The Secret Life of Perennials

Written by Paul D. Race for Family Garden Trains

They offer a far better dollar value than annuals, because you supposedly only have to plant them once. They are usually predictable and often easy to spread. Yet perennials can also be stubborn or behave in ways that surprise or disappoint you. This article is about a few of those glitches they don't tell you about when you a specimen home in a 3" pot, with visions of a well-established bank of the things gracing the far turn by September.

My family has a long history of perennial gardening, an enthusiasm I did not quite share until I became a homeowner and started pricing all those landscaping plants that my extended family traded back and forth for free. After buying a few plants, begging a few more, and making more than my share of mistakes, I gained a new respect for the "green thumbs" in my family. I also established a personal practice of focusing on plants that did not require serious attention once they had been properly established--a practice I continued on my backyard railroad empire.

When I started attending open houses at area garden railways, I discovered that many other garden railroaders used low-maintenance perennials in their other flower beds, just as I had been doing. Apparently, like me, they want things to look nice, but they have little patience or time for plants that require more attention, say, than twin grandchildren.

Though I'm more of a garden railroader than a gardener, I couldn't help but notice that many things I learned in the flowerbeds were applicable around my train stations and vice versa. I've recorded most of the "normal" facts about ground covers and other popular garden railroad plants in other articles. This article is a repository for the "goofy" questions that you only get from people who've followed all the directions, done everything right, and still can't get their perennials (big or small) to "behave themselves." Problems discussed include:

• Slow or Erratic Growth
• Delayed Naturalization of Vining Groundcovers
• "Leggy" Growth
• Succeptibility to Pests
• Fairy Ring Syndrome

• Plants are living things, and in certain cases may be no more predictable than children.
• Labels are applied by people who work for nurseries and make assumptions about your knowledge and the conditions of your garden.
• Stuff happens, and sometimes it's nobody's fault.

Best of luck, let me know if you think of something else I should touch on.

Slow or Erratic Growth

That said, you will also encounter unusual and sometimes frustrating growth patterns, such as two identical plants planted next to each other growing in entirely different ways. (For example, I have one bank of Creeping Thyme on my garden railroad that has spread out in three years to about three square feet of coverage. A bank of the same plant, literally across the tracks from the other bank, has grown to about a fifth that size in the same time period. If you are distressed by a similar circumstance in your garden, you might consider checking for slight differences between the two locations, even if they're only a few inches apart.

Gardeners sometimes speak of "microclimates" to explain why plants sometimes survive well outside their "expected" survival zone. For example, a cold-weather plant may survive on the tops of mountains in a subtropical region, or a warm-weather plant may survive in a region of bitter winters if it is planted against a stone wall with a southern exposure.

Your garden has many "micro-ecologies," whose differences go beyond issues of weather to include differences in amount of shade, soil chemistry, drainage, slope of ground, and so on.

For example, I once had three Maiden Pinks (Dianthus Deltoides), two of which were identical. I planted them in a row on the same terrace in my rock garden. Today one is thriving, one is surviving, and one is gone. On closer examination, the "thriving" plant, although it is only a few inches from the "surviving" plant receives about three hours' more sunshine in the summer than its neighbor. The "surviving" plant and its deceased neighbor (when it was alive), have thrown more leaves and growth toward the sunny part of the garden, and if the "survivor" survives, it may one day be right next to the other plant. The deceased plant, identical to the "survivor," and only a few inches away, also happened to be on the overflow path when my pond flooded three times in one year. Whether some chemical in the pond or the soakings themselves did it in, I don't know, but I know a good place not to try to plant another start of Maiden Pinks.

The "survivor" now faces a new challenge, it is being shaded by a Hosta that has crept down the hillside toward it. Whether this event hastens the Deltoides' migration toward the sunny side of the garden or hastens its demise, remains to be seen, but it illustrates the role that neighboring plants may play in determining the "micro-ecologies" for a particular plant.

If you think you've determined why a plant's growth is overly slow or erratic, you may experiment with changing its circumstances (such as trimming back a neighboring plant, improving drainage, and so on). But your best guess is only that, and you may find that your changes have no effect at all, or even have the opposite of their intended effect. In the meantime, remember, you're doing this for enjoyment, so don't take it personally if your plants react to your loving kindness in vastly diverse ways.

A few things you may check for when perennials grow unpredictably might include:

• Sunlight/Shade differences (perhaps a distant tree has grown taller, or a nearby tree has lost a branch)
• Soil Chemistry differences (for example, fallen maple leaves turn soil more alkaline, fallen oak leaves leave the soil more acid. You can try to compensate for changes in soil chemistry by using appropriate fertilizer, such as Mir-Acid.)
• Nearby plants that overshadow or have other negative effects on your plants (Overgrown "neighboring plants," decaying maple leaves, etc. In addition, walnut trees exude oils that will harm your pond and may affect growth of certain plants.)
• Drainage differences
• Heat differences (My sister-in-law's English Lavender, planted out in a traditional flower bed, does not grow nearly as fast as my wife's, planted up against the southern wall of our house.)
• Fairy Ring Syndrome (described below)

Delayed Naturalization of Vining Groundcovers

As gardeners, we wish all our plants should fare as well, especially our ground covers. In fact, you've seen banks of pachysandra, periwinkle, Baltic ivy, vining euonymous, and so on thriving and spreading in places where you know they haven't been tended for years, so you know it's possible. But there's still a huge delay between buying a flat of the things and seeing a beautiful bank of the stuff growing in your own backyard.

