根据这张表，标号 #28 的筛子筛出来的是粗沙。#30 的筛子的孔的直径是 0.595 mm，#25 的筛子的孔的直径是 0.707 mm，所以粗沙大约 0.65 mm 或以上。
砾石（gravel）的分类是这样的：小的砾石叫 pebbles，尺寸范围是 4~64 mm；大的砾石叫 cobbles，尺寸范围是 64~256 mm；更大的砾石叫做 boulders。
培育树苗需要粗沙。养多肉植物也需要用 2~7 mm 粗沙。
从野外、沙滩、石场等野外采集沙子必须经过热水冲洗，更进一步拿到炉子里高温消毒两个小时。
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Horticultural sand - 园艺用沙
Horticultural sand is very gritty sand made from substances such as crushed granite, quartz, or sandstone. Horticultural sand for plants is often known as sharp sand, coarse sand, or quartz sand. Usually when used for plants, sand consists of both large and small particles.
If you have difficulty finding horticultural sand, you can substitute horticultural grit or builders’ sand. Although the substances may not be exactly the same, all can be used to improve soil drainage. Builders’ sand will probably save you some money if you’re improving a large area.
园艺用沙是由碎花岗岩、石英或砂岩等物质制成的非常坚硬的沙子。园艺用沙通常被称为尖砂、粗砂或石英砂。当用于植物时，沙子通常由大颗粒和小颗粒组成。
如果你找不到园艺用沙，可以用园艺沙砾或建筑用沙代替。虽然这些替代材料可能不完全相同，但他们都可以用来改善土壤排水。如果你要改善一面积土壤，建筑用沙可能会为你节省一些钱。
园艺用沙一般冲洗过的。直接购买园艺用沙比自己采集方便。
建筑用沙含有一些很细的沙，此时可以用筛子筛过达到自己满意的粗细。
我发现多伦多市中心的 Fiesta Farms 有园艺用沙，50 lbs 一袋只售 $6.99。
2022 年 12 月 22 日周四更新：去了 Fiesta Farms，它的 Horticultural sand 十分差，可能比Bag-O-Sand sand bags 还差，也可能比大店的建筑用沙差。
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grit - 沙砾
grit 指的是非常小的石头或者沙子——小的粗糙的颗粒。
比如砂纸的粒度（grit size）或者砂砾数（grit number）指的是砂纸磨出来的颗粒的标号，这个数字越高，磨出来的颗粒越细。
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Chicken grit / Poultry grit - 鸡砂 / 家禽砂
鸡砂/家禽砂的标号分别有：#1 (1/16” - 1.5875 mm)、#2 (3/16” - 4.7625 mm)、#3 (5/16” - 7.9375 mm)、#4 (3/8” - 9.525 mm)，也就是 1.5 mm 到 10 mm 之间，将最常见的 #1 和 #2 鸡砂混合起来完全可以替代粗沙，但是鸡砂/家禽砂也很贵。
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建筑用沙 Builder's sand
附近的 Home Depot Canada 和 Canadian Tire 都没有园艺用沙，但是有：
- Play sand: Quikrete Premium Play Sand 25kg - Model # 111325 - Store SKU # 1000166231 或 SAKRETE Play Sand, 20 KG - Model # 13003020 - Store SKU # 1000109167。不是建筑用沙。这种沙冲洗过，但是太细太细了。放在盆里一加水，沙子全部流走了。
- All purpose sand: Quikrete 20kg Quikrete All Purpose Sand - Model # 115022 - Store SKU # 1000739637。它的说明说：QUIKRETE All-Purpose Sand is a washed, properly graded coarse sand with multi-purpose uses. Meets ASTM C 33 specifications. Use For: Underlayment for Brick Pavers; Mixing with portland cement and gravel to make concrete; Traction on Snow and Ice; Mixing with potting soil. 它里面含有很细的沙，但是也有其他尺寸的沙，可以用。店里没货。
- Multi-purpose sand: SAKRETE Multi-Purpose Sand, 25 Kg - Model # 13001130 - Store SKU # 1000109251。它的说明 A general-purpose sand for use in landscaping, decoration and in custom concrete, mortar and stucco mixes.
- Bag-O-Sand sand bags: Our sandbags are perfect for the do it yourself home improvement homeowners or contractors working on jobs of all sizes. A mixture of sand and pea stone our sandbags are perfect for: Temporary Fencing, Water Diversion, Signs, And More. 不知道是否冲洗过。
最好查阅 Quikrete、SAKRETE 网站上的数据指标。
建筑用沙都含有很细的沙，可以筛掉他们。
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perlite 或者 vermiculite + peat moss 或者 coco coir
也可以用 perlite 或者 vermiculite + peat moss 或者 coco coir 替代粗沙。
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2022 年 12 月 23 日周五
买的筛子到货了，分别有四种尺寸的网格尺寸（毫米）：0.7、1、3 和 5。
5 mm 的网格用来筛出 grit 和 pumice soil；
1 mm 的网格用来晒出细砂砾；
0.7 mm 的网格推荐那些做盆栽的人用，去掉细沙细土。
用 0.7 mm 的网格把一袋 Bag-O-Sand 的沙筛和洗了，筛出来的细沙比从 Home Depot 买的 play sand 要粗。
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Rooting medium 生根培养基
PROPAGATION OF SPRUCE BY STEM CUTTINGS By R. M. GIROUARD 说：
For many years, the standard rooting medium has been medium-to-coarse sand. Experiments performed during the late 1930s showed that addition of a well-decomposed peat of sedge origin was vastly superior to sand alone, or to a peat moss of sphagnum origin mixed with sand. The ideal mixture contained two volumes of sand and one of peat. To my knowledge, no report published after 1945 mentions use of peat of sedge origin. The reasons for this may be that the material was too expensive, not readily available, or that plant propagators failed to recognise differences between peats of different origin. In the early 1950s, tests with fresh sphagnum moss, mulched or mixed with sand, gave interesting results. Since then, a mixture of fresh sphagnum moss and sand, 1 : 1 by volume, has become quite popular in several Scandinavian countries. Perlite and BR.8 blocks have given good results but are expensive compared with other materials. Recent unpublished data, obtained by the reviewer, indicate that sphagnum moss mixed with sand is superior for outdoor propagation to perlite or a mixture of peat moss and sand.
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ROOTING OF NORWAY SPRUCE CUTTINGS BY JOHN L. FARRAR 说：
The medium used for growing the cuttings was a coarse builder's sand, four inches deep in the bench.
结论是这样的：
... It will be seen that the cuttings taken December 17 are much superior to those taken four and eight 。weeks earlier and four weeks later. The rooting curve rises rapidly from October to December and then drops off slowly in January. ...The best treatment-which was no treatment...the long cuttings (10 to 20 cm.) were better than the short ones (Y to 10 cm.), and the cuttings without a heel of the old wood were superior to those with the heel...Nearly all roots originated from the extreme basal end of the cuttings...
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VEGETATIVE PROPAGATION OF 10-YEAR-OLD BLUE SPRUCE BY STEM CUTTINGS By ANNE M. WAGNER, JAMES T. FISHER, AND GREG A. FANCHER 说：
Treated cuttings were immediately stuck in 160 cms polyethylene containers (Ray Leach tubes) containing a 1:1 vermiculite/ perlite mix (v/v), to a depth of approximately 2.5 cm.
这篇文章的结论是这样的：
In summary, the single factor that overrode every variable examined was collection date. Hormone treatment altered somewhat the inherent rooting capacity, but could not completely compensate for non-optimum collection date. Within a tree, cutting position and length do appear to influence rooting success. Overall, a general recommendation for rooting of 10-year-old blue spruce would be to take short cuttings from the lower portion of the tree in December with no hormone treatment. From the results, 10-year-old blue spruce does not appear to be easily mass propagated from field-grown stock plants. However, on a limited scale, such as propagation of superior trees for a breeding program, it would be possible to successfully propagate clones en masse, but perhaps with a narrowing of the genetic base.
通过 cutting 来培育 blue spruce 成功率很低，不那么容易。
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akadama - 赤玉土
zeolite - 泡佛石
perlite - 珍珠岩，一种类似珍珠得颗粒状的灰色火山玻璃
vermiculite - 蛭石，含水的硅酸铝、硅酸镁、硅酸铁
