Rain and other sea­sonal is­sues

The Tribune (NZ) - - GARDENING - WALLY RICHARDS

wal­lyjr@gar­de­news.co.nz

There’s been a wee bit of rain lately, and many plants do not like wet feet, or ex­cess wa­ter around the root zone.

Most semi-tropic plants hate wet feet, which ac­cen­tu­ates the ef­fect of lower win­ter tem­per­a­tures, and more of­ten than not they will die.

There are plants too that need a rea­son­able amount of oxy­gen in their root zone, and when sat­u­rated with wa­ter the oxy­gen goes and rots set in. Cit­rus trees are among these and will suf­fer and even die dur­ing wet times if their root sys­tems are sit­ting in wa­ter for too long.

I was sent a photo this week of cit­rus tree leaves that were curl­ing back on them­selves, and asked about the prob­lem.

The tree is one of a num­ber in a grove planted on rea­son­ably well-drained flat land in a sunny sit­u­a­tion with shel­ter from the wind.

Af­fected by curl­ing leaves and leaf drop, this tree was at one end of the grove. How­ever, nearby trees were start­ing to show signs of the same prob­lem while trees fur­ther away were ap­par­ently good as gold. The rea­son? The trees had been mulched. Mulches are a great way to re­tain soil mois­ture lev­els dur­ing dry times but this can be a big disad­van­tage dur­ing wet times.

Un­der the soggy mulch, the soil can’t breathe, mois­ture is trapped and then the roots rot.

A sim­i­lar prob­lem af­fected ex­pen­sive ornamentals another gar­dener had planted on a slope.

She had placed old car­pets down as a mulch to con­serve sum­mer mois­ture on the slope. Then win­ter comes. Rain falls, the ground gets soaked, wa­ter can’t evap­o­rate be­cause of the car­pet, roots rot, ex­pen­sive ornamentals die.

At a pre­vi­ous prop­erty of mine, parts of the back yard could re­main un­der wa­ter for weeks.

To solve the prob­lem caused by heavy clay soil and no drainage, I planted a twisted wil­low in the far cor­ner to soak up wa­ter.

A few cab­bage trees fol­lowed and as they ma­tured other hardy plants were able to sur­vive.

I also laid a length of Nova pipe which drained into a sump hole us­ing a sub­mersible pump to suck up wa­ter into the storm wa­ter.

Even then, pond­ing still took place, but I was able to grow cit­rus trees in con­tain­ers partly buried in the ground.

Large holes were drilled into the sides and base so the roots could pen­e­trate out into the sur­round­ing soil, but most of the roots were in com­post above the wa­ter level.

The re­sult was ex­cel­lent cit­rus trees that were happy in the mid­dle of a lake of wa­ter.

If you have cit­rus or other plants where the leaves are curl­ing and drop­ping then likely they are in wa­ter

soaked soil and their roots are rot­ting.

It could be that the trees have been there for years and no prob­lems in the past, but things can change.

New con­crete paths and foot­ings even on a neigh­bour­ing prop­erty can al­ter how wa­ter drains.

More rain­fall than nor­mal soak­ing the soil for longer pe­ri­ods does not help.

With cli­mate changes, ar­eas prone to heav­ier rain­falls will need to look at long-term so­lu­tions such as un­der­ground drainage sys­tems and soak holes. If your cit­rus (or other plants) are suf­fer­ing from wet feet, firstly en­sure that any mulch is re­moved.

Next, just out­side of the drip line dig a trench about one-and-a-half spade blades in depth and re­move the soil from the area. It is an old method that causes the wa­ter from the sat­u­rated soil to move into the trench where it will evap­o­rate more quickly through sun and wind.

Next spray the fo­liage with Perk­fec­tion Supa at full strength, and a month later at the lesser rate. Con­tinue for another 3-4 months.

This will help the tree over­come the root rot prob­lems if it has not gone be­yond the point of no re­turn.

For those who have had their prop­er­ties flooded, there will likely be a lot of river silt about.

River silt will en­hance the soil as it is rich in min­er­als and nu­tri­ents.

An ex­am­ple is the an­nual flood­ing of the Nile which en­riches crop­ping ar­eas.

As for sewage con­tam­i­na­tion, there is no need to pull out crops.

Sewage is great ma­nure; the only cau­tion is to wash pro­duce well af­ter har­vest­ing, to wear la­tex gloves when work­ing in the gar­dens and to

wash well af­ter­wards.

PHOTO: FAIR­FAX NZ

Rain­drops on le­mons are fine at the top end of the tree, but un­der­neath, wet feet can cause curl­ing leaves, leaf drop and even­tu­ally the tree’s demise.

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