Broom species identification (genus Cytisus)

Broom species (“Giesta” in portuguese) of the genus Cytisus are all invasive species in Madeira Islands. After their introduction they have become naturalized and now dominate vast areas, replacing native and endemic species of the islands flora. Due to their aggressive seed dispersal broom removal has proved very difficult.

Well, if we cannot eradicate it easily at least we can try to appreciate it a little. In spring/summer you can find much of the landscape covered by yellow (or white) which can be a beautiful sight. And knowing how to tell the different species apart can make you find it less monotonous when you walk through a broom landscape, and it can help you understand to what extent each species has expanded its territory in Madeira.

The Cytisus species present in Madeira are:

  • Cytisus scoparius (common broom)
  • Cytisus striatus (hairy-fruited broom)
  • Cytisus multiflorus (white broom)

Color of flower

The C. scoparius has yellow flowers (sometimes with a reddish tinge), the C.striatus has yellow flower and the C. multiflorus has white flower.

Fruits and seeds

When there are no flowers around you can identify the broom species by observing its fruit. The C. scoparius has flattened fruits that have hairs only at the edges. The C.striatus has shorter more rounded fruits that have hairs all over it. And C. multiflorus has flattened fruits (usually shorter than C. scoparius) and hairs all over it (shorter hairs than C. striatus). See the image:

Cytisus-scoparius-striatus-multiflorus-fruits

The seeds of each of the Cytisus species:

Cytisus-scoparius-striatus-multiflorus-seeds

Stems

When there are no flowers nor fruits to observe you can still identify the broom species by observing its stems. The C. scoparius has ribbed stems usually with 5 ridges. The C.striatus and C. multiflorus are also ribbed but they have about 8 ridges. The difference between them is that C. striatus has less space between ridges than C. multiflorus (When I tried to introduce my nail between ridges I was able to do it in C.multiflorum but not on C.striatus). See the image:

Cytisus-scoparius-striatus-multiflorus-stems

Cytisus identification Key

There are other ways to distinguish the species. The ones I told you about are the ones I find more easy to use myself. If you are looking for a more precise way to tell the Cytisus species apart you can use the following Cytisus key [1]:

1. Corolla generally white, dark or purple lines or spots or not; banner < 10 or 10–15 mm ….. C. multiflorus
Corolla pale or golden yellow; banner generally > 10–25 mm ………………………………………… 2

2. Calyx glabrous; fruit flat, glabrous except margin; branches generally 5-angled ……………. C. scoparius
Calyx appressed-hairy; fruit ± inflated, densely white-hairy; branches generally 8–10-angled …. C. striatus

Other broom species

There are also endemic broom species in Madeira

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