selection as to be uninteresting or unexciting. I can see what people who make such comments are getting at, but ultimately I don’t buy either of these points as valuable refutations of the green code provisions as originally proposed. For me this whole issue really comes down to water use: that should be the central focus in crafting this provision. So in this post I shall attempt to demonstrate that nursery plants are not really that difficult to produce or cultivate. In a future post I may attempt to expand upon point number two.

In my letter to the Seattle City Council, I stated that “native and water-wise plants are, broadly speaking, not difficult to grow either in nurseries or gardens.” This is likely a somewhat controversial statement, since its runs contrary to what most other people writing letters to the Seattle City Council on this topic (at least, the ones I got to see) seem to think about growing our native plants. So while not everyone may agree with me, I still consider this to be a matter of education and adjusting to different practices from what nurseries and gardeners are usually accustomed to. For that reason I am happy to divulge some of our methods when it comes to successfully producing and maintaining these plants. Perhaps over the winter I will have time to revise and expand this into more of a formal article and put it on the Desert Northwest web site.

Dryland Plants in the Nursery

Some think that dryland and/or native plants are unamenable to nursery production and therefore will never become popular. Our starting assumption, then, is that there is nothing wrong with the plants, since they are obviously well adapted here, being native; so there must be something wrong with conventional nursery production. And, based on our experience, we find that the main thing that can go wrong with these plants is supplying too much water, especially in the summer. Most growers have their plants on a sprinkler system that is timed to water at regular intervals. Frequently the sprinklers are set to run for a couple hours every day (overnight, ideally) during the growing season. A few smaller growers hand-water everything and can use that method to regulate how much water plants get. It should come as no surprise that we do not believe one should indiscriminately water the crap out of everything in a climate that has a pronounced very dry season occurring reliably every summer.

So we don’t want to soak our plants to death with timed waterings, but we sure as heck don’t have time to hand-water it all either. So we have decided to say “no” to timers and “yes” to sprinklers. Using sprinklers, we water more or less often depending on what the plants need to maintain good growth, and on the weather. What this looks like is during a typical summer heat wave, the plants get water perhaps every 36 hours or so. During periods of cooler weather watering goes to a 60 – 72 hour schedule. We think it best to give the plants a very thorough soaking when watering, and then let the plants dry out somewhat between waterings. We just wait until they really need it before we turn the sprinkler on. (As an aside, some nursery people are afraid to thoroughly soak plants when watering, because they may get too wet and start to rot. We believe this is only a problem if your soil mix is too heavy, or if you are not letting the plants go dry enough between waterings.)

In conventional nursery production, the problem of keeping plants watered is frequently aggravated by over-fertilization. Potted nursery stock that is given the maximum amount of fertilizer it can handle without burning frequently develops an excess of top growth that is not able to be sustained by the amount of roots in the pot. Such plants also get very rootbound which is not ideal. Sometimes retail nurseries find themselves having to water such plants twice a day to keep them from drying, which is always a hassle. Additionally, once these plants are set in the ground it takes a couple years for them to develop a large enough root system to sustain the top growth. Although such plants will frequently come out just fine in the end with proper care, we don’t think this is the ideal way to grow plants.

Our method is to give plants basically as little fertilizer as we can get away with without compromising quality. Also, we use only organic fertilizers. Sometimes our plants may not look quite as full as conventionally grown stock (but then again, sometimes they do!) but we know that it is important to have a plant with a strong and healthy root system so the plant will experience little or no setback when transplanted to the ground. However – and here it might sound like I’m totally contradicting myself – “as little fertilizer as we can get away with” is often more than might be expected for certain plants. For example, we find that Ceanothus and Arctostaphylos are pretty heavy feeders in general, and sometimes surprisingly so, despite their preference for harsh sites in the wild. Really clever soils people could probably explain this, but all I can say is “go figure.” (Well, now that I think about it, there might be some connection with their adaptability to fire ecology.)

