I have no germination problems, but I use a mechanical planter which does set them at about 2 inches. Usually germination is most efected by soil temps. They need much warmer soil than common beans. They are also more susceptible to Phytophthora

Before I got to Farmerdill's answer, I was thinking maybe your soil just isn't warm enough. So that's two votes for checking your soil temperature.

Definitely need warm soil for limas. Limas hate cold and/or wet soil. I have heard and read that it helps to place the eye down.

Low soil temperature + high moisture is the most likely cause of poor germination. In combination with heavy, poorly-drained soil, seed rot can be severe. In the Northern states, there have been a lot of wet Springs in recent years... guessing from your zone, Creek-side, you might have experienced some of that.

As already stated by others, limas need higher soil temps than common beans to get good germination. Soybeans need about the same soil temps as common beans, but in my experience, edamame types are more sensitive to poor conditions than field soybeans... especially excessive moisture.

Planting depth might be an issue if you have heavy soil that crusts over after heavy rains; the soil where I garden is like that. To make it easier for the seedlings to emerge, I plant a little more shallowly (just over 1") and place seed in groups ("hills") rather than spaced widely in rows. The clusters of seedlings make it easier to break through the crust; when the seedlings are healthy, I thin to their final spacing (cut, don't pull). For sandy well-drained soil, the hill method would not be necessary, since the seedlings can emerge easily... the 2" depth recommendation would probably be necessary for sand, to prevent the seeds from drying out.

I would recommend against mulching the soil after planting beans. It helps to preserve moisture (which can be a good or bad thing) but it also prevents sunlight from warming the soil, and can harbor insects which will attack the newly-emerged seedlings. Once the plants have their first true leaf, they have toughened enough to mulch the soil around them. I never mulch soybeans, since it has been my observation that they don't seem to be as sensitive to mud splash as limas & common beans.

Personally, I've tried the "eye down" method with limas (and other beans) and didn't see any improvement over just dropping seed into the hole.

When I start limas in pots (my preferred method, given my short seasons) I find that laying the seeds on their sides & covering lightly gives the best results. Makes sense when you think about it, since that is how they would fall in Nature. The best germination rates I've had for limas were in peat pots, with starter mix packed tightly to within 1/2"-3/4" from the top, the seed laid on its side & pushed to make firm contact, then covering with screened play sand to the top. Level the top by scraping off the excess sand with a straight edge. Soak the pots in a tray overnight, then drain off all excess water; add water only if necessary, being sure to pour off any excess. Put the tray into direct sunlight as soon as germination begins, preferably in a protected enclosure. Germination rates have generally been around 90% using this method (100% this year). Pole limas are very cost effective as transplants, since the yield per plant is so high... and it avoids most of the germination issues.

Geez...I never planted my Edamame or Limas more than an inch deep and I had about 100% germination. Not saying my way is right, just what happened. My soil was total sand at the time and it was warm out.

Great stuff, folks. I suppose that the soil temp you can risk has a little to do with how wet the weather is going to be. Would 60 degrees be the absolute low end?

And I like the hilling idea. I am always surprised how the little fellers can punch through my soil when it gets crusty, but I'll double or triple my purchase and make sure I get a good crop this year.

There are a lot of charts out there listing the soil temps that are best for most garden vegetables; I'll link one below. Look for charts that list min, optimal, and max soil temperatures. The consensus seems to be that 60*F is the minimal soil temp to plant limas... but I won't plant beans of any kind until the soil temp is at least 70*F. Warmer is better for limas (and yardlongs), I germinate my transplants of those at 80*F.

Zackey, your conditions are pretty close to optimal for limas... warm temps (most years) & sandy soil. And probably a lot more sun than I get up here. ;-)

Here is a link that might be useful: Vegetable seed germination temps

Interesting.

Thank goodness for those minimum temps; the optimums don't appear achievable any time in May for me.

I don't plant beans in May since I know that the soil temperatures are too cold here for real success.

A few strategies that might increase your success:
- Warm the soil with black plastic or row cover over hoops before you plant.
- Plant in raised beds, which drain better and warm earlier that conventional in-ground beds.
- Plant later and use a short season variety that has time to ripen from a mid-June planting like Envy (linked below) that was developed here in NH. The link is to Johnny's Selected Seeds which carries many shorter season varieties. I have found that the germination charts that are included are a really good guide. I haven't grown Envy, but I have been successful with Butterbeans from Johnny's which produce in about 3 months, so a mid-June planting worked for me with them as well. I can attest to the great flavor and texture of the Butterbeans.

Here is a link that might be useful: Envy soy beans

"Thank goodness for those minimum temps; the optimums don't appear achievable any time in May for me."

Same for me. If it is warm & relatively dry, I might plant beans in mid-May; but those conditions are the exception here - maybe one year in five. Most years my target date for planting beans is around June 1st. If planted in the "minimum" conditions, germination will often be slow and/or spotty, which might require replanting the dead spots later. Personally, like Nhbabs, I prefer to wait for better conditions.

Some beans seem to have better cool-soil germination, particularly those with dark seed coats. "Fortex" and "Emerite" have both shown that ability in my gardens.

Good advice above this post by Nhbabs, on tips to get an earlier start... to which I would add the transplants I mentioned previously. Once germinated indoors, the seedlings will tolerate cool soils better than seeds sown under those conditions.

Lots of great info. Thanks again. I'm wondering if any of the varieties mentioned here are ones from which I can be successful saving seeds.

Lots of great info. Thanks again. I'm wondering if any of the varieties mentioned here are ones from which I can be successful saving seeds.

"I'm wondering if any of the varieties mentioned here are ones from which I can be successful saving seeds."

Reading back over this thread, I realize I drifted away from the original question in my last post. "Fortex" and "Emerite" are pole snap beans, not limas. I have, however, been able to save seed from both. "Fortex" is very slow to mature, and a bit of a challenge to get dry seed here.

Not sure of your location Creek-side, but I assume your climate is not much different that my East-central Wisconsin location. Chances are that unless foul weather prevents you from planting on time, you should be able to save seed from almost any commercially available edamame soybean. "Envy" and "Agate" (and "Cha Kura Kake", if you can find it) are early varieties; you are almost certain to get dry seed from them, even in less than perfect years. "Butterbean", "Shirofumi", and "Sayamusume" are later, and might be racing the frost for maturity some years... but I have saved seed from all of them successfully. The later varieties tend to have the largest seeds & heaviest yields.

Limas are more difficult (especially if direct seeded) for the reasons already given. Small-seeded bush varieties like "Henderson" and "Thorogreen" are the earliest, and probably the best bet to save seed from. Large-seeded bush varieties like "Fordhook 242" and "Burpee's Improved" are possible to save seed from (I have) but you might get very little - or none - in cool or wet years.

"Sieva" and "Carolina Red" are two of the earliest pole varieties, and the only two that are reliable here when direct seeded. If planted on time (June 1st for me) they should produce plenty of dry seed. Large-seeded pole limas are difficult to get seed from in our climate, at least on a reliable basis. However, most limas will (usually) give you a good crop - and at least some dry seed - if started early as transplants.