Seed damage? Honest encouragement please

Having a bit of a nightmare this evening. I had a large batch of seeds ( very expensive for use in a public landscape project) and left them in my car all day with the doors and windows closed. It was British wildflowers and grass mixes ( to the value of about 800 US dollars). It was a warm sunny day with temperatures reaching about 16 degrees C ( 61 farenheit) and I'm guessing in the sun that temperature in the car got up at least twice as high.
I'm very worried that the seeds may have become damaged. Have sown some as a test but will have to wait ages. Have alo tried floating them and most did float ( although I don't think that is a true indicator of damage)
Has anyone any experience of this?. Any advice/ words of wisdom?
Apart from the cost I'm concerned about taking time sowing them, if they turn out to have lost viability. Also, the delay if it turns out I have to buy more.

Mr_Canthus, No experience with this, but I will offer my two cents worth. First off, floating seeds has absolutely nothing to do with seed viability, it is simply an old wives' tale. Second, wildflowers are very sturdy compared to many of the other cultivated hybridized flowers and should be more tolerant of conditions. Also, grasses may have more tolerance (particularly if they are warm season). Although the temps probably got to around 100 F, they were exposed to it for a short period of time, it's not like they were stored at those temps for a long time. My gut feeling on this is that the majority of the seed would be ok. I would proceed your planned plantings and not worry about it.

I have many areas that I have seeded back into native prairie/ wildflowers (American Midwest) and it can take time for many of those species to germinate. In my plantings, I am constantly evaluating populations of each species and I am always reseeding certain species to get the populations that I want.

I would plant as planned, evaluate populations after a year and reseed individual species if necessary/desired. Seeding wildflowers never results as you envision it and the look of wildflower/native plantings change from year to year. Not to mention that it can take 3-4 years for some species to mature enough to flower. I have some areas that are 5 years and older and I am still planting some species into those areas to achieve the look I want.

Relax, and remember that even if you use the same seeding mix on two different areas, they will never look alike and that is part of the joy of using wildflowers/natives.

Let us know how it goes with your seed and I am also interested in what species you are using - if you could post a link or a list of some of the species I would appreciate it.

Thank you very much for your assuring and considered response. I sudenly started getting that sinking feeling when I realised I'd forgotten to take them out of my car, and felt how warm the polythene bags of seed had got.
I'm very intersted to read your experiences with creating new flowery grasslands using your native species. The link below is for the seed supplier I used.

http://www.meadowmania.co.uk/wild-flower-meadow-htm

The seed mixes I had in the car were 80:20 ratio grass -wildflower mix for loamy soils and also some of the general purpose mix. I also had some cornfield annual mix which I'm going to combine with some of the meadow mix in one area to generate a bit more colour in the first year ( it is a very public project). The soil I'm going to be sowing on is sediment dredged from the bottom of a pond. It appears quite rich and organic and has a pH of about 6.5 so I'm expecting that ultimately there may be some problems with competitive dominance by vigorous weedy species. A major reason for sowing these mixes is to offset the undesriable visual impact of the sediment having been deposited on some public open space near a residential area.

I will definitely keep you posted

Mr_Canthus, Thanks for providing the link for your wildflower mixes. I find it interesting to see the differences between the natives in our two countries. In particular I see that wild carrot is in many of the mixes whereas here in the US (Midwest in particular) wild carrot is a troublesome weed that colonizes waste areas rapidly and even moves into garden areas.

Here is a link for the seed source I use for much of my wildfowers: http://www.prairiemoon.com/ I include this link as they have some very good information on establishing and maintaining wild areas that you may find useful.

I established my wildflower areas in the fall of the year (many species needed stratification) so I had some advantages relative to weed control that you won't have with a spring planting. In late summer I applied glyphosate to the area for planting, waited for two weeks for a complete kill and then roto tilled the area. I then waited another two weeks for additional weeds to germinate and sprayed again. I ended up spraying three times to lower the weed pressure. After the initial tillage I didn't disturb the soil, in essence creating a stale seedbed. Before fall seeding I raked the soil, seeded and then raked again.

The following spring I did a lot of hand weeding of annual weeds and didn't mow anything as most recommend in establishment procedures. If I had a larger area I would have definitely mowed it, but the first areas I established were small enough to weed by hand. Another advantage I had was my initial plantings were forbs only with no grasses, therefore I was able to use a selective grass herbicide to control grassy weeds (sethoxydim). Now that the areas are established I still spot treat problem weeds with glyphosate and mow each year in the spring (I leave them alone through the winter for birds to feed).

Another thing I did with my initial plantings was to raise transplants of many of the species to insure I had good populations of some of the more desirable flowers. I know this skewed the mix of natives, but I wasn't necessarily going for a totally native look, just one using only wildflowers. In fact, I still continue to raise native plants from seed to transplant. Usually, these are new native species I am using to expand the diversity. In choosing additional species, I was trying to extend blossom from early spring to late fall, balance colors and add varying structure. While you probably don't have the ability to raise transplants to "spike" the planting, you can easily reseed certain species or add species to the planting in the future to achieve the desired look.

Finally, remember that seeding natives is a process and will take up to three years or more for your area to achieve maturity and stability. The first year you will of course see mostly annuals, with the possibility of late season blooms from some of the perennials, the second year, the annuals will be mostly gone with many perennials blooming for the first time. Finally in the third year, the perennials will really take off and provide a show.

Good Luck with your efforts, and be sure to come back with any questions you might have. Also to share your success.

Thanks for all that first hand experience trc.I have a little bit of experience with creating native flower rich grassland ( from seed and plugs) and the main obstacle I find is soil fertility being too high. This might indeed be an obstacle for me on this occasion. Using no grass I'm sure would help but wasn't an option here ( for other reasons).
Good thing though is that a sample of those seeds I left in the car have started to germinate on some damp kitchen towel I used as a test bed; only three of the species but its a start and makes me feel better.
I really appreciate your taking time to write about this which is a truly interesting and potentially rewarding activity.
I'll keep you posted.