Tag Archives: cabbage whites on brassicas

In the Garden: March 19, 2010


The rows of corn in the garden are interplanted with food for the butterflies here

The rows of corn in the garden are interplanted with food for the butterflies here


  • The push hoe is an invaluable tool but one best used in dry conditions when severed weeds can be left on the surface to wither. This means that our current dry early autumn conditions are still a good time to do a push hoe round. This week’s rain has only penetrated the top centimetre or so of the soil here and unless we get some gentle, steady rain over a few days we will remain dry a while longer. Hoeing also gently tills the soil and discourages the build up of liverwort and moss which you see on compacted ground. Keep your hoe sharp for best results – using a file on it is fine.
  • Naturally everybody has heeded our oft repeated advice and rushed out to plant brassicas in abundance for winter. Keep an eye on the white butterflies which may be hovering around your plants and laying eggs already. The hatching caterpillars will wreak havoc on your baby plants. They will be less of a problem when colder, wetter conditions set in but you may need to take action now. If you don’t wish to use a proprietary insecticide, you can resort to common flyspray for a quick hit or one of the organic based oil sprays (up to 10 ml of light cooking oil and a squirt of detergent per litre of water). Thuricide is a bacterial spray that attacks the caterpillar gut and is effective and selective (only attacks the one target) – you can buy it from your garden centre. If you have a really heavy infestation, you may need to spray and then cover your crop with old net curtaining to prevent reinfestation.
  • If you have cauliflower or broccoli maturing already, bending the outer leaves over the head is the practical and time honoured means of stopping sun burn on the edible portions.
  • Start the autumn feeding round now while plants are still in growth and can absorb the nutrients. It is a waste of time and money to feed when conditions are cold in winter and plants are dormant or semi dormant. More is not better with fertiliser and if conditions are too dry, it can burn the foliage so keep to recommended application rates and preferably spread it immediately before rain.
  • It is trimming time for formal hedges. We plan an Outdoor Classroom on the topic next week.
  • It should be safe to sow grass seed for new lawns now although you may have to get the hose out if we get another dry spell. What you don’t want to happen is for the seed to germinate and then fry in sunny, dry conditions so keep an eye on it.
  • We are enjoying a fantastic crop of sweet corn here and Mark, who harvests it only as required so it is a matter of minutes from being picked to being cooked, is warning that there is a veritable deluge of corn to come over the next two to three months. This compensates for the lack of onions and water melons this season.

November 13, 2009 In the Garden

  • We are starting to dry out already. Keep a close eye on container plants. If they are showing signs of stress, it is likely they are either badly root bound (should have been potted on when we told you in winter), hungry or dried out. To get water back into dehydrated plants, a squirt of dishwashing detergent or surfactant will help absorption. However, ignore any advice given elsewhere to add water holding crystals (also called Crystal Rain) to potting mix for anything other than annuals. In our climate with high rainfall, woody plants and perennials will rot out in winter if you add these crystals, however tempting it may be in summer to use them. Partially burying pots and containers into the garden (called plunging) can reduce excessive drying out. It also stops pots with taller plants from blowing over in the wind.
  • It is late in the season for planting out woody trees and shrubs, especially if they are large or root bound. Our advice is to heel them into the vegetable garden until autumn. If you are determined to plant into other garden positions, make sure that the root ball is soaked right through. A watering can just will not do. It can take hours (or leave overnight) to get the water into the middle if it is very dry. Once planted, mulch to conserve moisture and keep an eye on the plant until Christmas at least to ensure that it has not dried out again.
  • If you spray for thrips on rhododendrons (the leaf sucking critters which cause silver leaves), get the first application on when you see the insects on the under side of the new growth. We are not keen on this practice and will only spray one or two special plants ourselves. We would be much happier to hear of gardeners opening up around the plant to encourage air movement, feeding and mulching to encourage more health and vigour and taking out plants which are particularly susceptible to replace with healthier selections. We have drawn a line under many of the cold loving German and American hybrids here and said that we just can not grow them well in our mild, coastal conditions.
  • It is the optimum time for planting kumara runners. This is one plant which really loves warm, light soils.
  • As soon as we get more rain, fungi are likely to attack potatoes and tomatoes. A copper spray applied as soon as the foliage has dried out after rain is usually necessary if you wish to guarantee a harvest later.
  • Brassicas will be under siege shortly, if not already, from much of the insect population and in particular the dreaded cabbage white. This is the single biggest reason for not growing brassicas for summer harvest in our climate. If you don’t wish to spray with an insecticide, you have to start getting creative with old net curtains and the likes. However, this only stops the cabbage white laying more eggs and does nothing to deal to existing caterpillars in residence. We will be eating our remaining brassicas soon and not replanting until autumn, with the exception of brussel sprouts which are best sown in the summer for harvest next winter.
  • Leeks can be sown now.