Growing medium for a crevice garden

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Novak
Title: Member
Joined: 2009-10-07
Growing medium for a crevice garden

I'm looking for input on the planting medium to use in a crevice-y tufa garden. In my readings, I've found very different recommendations on soil mixes to use.

I'm starting with a berm, and the tufa form a ridge in the middle. I'm going to try to place the tufa pieces tight together, though given their irregular shape, the crevices between them will be fairly wide. My climate is relatively warm and humid (mid-Atlantic).

Should I stick to a sand/gravel mix to keep things lean? Or will sand and gravel be too unstable, washing out from between the rocks? And finally, should I use the same mix in the berm as in the crevices?

I'm looking forward to hearing from those who have constructed similar gardens.

Janet

Lori S.
Title: Moderator
Joined: 2009-10-27

Hi, Janet,
I hope some people will respond to your question - until then, here is some advice and experiences from past threads:

http://nargs.org/smf/index.php?topic=240.msg17637#msg17637
http://nargs.org/smf/index.php?topic=240.msg11153#msg11153

Lori
Calgary, Alberta, Canada - Zone 3
-30 C to +30 C (rarely!); elevation ~1130m; annual precipitation ~40 cm

Anne Spiegel
Title: Member
Joined: 2010-01-26

Janet, I use sand (coarse) and 1/4" gravel in the crevices.  When I plant, I use a variety of tools (shish-ke-bob sticks, carving knife, horse hoof pick) to make the planting hole and I dribble in some subsoil "marbles" at the bottom.  The soil here is clay so I roll some in my palms and make tiny balls for a little waterholding capacity.  If plants look like they need fertilizer I'll take care of it.  In the humid northeast I just don't want to deal with any humus in a confined space.  So far it's worked well for me but every garden is different.  The crevice gardens here (but one) are sunny, open and windy.

Novak
Title: Member
Joined: 2009-10-07

Lori, thanks for the links. That thread on your tufa garden has already been an inspiration to me.  The most recent post is from last May... how has the tufa garden been doing since then?

My garden will be quite a bit smaller, since I have only 800 pounds of tufa. And I won't be able to use tufa gravel for topdressing. Having that much tufa is something gardeners in this area can only dream of.  :)

Janet
Philadelphia, Pennsylvania, zone 7a
Webmaster for the Delaware Valley Chapter (dvcnargs.org)

Novak
Title: Member
Joined: 2009-10-07

Anne, thanks for the information on your methods! I'm going to bug you for details. For example, what ratio of sand and gravel do you use? How many subsoil marbles per plant? And how deep? Are they just at the bottom of the rootball, or do the plants have to reach their roots down to get to them?

I saw your garden when the Delaware Valley chapter visited -- around 8 years ago and much earlier in my development as a rock gardener. (You probably don't remember me, but if you do, I was the one who pointed to the Edraianthus and asked which species of Campanula it was.) Your garden has given me something to aspire to.

Janet
Philadelphia, Pennsylvania, zone 7a
Webmaster for the Delaware Valley Chapter (dvcnargs.org)

Lori S.
Title: Moderator
Joined: 2009-10-27

Janet wrote:

 The most recent post is from last May... how has the tufa garden been doing ?

Overall, reasonably well, I suppose... ?  Some successes, some failures, of which I suppose some may be due to inappropriate plant choices for my laissez-faire style of gardening.  ;)

Lori
Calgary, Alberta, Canada - Zone 3
-30 C to +30 C (rarely!); elevation ~1130m; annual precipitation ~40 cm

Tim Ingram
Title: Member
Joined: 2011-04-27

Janet - this is something I don't have experience of but would very much like to make too. If you can get hold of it, from the AGS, there is a super little booklet by Zdenek Zolanek on Crevice Gardens. He recommends using a richer soil based mix in the actual crevices, the roots then growing down to a sandier mix below. To stop the soil washing out of crevices you can use little slivers of rock and clay soil. Once you have made one bed you will almost certainly want to make another, so can try slightly different techniques. There is a lot of info. on the SRGC Forum too.

Dr. Timothy John Ingram
Faversham, Kent, UK
I garden in a relatively hot and dry region (for the UK!), with an annual rainfall of around 25", winter lows of -10°C and summer highs of 30°C.
 

