The biggest problem that I have with growing eggplant in a cool climate is attack by Verticillium wilt. Losses for me have been as high as 50-75% with susceptible varieties in a cool, wet year. Most of the commercial Asian varieties that I tried (and many heirlooms as well) were susceptible; "Pingtung Long" is especially so.

But two heirlooms have proven to be extremely reliable:

"Casper" is an Asian-type white eggplant, with tall upright growth. It actually seems to prefer cooler temps, and bears early. During hot summers, it will stop bearing for awhile - then bear again _heavily_ in late Summer / early Autumn. My last harvest is usually just before frost. The flavor is very mild, almost completely non-bitter... my absolute favorite for basic battered & fried eggplant.

"Diamond" is a purple Asian-type, with a lower, more spreading growth habit. The fruits are elongated, glossy, and attractive, but shorter than most. However, it has the heaviest, most reliable yield of any eggplant that I have ever grown... the fruits are borne in clusters, and it is not unusual to harvest 4-6 per plant in a single picking! You'll be giving them away like zucchini! It bears well in Summer heat. The flavor is stronger than "Casper" with a firmer texture, making it a good choice for eggplant dishes.

Both of these are highly Verticillium-resistant, exceptionally early, and have stout stems that hold up well to strong winds. I highly recommend the combination of the two... one or the other is always bearing. They also freeze well, maintaining almost-fresh quality for a long period if vacuum sealed.

outsider

If you have access to an Oriental,preferably Korean,the Korean eggplant does very well here in the PNW. The plant is very beautiful,with purple/blue green leaves and makes a nice potted plant with the benefit of a very tasty vegetable. If your interested i can get/send you some seed.

There is a good website for Asian vegetables, www.evergreenseeds.com

Have you tried PingTung eggplant? Not sure if they are heirloom but many asian market sell this type of eggplant, long purple oblong. Seeds are readily available mailorder and seed racks in asian markets.

I've been growing 'Pintung Long' for about 20 years now. I started because I couldn't get the Italians to grow (I think they require a more fertile soil) One year I got some seed for "Farmer Long", I think a hybrid but I haven't found it since, it was very prolific. Have also had luck with 'Louisiana long green' and 'bride' as well. I start the seed myself and use remay type fabric to keep the flea beetles away until they blossom. Then pick, grill, and eat. Wonderful! They also freeze well, brushed with oil and broiled/baked.