Crumb cakes are really more like a coffee cake rather than a dessert cake and they do tend to be on the dry side. Often they will call for milk, buttermilk or sour cream as the moistening ingredient and you can bump those up slightly for a moister texture. Also baking for a slightly less time will result in a moister cake. Having a piece with your morning coffee or with afternoon tea will eliminate the need for ice cream.........which just doesn't go at all IMO :-))

It's called 'crumb' cake because of the crumbly streusel topping.

ETA: Shelled walnuts can be stored in the freezer to extend their shelf life. For months :-))

No, it's not supposed to be dry. Dry cakes often happen when they're baked at too high a temperature. I'm guessing you'd notice if it were overall baked too long. Whole wheat flour is usually drier in baking, unless you give it soaking time, than white, but it's possible it also retains moisture well--I haven't made enough whole wheat cakes to really know on that (you didn't say if you did a traditional yeast crumb cake or baking powder). You used cane sugar, right? If not, that's probably your answer. It might also be that your shelled nuts aren't as oily as it counted on, but I don't know that that would have had as much effect on the texture of the cake itself. If your oven is newer than the cookbook, it might be more accurate and bake hotter.

It should be dry enough to hold together when you dunk it in coffee!

I agree with gardengal and plllog. Crumb cake is coffee cake with a crumb frosting. Wheat flour caused the dryness. AP flour is recommended for crumb cake.

No....I would suggest it's a bad recipe....but a crumb cake is not a heavy moist cake...it's sort of a carrier for the streusel topping!
I forget where you live, but a streusel topped crumb cake is a "New York thing"...or New Jersey or Pennsylvania....but I have not seen a real crumb cake anywhere else....unless I made it!
But whole wheat flour? Not in any that i know of!....and no struesl in the middle and no walnuts.
I have a lovely moist cake, with sour cream that calls for brown sugar and nuts in the middle and on top if you would like....shout and I'll dig it out.

Shout!

Merks Coffee Cake ..make topping before making cake

.1/2 cup shortening
3/4 cup sugar
1 teas. vanilla
3 eggs
2 cups flour
1 teas. baking powder
1 teas. baking soda
1/2 pint sour cream

6 Tablesp. butter, softened
1 cup brown sugar
2 teas. cinnamon
1 cup chopped nuts

Cream shortening, sugar and vanilla thoroughly. Add eggs, singly, beating well after each addition. Sift flour, baking powder, soda. Add to creamed mixture, alternating with sour ceam, blending after each addition. Spread half of batter in 10" tube pan that has been greased and lined on bottom with waxed paper. Cream butter, brown sugar and cinnamon together. add nuts, mix well. Sprinkle half of nut mixture evenly over batter in pan. Cover with remaining batter; sprinkle on remaining sugar mixture.

Bake at 350° for about 50 min.

Crumb cake is originally German, and I've read that American coffee cake is based on it, coffee cake being a sweet somewhere between a breakfast pastry and a dessert cake so just right to serve at a morning social coffee visit. Coffee cake is somewhat out of style (though probably being revived by hipsters), but crumb cakes are still common. We have crumb cake in California, both the traditional yeast cake and an open textured baking powder cake. It often does have chopped walnuts or other chopped or slivered nuts mixed with the streusel, and sometimes has a ribbon of the streusel running through the body rather than just on top. I think it depends on how much the baker likes streusel, or if she/he made too much. :) The whole wheat is definitely an innovation, seeing as whole wheat cakes are now in style.

Jerzeegirl, I've never heard of dunking the cake (or coffee cake for that matter) in coffee being a thing--I can certainly see someone doing it since people dunk doughnuts and other stuff but I've never seen or heard of anyone doing it. I agree with you that if that's the purpose of this crumb cake recipe, then the recipe may be accurate as made and supposed to be dry. Biscotti--the real kind that are hard as rock and dry as the desert--are definitely for dunking. :)

I'm listing the ingredients here if anyone wants to examine it, maybe it is just a bad recipe. I found it in the Pillsbury Complete Book of Baking published in 1993:

Streusel:

1 cup chopped walnuts

1/3 cup brown sugar

1 tsp. cinnamon

Cake:
2 cups whole wheat flour

1 cup sugar

3 tsp. baking powder

1/2 tsp. salt

1 cup milk

1/3 cup softened butter

1 egg

Glaze:

1/3 cup powdered sugar

2 tbs. water

The streusel is a layer in the middle and a layer on top.

