Best time to plant a tree? Prob­a­bly now

Roots get es­tab­lished in the ground be­fore stems grow in the spring

The Morning Call - - Life - By Lee Re­ich

Plant­ing a tree is one of the best things you can do to help the planet, and th­ese days it’s got­ten eas­ier. There’s a bet­ter un­der­stand­ing now of what trees need, in­clud­ing when they should gen­er­ally be planted (the fall).

Why plant trees? It’s well-known that trees mit­i­gate global warm­ing by tak­ing in and stor­ing car­bon diox­ide. Their shade can cool things down in sum­mer. As wind­breaks, they can slow heat loss. Their beauty and de­li­cious fruits and nuts are other perks.

Ex­perts used to rec­om­mend plant­ing trees in spring. But that’s changed for most species.

With spring plant­ing, there’s a dan­ger that stems can start to grow be­fore the roots are es­tab­lished in the ground. Fall plant­ing helps avoid that. Stems can’t grow un­til they have ex­pe­ri­enced a win­ter’s worth of cold. Roots, on the other hand, grow when­ever the soil tem­per­a­ture is above about 40 de­grees, so they can still make use of sum­mer’s lin­ger­ing heat in the ground.

Best plant­ing tech­niques are also eas­i­est

Smaller nurs­ery trees es­tab­lish more quickly in their new homes than larger ones, and usu­ally out­grow them.

But you don’t need to dig as deep as con­ven­tional wis­dom has held. New re­search shows that tree roots take hold best in a cone-shaped plant­ing hole only two to three times the di­am­e­ter of the root ball, and no deeper than nec­es­sary to stand the plant at the same level as it stood at the nurs­ery. Or higher, if a mound is needed for im­proved drainage. The shal­low hole sets plants on a firm base of undis­turbed soil that won’t set­tle with time.

The prac­tice of dump­ing gravel or some other coarse ma­te­rial into the bot­tom of the plant­ing hole to help drain away ex­cess wa­ter is an­other dated no­tion. What re­sults is the op­po­site of what was in­tended. A “perched” wa­ter ta­ble forms above the layer of gravel; it doesn’t drain un­til the up­per layer be­comes sat­u­rated.

Yet an­other myth is the rec­om­men­da­tion to mix plenty of com­post or other or­ganic ma­te­ri­als into the soil from the plant­ing hole. The idea was to cre­ate a fluffy, rich sub­strate for the de­vel­op­ing roots. But if you were a young root grow­ing in such a place, would you ever want to leave? No. Spread com­post and other or­ganic ma­te­ri­als on top of the ground as mulch.

Prun­ing? Stak­ing?

No need to do a lot of work with your prun­ing tools ei­ther. Myth held that the tops of newly planted trees needed prun­ing to bal­ance the loss of roots that oc­curred dur­ing trans­plant­ing. But many trees to­day are sold grow­ing in con­tain­ers, so they lose no roots at trans­plant­ing.

More im­por­tant is that for ev­ery kind of nurs­ery tree, the buds on stems, es­pe­cially those near the tips, pro­duce hor­mones that ac­tu­ally stim­u­late root growth. In gen­eral, limit any prun­ing to to­tal re­moval of a few stems rather than lop­ping back many stems.

Once a tree is in the ground, stak­ing is the tra­di­tional next or­der of busi­ness — an­other prac­tice need­ing re­con­sid­er­a­tion. Gen­er­ally, don’t stake a tree un­less it can’t sup­port it­self, if trunk move­ment causes the root ball to rock, or if wind might up­root the whole plant. Even then, sup­port for any young tree should let the top move freely and al­low for some wig­gle of the trunk, all with­out caus­ing abra­sion where the tie or ties make con­tact.

The sooner the stake or stakes are re­moved, the sooner the plant can de­velop a strong trunk and root sys­tem. With most small trees, re­move stakes af­ter one year; larger trees might re­quire stakes left in place for two years.

Watch­ing year-to-year growth of a rel­a­tively small, young tree is sat­is­fy­ing. Be­fore you know it, the tree will ap­pear as a bold, beau­ti­ful and use­ful ad­di­tion to the land­scape.

LEE RE­ICH/AP

Ja­panese and sugar maple trees in Bryn Mawr, Penn­syl­va­nia. Trees ben­e­fit our planet in many ways, as well as pro­vid­ing us with beauty, food and shade.

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