How lean?

cassiope(03/WI)January 29, 2005

I'm curious - does everyone follow the rule, that alpine soil should be lean? That's what I've read and have been told by experienced alpiners, but it doesn't make sense to me. The mail order nursery, High Country Gardens sells some plants that can be used as alpines, and they suggest using all kinds of micronutrients, manures, etc. when preparing the soil and caring for the plants because they say xeric plants need a good supply of it. My garden has been going for a few years now, so whatever minerals were available, have surely become depleted. It's also been suggested to me to completely redo my soil every few years.

I appreciate all comments!

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leftwood(z4a MN)

Oh my Gosh! Redoing an alpine bed every two years would be certain death to some alpine plants hardship for many others. Real alpines have roots that go WAY down. He(she) must have been getting mixed up with annual beds. I supposed you coud redo a bed that often with most perennials, but they just begin to mature in two season and then you "start over"? If that person is redoing her beds in two years, he(she) is not doing it right the first time. Alpine beds should never need to be redone, if done right the first time.

Some alpines can tolerate rich soils, and consequently can be grown in both an alpine environment and perennial garden. Examples are the Sedums and a good portion of the Penstemons. Others, though they may survive, exhibit the floppy syndrome. Even the aforementioned Sedums and Penstemons will look and be more healthy in a leaner soil.

This is what can happen when the soil is too rich:

Front: Escobaria leei, Sempervivum 'Red Ace', Delospermum nubigeum
Top: Escobaria viviparia. Back: Jovibarba allionii.

The overgrown plant is Delospermum nubigeum. It is a fall season photo(with fall color) of a trough I planted new 5 months before. The soil was too rich. Fortunately the well known Scottish alpine gardener, Ian Young, was at my house and he said not to worry about it in a trough. The small volume of soil's limited nutrients will get "used up" and the ice plant(Delospermum) will settle down.

As a general rule, when plants are grown in soil to rich for there liking, blooms are non-existant or sparse. No blooms on that ice plant - at all.

Notice in the photo that other plants in the trough seem to be unaffected. Most probable is that the "non-reaction" is just inherent in species, or the ice plant is so vigorous that it stole away the water and nutrients, making the remaining soil leaner for the other plants. I am really learning about ice plants and I suspect the answer is both.

I like High Country Gardens. I got the Escobaria leei from them. But they are based in New Mexico: a different environment than ours and different soils, even when we ammend ours. This includes the mountainous areas they collect seed from too. Here our soils are inherently richer. Adding more micro nutrients, with a weak solution of epson salt for example, can't hurt. But one application will be good for many years. Micro nutrients are used in such tiny amounts. The overgrowth of my ice plant was due to an excess of macro nutrients, mostly nitrogen. Macro nutirents are nitrogen, phosphorus and potassium. N,P and K respectively. These are the nutrients we attempt to control with lean or rich soil.

As mentioned before, the reaction to rich soil is dependent on the species. In my experience, succulent or not, the leafy plants in general react, and cactus do not, as long as it stays pretty dry. There is a heavy duty cactus man here in Minneapolis. For his cactus soil, he uses varying sizes of trap rock(half inch to 1 1/2 inch angular rock) and just enough rich black soil to fill the spaces between.

Cassiope, unless you are seeing a reduction in growth/flowering in your perennial garden, I doubt soil nutrients are "surely depleted" in just 3(?) years. But yes, the macro nutrients do get used up over many years.


    Bookmark   January 30, 2005 at 10:47AM
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Rick - thanks for your answer, I always learn a lot from you!
- Not only am I disappointed in the amount my alpines flower, but some of them haven't reached the dimensions listed by the grower (Siskiyou). (examples: Erinus sp., Androsaces sp., some Penstemon).
This is a horrible confession, but I probably don't have a Alpine garden at all. Really and truly mine is probably more of a mountain meadow type. So I'm pretty mixed up - I've read so many books, but have been relying on my memory for how I want my garden to look. I do like plants to look robust and lush - probably not a good idea in a true alpine garden.

Probably I'm doing something else wrong. I do water an awful lot - maybe too much.

    Bookmark   January 30, 2005 at 9:34PM
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leftwood(z4a MN)

Alpines naturally take longer to reach mature sizes.

Maybe that is what you want - a meadow. There are crossover alpine plants for that too. And alpines that prefer a meadow environment. Most alpines are use to frequent rain, but the soil is so perfectly free draining that it doesn't translate to watering here. If you don't have good alpine soil, yes you're probably watering to much.


    Bookmark   January 31, 2005 at 3:31PM
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I'm sure you are right about the watering. Last year after a wet period, my beautiful Little Plum Lewisia died, as did my Delosperma.

When I was setting up my garden, I tried to follow it by the book, but my soil is extremely sandy, so I didn't add sand to it. Also my regular garden needs frequent watering because it drains so well. (the neighborhood I live in had it's top soil removed, and what remains is mostly sand). I probably have been overcompensating with watering.

This is good, Rick, Thanks - it gives me something to work on! I think I may adjust the soil for some of my alpines.

    Bookmark   January 31, 2005 at 8:34PM
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