We never stop learning about plants
Fascinating facts I’ve learnt from recent revelations
OVER the many years I’ve been involved in horticulture, I’ve never stopped learning new and interesting facts about plants and soils.
As an educator, it’s vital to keep up with the ever-growing range of new plant varieties, changes to plant names, novel growing techniques, innovative fertilisers and new horticultural technology.
To cap it all off, there are new things I learn that really aren’t all that new – facts that are well known within the inner circle of those who deal with say, a small range of plant varieties, but not well known to the broader horticultural community, and, yes, gardeners! (At this point it would be usual to refer to Donald Rumsfeld’s “known knowns and known unknowns”… but for sanity’s sake, I won’t!)
So how’s about we take a squiz at some “known unknowns” (KUs) of the horticultural world this week?
KU 1. I was very surprised to recently discover that many “seedless” grape varieties are treated with a plant growth hormone to make them large, plump and juicy for sale in supermarkets and fruit stores.
It’s a fact that many seedless grape vines produce quite small fruit, as most are closely related to the Sultana grape.
Growers of these seedless varieties discovered that spraying a growth hormone, gibberellic acid, on the flowering stems about two weeks after bloom, reduced the fruit set and lengthened the cells in the developing berries and made them larger.
What does this mean for home gardeners? Well, it means you may be disappointed with the size of your grape if you purchase varieties such as ‘Thompson Seedless’, and ‘Crimson Seedless’, and grow them in your backyard.
They’ll still produce grapes, but these will probably be very small when compared to those you see in the supermarkets. Some newer seedless varieties may be slightly larger than a Sultana grape, but many will not reach the natural size of seeded grape.
The largest seedless varieties are ‘Flame’ and ‘Fantasy’, with ‘Flame’ known to be available for sale in Australia for home gardeners. ‘Menindee’ is a beautifully sweet, medium sized seedless cultivar.
KU 2. Another interesting horticultural fact I discovered just this week is that European honey bees aren’t necessarily the major pollinators of many of our horticultural fruit, nut and vegetable crops.
I happened to bump into a past TAFE Horticulture student who has continued studying Science at university, and he mentioned that he had returned recently from assisting with research into pollination of North Queensland fruit tree crops.
It’s now been discovered that many other insects and animals can be more efficient pollinators of crops such as mangoes, the list including flies, beetles, moths, butterflies, wasps, ants, birds, and bats, among others.
We’re all probably aware that the honeybee population is in serious decline in the Northern Hemisphere, and is under threat in Australia as well due to the use of neonicotinoid insecticides and the effects of climate change.
It’s also been discovered that climate change, in reality, results in a population increase in the wild, native pollinators, replacing the services of the imported bees.
Two pollinators have already been recognised as major contributors, apart from honeybees, to fruit set in mangoes. One is the native bee, and the other, surprisingly, a blue blowfly. Another great pollinator seen in many of our ornamental and productive gardens is the hover fly, helping to spread pollen whilst devouring nasties such as aphids.
KU 3. A couple of weeks ago our gardening class decided to “whack on the waders” and clean out the pond at TAFE Horticulture.
There’s a wide range of aquatic plants to be found in our pond, including waterlilies, elephant’s ears, dwarf and tall papyrus, and nardoo.
Another plant that pops up each year, growing into a thick, submerged mass of thread-like, matted stems, and no roots, is the humped bladderwort, Urtricularia gibba.
This sometimes weedy plant generally will go unnoticed until it produces its small, yellow flowers on stems held above the water’s surface. Whilst it can be a very persistent pond or aquarium plant, its benign appearance masks a sinister secret, not known to many gardeners. Humped bladderwort is a carnivorous plant!
Attached to every one of the thousands of thread-like underwater stems are small, rounded bladders, topped with tiny hairs.
Each hair is actually a trigger, waiting for a minute pond organism to swim by. If the organism happens to touch one of the hairs, it causes the bladder to instantly expand, creating a vacuum that sucks the animal inside.
A small flap then closes over the opening and the animal is slowly digested by the plant, turning it into nutrients on which it lives. If humped bladderwort is present in your pond, it’s a sure sign of a healthy habitat for both plants and microfauna, so resist the urge to remove all of it!