Autumn is the time to clear the garden of spent summer crops and plan next season’s garden. Successful gardening needs good soil, the right plants for your climate and sunshine. We are lucky here as our temperatures rarely freeze, so we can grow most things year-round.
To combat some of the challenges with our coastal clay or sandy soils, it’s a good idea to grow plants in raised beds. These are easy to make and great if you have limited space or challenges bending down.
First choose a spot that has 6 to 8 hours of sun a day. If you are building the bed on lawn, put a layer of thick wet cardboard down first to avoid the grass growing through. You can buy kitset raised beds from garden suppliers, or make your own. Wood is a common material to use – if it is treated, staple plastic to the inside to prevent leaching of the chemicals into the soil. If untreated, the soil can touch the sides but that means it may rot after a few years. You can also use bricks, stones or recycled plastic – whatever works with your budget and creativity.
Ensure you can reach the middle of the bed from each side. Our community garden raised beds are 2m x 1m which seems to work well. The depth will depend on how high you want it – 60cm works well for us. Building it higher will help your back, but filling it can be expensive.
If you totally fill your bed with soil from the garden centre, not only will it be expensive, but your plants will only grow for a year before the soil is depleted and you will have to start again. To keep costs down it’s a good idea to fill the bed using the lasagne technique. This involves putting logs and sticks in the bottom to help drainage, hold water and, when they rot, they will release nutrients to the plants. Then layer up with green (kitchen waste, coffee grounds, weeds, etc) and brown material (leaves, cardboard, newspaper, etc). This way you have ongoing nutrients available to plants. Finally, about 10cm from the top, add compost and potting mix from the garden centre or landscape supplier. This layer will be ready to plant in. Choose your plants according to the season and your taste and keep moist.
In our garden this season we are planting broccoli, cabbage, lettuce, cauliflower, coriander, carrots, beetroot, silver beet spinach and radish, as well as flowers for the bees.
Every change of season, add some compost. Feed with an organic fertiliser once a month in autumn, but reduce that as winter comes. You can make your own organic fertiliser (more on that in future columns).
One way of keeping heat in the soil as winter approaches is to give your plants a ‘blanket’ of mulch (pea straw, shredded newspaper, woodchips, any organic material) spread on top of soil. This will help crops to produce flowers or fruit for a little longer and feed the soil as it breaks down, while keeping in moisture and suppressing weeds.
To see some examples of raised bed growing, visit Ōrewa Community Garden, 216 Hibiscus Coast Highway on any Wednesday or Saturday 9am-11am and we can talk you through the process. Happy autumn gardening!