The sausage tree (Kigelia africana) is a large tree of the Bignonia family (Bignoniaceae). Found throughout much of Africa south of the Sahara, it produces long hanging stems of blood-red flowers that are sometimes pollinated by insects or birds, but usually by bats. In fact, everything about the flower, from its open, cuplike shape to its musky scent, most intense at night, and its hanging habit (it’s placed well below the branches, out in the open where there are no obstacles bats will run into), is designed to attract bats. The flowers are followed by huge sausage-shaped fruits that measure 12 to 39 inches (30–100 cm) long and up to seven inches (18 cm) in width, each weighing from 11 to 26 pounds (5 to 12 kg).
Hint: never set your lawn chair under a sausage tree full of fruit, because if one of those babies comes crashing down on your head while you snooze, you’ll be toast!
The fruits are woody on the outside and tough to open, unless you have very strong jaws and a huge mouth … or you’re an elephant, a hippopotamus, a rhinoceros or a giraffe, all of which adore the fruits, although other animals, like monkeys and parrots, do manage to break them open to feed on them. Oddly, considering how so many wild animals relish the sausages, they’re toxic to humans, although can be consumed after proper drying, roasting or fermentation. Even so, they are rarely eaten as is, but rather used to make a beer like alcoholic beverage (leave it to humans to turn almost anything into alcohol!).
The fruits are quite a sight (and indeed, so are the flowers, dangling as they do from a rope-like hanging stem 6 to 20 feet [2 to 6 m] long!), leading the sausage tree to be planted in gardens in tropical gardens well beyond its natural range. However, the problem is how to pollinate the flowers. After all, with no pollination, there’ll be no fruit! And not many areas outside of the tree’s native range have the right flower-pollinating bats.
And that’s not the only complication: the flowers have to be cross-pollinated! Only the pollen from the flower of another tree will cause fruit to form. Even in Africa, isolated trees bloom their heads off, yet produce little to no fruit. Imagine the situation when there is only one tree in the entire country (the case of the Canary Islands’ one sausage tree, notably)!
Match-Making in the Midwest
And that brings us to the lonely sausage tree in the Lincoln Park Conservatory in Chicago, Illinois. You’ll see it as soon as you enter the door … but for years, it bore flowers galore, but with no other sausage tree for cross pollination, there was, of course, no fruit.
However, it turns out there is another sausage tree nearby. Well, sort of! It’s in the Mitchell Park Domes in Milwaukee, Wisconsin. That’s 90 miles away and in a different state. So far, there’s been no luck in convincing flower-pollinating bats to fly from one greenhouse to the other. In fact, there are presently no flower-pollinating bats in the region.
That’s why, when both sausage trees are in bloom simultaneously, someone from the staff of one of the gardens fills a basket with freshly cut sausage tree flowers and makes the 1-hour 40-minute trip to the other greenhouse, drops off the basket and picks up their basket of flowers, then immediately drives back so the pollen will be as fresh as possible.
Once the basket of blooms is handed off, gardeners in each greenhouse will climb up on stepladders and carefully hand pollinate each flower. With a little luck, small fruits will begin to form. If not, several more flower exchanges may be necessary.
When the fruits do form, visitors will be able to gawk at the huge sausage-like fruits that hang over their head and that can remain on the tree for months. That would be reason enough to visit the Lincoln Park Conservatory on its own, but it also includes a wide range of other spectacular plants and is well worth a visit in any season!
Why Not Plant a Companion Tree?
And the above begs the question: why doesn’t each greenhouse simply grow a second sausage tree from the now fertilized seeds? True enough, sausage trees can grow to monstrous sizes: up to 65 feet (20 m) tall in the wild, far taller than either greenhouse. However, by selectively pruning the trees, they can be kept at about 20 feet (6 meters) tall, as they are right now: large enough to bloom, yet small enough to fit into a large greenhouse structure.
As a laidback gardener, that’s what I’d do. Plus, I’d definitely release fruit pollinating bats into the greenhouse to make pollination even easier.
Oddly, I’ve had no offers to work at either of the greenhouses … but I’m still hopeful!