Weather and soil conditions dictate which fruits and vegetables grow successfully on the North Island. Proficient gardeners adapt to those conditions, using various methods to diversify their crops and improve the quantity and quality of their harvest.
The following table illustrates weather facts and regional differences that are critical to plants – excess of rainfall over evaporation, summer temperatures, and quantity of sunlight:
North Island soils are quite variable but one aspect is common to them all: nutrients are concentrated in the clay and the organic matter. Those nutrients, the plants’ food, are soluble in water. Imagine placing a pumpkin and a tablespoon of salt in the sink and turning on the tap. The pumpkin doesn’t change, but the salt dissolves and runs down the drain.
So too are nutrients leached by all that excess, unevaporated, rainfall running through the soil and taking the nutrients with it. These leached soils tend to have low pH (acidic) levels. Vegetables generally prefer a higher, near neutral pH.
Poor drainage presents an even greater problem than leaching. Excessively wet soils directly damage crops both above and below ground. They are low in oxygen, which is essential for plant roots to function, and can harbour plant destroying fungi and toxic compounds, especially where there is stagnant water.
Improvement and Mitigation
Drainage can be improved and leaching mitigated. Raised beds, given the right soil, will drain efficiently. Swales, ditches, and drains to carry off excess water also work.
Add organic matter, as compost or mulch, to improve aeration and drainage. Organic matter holds nutrients more abundantly and more strongly than clay, improving nutrient availability and combatting leaching. Plus, it helps plants overcome soil pH levels that are too low or too high. Selecting cultivars which are tolerant of wetter soils or lower
temperatures and sunshine is important, as is choosing the most appropriate site available for different crops.
Use greenhouses, floating row covers, cold frames, cloches and polytunnels to raise soil and air temperatures and protect plants from rain damage. Reduce winter nutrient loss with cover crops and green manures.
All around the North Island there are healthy, abundant food gardens. Gardeners can and do meet the challenges!
Dawn Moorhead and David Lang are longtime practitioners of organic agriculture. They welcome your comments or questions at firstname.lastname@example.org