Could you please advise me on the best mixture of compost for my containers

Jimbow. I am sure someone with knowledge in this field will step in soon to answer your question.

Hi Jimbow, and a big to All Things Plants.

What type of alpine plants are you growing? And what are your growing conditions/weather/soil like?
There are many alpine type plants that will do well in normal garden soil that is amended with forest type compost and gravel (small pea gravel/chicken grit).
I have raised beds filled with forest compost, sand and pea gravel. I also have some beds filled with sandy loam compost. Most plants are top dressed with a nice layer of chicken grit or pea gravel after planting. If you are using raised beds it will provide you with better drainage and it is easy to provide pockets of special growing conditions for individual plants with specific needs.

Twice when I tried to buy 50 pounds of granite chicken grit, the warehouse guys gave me oyster shell grit.

Or some other kind of shellfish grit.

Maybe double-screened crushed stone would work as well (dust and sand removed), if you can't find chicken grit.

Since I started screening my own pine bark shreds and nuggets, I haven't bought much grit. But I don't grow alpine plants.

P.S. Have you seen this vendor of Western US wildflower seeds? Huge variety of plants I never heard of before.

http://www.alplains.com/

Oh Rick, that is a most amazing site. Thank you so much for posting it.

As Lynn says, there are a lot of easy alpine plants, and also difficult ones. If you live in the mountains, they are easier to grow, in general, than at lower elevations. Alpine plants naturally grow in mineral soils with very little nutrition. The main thing is fast drainage. In containers, I use a mix that is approximately three-quarters mineral, one-quarter compost(or regular houseplant potting mix). The mineral component can include sand, pea gravel, grits of all types, pumice, limestone, perlite, etc. --- all different aggregate sizes. Try not to use all sand (or all small particle size), and never use the fine particled sand like what is used for cigarette depositories. Small particles hold much more water and have fewer air spaces. Varying particle sizes is best. For the compost component, larger particles are better, as they continue to decompose anyway.

An alpine container mix and my favorite compost material-Fafard 52 mix.



Granite grit is what is available for me, and sometimes it comes with an excessive amount of fine particles and rock dust. I use a regular window screen to sift the fine stuff out. In the mix above is sizes #2 and #4. As mentioned before, there are a lot of alpines that tolerate less than ideal soils, so you will find that this mix may not be needed for every alpine plant species.

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Alplains is a well known and respected seed source among alpine and rock gardeners.

Great explanation Rick.

Thanks, Lynn. I was awestruck by how much variety Alan has. The ordering process isn't glitzy or "modern", but he sent exactly what I asked for and pretty fast, too. If I recall, the per-packet price was very reasonable.

He even had detailed instructions for germination, including types and timing off startification.

I wish I could give him acorns! I did give him a good review here. It couldn't hurt if other people who think he's good add their comments to our Vendor Recommendations.

http://garden.org/reviews/view...

Thanks for the information, Rick R!

>> a mix that is approximately three-quarters mineral
>> all different aggregate sizes. ... Varying particle sizes is best.

Good to know!

>> Granite grit ... sometimes it comes with an excessive amount of fine particles and rock dust. I use a regular window screen to sift the fine stuff out.

When I got the #2 GRANITE chicken grit, it was immaculately free of dust, sharp and irregular. Perfect. But I agree that you have to remove the dusty fines and fine sand or wind up with no air in the soggy mix.

I wish I had something coarser than window screening (24 mesh?) I want it for for de-dusting bark fines.

Hardware cloth 1/8" mesh is too big - I want to retain 0.1" grains and fibers, in fact fibers as thin as 1 mm would be good for me, especially if they are longer than 3-4 mm. Say, do you ever worry about plant roots finding the endo-mycorrhiza they need, when we start them in mixes without much or any real soil? I keep looking at bottles or packets of mycorrhiza but they are expensive and don't stay fresh long.

Looking Fafard 52 up, I don't see that it has mycorrhiza added.

A thought:
What size mesh is the stuff crafters use to make rugs?

The subject of mycorrhizae is straying way of the topic here. If you would like to know what I think about it, you can treemail me or start a topic elsewhere and send me a link to participate. Or maybe there is already an appropriate topic somewhere here on ATP.

>> What size mesh is the stuff crafters use to make rugs?

I don't know, but at least it would be available in wide widths.

I have gotten some 1/8" black nylon mesh fabric, but it;s holes are larger than 1/8" hardware cloth. Next time I'm in a fabric store I'll look for a finer mesh. I can always use 1/4" hardware cloth to support the flimsy fabric.

What alpine plants do best in which type of soil

RickCorey said:>> What size mesh is the stuff crafters use to make rugs?

I don't know, but at least it would be available in wide widths.

I have gotten some 1/8" black nylon mesh fabric, but it;s holes are larger than 1/8" hardware cloth. Next time I'm in a fabric store I'll look for a finer mesh. I can always use 1/4" hardware cloth to support the flimsy fabric.

If you're out west in Washington, I bet you could find a rock shop that has sieves for gold panning. I got a sieve smaller than 1/8" hardware cloth that I use to wash sand. If you get official Tyler sieves for aggregate gradation, they're pretty expensive, but the gold panning ones I found were affordable. I found some on ebay, and I'm sure Amazon has them too, but I'm getting pretty sick of Amazon lately.