I'm so sorry for your loss
You can grieve no matter how old a baby was. You've still lost a baby. They will always be with you and a part of you.
I lost my baby at 10 weeks at Christmas and knew instantly what was happening. I knew the one thing I wanted to do was catch what came out. I inspected it all making sure not to miss anything although my hands were shaking and I was scared. But it was really obvious when I lost my baby. I was expecting to see a bubble shape but no. I held my baby in my hand.
Your idea of planting something is what I was going to suggest. We buried our baby in a big planter with flowers. They're indoor plants and we're moving so we didn't like the idea of burying outside. It was too soon to say goodbye no matter what time we buried our baby. We gave him or her a unisex name as we also don't know the sex. It means 'at peace' and 'rebirth'. It hurts. I wish I could refer to our baby as he or she.
You could also bury something of yours and say something then plant flowers to remember them by. It might help you to let your baby know you'll remember them forever. Write a letter for your baby to bury to get your words out. I want to do that at some point, just wanted to wait until I somewhat had my head straight from the shock.
My sister went to the hospital with all of hers so she never had anything to bury but she says she still remembers all of the dates. My other sister also lost a baby at 6 weeks, but let it go, so she doesn't have anything either. I was told to appreciate that I had my baby to bury and move on but that doesn't help. I'm still hurting. I still lost my baby. I saw my baby with everything. Not everyone has their baby to bury but it doesn't mean that they would have loved their baby any less.
People can be dismissive with early miscarriages. If they've been through it they may understand but still some can say 'get over it' too soon just because they might have. But, like with births, miscarriage experiences can be different also. It's really early for you right now. You need to grieve for what you've lost. Cry if you want. Don't listen to anyone that thinks you should be fine, it's not fair. They haven't seen what you've seen.
I cried everyday for over a week. If I'm left to think about it now, I'll cry. I miss what I lost and what could have been. I can't have my baby back but I know I will carry my baby with me everywhere, everyday.