Gardening in Hong Kong: How to deal with pests in your garden this Spring
25 April 2013
Spring has well and truly sprung. This is the season when everything in the garden seems to double its rate of growth. The combination of higher temperatures and higher humidity brings a satisfying rush of new leaves and flowers on all sides, but the downside is the army of new pests and weeds, especially the dreaded Mikania micrantha (mile-a-minute) that seem to grow as you watch. Learn to recognise the unwanted seedlings and remove them before it becomes a major task.
Snails and slugs have emerged from hibernation and are chomping their way through everything as fast as they can to make up for lost time. Snail bait is the simplest way to keep them under control, but unless you can source a non-poisonous type (not available in Hong Kong, as far as I know) it’s not an option if you have pets or children. The only way is to be vigilant and catch the pests at work.
Spread a few lettuce or cabbage leaves in sheltered spots and you might catch a good haul of baby snails on the underside in the morning. For adult snails and slugs, the best strategy is to go out with a flashlight after about 9pm when you will be surprised at how many marauders you find, especially on a damp evening. It’s hard to believe, but I’m told that the destructive giant African snails can be eaten like French escargots. So far I’ve not been brave enough to test the truth of this for myself, but I dream of starting a cottage industry involving collection and export of wild escargots from Hong Kong. That would have everyone hunting these insatiable creatures to extinction in double-quick time.
This is the Year of the Snake and at this season snakes are just slithering out of hibernation. Some are still too comatose to take evasive action, so watch out when clearing undergrowth. French marigolds (Tagetes) are believed to control aphids and other insect pests and also repel snakes. Traditional local gardeners say Houttuynia (fish-cheeked mint), discourages reptiles. But it can rapidly spread to become a major pest that is hard to eradicate, so be cautious where you plant it.
If you saved pots of caladiums from last year they should already be sprouting new leaves once temperatures settle above 20 degrees Celsius. For best results re-pot them in a good rich mix. Three tubers to a 20cm pot will give a good show. Plant them about 2.5cm deep and water sparingly at first, increasing the water as the leaves start to grow. If the soil is boggy, they will rot. Caladiums will flower, but it’s not a spectacular bloom and as it drains energy from the main tuber, it is best removed from the plant when you spot it. If you left your caladiums in their pot through the winter and there is no sign of life, check carefully to make sure that the tubers have not rotted away through the winter or been eaten by cockroaches.
Caladiums need good light if they are to look really good. Some can thrive in the sun if they receive plenty of water. They will grow in full shade although the colours will be less striking and the leaves will look less healthy. Caladiums vary greatly in form as well leaf pattern and colour. Some will produce leaves up to about 60cm in length, although others will keep their dainty miniature proportions. Narrow-leaf types can generally withstand brighter light than the bigger leaves.
If you can source caladium tubers, they will be cheaper than buying a growing plant. Select the largest tubers that you can find as they will produce the greatest number of leaves. Hurricane Katrina virtually wiped out the major caladium growers in Florida, so tubers have been scarce in recent years. Now, however, supply is almost back to normal and if you look online you may be able to order some special varieties.
I have read that if tubers are planted upside down they will produce lots of small leaves rather than a few, large and spectacular ones. The challenge is to know which way is up. Sometimes you can see a few dried roots on what is the bottom. And if you feel carefully you may be able to detect small growing points for new leaves – this is the top end. When in doubt, plant them on their sides. Caladiums will do fine in the ground, provided the soil drains freely – mix in plenty of sand or perlite if necessary to help drainage after heavy rain. And watch out for them once they are dormant. In the growing season caladiums are greedy feeders and need regular doses of fertiliser with an NPK rating around 6:6:6.
Caladiums are tropical plants from South America. But even in the tropics their season lasts for only about six months before they need to rest. They are perfectly suited to Hong Kong’s seasons as they put on a great show through our hot and humid summers and are ready to rest during our cooler, dryer winter. Once they start to look tired it’s time to stop watering and fertilising them and move them to a sheltered place away from the rain. Once they have totally died back, you can remove the tubers from the pots and store them in dry sawdust, peat moss or perlite until spring. Or you can just leave them in their growing pots as long as you keep them dry and remember to tend to them before their next growing season starts.
On a recent visit to a local golf club I was impressed by the way the gardeners use sunken (empty) pots amongst permanent shrubs in borders and flowerbeds. It is a simple matter to drop in a plant in peak condition for instant effect. And the temporary plant can be removed equally easily when it is past its best to make way for something else. In Bangkok Airport I saw a similar technique used on high pedestals alongside a moving walkway. The central container held showy orchids that can easily be replaced as required, while the outer layer was of more permanent plants that formed a frame for the stars. This idea can be easily adapted to a variety of settings using whatever plants you have to hand. Caladiums are among the many seasonal plants that lend themselves to this kind of easy and effective display indoors or outdoors.
Jane Ram is a long-time Hong Kong resident, the immediate past chair and long-time committee member of the Hong Kong Gardening Society and a well-known broadcaster and writer on garden-oriented topics.