350 for 25 to 35 minutes, I baked it for 30 in 13 x 9 pan.

I'm not expert in baking enough to figure out if a recipe is inferior, but I know a lot of you are.

My mother made something that she called crumb cake. It's one of the few recipes of hers that I have. I guess I must have liked it as a kid, but I know that I've not made it in 30 years. I wonder if I will still like it. Her recipe starts out with the making of the crumbs (flour/butter/sugar), reserving a portion of the crumb for the topping and using the rest in the batter. There are raisins and currants in the recipe, but no nuts.

Crumb cake is not supposed to be dry. I'll link the America's Test Kitchen recipe for New York Style Crumb Cake. It's not from the ATK website though, cause for that you need to be a subscriber. I've tried this recipe, and it's moist, though IMO the proportion of crumb topping is too big. But otherwise it's a very nice crumb cake.

http://www.geniuskitchen.com/amp/recipe/new-york-style-crumb-cake-americas-test-kitchen-360198

Yep...it's a bad recipe!...no flour in the topping and no butter....2 cups of WW flour and a whole cup of sugar? And glaze? Crumb cake doesn't have a glaze, it has strusel!
I grew up with a real German bakery, owned and run by a German couple who barely spoke English a block away....and they lived a few doors from me....but you never saw them because they got up very early and stayed at the store until very late. But, they knew crumb cake, and it was called coffee cake and was for dunking in your coffee....and it was a quick based cake, not yeast dough.
And true to what you find on the web, it was what people call a New York crumb cake....here's the recipe I use....less eggy.

New York
Crumb Cake

Baking time 20-25 mins. Oven 325degrees

Sift together:
l-1/2 cup flour
1/2 cup white sugar
2-1/2 teaspoons baking powder
1/2 teaspoon salt

Whisk together in separate bowl:
1 egg
l/2 cup milk
2 tablespoons vegetable oil
2 teaspoons vanilla

Combine both by stirring with wooden spoon. Grease and flour baking
pan,approx. 13x8" (brownie pan). Spread batter evenly, it will look scanty
but don't worry.

Topping

1 cup melted butter
1 cup brown sugar
2-1/2 cups flour
1-1/2 teaspoon cinnamon

Stir Topping ingredients together with a fork, or crumble together by hand.
Sprinkle crumbs thickly on top of cake batter. Bake cake for approx. 20 mins.

Cool cake (in pan) for 10 mins., then sift a bit (about 1/4 cup) of
confectioners sugar (powdered sugar) over the top, cut into squares and serve.

Linda, thanks for analyzing that recipe for me. I'll try yours at some time after I figure out what to do with all these walnuts. I did divide the bag up into 1 cup portions and froze them, that one cup I used didn't make a dent in it. I prefer pecans to walnuts, DH wasn't thinking when he bought them.

I buy the big bags of walnuts and pecans at Sam’s. Used to have freezerfulls of home grown pecans but not anymore. I made several pecan pies using walnuts in place of pecans to sell at our local farmers market. They were good and very well received

If you have lots of walnut, you can eat 10 of them a day without getting too many calories. They are a fantastic health food.

So. New York crumb cake. That explains it. I remember when I first encountered New York cheesecake. People from the East raved about it, but it was so different from the light, delicate Italian style cheesecake that used to be popular around here that I was totally flummoxed. Then last year, we learned in the CF about New York Pavlova (I think it was New York. Or maybe New Jersey), which is a kind of walking treat in a cup and eaten with a spoon.

So I did some looking. Online, the kind of yeast crumb cakes I'm used to are called German crumb cakes, I guess to differentiate from "New York"--a lot of the "German"recipes I've looked at actually come from New York.

For me, based upon my experience, crumb cake is a yeast dough made in a flat layer (though possibly filled with streusel) and totally covered with streusel, at least some of which is left blond, there may be small chopped or slivered nuts in the streusel or over the top, but that's a variation. I have eaten baking powder variants which were a bit dryer and less flavorful, though thinking on it the flavor component may just have been the yeast itself.

A coffee cake, also yeast dough, while no taller, is shaped into whorls, and has hills and valleys of crunchy (hills) and soft (valleys) of crust, deeply browned, sometimes decorated with sugared pecan or almond halves, a little streusel in the valleys, and plain sugar icing piped in a pattern on top.

No one I know dunks it in coffee, but as I said, I do understand that it's a thing.