Plants and Tips for Clay Soils
Check out all the plant varieties that we have tested in our local soil here.
Within Horfield, Filton, Bishopston, Ashley Down, Lockleaze (apart from the very north end of Landseer after the turn off for Hogarth Walk), Southmead (to the east of Coleford Road and to the north of Greystoke Avenue), and Henleaze (to the east of Henleaze Rd/Linden Rd) we have lime-rich loamy and clayey soils with impeded drainage (source: the Land Information System www.landis.org.uk/soilscapes).
That means our soil falls between a clay and a loam, and between poor drainage and well-drained. It is also reasonably fertile, and it it alkaline (the opposite of acidic).
This applies to the places within the sandy brown
area of the map.
Our soils can be considered 'moist but well-drained'; they have some drought resistance but aren't heavy clay. They don't need a lot of added fertiliser (depending on what you are growing). Plants that like chalk should do well provided they don't need a very well-drained soil, whereas plants that need acid soils won't thrive without the addition of ericaceous compost.
Within the area on the map, there will be some variation. Your garden may have a clay-to-loam soil with reasonable drainage, but also patches of ground that get waterlogged. It is worth looking out for these because most plants will die in waterlogged soils. If you spot water pooling on the surface after heavy rain this can be because 1) the underlying drainage is poor, 2) the soil has become compacted* or 3) the water table is high after lots of heavy rain. To find out which of these is the cause of the water pooling and to help you decide what to do next, all you have to do is dig a hole.
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When the weather is going to be dry for a day or two, dig a hole that is 60-100cm deep. If the hole fills with water as you dig it then the water table is currently high and you will need to wait for it to drop to test how well your soil drains. Once you have an empty hole and some free time, fill the hole with water. Check back every 15 minutes or so and record how long it takes the water to drain out of the hole. If it takes over six hours then this is classified as poor drainage. When we tested a wet part of our Horfield garden the water drained in 4.5 hours so the drainage was on the slow side (impeded) but not classified as poor and is good for plants that like a 'moist but well-drained soil'.
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*Clay soils will become compacted if people (or vehicles) walk over them in wet weather. If there is an area of your lawn that you regularly walk across you will probably notice that the grass doesn't do as well and water pools on the surface in winter. This is bad news for worms and bad news for plants because their roots are starved of oxygen when the soil is waterlogged. If you have a clay soil then the good news if that it's not a good idea to do a lot of gardening in wet weather!
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