It is not only possible to add perennials to your garden in August, some great native plants are going to be available as potted plants only in late summer.
Case in point: Poke or American Pokeweed (Phytolacca americana). This tall purple-stemmed perennial is a warm-season plant that doesn’t get going until the soil warms. It is impossible to start it from seed and have it up to any size for sale in the spring. With an enormous fleshy root, it also hates overwintering in a pot. Now, Poke is not difficult from seed and it grows quickly. Because it is at the very northern edge of its range here, Poke may be fussy to site. It needs a relatively warm, well-drained site to survive the winter. You may need several tries to get it in a favourable site. So, it makes sense to get a packet of seeds from us at Seedy Saturday and raise your own, to have some spares to experiment with – if you are handy at raising perennials from seed. If you are not experienced with perennial seeds and you would like to acquire a Poke plant growing in a pot, August is your best, or, indeed, only time to do so.
Get your Poke plant into the ground while the soil is still warm. Once you have a well-grown specimen, birds will eat the fruits and spread the seeds about and you will see volunteers from time to time. This is a good thing because you may well lose your original Poke in a harsh winter. In the mid-Atlantic states, Poke is a prodigious seeder and it is considered a weed. This far north, the volunteers are nothing to be feared.
Wild Lupin (Lupinus perennis) is another native plant that is really best raised from seed, direct sown where you want it. Wild Lupins are deeply tap-rooted and I find I cannot hold them in pots for very long. If the plants do not get into the ground at a fairly young age, they wither and die. This species only thrives in very well-drained, sandy soil; it will not succeed in tight clays. I will be bringing some young Wild Lupins in pots to the Westboro Market this coming Saturday (August 10). They can be transferred to the garden with care – note the extraordinary length of the taproot as you remove the still small plants.