If possibly, it is always advisable to carry your tripod for Macro or Close Up photography. This is almost imperative if you are using a DSLR. One can jack up the ISO and obtain higher shutter speed to offset the possible 'shake' but that is not the ideal way to get a tack sharp image in the close up zone. I am saying this from my personal experience in this field. Even using a Monopod gives a better result than handheld shots.
Coming to tripods, it is better to invest on a reasonably sturdy tripod with preferably a Ball Head. Swevel/Tilt heads are not too convinient for nature photography. Ball Heads are more flexible though more expensive. Bogen/Manfrotto tripods and monopods have reasonably priced products and the built quality is certainly better than 'cheapo' Velbon or Vivitar tripods. It is very important to have a totally stable stand for your expensive DSLR with Lense. Watch out for the rated load bearing capacity of the tripod/monopod and it's head. Ideally one should limit the load at least within 75% of the maximum load bearing capacity for the sheer safety of equipment.