As far as I can determine, the problem is treating these groundcovers like tomatoes. You clear out a patch of soil, prepare some holes in the dirt with potting soil or some such, insert the little starts and wait, and nothing happens. But tomatoes root downward (and therefore into soil you've already prepeared). The groundcovers I've mentioned won't thrive until they can root and spread outward. To do that, they need to be surrounded by soil that is soft, yet stable, and constantly moist--nothing at all like the sun-baked crust surrounding your tomatoes. To your dismay, you may discover that your vining groundcover spreads best when it has the chance to invade the space of another plant that is already stabilizing and the soil and keeping it shaded and moist.

So how do you replicate this environment without setting your new groundcover at war with something you already own? I think you would get the best results as follows:

• Prepare the entire patch of ground you wish the groundcover to inhabit, not just the holes around the plants. In other words, don't go "deep" as much as you go "wide." This may mean breaking up the top couple inches of your soil (especially if it's mostly clay) and raking in a little bit of topsoil or potting soil to keep it a little loose,
• Prepare the hole where the start is to go as you ordinarily would (dig a hole 2-4X as big as the root ball and backfill with potting soil or some such),
• Mulch the entire area with a fine-grade mulch.
• Keep moist.
• Keep weeded--unfortunately you have created the perfect environment for a wide range of weeds, including maple seedlings and the like. Until your groundcover is completely established, you will have to be extra vigilant.
• Fertilize the groundcover plants directly as much as you can without overfertilizing the "bare areas" and needlessly encouraging weed growth (a watering can approach like Miracle Grow will help).

"Leggy Growth"

Unfortunately, getting most plants to sprout more foilage on lower branches is almost impossible. Consequently, prevention is far easier than attempting a cure. With dwarf trees and woody bushes, especially, you need to keep an eye on their growing patterns so you can intervene before they are too far "gone" to rehabilitate.

That said, many perennials do handle trimming back. Just try not to let them get so "leggy" that the "trimmed back" version is nothing but a stick or a cluster of sticks--that will stress the plant much more than necessary. If the plant loses its leaves in the winter anyway, and you must trim it radically, try doing it in late winter before things start warming up again. (Note: Never radically trim back Japanese maples or ornamental junipers; your "tree" may be a "generic" maple or juniper trunk with a Japanese maple or Dwarf Procumbens branch grafted on the top, so the foilage that grows back from the trunk could be much different than you may expect.)

Succeptibility to Pests

Even if you can win the war against pests in some regions, you may be stumped when you have to fight those pests around your pond--many insecticides and other garden chemicals will kill your fish if not your pond plants. I have one bank of hostas that the garden snails apparently love. But if I use "snail bait" or similar treatments in that bit of the garden, I run the risk of a rainstorm washing it into the pond. This is a great illustration of why you should design your pond so that runoff from the rest of the garden is diverted in another direction, but that hindsight doesn't do my hostas any good. I can either move them away from the pond or use an organic alternative for snail bait. (I understand that saucers of beer will do them in.)

Fortunately, most area nurseries are familiar with regional pests and can offer advice and solutions. But you should be aware that plants that have survived floods and droughts for decades may still be taken out in a season by something you can't even observe with naked eye.

In addition to treating endangered plants when I can, I also make it a practice to keep "spare" plantings of plants I am dependent upon. That way if one planting is decimated overnight or suffers for some other reason, I don't have to go back to the nursery and pay big bucks for something I've already had growing in my back yard. Often it's just a matter of transplanting some of the healthy stock back to or near the disaster site.

Fairy Ring Syndrome

There are at least two other explanations for plants moving outward that you may find more helpful:

• Soil Chemistry Changes--Some plants require much of a certain chemical, and as that chemical is depleted around the original planting, the roots (and eventually the leaves and blossoms) spread outward where it can still be found. In this case, you can either replenish the chemical in the center of the "fairy ring," or simply stick another plant into the middle. But transplanting pioneers from the outside edge of this kind of fairy ring isn't likely to be successful if you don't change the soil chemistry at the same time.
• Death of "Root Stock"--Many perennials (wild daisies, for example) come back for several years, then die for no apparent reason besides "old age." By the time the original "root stock" dies, it has reseeded or otherwise spread outward, but the death of the original plant leaves a hollow in the middle. Some of the "Sudden Thyme Death Syndrome" I've observed in my gardens seems to be of this category. Where I had a nice bank of thyme, I now have a dead brown patch with a green-looking outside fringe. In this case, the chemistry of the soil has almost nothing to do with it. I can either transplant "fringe" plants back to the site of the original plant, or wait a season until the fringe plants themselves spread back toward the center.

  My bearded Iris have formed "fairy circles" in several beds where pests devoured the healthy old plants with huge roots but missed little starts at the fringes. In this case, once I have re-treated the soil for grubs, I can usually encourage more compact growth again.

Others

Best of luck!

Update, 2021

I just spent some time reformatting this document, originally written in the early 2000s. I also read it through carefully to see if there was anything I would add or change.

Nope.

This is worth mentioning, because, when I originally published this article, a fellow garden railroader who was considered an authority on many related topics "took me to task" on several points, most especially when I explained why plants besides mushrooms may die out in the middle of a clump and flourish on the outer edges.

In the intervening years, I realized that the other fellow has mostly lived in areas with very low rainfall, so the way things grew for him was not necessarily the way they grow for me. Still, it's a long reach from "this hasn't been my experience" to "that never happens."

That said, I didn't see any reason to adjust the content of this article back then, and two decades of additional garden and garden railroading experience have not changed my mind on any point.

If you find something wrong, inaccurate, or incomplete about anything I publish, you are certainly welcome to contact me. I love hearing from readers, truly. In fact, reader questions are the biggest reason we've published so many articles.