Ques­tions of po­plar (and other) in­ter­est

Winnipeg Free Press - Section G - - HOMES - MICHAEL ALLEN

IGET hun­dreds of re­quests for in­for­ma­tion about trees and shrubs ev­ery year. Here are a few I thought might have pop­u­lar in­ter­est for read­ers of this col­umn.

QUES­TION: For the last cou­ple of years, the leaves of my large po­plar tree turn yel­low in early Au­gust and fall from the tree. What’s go­ing on with them?

AN­SWER: The poplars are vic­tims of high sum­mer hu­mid­ity and heavy rain­fall. If you look at the leaves, you will see yel­low spots slightly raised above the leaf sur­face. These are in­fec­tion lo­ca­tions of the po­plar leaf rust, fun­gal dis­ease. You will also see grey blotches on the leaves. These are lo­ca­tions that have been dam­aged by the fun­gus.

As long as this leaf drop does not hap­pen year af­ter year, the trees will re­cover. Pro­longed in­fec­tions of this dis­ease over a num­ber of years will lead to in­jury to the tree. Col­lect the leaves and dis­pose of them. Do not leave them ex­posed in an open com­post pile as the spores in those in­fected lo­ca­tions can re-in­fect other trees in the fol­low­ing spring.

QUES­TION: I seem to have a yard full of un­healthy shrubs. They all seem to look sickly, es­pe­cially my cran­ber­ries, alpine cur­rants and roses. What can I do about this?

AN­SWER: In most yards I visit, I see a com­mon prob­lem: over­crowd­ing of woody shrubs. Of­ten the shrubs are ‘fight­ing it out’ for sun­light with trees. Many prop­erty own­ers tend to over­plant their yards and squeeze as much plant ma­te­rial into beds as pos­si­ble.

Over­crowded shrubs be­come dis­eased quickly, es­pe­cially dur­ing pe­ri­ods of pro­longed rain­fall and high hu­mid­ity. Mildew com­monly af­fects many shrubs, es­pe­cially alpine cur­rant, Euro­pean cran­berry, rose, lilac, ninebark, nan­ny­berry, grape vine, Vir­ginia creeper and oth­ers. Crowded dog­woods are in­fested with aphids. Cran­berry and Amur maple can be over­run with leaf mites and gall mites.

The sickly yel­low leaf colour of pink flow­er­ing spirea, rose and ninebark, co­toneaster, Ja­panese bar­berry (Rose Glow), Euro­pean el­der­berry, dog­wood and hy­drangea is a re­sult of poor ni­tro­gen lev­els made worse by heavy rain­fall leach­ing nu­tri­ents from the soil. These plants need to be fer­til­ized (24-8-12 is a good tree and shrub fer­til­izer) along with added iron chelate. These prod­ucts are avail­able from gar­den cen­tres.

Depend­ing on the prob­lem, there are usu­ally mul­ti­ple an­swers for re­me­dial ac­tion for all of these shrubs and vines. Typ­i­cally, the crowd­ing needs to end. Ju­di­cious fall prun­ing to re­duce the size of shrubs is ad­vised. I put on a num­ber of or­na­men­tal shrub-prun­ing cour­ses each year. Email or call me and I will send you a cur­rent sched­ule of cour­ses. Some shrubs are too large for the small space avail­able for them in some gar­dens and they should sim­ply be re­moved. Timely and proper fer­til­iz­ing will im­prove the health of nearly all shrubs once the crowd­ing sit­u­a­tion is re­solved.

QUES­TION: When is the best time to prune my fruit tree?

AN­SWER: Fruit trees, as well as al­most all other de­cid­u­ous trees, should be pruned when their like­li­hood of get- ting dis­ease is low­est. That time is the fall sea­son — usu­ally Oc­to­ber or Novem­ber. Many prun­ing books (printed in the United States) will tell you spring is the best time. Maybe if you live in spring frost-free ar­eas of Bri­tish Columbia, Ken­tucky, Mis­souri or Texas, but not the Cana­dian Prairies. Late­spring frosts can dam­age re­cently pruned ten­der woody shoots of fruit trees. No one can pre­dict dam­ag­ing frosts, but they are rare in early Oc­to­ber. This is by far the best time to work on fruit trees, es­pe­cially with no leaves in the way. I run prun­ing and fruit-tree care cour­ses that pro­vide suf­fi­cient in­for­ma­tion to prop­erly look af­ter fruit and other trees.

Left: Po­plar leaves turn yel­low early due to hu­mid­ity and rain­fall. Right: Mildew

com­monly af­fects many shrubs, such as Euro­pean cran­berry.

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