The Garden House Tasks for March

Posted:21 March 2025

Weather watching is essential as sunny days can give you a false sense of security – so check night and day time temperatures and don’t be tempted to either sow seeds to early or put out your tender plants until much later when danger of frost has past – usually late April – or mid May here in the south.

Please bear in mind these tasks are not a comprehensive look at all garden aspects, but relate directly to our monthly work in the Garden House garden, inspiring and teaching the volunteers, students and Friday group gardeners who get stuck in and support the development of this unique Brighton garden.

Continue to sow hardy annuals and also perennial seeds – don’t forget they will all need pricking out and potting on so go easy!

You can begin sowing half hardy annuals but not until later in the month – the light levels will be higher then and it will also be warmer (fingers crossed).

Start off Dahlias in pots under cover – protect with horticultural grit so emerging shoots don’t get eaten.

Finish pruning roses before they start to come into leaf.

Also prune Buddleja davidii, Caryopteris clandonensis, Ceratostigma, Hydrangea paniculata, Leycesteria, Lavatera, Perovskia and hardy Fuchsia creating a neat framework. 

It is also time to prune back late summer and autumn flowering Clematis to a pair of healthy buds around 30 cm from the base – always feed and water after pruning

Weeds will begin to germinate now so familiarise yourself with the weeds in your garden so you can recognise the seedlings – much easier to remove with a hoe

Watching the sown seeds is a twice daily task – and pricking out begins as soon as the seeds are large enough to handle – Great Dixter begins pricking out before the true leaves appear so we will try that method this year – it is said to develop better roots.

Cut down all the deciduous grasses now and make sure that the new growth remains intact.

Plant out herbaceous perennials now and note where they are to avoid other perennials already coming up.

Make sure tomatoes, chillies and aubergines are sown by the end of the month.

We are trialing growing salads in gutters and boxes – a variety of leaves, including mizuna, rocket and cress.

Mulching borders with our home made compost is important at this time of year – try to add 10 cm of the mulch of your choice, eg community compost or homemade compost to suppress weeds, retain moisture and act as a duvet when the temperatures drop.

Start slug prevention on Hostas, we are going to try a garlic spray this year (our recipe below!). This needs to be applied regularly to avoid slug and snail damage:

• • Boil Garlic: Place the garlic bulbs in a pot of water and bring to a boil.
  • Simmer: Reduce heat and simmer for 15-20 minutes, allowing the garlic to infuse the water.
  • Cool and Strain: Remove from heat, let cool, and strain the liquid through a fine-mesh sieve or muslin cloth to remove the garlic pieces.
  • Add Soap (Optional): If using, add liquid soap to the strained liquid.
  • Dilute: Dilute the concentrated garlic liquid with more water (approximately 1 part concentrate to 4-5 parts water).
  • Store: Store the diluted spray in a clean spray bottle.