Some people – and we went through this phase for a while there – think dryland plants need extra gritty soil for the super good drainage they need to survive in containers. This, we think, is sometimes a little bit true, but mostly not really. As long as you are not watering too frequently – and that’s the important part – most dryland plants will grow just fine in an ordinary, reasonably well-drained commercial potting mix. This is even true of seriously deserty plants like sagebrush. A bark-based mix with some pumice is ideal, and a little compost won’t hurt anything either. It’s true that certain plants require extra grit, but these tend to be in the minority (unless you are specializing in alpines, in which case you probably already know what you are doing and don’t need to read this). Beyond “alpine” it is difficult to generalize about which plants these are: usually just a few species per large genus. Cacti and succulents are a mixed bag; many of these do require gritty soil, but a surprising number of hardier types really don’t care what you put them in and may even respond to a richer mix by putting on vigorous growth; bearing in mind the aforementioned caveats about watering.

Finally, since we have dry summers, a lot of our native plants are adapted to stop growing in the summer. We find that they are better not messed with in summer. Potting up, planting out, anything that involves messing with roots should be done in spring if possible; the second choice would be fall. Of course they’re not doing much in winter either, and wet/rot can be an issue when transplanting at that time, though many species don’t mind.

Dryland Plants in the Garden/Landscape

Water-wise plants, including our dryland natives, may fail in the landscape for numerous reasons, but I think the most frequent are too much water, not enough water, and inadequate soil preparation. There are definitely some misconceptions that need to be addressed in this area. For one thing, dryland plants are (for the most part… most succulents excepted) not so tough that you can just plunk them out in a harsh, awful site with terrible soil and not water them at all. Why not, you ask? They’re native. Well, when something seeds itself in the wild, the first thing it does is send a taproot straight down into the subsoil as fast as possible so it won’t dry up in its first summer. The same species planted out of a container doesn’t have this advantage (especially if the soil has been compacted or scraped off), so it will need a little help to get established.


Time sequence of container-grown plant vs. self-seeded plant.

In actuality, native plants, generally, will appreciate much of the same treatment that is usually provided for “normal”/”conventional” (whatever) plants: they respond as well as any plant to soil amendment and mulch. The main thing one must do differently is watering.

But let’s back up for just a moment and address soil amendment. This does not have to be complicated. Some swear by double digging, but we are of the opinion that this is generally unnecessary. Usually a healthy top-dressing of compost, left on the surface to decompose over time, does the trick. If you want to use less compost, even a little circle of it around each plant, several inches deep, goes a long way towards successful plant establishment. The only time we might not think soil amendment so important for dryland plants is if you actually have existing native topsoil at your planting site. Unless your house is really old, this is probably not you. Usually the native topsoil is scraped off and/or compacted beyond usefulness during new construction.

So, having amended the soil and mulched – and mulch an be a lot of things, including wood chips and rock; but not beauty bark, which is evil because it does not promote healthy soil – the big question is how to water. It probably goes without saying that dryland plants will not grow in a swamp, so we will assume average to well-drained soil here, though a surprising number of these plants will be fine on heavy clay as long as it dries out for a couple months in summer. The best way to water is with the watering basin method. You want to finish your planting hole with a nice, big, deep watering basin so that when you go to water you can fill the hole up all the way, and the water will work its way straight down into the soil. This will encourage deep rooting, as opposed to the shallow rooting that often takes place under conventional irrigation that only sprinkles the soil surface. How often you will want to do this depends on your soil, and how established your plants are; but generally you will want to do this as infrequently as you can get away with before your plants start to wilt, which may be anywhere from about once per week to once per month during the dry season. So we see it is not really a major time-consumer, because you are not out there all the time watering things by hand daily: you just have to pay attention. You’d better believe those new little plants are sending roots straight down as quickly as they can during this process.


Plant root development under various watering techniques, redrawn from The Dry Gardening Handbook by Olivier Filippi.

