Tree Stuff Blog
Organics in a Commercial Nursery, by Ben Gaia
www.dialatree.co.nz


Dial-a-Tree Nursery is a bit different. It is totally organic. We use no fungicides so any trees liable to rot have already been selected out. A garlic/chilli solution is sometimes sprayed to deter fungus and psyllids. Our soil is full of natural micorrhizae which catalyse mineral uptake by plants. Fungicides would remove these helpful fungi. No chemical fertilisers or pesticides are used. The potting mix is a compost base. Organic plant foods feed the trees without pampering them with excess nitrogen, and seaweed and fish based fertilisers add essential trace elements for slow release nutrient supply. There is a large population of beneficial predator insects and spiders which keep pests in check.

Willing wild birds like wekas and blackbirds sift through the plant area removing slugs and snails. Fantails and moreporks keep moths to a manageable level, encouraged to the nursery by the planting of native trees. Despite what many nurseries would regard as a messy chaos full of liverwort, spiders and lichen, Dial-a-Tree Nursery supplies healthy robust plants that transplant and recover well in their new homes. We ship hardy trees all over New Zealand, making a living for about half the year.

Could all nurseries go organic? Some years ago I worked in a friend's large commercial nursery in which he grew thousands of pines and eucalypts, as well as lots of shelter natives, for the Canterbury area. Whilst we share some techniques in our nurseries such as hand weeding and laying down thick pine sawdust or chip for a shadehouse floor, Mark was very conventional, and loved his pre-emergent herbicides and fungicides and slow release fertilisers. Consequently, growing tons of identical forestry trees in small rootrainers, his nursery looked tidy, uniform and professional. On the other hand, there were always areas of weeds in the back which had got away due to lack of hand weeding, but these would be mercilessly sprayed and eventually cleared up. Some weeds became spray resistant - particularly rosebay willow herb, threatening to be "superweeds". The trick is always to weed them out before they seed everywhere.

Then I too tried to raise thousands of pines and eucalypts in my own wet, shady West Coast back yard with up to 12 metres of annual rain, snails and moulds. I found that neither species thrives in bulk when young; and my success rate from seed to saleable tree was about 3% in each case. I concluded that bulk pines and eucalypts probably cannot be grown well organically.

But in looking for alternative bulk forestry species that will handle fungus- and moth-filled shadehouses I ended up growing Cypresses and Cedars, as forestry species, along with native shelter and exotic fruit plants. All these strike well and survive at over 80% from seed to sale. Despite moth caterpillar challenges, dealt with by hand control and pepper sprays, proud rows of large rootrainers now hold good healthy tree stock with few weeds, and very little fungal die-back.

Organics in a tree nursery doesn't mean hippy tree worship, but practical methods of reducing chemical dependency and fostering a whole ecosystem around the nursery which supports its tree growing aims. Money saved on expensive sprays can be spent on hand weeding, which if done in a timely way can interrupt all weeds from seeding. Within a few seasons weed invasions are much lessened. Reading the needs of the plants you grow and reacting to them with, eg, less or more water, or a foliar feed, is part of the tree nurseryman's art learnt over the years. Training your helpers to recognise and remove problem big-rooted weeds like clover and puha at an early stage is important to avoid having to re-pot plants.

To be continued...




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