Perhaps true to character for some, poison ivy has taken over this thread. My search for "understory shrubs to shade out weeds" led me here. I am in North Florida, and I like to have safe access to my mature loblolly grove to clear out by hand or weed wrench the returning coral ardesia, nandina, air potato, and broad leaf privet. (In my experience "done once and for all" and "gardening" are mutually exclusive.) But the poison ivy also overgrown there is an obstacle course. Would introducing lots of some native shade loving plants out compete the above listed exotic invasives, so I could let the poison ivy alone? Or would the PI eventually fill up the chain link fence and smother the old camelias there? We are talking fairly deep shade on the ground but dappled sun on the camelia branches. What natives if any?

Yep, I gather that a good diversity of flora is an indicator of age. I was about to moan about the lack of diversity in ours - true the trees are poplar, hawthorn, elder and oak...but we seem to have quite a large number of herbaceous flora (weedy though) - a big selection of umbellifers, lots of labiatacae (sp?) silene, hemp agrimony, sweet flag, willowherbs (3 types) bluebells, water avens and herb bennet gallium, stellaria , burdock, artemisia, chamomile...and thousands of felicitous snowdrops thanks to Heyrick Greatorex, who planted his famous doubles all round the hedges and verges. As an inveterate meddler, I have reined myself in considerably but even so, I have been adding quite a few US woodlanders such as mertensia and stylophorum, as well as plundering the whole area for seeds. desperate to grow peucedanum palustre for the swallowtails and have finally managed to source plugs for next Febnuary since seeds, which must be fresh, are impossible to find. I do have an image in my head which, if it comes off, could be really quite iconic with no resemblance to traditional shade/woodland gardens with neat clumps of hosta and the like - I am seeing tiny ground huggers (primulas, celandines, wood anemones, extending in layers through bulbs and aqulegias, lunaria, ranunculous, mertensias, astrantias as the season progresses, ending with moor grass, angelicas, eupatoriums, and wood asters by the end of the summer - along with native grasses and (no doubt) weeds - terribly vain but still, a chance to create a small, temporary, legend. Chalara is running amok in Norfolk - how about Cornwall?

It will greatly depend on where you live but the general rule is you plant woodland perennials when they are still dormant or only just waking up. In PNW I plant January through April as long as the soil is not frozen. In Illinois you probably have to wait until the soil thaws out and becomes workable. There might be few reasons why they do not return for you, from being eaten by under or overground creatures to wrong place (too heavy soil, too wet, too dry etc.) to receiving non-viable plants. It's also important to know that some plants can sulk for a season or two after transplanting before they put on new growth.

I only have experience with trilliums.... They grow well around here. There were a few already here when we bought this property in 1999 but we're added to them since. What has worked for us is to plant them dormant in mid summer, plant them in areas with lots of leaf litter - under trees, and never water or disturb them while they are dormant! There are lots of squirrels here and, as far as I can tell, they've never bothered them. The white trilliums are more vigorous for us than red ones - white ones are the provincial flower of Ontario so that might be a sign that they are particularly suited here. They are now spreading by both offsets and seedlings. Some pictures....: Cole in the nearby 'trillium wood' that is my reference for what I'd like to have here! White trilliums near the shed in our garden: A closer view from 2015 where you can see seedlings getting big enough to start to bloom: (Note the plentiful oak leaves in those pictures! The trilliums seem to like those conditions....) Red trilliums don't seem as happy here and are spreading much slower: On the issue of squirrels and tulips.... Here the squirrels seem inclined to ADD tulips to our garden! Several years after we started gardening here, a clump of orange tulips appeared under the oak tree in the back yard. We didn't plant them and the tulips looked suspiciously like ones in a neighbour's yard down the street! :-) So we assume the squirrels planted them..... Aside from deadheading the tulips once the flowers fade, I do nothing to them - they keep returning and the clump gets bigger as the years pass. The oldest picture I can find on this computer is 2010 but I think they first appeared before that. 2010: 2015 (apologies for the poor picture quality!) Some salmony-pink tulips appeared in the front garden 2-3 years ago that I was sure we didn't plant and, looking around, I saw the same ones in a garden across the street! So squirrels might dig up the occasional bulb, but they are probably gifting it to a neighbour :-)