First of all, never accept legal advice from folks on a forum as gospel, including any I may suggest. Check the laws for yourself to be certain of your postion. First I'll touch on the laws I was able to view and toward the end, will ask a few questions that you might consider.
First, let's look at the language of your state Constitution:
Article I, Section 24
The right of the individual citizen to bear arms in defense of himself, or the state, shall not be impaired, but nothing in this section shall be construed as authorizing individuals or corporations to organize, maintain or employ an armed body of men.
The simple meaning here is that citizens have the right to have a weapon. Note, however, it says nothing about concealed carry there. However, it appears open carry is generally permissible.
Washington State follows British legal tradition, which states that anything that is not proscribed as unlawful is lawful.
Now let's check a specific law that states what limitations you have on carry:
(1)(a) Except in the person's place of abode or fixed place of business, a person shall not carry a pistol concealed on his or her person without a license to carry a concealed pistol.
Since your property is at the place of your abode, it appears that you can carry concealed on your own property. If you leave your property, you'd need a concealed carry license.
Now the questions.
If you are on your own property, and you actually are carrying CONCEALED, how would anybody know? In order for a police officer to approach you regarding a weapon, they'd need to know it is there. If it is concealed, nobody is going to know that to be the case. There won't be a MWAG call to the cop shop. The only person who will know you have a gun is you. The police are very unlikely to show up at your home and search for a weapon unless you have other issues, such as an outstanding warrant. Why would police be there to learn you are armed if it is concealed and nobody knows about it?
The problem I have is that the question "can I carry concealed on my own property" just doesn't make sense? Who is to prevent it? The police would need some reason to come onto your property, and if that isn't likely, what's the problem?
Meanwhile, you can certainly open carry without expectation of trouble on your own property, and you don't need a license to open carry.
But again, as I said at the outset, do not depend on a forum such as this for legal advice. You'll get opinions, frequently good ones, but I've seen some that weren't all that shiny.