Genetics - Is this hybridization possible?
Flower Color

A Heterozygous (Rp) x Homozygous recessive (pp) cross can produce the distribution:

         p      p

   R    Rp     Rp  = Red, Red

   p    pp     pp  = pink, pink


Stalk Length

To me, there appears to be another allele involved or a lack of allele, and definitely Co-Dominance. The only way I could think of a way to get the ratio of stalk lengths in the question after a few minutes thought is if one of the plants are missing a gene before the cross (akin to Turner Syndrome) - the example that follows puts the missing gene on the Short-stalked parents:

SS = Short
TT = Tall
ST = Medium
SX = Short
TX = Tall
X = Missing Gene / Nothing

         S      X

   T    ST      TX = Medium, Tall

   T    ST      TX = Medium, Tall


So ultimately the cross would look like this:

        Sp     Xp

   TR   STRp   TXRp = (#3), (#1)

   Tp   STpp   TXpp = (#4), (#2)