Answer: Clay based soil often has "window" of time when it can be worked. Clay soil will naturally dry very hard, as you have seen. When it is dried out and hard like that it is not workable, no. It is also not workable when it is overly wet -- it will stick to your shovel and also form hard clods once it re-dries, so digging it when it is very wet is also not an option. Once you have some rain to rehydrate it, however, the soil should soften up a bit and become workable. You will need to wait a few days after the rain so it is not too wet to dig -- trial and error will tell you when it is ready.
To try to improve the soil and make it better for gardening (and for the plants roots) you may want to work in some organic matter such as compost, or rotted chopped leaves, or well-rotted stable manure and bedding mix, or rotted down mulch, along with some coarse builders' type of sand. These will loosen the soil and make it easier to dig, it will also improve the structure so that it can hold both air and water, this is healthier for the plants. You should also run some basic soil tests and see if other amendments such as lime to adjust the pH and possibly nutrients also need to be added. Your local county extension should be able to help you with the tests and interpreting the results. Fall is a great time to do this type of work. You could prepare the soil and also plant a cover crop such as annual rye to add additional organic matter by spring. After that, using an organic mulch year round will help add organic matter on an ongoing basis as it rots down slowly over time.
Bulbs in particular require a well drained soil, so when you plant your bulbs you might consider using a slightly raised bed or if possible planting on a slope. In any case, avoid planting them in a low spot where excess water will collect.
It is really too early to plant bulbs -- the soil is still too warm right now and they need moisture to root. Usually there is some seasonal fall rain activity that helps soften and moisten the soil so you will be able to plant them in the coming weeks as the weather begins to cool the soil -- you can actually plant all fall up until the ground freezes although mid-October or so is usually considered about best. If you are able to prepare your soil now, there is no benefit to waiting until next year, and spring blooming bulbs are planted as bare bulbs in the fall. (Otherwise you would purchase pre-planted, potted, forced bulbs in the spring at much higher expense.)
The earthworms tend to move deeper into the soil where it is still moist and cool, so not seeing them right now is not terribly surprising. They also tend to migrate to soil that is rich in organic matter, so adding the materials above will encourage them as well. You should see more of them in the springtime, especially if you add organic matter this fall. You really should not need to purchase any, and if you did they would soon disappear unless conditions are right for them.
I hope this helps.
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