My experience gardening under a big evergreen tree is a 15-year nightmare; I almost wish I'd never started. Mind you it's not a pine but a Chamaecyparis. But even so, I suspect some elements are common - having to water constantly in summer, which is probably not good for the tree; the soil level creeping upward as each year's natural mulch is deposited and burying plants as well as landscape materials, the extreme dryness creating good habitat for pests such as weevils and cutworms which reproduce and feed ecstatically, and the fact that you can't dig enough to plant big plants but when you plant them small they never grow because they can't seem to extract enough nutrients (and maybe water) from the acidic soil. Big trees are lovely to have in many ways, but they are essentially thugs, and they don't respect the rights of people, buildings, or other plants. After all these years of re-landscaping about every three years to try to accommodate the tree, I've settled on hardscaping that I can easily keep clear of debris, and containers for planting. I do have two small raised beds, with very limited success (they get infiltrated by tree roots within 2 years). If I had a bigger yard and could garden elsewhere, I'd just give up and let the tree have its base clear. (I haven't considered removal because the tree belongs to a neighbour in my case, but due to our increasingly windy climate and the fact that the tree leans lovingly toward my tiny house, the neighbour has actually agreed to remove it this year). Having said all that, there are plants that might really thrive under a pine - cyclamen? - but for me, the lush shade garden I keep working towards remains elusive and if you can get close it's at the cost of serious labour. Even my ferns, and I've tried plenty, either don't thrive or eventually get smothered by the debris.

My experience - and only that backed up with absolutely nothing scientific... for several decades, my yard has had some successful garden areas planted under arborist limbed old Spruce - several times the age of yours. The spruce are fine, the underplantings are fine, and the soil with years of needle fall is loose and fine. The light conditions vary during the day, but plants including hostas, ferns, astilbe, dicentra, dianthus, some can't bear to compost pieces of Stella d'Oro, daffodils, squill, forget-me-nots, and muscari all seem to thrive. I don't fertilize, mulch or add anything beyond a compost topdress periodically; I'm a hand weeder so I don't dig around dinging roots, etc. and everything gets watered when it rains.

conifers are conifers.. because .. they have cones ... and conifers are trees ... so name the tree .. then add 'cone' ... so.. as noted.. your spruce has spruce cones ... go figure on that logic.. lol ... anyway.. enough on that ... there are 3 basic things plants need PROPERLY ... to be PROPERLY planted ... to be in PROPER light ... [you arent going to grow sunflowers under there, eh .. being rather literal] .... and PROPER watering ... and i will focus on water like a laser ... new transplants need more water than an 'established plant' ... until they can grow the roots needed to support the plant ... or get those there.. working again after you disturb them thru planting ... for the first month or so ... most perennials should NEVER dry ... no matter if it is a plant that can TOLERATE dry shade ... but once they get going ... then their true characteristics come out.. and tolerance to dryness will surface ... make sense??? anyway .. perennials can take years to grow into large plants.. so what you do .. next season.. is put in BOTH perennials for the long run .. and some annuals for instant impact ... but be aware .. there are very few annuals that are dry tolerant.. other than weeds.. lol ... once again.. you have not.. or i missed it .. the actual sun on the space.. i might consider ringing the rocks with impatiens if shade.. and maybe allysum or petunia if sun ... covering about the first foot in .. then some other annuals .. interspersing them with perennials for the following year ... it looks like you have a struggling heuchera or coral bell there ... so that indicates that with a little more TLC.. those will grow there ... below is a pic of maple roots ... to show you the 'potential' of what you are dealing with under the soil .... a spruce is NOT going to be that extreme ... but i hope it makes you appreciate what i meant when i said trees are super competitors ... i really have no clue what the grass is growing in .... that is the neighbors septic rebuild.. it took me two years to convince him to get rid of that maple or face another rebuild in the future ... he finally did last summer [4 years???] ... i gave up long ago.. trying to grow much of anything under maple.. but i digress .... good luck ken

Pictures please. Closeup of flower, if possible, and leaves/habit. Don't bring them inside to take pictures.