Per­fect mix for pot­ting power

Sunday Tasmanian - Tassie Living - - HOME - Tino Carnevale

HU­MANS have been us­ing pots to trans­port plants from camp to camp since pre­his­toric times. We have come a long way since then, and so have the plants the pots and the mixes in which they grow.

Many gar­den­ers of my grand­fa­ther’s and even my fa­ther’s gen­er­a­tion dug soil out of the gar­den to use in pots.

This can be a prob­lem as soil does not be­have the same way in pots as it does in the ground. Sandy soil will drain too well and then be­come hy­dropho­bic and clay soils can stay too wet and will set like con­crete.

There are a few qual­i­ties that a good pot­ting mix should have, one is that it should drain well and the other is that it should have good wa­ter ca­pac­ity.

This last state­ment may sound like a con­tra­dic­tion in terms but there are a few dif­fer­ent classes of wa­ter.

The mix should be able to hold onto wa­ter in its pores – this is called cap­il­lary wa­ter – but ex­ces­sive wa­ter should be free to drain away, this is re­ferred to as grav­i­ta­tional wa­ter.

A good mix should hold and re­lease nu­tri­ents well and it should have a neu­tral and sta­ble Ph.

In nor­mal gar­den soil, neu­tral Ph is about seven, this is when all the nu­tri­ents are un­locked and ac­ces­si­ble to plants, but in pot­ting mixes which are com­prised of a lot of or­ganic mat­ter, neu­tral is about 5.5 to 6.

You may have come across the term “air fi eld poros­ity” in re­la­tion to mixes, this just means how light and fl uffy the mix is.

This is es­pe­cially im­por­tant in re­la­tion to seed rais­ing mixes be­cause airy mixes mean good root devel­op­ment.

Most mixes should have a fairly reg­u­lar par­ti­cle size and they need to be dense enough to pro­vide the plant with good sup­port so it does not just fall over.

You can ei­ther start from scratch and make your own pot­ting mix or you can adapt an ex­ist­ing mix to your own needs.

There are sev­eral in­gre­di­ents you can play around with that will form the main part of your mix:

Coir fi bre: Has good wa­ter and nu­tri­ent hold­ing ca­pac­ity.

Coarse washed river sand: Is dense and adds struc­ture to the mix and also pro­vides good drainage.

Com­posted bark: Good nu­tri­ent and wa­ter hold­ing ca­pac­ity.

Mush­room com­post: Pro­vides good sta­bil­ity, wa­ter and nu­tri­ent hold­ing ca­pac­ity.

Ver­mi­culite: Good wa­ter and nu­tri­ent hold­ing ca­pac­ity.

Per­lite: Good to lighten the mix, it can be ad­vis­able to wet it down be­fore use as it can be dusty.

Fer­tiliser: This can be blended through the mix or added to the pot af­ter. Re­mem­ber, what fer­tilis­ers you use will de­pend on what plants you are grow­ing. Per­son­ally I pre­fer a com­plete or­ganic fer­tiliser as this feeds the pot­ting mix as well as the plant.

Seed rais­ing mix: Equal parts per­lite and coir fi bre. I mulch the top of the pot or tray with a thin layer of ver­mi­culite to pro­tect the young seedlings and keep them moist.

Cut­ting mix: Equal parts course sand and coir fi bre.

Ba­sic mix: One part course sand, one part com­posted bark and one part mush­room com­post.

There are many pot­ting mixes avail­able on the mar­ket and mak­ing your own will not nec­es­sar­ily be any cheaper but you are able to tai­lor the mixes to the needs of the plants you are grow­ing and it is also loads of fun. It is the gar­den­ing ver­sion of bak­ing a cake.

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