Blue spruce

Alberta Gardener Magazine - - Contents - By Dorothy Dob­bie

Tall and stately, one of the most beau­ti­ful ev­er­greens is Colorado blue spruce. A na­tive of the Rock­ies in Western Amer­ica, it has be­come widely dis­persed as an or­na­men­tal tree, adorn­ing gar­dens and parks all over Canada and the United States. It is hardy in zones 2 to 7. The Colorado blue spruce (Picea pun­gens) has sil­very blue nee­dles and a lovely pyra­mi­dal shape. It grows from 50 to 75 feet in a city gar­den and can spread 10 to 20 feet – even be­yond, if it’s per­fectly happy. A moder­ately slow grower, its strong leader takes it up 12 to 24 inches each year if it is in full sun. Near its crown in the up­per branches, light brown cones hang down three to four inches and are much beloved by squir­rels. To keep blue spruce free of its troublesome pests – adel­gas gall mites, spruce bud worm, spi­der mite and pine nee­dle scale – spray the tree with a wa­ter hose two or three times a sum­mer. This will help to dis­lodge any of the shel­ter­ing beasts be­fore they be­come too com­fort­able in the tree. Keep an eye out for any sooty mold and clean the branches of this in­fec­tion as you work. The hose will re­move some of the pow­dery white coat­ing on the nee­dles, which gives the tree its blue cast, but it’s worth do­ing to keep the tree healthy. The new nee­dles that are pro­duced at branch tips each year will bring back that blue glow.

Blue spruce also be­comes host to nee­dle cast dis­eases, which are most troublesome in cool, wet weather. There are two dif­fer­ent types and both are fun­gal dis­eases that man­i­fest in lit­tle black dots, re­plac­ing the white stom­ata (breath­ing ves­sels) on the un­der­side of the nee­dles. The tree will be­gin to turn a brown­ish-pur­ple and then the older leaves will be­gin to die and drop. Treat with fungi­cide be­fore the dis­ease takes over and be sure to keep your tree well fer­til­ized and prop­erly hy­drated so that it can fight off any in­fec­tions be­fore they get too se­ri­ous.

If treated on time and for two or three years, your beau­ti­ful blue spruce can re­gain its good looks so it is well worth the trou­ble of treat­ing it.

It should be noted that blue spruce lose their older nee­dles ev­ery four to ten years from the branches near­est the trunk. New growth ap­pears at the tips. Stress can ac­cel­er­ate this process. If the loss seems overly rapid, check for spi­der mite. Hold a sheet of white paper un­der a branch, shake vig­or­ously, then smear your hand across the page. If red streaks ap­pear, it is spi­der mite. Turn on that hose.

For­tu­nately, deer are not at­tracted to blue spruce, thanks to the inch-and-ahalf-long, sharp and strongly scented nee­dles.

Use in the land­scape

While a lone blue spruce makes a lovely state­ment of its own, re­mem­ber that this mag­nif­i­cent tree needs a fair amount of space so be sure your yard is large enough to han­dle it.

It can also be used as an ef­fec­tive wind­break or hedge on a large prop­erty. Plant the trees 10 to 12 feet apart so that the adult tree branches will min­gle with those of its neigh­bour.

There is also a colum­nar blue spruce, (Picea pun­gens ‘Fasti­gata’) that grows in a cigar shape and adds six to 12 inches a year in height, even­tu­ally reach­ing 15 to 25 feet with a spread of three to six feet. The fo­liage is steel blue and it keeps its tidy shape with­out need for prun­ing. It can also be used to make a hedge. There are weep­ing, pros­trate and dwarf forms of this blue tree as well.

A blue spruce can make an em­phatic state­ment if planted in a group­ing of trees with con­trast­ing leaf colours – pur­ple leafed cher­ries or au­tumn blaz­ing Amur maple. Just re­mem­ber how big they get.

Keep­ing your blue spruce blue

The blue cast on the nee­dles is ac­tu­ally from a pow­dery look­ing, waxy sub­stance that coats them, help­ing to keep mois­ture in the nee­dles. To keep the colour, avoid ex­pos­ing the tree to abra­sive winds or other con­di­tions that will af­fect the coat­ing. Wa­ter your tree at the soil line and fer­til­ize with a fer­til­izer cre­ated for acid lov­ing plants in spring – not past July 15. Make sure the tree gets enough sun­light – at least six hours a day. Slow down wa­ter­ing in Au­gust and Septem­ber then wa­ter well in Oc­to­ber.

You can ex­pect some dark­en­ing of the leaves in win­ter. The blue tone will re­turn in spring­time.

The sil­very blue nee­dles of the Blue Spruce.

Spruce tip blight blue-green-yel­low rust tran­si­tions.

Nee­dle cast.

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