But, short of time to do research and experiment in flower cultivation, I am no garderner at all.等于：

But, because I am short of time to do research and experiment in flower cultivation, I am no garderner at all.

理解为省略也可，理解为形容词短语作状语也可。

如果理解为省略的话，必须具备：

1. 主从句的主语一致；

2. 从句的谓语部分是：be + 形容词短语。

又如： Fond of music, she bought an MP4.

Pleased with my work, Father gave me a present.

从句中省略有关成分，是很常见的事情，具体情况详见：

http://www.yygrammar.com/Article/201501/3815.html