I was just reading this last night from a FAQ's page at Welburn Gourd farm:
Can gourds be used as planters?"

This is one question that is asked a lot, and depending on who you ask you will get different answers! Some people say the gourd must be sealed before using it as a planter or it will rot. My experience is, you can plant directly into the gourd without doing a thing, even without drainage holes.

I have three gourd planters in my house that were made by Teddy and Felix Garnsey over 40 years ago. (As many of you know, Felix Garnsey was the man who originally started growing gourds in De Luz; he grew them for a few years, then decided he wanted to retire. So in 1979 he passed on his gourd knowledge and seed stock to Doug Welburn.) These gourd planters were never sealed or treated in any way, and two of them donÂt even have drainage holes, yet theyÂve lasted over 40 years and still show no signs of decay.

The gourd planters in my house are definitely made from gourds with dense, thick shells, so I would assume this has played a role. If you would like to make gourd planters, start with quality, thick-shelled gourds. ItÂs also a good idea to put drainage holes in it, just to be on the safe side. Be sure to use a light potting mix. If your soil is too heavy, it will hold water much longer and increase the chance of the gourd rotting.....Phoebe Welburn

Someone on another Q&A site says they use wax to coat the inside of the gourd to waterproof it for planters and drill drainage holes in the bottom.Gourds have been used for centuries as vessels of all kinds,for carrying and storing water,wine and other liquids.I don't see why they couldn't be used as planters in their original state without coating the inside with anything as long as they are cleaned properly.I made a tabletop fountain out of a gourd and coated the inside with silicone tub and tile sealer.It works fine,but I don't know how it would do for a planter.Guess it would work but probably wouldn't be necessary............Lillie

I would use shellac, and do it AFTER putting the holes in it. But use the real shellac, not a synthetic -- Bullseye is the only one I've found here. I used two coats of shellac on my chicken pen, and it looks really good. Non-toxic when dry (alcohol based, I think), and quick-drying. There is a clear kind and a dark golden tinted kind.

Tung oil might be something to try, also.

Sue

If you plant directly in a gourd even with drainage holes, it will eventually rot.

I have made many gourd planters. I first cut one or two large planting holes in the gourd with a key hole drill attachment. I then clean it out and fill with melted parafin. I pour that out while still liquid. When the wax is dry, I drill small drainage holes in the bottom. Most of my planter gourds are planted with succulents such as aloe vera and hens/chicks. Obviously, I start with very tiny plants since the planting holes are small. They grow quickly and fill up the gourd without over-crowding. Also, the succulents need very little water.