Anne Spiegel
Title: Member
Joined: 2010-01-26

Hi Janet.  The ratio is a lot more sand than gravel, but almost all gravel and rock around the crown of the plant.  The sand is very coarse, not mason's sand. My clay marbles go at the bottom of the planting hole which is usually deeper than the roots of the new plant.  I want the roots to reach down for water.  It really depends on how dry or wet your climate is.  We can have wet winters and wet springs and usually hot and dry summers.  By then the roots have hit the clay marbles.  There's no science to the number of marbles - it depends on what kind of roots I think the plant will make and how extensive I think they may be.  Eriogonums, for example, can be like icebergs.  I once dug out a dead eriogonum and showed it to a visiting group.  The top growth was maybe 6-7" (it was Eriogonum douglasii), and the twisted, thick roots when stretched out were more than two feet long, quite amazing.  It was a plant that died from old age and the roots were quite woody.
All the crevices in the various crevice gardens are a minimum of 18" deep at the ends and up to 3' or morefarther in. 
Hope this helps.  In the end you try different things and do what works for you.  Rich mixes were a disaster here so I don't use them.  Of course, it also depends on the types of plants you grow.
I

Peden
Title: Member
Joined: 2012-01-04

It's kind of an embarrassment but I love it any way. I made this little tufa thingy a couple years ago as experiment. There isn't much to see yet because it's March and because everything there big enough to see without a magnifying glass is growing from seed. It's about 3 x 4 feet. I did not break any of the stones whereby I might employ Harvey Wrightman's clay crevice technique or something similar but, instead, set them as close together as I could get them to fit. They are set on naturally sandy level soil (over the grass or weeds as was probably the case here). In the climate here they would probably shift excessively for happy rock plants if they were set on disturbed clay soil especially on a berm. Frost does that to things here. Likewise I considered the mix going in to the spaces remaining. I think it good advice for gritty/sandy mix for same frost-heave reasons. I put a little clay into mine, or used a clay rinse as I sometimes do, because that substance is naturally non existent here and many rock plants seem to like it. My goal was to minimize spaces between the tufas; it's to be a tufa garden, after all. The tufa is one stone thick as I plan to grow no deep rooted things on it (there's Silene acaulis and some little Androsaces on it now), but I did strive to lay them in a more or less vertical manner; it sits on sandy ground, wet in spring (as said by others; every situation different!) so is somewhat situated atop a giant plunge bed. I recently began careful addition of crushed (shale/limestone) to the surface of the thing. Careful because I've gone and put it inches away from supposed acid lovers. If you have good loam compost on your property you might use just a touch of that to give your grit a little oomph. You might avoid mix that's too well draining if the area is to be raised unless you plan to keep the hose on it. Be careful with a berm that's too high for its width 'cause that may slump too. I really think good crevice plants need good anchoring. One of my latest things here is using relatively pure (few additives in mix) stone dust from the local quarries. This is naturally graded from dust up to large sand grit in size and seems to weather in to a nice "hollow" type mix that, at least, resists heaving. You won't get it right the first time unless your really lucky so no need to worry; just go at it. Building a new rockery is always fun. Keep us posted Janet!

I should add that this will never be home for choice Eriogonums, Acantholimons or anything else deep rooted and preferring alkaline conditions.

Michael Peden
Lake Champlain Valley, zone 4b
Four and a half months frost free
Snow cover not guaranteed

Novak
Title: Member
Joined: 2009-10-07

Thanks to all of you for the advice. Tim, I've just ordered the booklet, and I'll check out the SRGC web site. Michael, your tufa garden looks realy nice. It looks like you've gotten the stones very close.

Janet
Philadelphia, Pennsylvania, zone 7a
Webmaster for the Delaware Valley Chapter (dvcnargs.org)

Novak
Title: Member
Joined: 2009-10-07

Spiegel wrote:

It really depends on how dry or wet your climate is.  We can have wet winters and wet springs and usually hot and dry summers. 

Anne, I'm in Philadelphia, so my climate is basically a warmer version of yours. We get mild winters and hot, humid summers, with rainfall evenly spread through the year. 

Janet
Philadelphia, Pennsylvania, zone 7a
Webmaster for the Delaware Valley Chapter (dvcnargs.org)

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