Ask Alex

“Do I need to lift my dahlias to get them through the winter?“

My answer:

Yes, if you want to be sure of keeping them. Lift dahlias, gladioli, cannas and other tender tubers and bulbs – before the frosts.  Or if they’re in pots, bring the pots in. Allow to dry out a little in a well ventilated, dry shed or garage and then store in a cool but frost free place that’s also well ventilated. You can leave them in their pots if you’re short of time, but they are more likely to rot, especially if the compost is very wet.

In March bring them into a light place, water lightly and watch for new shoots.  When they start to shoot water a little more and feed gently.   We recommend Osmocote Hi-K (high in potassium, to help flower production).  In May, harden them off by bringing them outside in the day but taking them in at night.  After all risk of frost has gone, you can leave them out at night.

If you really don’t want to lift these slightly tender plants, cover with a thick mulch of compost/bracken etc and cross your fingers!  In spring, watch out for emerging shoots, remove the bracken to let in the light and prevent moulds.  You will still need to protect them from frost, as well as from slugs/snails.

A customer at the Winslow Show asked:

“I have heavy clay soil that either sticks like glue or is rock hard – what can I do to improve it?”

My answer:

The soil at the nursery is heavy clay and here’s what we do:

  • We add well composted organic matter such as home made garden compost or ‘Mulch ‘n’ Mix’, laying it on the surface and forking it in gently (you don’t want to damage the roots of surrounding plants). Very well rotted farmyard manure can be used in spring or summer.
  • When creating a new bed or replanting an area, we grab the opportunity to add a 4”/10cm layer of organic matter and a 2”/5cm layer of sharp horticultural grit.  Manure is too rich to use in these quantities. We dig it into the top spade’s depth of soil and it helps keep the soil friable, maintain soil moisture in summer, reduce cracking, and (oddly) it helps drainage in winter.
  • When’s the best time?  Whenever you get around to it!  As long as the soil is moist…

“What’s the best way to get rid of slugs and snails?”

  • Do you really need to?  I recommend that we tolerate some damage, and only act to protect certain plants that are precious to us. That might be hostas, or veg, or anything.  I confess that this year they have been eating everything in sight, so I have had to take action myself.
  • Traditionally people used slug pellets to kill them, but there is lots of evidence that both metaldehyde and the (possibly less harmful) ferrous sulphate pellets can slowly poison the creatures that eat the slugs and snails that have eaten the pellets.

There are alternatives:

  • Use copper tape around pots and make sure the slugs/snails can’t walk across other plants to reach the plants in the pots you’ve taped. Or place your pots in a wide saucer and keep it filled with water – they don’t actually swim. Make sure the pot is propped up on something inside the saucer so that the plants’ roots aren’t permanently wet.
  • Using sharp grit as a mulch can help dissuade them

If you want to kill some of them:

  • Water on nematodes during warm weather, which invade the slugs and kill them; follow the maker’s instructions carefully to get best results
  • Use beer traps – they work, and the creatures die happy!
  • Collect them up using a torch when they’re out to dinner on a damp evening. Or during the day, look in hidden corners near the plants they eat – they’re lazy and don’t travel far.  You can also put down upside down grapefruit skins, plastic plant trays, or anything else to create an apparently safe home. Then:
    • take them elsewhere (but they may return)
    • or crush them if you have the stomach for it – the quickest and least cruel way? and you can leave the carcasses for the birds if you like.
    • or drop into a bucket of salty water.  Disgusting but effective. If they try to climb out of salty water, you haven’t put in enough.  Add more to kill them faster. I do not recommend sprinkling salt direct onto them in the garden, as the salt can harm other wildlife, and your plants.
  • If all else fails, if you’re determined to use pellets, use ferrous sulphate ones instead of metaldehyde, and use very sparingly, scattered thinly. Never pile them in heaps. Make sure dogs and children can’t reach them. Preferably put the carcasses you can find in the bin.

Or chill out, have a glass of wine, and forget about that veg you dreamed of eating on a beautiful summer’s evening.  There’s always next year!