Drought Gardening

Speaker: Kelvin Mason
Date: 30th January
Year: 2019

Kelvin spruced up!

Kelvin Mason, our returning speaker has a wealth of experience and knowledge of Horticulture spanning over 30 years. He is a tutor at Sparsholt College in the Horticulture Department, and teaches RHS Level 2 and 3 Practical Horticulture Courses.

Kelvin is a well-established garden club speaker, a secretary for the Hampshire Federation of Horticultural Societies, an is also a member of the Institute of Horticulture and Groundsmanship, just to name a few.

We were expecting his usual expert and comprehensive advice, and we were not disappointed. His talk was centred around water recycling, conservation and watering methods.

The biology of plants was also covered, and for instance plants are 97% water, so if they dry out for a day and wilt they will recover if watered. If the plants are left dry for longer the wilt will become permanent and the plant will die.

Plants become stressed by drought and give off hormones, so that they can attract pests, watering plants well will help reduce the stress.

93% of the water uptake is from the roots and is transpired, leaving 7% to be used by the plant. Wildlife also suffers in drought conditions which is important as they keep the soil in good heart.

Different soils types are affected in many ways, for example sandy soil dries out quickly, clay soil holds onto water, as it gets trapped between dense particles. Clay soil needs organic matter to open up the structure, so that plants can access the water.

Different types of plants have unique water requirements, for instance tomatoes need a lot of water whereas cacti don’t, as their leaves are smooth and shiny, and also retain and recycle water. Mediterranean herbs grow well on dry soil.

Weather conditions are also an important factor, as windy weather dries out the soil by evaporation.

The Penman formula was developed in 1948 by Howard Penman as a semi-empirical equation combining mass transfer to measure evaporation from the land and sea.

If SI units (International System of Units) are used it gives the evaporation in kg/m2s. For example kilograms of water evaporated every second for each meter of area, therefore water must be supplied to put the water back.

Ideally the regime should be water well and then test how far the water has gone down. Roots are roughly 2” below the surface so the water must penetrate at least 2”.

Watering should be done in the evening for preference, and water once or twice a week for 1.5 hours. Two full watering cans per tree is recommended.

Water may be stored in butts or other suitable receptacles. Shop for discounted water butts from Southern Water for example. Rainwater which is slightly acid is best for most plants but not seedlings.

A covered water butt keeps the water sweet for ages, it gets dirty if not covered. Silver tablets can be used in water butts to kill off bacteria and butts should be cleaned out once a year. Several butts are the ideal connected to the house or greenhouse, 30,000 to 40,000 litres per year of rainwater fall in Hampshire.

Grey water can be collected from washing up, baths and dishwashers but should be used within a couple of days. There is no health hazard in the UK with grey water. Only washing machine water which doesn’t contain bleach can be used. Prioritise where you use grey/rain water.

To conserve water in the soil don’t dig or cultivate it in the summer. Regular hoeing will suffice to keep down the weeds, which don’t get as stressed as plants unfortunately.

Watering lawns too often, too little or at the wrong time of day promotes disease, moss, weeds, weed grasses such as annual meadow grass and shallow rooting. Better no watering than watering incorrectly! Plants should also be well spaced out to cope better with drought conditions.

Use organic matter to retains water, as this improves and breaks up the soil. Just mulch it on the soil surface for the worms to digest it. Green manure seeds can also be used and obtained from Cotswold Seeds and other gardening outlets.

Mulch with 2” of bark or 4” of wood chips, this helps to stop evaporation and keeps the soil cooler and leave a gap around the plant stem. Wood chips can be made into compost if left in heaps from 8/9 months, they do however leach nitrogen out of the soil. Other materials can be used as mulch, leaves, manure, cardboard, paper, and also commercial fabric mulch, this can last for years but is not organic.

Other useful tips

Use water retaining gels for tubs and containers then line them with plastic. Put coconut coir in the compost. Plastic bottles with the bottom removed can be dug into the soil, this is to get water down to the roots easier.

Kelvin spoke for an hour with no slides but he held our attention throughout with science, hints and common sense.

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