Blood flower and Silkweed

Blood flower noun - Tropical herb having orange-red flowers followed by pods suggesting a swallow with outspread wings; a weed throughout the tropics.

Silkweed and blood flower are semantically related. In some cases you can use "Silkweed" instead a noun phrase "Blood flower".

Silkweed noun - Any of numerous plants of the genus Asclepias having milky juice and pods that split open releasing seeds with downy tufts.

Blood flower and silkweed are semantically related. Sometimes you can replace phrase "Blood flower" with "Silkweed", this terms are similar.