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Through the Garden Gate

Rain, Rain, Rain – Too Much Water Can Kill Plant
What an amazingly wet and windy winter and spring we have had. The rivers rose, the drains filled and the ground has become saturated. This is bad news for the many plants that do not like to have wet feet.

Wet feet is a major plant killer.  It happens when the soil around a plant is saturated with water for more than a day. This causes a lack of oxygen in the soil around the root zone, preventing plants from taking it up through their roots. This is exacerbated if there is a lot of organic matter in the soil because any available oxygen is used up as it decomposes. You might be able to detect a slightly septic smell and the plants will start to die.

The solution to wet feet is not to stop using organic mulches and compost. Organic matter is great as a soil conditioner and it helps to retain water in our usually dryer climate. What we need to do is observe the patterns of saturation or pooling and look for ways to improve drainage.

Planting in raised beds or on mounds is great for plants that like very well drained soil and in areas which can become very wet.  Work on the general premise that flowers and shrubs need about 30cm depth of well-drained soil around their roots and small trees need about 50 – 60cms depth of well- drained soil. Another option is to observe the drainage in your garden and select plants to suit each situation – harder to do with such climatic variation over time.

In an established garden, dig some small trenches to carry pooling water away or create some swales (small banks of soil), that will direct water away from particular areas. We have water that comes on to our property from the road. In the drought years that is no problem but when we have lots of rain, the last row of trees in our orchard can be sitting in water for weeks at a time. We built a bank which now directs that water away from the orchard and into a small catchment area.

It is harder for water to get away in some areas, particularly ones where there are hard surrounding surfaces, retaining walls or buildings. Look at adjusting the slope of the soil surface for more efficient drainage or raising the garden beds. We have put in a slotted agricultural drain to take water away from the little courtyard at the back of our house. Simple spoon drains at the edge of the hard surface can also re-direct excess water.

Plants in pots are also susceptible to wet feet, if the pot is sitting on the soil. I got a good tip when I visited a friend’s garden, where large feature pots were placed within garden beds, each one sitting on a flat rock to ensure good drainage.  

Plants which dislike wet feet include grevilleas, correas, maples, rhododendrons, proteas, weeping Cherries, silver birch, pittosporums, gardenias, azaleas, English box, figs, honey suckle, citrus, fruit trees, avocadoes, succulents, lavenders, roses, daphnes and other low water needs plants.  Plants which cope with more water include nandinas, photinias, liriopes, cistus (rock roses), hydrangeas, viburnum, wiegelia, alders, Chinese elms, plane trees, ash trees, callistemon, melaleucas, tea trees and some eucalyptus.

Happy gardening, 

Christine and Keith Windle, 

Garden Gate of Inverleigh Nursery,  0403 267 286     
cnr Winchelsea Rd and McCallum Rd, Inverleigh, 3321