Peter Cun­dall:

As soils warm and day­light hours in­crease, the most ur­gent gar­den­ing task now is to re­spond to the nu­tri­tional needs of our plants, ad­vises PETER CUN­DALL

Sunday Tasmanian - Tassie Living - - TASSIE LIVING -

It’s time to spring into ac­tion

It hap­pens ev­ery spring. As plants emerge from win­ter they ur­gently de­mand fuel. Spring is the cru­cial time when need for fer­tilis­ers is at its high­est and if many plants are left un­sat­is­fied, growth and vigour can suf­fer for the rest of the grow­ing sea­son.

The most ur­gent gar­den­ing task now is to re­spond to the nu­tri­tional needs of our plants as soils warm and day­light hours in­crease.

Dif­fer­ent plants have dif­fer­ent needs. There is lit­tle point in scat­ter­ing ma­nure and other fer­tilis­ers in­dis­crim­i­nately around. It’s the quick-grow­ing leafy plants that need high-ni­tro­gen fer­tilis­ers such as de­com­posed chook ma­nure or di­luted fish emul­sion.

In the vegetable gar­den the greed­i­est plants in­clude let­tuce, cab­bage, Brus­sels sprout, sil­ver­beet, Chi­nese cab­bage, ori­en­tal mus­tard, mizuma greens, Pak choi, rhubarb and spinach. All these plants ben­e­fit from be­ing grown fast and high-ni­tro­gen fer­tilis­ers reg­u­larly ap­plied dur­ing growth are the main driv­ing force.

Other veg­eta­bles that do well in a slightly less en­riched soil in­clude cel­ery, leeks and pota­toes. Many pop­u­lar veg­eta­bles have a sur­pris­ingly-low need for ni­tro­gen-rich fer­tilis­ers. They in­clude as­para­gus, zuc­chini, cu­cum­ber, car­rot, parsnip, globe ar­ti­choke, kohlrabi, radish, sal­sify, swede and turnip.

Legumes such as beans and peas can fix their own ni­tro­gen from soil at­mos­phere. They re­sent and even re­act against high-ni­tro­gen fer­tilis­ers and ma­nures. Even leaf veg­eta­bles such as broc­coli and cau­li­flower can be over-fed and re­spond by pro­duc­ing masses of leaves and de­layed heads or curds.

Over-fer­tilised car­rots and beet­root be­come ‘all top and no root’ and top­ple over. Should the soil also con­tain too much or­ganic mat­ter car­rots be­come too badly-forked to be of much use.

Long-keep­ing onions and gar­lic grown in ni­tro­gen-rich soil can be a dis­as­ter. They pro­duce bloated bulbs which are soft, fail to keep, have an in­sipid flavour are prone to fun­gal dis­eases and black aphid at­tack.

In the or­na­men­tal gar­den many at­trac­tive flow­er­ing shrubs have low ni­tro­gen re­quire­ments. They in­clude

Dif­fer­ent plants have dif­fer­ent needs. There is lit­tle point in scat­ter­ing ma­nure and other fer­tilis­ers in­dis­crim­i­nately around

rhodo­den­drons, aza­leas, camel­lias, er­i­cas, pieris, daphne, proteas and cis­tus. All these plants grow con­tent­edly with one feed a year, prefer­ably as a low-ni­tro­gen sheep or cow ma­nure mulch dur­ing spring.

Roses grow hap­pily with an oc­ca­sional sprin­kling of blood and bone with a lit­tle potash added while hy­drangeas thrive when reg­u­larly wa­tered with weak ma­nure wa­ter.

Most Aus­tralian plants grow con­tent­edly and strongly in rel­a­tively hun­gry soils, of­ten with­out any added fer­tilis­ers. How­ever, most re­spond if mulched an­nu­ally with well-rot­ted an­i­mal ma­nures but go very easy with chook drop­pings.

Sta­ble ma­nure when fresh can be deadly around all plants. Aus­tralian plants are es­pe­cially sen­si­tive. It is far bet­ter to pile it in a heap to thor­oughly rot down be­fore us­ing.

Na­tive plants from low-rain­fall dis­tricts are used to slightly-im­pov­er­ished soils and are best left un­fer­tilised in most home gar­dens. Some, es­pe­cially species of banksia, hakea, gre­vil­lea, aca­cia and most eu­ca­lypts re­act badly to even small amounts of su­per­phos­phate so avoid us­ing the stuff.

Al­most all plants grown in con­tain­ers are our pris­on­ers. They are to­tally de­pen­dent on us for their sur­vival and also have dif­fer­ent fer­tiliser needs ac­cord­ing to species.

Liq­uid fer­tilis­ers are prob­a­bly the best means of feed­ing pot-grown plants but they must be heav­ily-di­luted. They should only be ap­plied to pot­ting soil af­ter it has been given a good wa­ter­ing. It also pays to wa­ter again af­ter­wards to be dou­bly safe.

Most vig­or­ous house or tub plants grown for lush, at­trac­tive leaves in­vari­ably ben­e­fit from ex­tra-weak liq­uid fer­tilis­ers ap­plied monthly dur­ing spring and sum­mer. Such plants in­clude aphe­landra, Be­go­nia Rex and B. gran­dis, Solenos­te­mon (Coleus), fi­cus, mon­stera and philo­den­dron.

On the other hand flow­er­ing house­plants, es­pe­cially or­chids and African vi­o­lets bloom more per­sis­tently if fed with di­luted, potash-based fer­tilis­ers.

Un­less in a heated green­house, most con­tainer plants are not fed dur­ing win­ter in Tas­ma­nia

Cacti and other suc­cu­lents re­spond well to weak liq­uid fer­tilis­ers con­tain­ing a bal­ance of nu­tri­ents.

A small amount of sea­weed con­cen­trate added to com­post tea or heav­ily-di­luted liq­uid ma­nure en­cour­ages steady growth.

Dur­ing win­ter the pot­ting soil around these plants should be just moist with no fer­tilis­ers ap­plied.

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