Duplicated results when querying 2 tables

Hi everyone, I have multi-table database that contains data for the same plant varieties but in different times,
for example "Winter_2012" and "Summer_2012", lets say I want to query the plant variety "X" in these 2 tables.
If the plant results are as follows in each table (when querying separately)
"Winter_2012"
------------------------------------
__Month_|_Variety_|_Quantity
------------------------------------
__Jan___|____X____|___100__
__Feb___|____X____|___210__
__Mar___|____X____|___150__

"Summer_2012"
------------------------------------
__Month_|_Variety_|_Quantity
------------------------------------
__Jun___|____X____|___160__
__Jul___|____X____|___200__
__Aug___|____X____|___100__
__Sep___|____X____|___140__
__Oct___|____X____|___170__

The problem is when I want to query the variety "X" with the following statement to make one report

SELECT Winter_2012.Month, Winter_2012.Variety, Winter_2012.Quantity ,Summer_2012.Month, Summer_2012.Variety, Summer_2012.Quantity FROM Winter_2012, Summer_2012 WHERE Winter_2012.Variety = "X" AND Summer_2012.Variety = "X" 

I got the following results

-----------------------------------------------------------------------------------------------------------
Win_Month | Win_Variety | Win_Quantity | Sum_Month | Sum_Variety | Sum_Quantity
-----------------------------------------------------------------------------------------------------------
____Jan____|_____X_____|____100_____|____Jun_____|_____X_____|_____160_____
____Feb____|_____X_____|____210_____|____Jul_____|_____X_____|_____200_____
____Mar____|_____X_____|____150_____|____Aug____|_____X_____|_____100_____
____Jan____|_____X_____|____100_____|____Sep____|_____X_____|_____140_____
____Feb____|_____X_____|____210_____|____Oct_____|_____X_____|_____170_____

As you can see, I got the "Jan and Feb" results duplicated at the end of the table
I'm sorry for too much explanation.
Thanks in advance for any suggestions