Barrel cacti

Echinocactus grusonii. This is one of the most popular cacti for collectors. The one in this photo is now over 12cm. in diameter.
If well looked after it can eventually grow to be over a metre wide. As it gets older the spines become a deep golden yellow.
The yellow flowers grow from the crown but you need to be patient s they will not appear until it is as big as a football which is several years away.

It is however a handsome plant and is easy to grow in a sunny greenhouse. If there is no heat it should be brought into the house for the coldest months of the year.
It makes a useful blip when it is pouring with rain outside.