Conventional methods, by contrast, suppose that once you have installed your irrigation system and set the timer, you can pretty much forget about things. This mentality leads to the failure of native plantings that end up getting too wet. It is motivated by the short-term convenience of not having to pay attention to the planting and hand-water until the plants become established. If we consider how much it costs to install and maintain an irrigation system (they always break, of course), and the cost of all the water that is used, perhaps we can say it is time to re-educate people about more practical ways to create sustainable plantings and gardens. A little more care in the first year or two after planting goes a long way towards sustainability of a water-wise landscape.

And that is where I shall leave it for now. I hope that has been helpful, or at least interesting.

On a completely different note: you still have one more day to come and visit us at our September Open House! Don’t worry, we haven’t sold out of awesome plants yet. Come and see us if you can!

Advertisements

5 Comments (+add yours?)

  1. Riz Reyes
    Sep 04, 2012 @ 01:25:52

    Great post, Ian. Very informative and takes me back to early hort classes.

    You bring up a lot of good points concerning natives. I didn’t realize that people bitched about natives being difficult to grow. They’re just like any crop; adjust to their needs and you’ll be successful. You and the guys at Xera seem to do okay and turn out very good plant material!

    The problem also lies in the fact that many landscaper’s repertoire of natives is very limited. Though I focus mostly on exotic plants, I make an effort to know my natives and the wonderful diversity and variation that exists in them. When clients ask for “natives only”, they’re immediately assuming that it’s going to be low maintenance, but they also have the mentality that you can plant a native and just forget about it. I don’t know who the fuck keeps on feeding this bullshit to innocent gardeners and homeowners, but it needs to stop.

    Unless you’re doing a full-on restoration of an existing ecosystem, plants are going to require ongoing maintenance and care just like any plant, native or non-native. Some plants are more adaptable than others, but our growing conditions, especially in the urban city, that really varies and we must make our selections carefully and consider their establishment and upkeep. At times it takes trying out a few different plants to see what thrives.

    You also have to consider what kind of gardener someone is. If you don’t really care to work in the yard, get your hands dirty, but what things to look kept and tidy, then there are alternatives and solutions too, for that situation. But the answer is not just mostly natives. There are wonderful selection of plants that are native, but, like you said, many gardeners don’t really know about them or how to use them in a managed landscape setting. Perhaps there aren’t enough examples or people are just too fixated on what a garden should look like: lush and green with lots of colorful flowers. You can certainly have a landscape like that, but don’t expect all the plants to be native to your region.

    I think the main concern I had with the 75% natives rule is the image that all landscapes will look the same because landscapers are afraid and unmotivated to try other species that may be better suited for a “all natives” planting.

    Reply

  2. Arlene Mikelsons
    Sep 04, 2012 @ 09:23:06

    Very good post! Having lived most of my life in areas where it rains in summer, I am still trying to get the hang of dry land watering.

    Reply

  3. Ian
    Sep 05, 2012 @ 07:42:34

    Riz, the problem is that certain, mostly boring, native plants are actually quite easy to grow, as this very limited palette is what most gardeners and nursery-folk are familiar with. These tend to be the woodland plants and/or water lovers, not totally but to some degree. It’s the much greater diversity of alpine and dryland native plants – those that have much more value in our urban settings – that are perceived as difficult. I need to clarify this, so one more blog post coming up I guess.

    It is apparent that I need to do more to raise awareness of all the wonderful native plants we have that are not boring. Most people just don’t know about them at all!

    Arlene, well where you are, at least summer heat doesn’t stress out the plants too much, compared to Seattle or Portland!

    Reply

  4. Trackback: The Unrealized Allure of Northwest Native Plants « THE DESERT NORTHWEST [blog]
  5. Maya
    Jun 19, 2013 @ 19:41:52

    The three main types of retaining walls are gravity walls, piling walls, anchored walls or cantilever walls.
    It’s common for a homeowner to have many different ideas regarding how this can be done, and this is also one of the many reasons that someone in this position should obtain the help of a landscaping service in San Diego. Excellent as formal hedgerows, it can also be easily pruned into customized shapes.

    Reply

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: