FOREST iNURSERY PRACTICE 149 



and dry conditions follow closely after each other and it is thought that 

 this systemn may have some value in controlling damping-off. At most 

 of the nurseries half shade is provided and there is a tendency to use 

 such shade during the tirst season only. Bull pine (pinns ponderosa) 

 has been grown at the Wasatch nursery without shade with good 

 I'esults and there is a possibility that northern nurseries may be able 

 to produce better seedlings of certain species without shade than with 

 it. In either kind of shade frame the lath should extend from north 

 to south rather than rrom east to west since a continual change of shade 

 is secured. 



If high shade frames are to be used large posts are necessary. 

 Such posts should extend at least seven feet above ground in order to 

 allow a man to work while standing erect without striking connecting 

 two by fours. It is generally considered that these posts should be set 

 in rows 8 to 12 feet apart each way and wherever possible such posts 

 should be treated with preservative to lengthen their life. This is 

 needed because of the large amount of artificial watering which is often 

 necessary in forest nurseries and which tends to rot posts more rapidly 

 than would otherwise be the case. Creosote paint, tar, charring, and 

 charring with tar applied afterward have been used. Usually two by 

 four stringers are used to connect the tops of the posts from north to 

 south. Similar stringers may be run at right angles but are not usually 

 considered of sufficient advantage to pay for the increased cost. Wires 

 are used in place of the two by fours by some nurserymen being run 

 at both right angles and diagonally in order to give sufficient strength. 



Overhead shading may be provided by machine woven lath. Building 

 lath are connected by five double strands of woven wire and are spaced 

 according to the amount of shading desired. In southern California a lath 

 house was constructed in which the lath were nailed to two by fours and 

 other smaller stringers overhead and on the exposed sides of the nur- 

 series. The cost of the high shade frame system varies from $800 to 

 $1500 per acre according to local conditions. The woven lath may be 

 purchased at 40 to 80 cents per running yard according to closeness of 

 bids and freight rates. Stripes of woven lath 180 to 200 feet long may be 

 streched by the use of a windlass or a block and tackle. The disadvant- 

 ages of the system consist of the high cost, impossibility of carying light 

 and heat conditions, and the necessity of covering paths as well as beds. 



Small aspen poles have been used in place of lath in the high shade 

 frame system in Colorado and brush is likewise used by some of the 

 commercial nurseries. Peeled poles are desired as the falling bark inter- 

 fores with the beds. This system furnishes irrugular shade and may be 

 built much cheaper than when lath is used. 



Low shade frames, 12 to 24 inches above the seed beds, are usually 

 constructed from lath and stringers smaller than two by fours. If these 

 materials are not at hand in mountain regions one can frequently induce 

 a sawmill man to saw to order whatever may be needed. It is usually 



