Let's assume the number of tulips in Claire's garden is $x$.
According to the information given, there are four times as many roses as tulips. Therefore, the number of roses in the garden is $4x$.
Claire picked half of the number of roses, so she picked $\frac{1}{2}(4x) = 2x$ roses.
After Claire picked the roses, 140 roses were left in the garden. This means that $4x - 2x = 140$.
Simplifying the equation, we have $2x = 140$.
To find the value of $x$, we divide both sides of the equation by 2:
$\frac{2x}{2} = \frac{140}{2}$
$x = 70$
So, there were 70 tulips in the garden initially.
The number of roses in the garden is $4x = 4(70) = 280$.
Answer: There were 70 tulips and 280 roses in the garden initially.