Penstemons are graceful flowers that always make a great impression whether planted in herbaceous borders, rock gardens, woodland areas or in more formal settings.
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Their tubular-shaped flowers carried on tapering spires come in shades of blue, pink, red, lavender, white and bi-coloured.
Varieties range in height from tiny mat-forming plants like P. barbatus with its bright pink or scarlet flowers to fast growers reaching 1.2m tall.
Penstemons belong to the same family as foxgloves, Scrophulariaceae.
To encourage re-blooming, deadhead spent flower spikes throughout the summer season by removing those blooms that have died.
You need to sacrifice the uppermost last flowers on each stem and cut them down to where new shoots are emerging below the first spent flower.
These will produce the next flush of flowers.
Most cultivars of penstemons are derived from species that are native to the United States of America and Mexico, thus they will not stand cold wet, feet in winter.
These frost-tolerant plants need well-drained, fertile soil in a sunny position. Water well during dry spells.
Their fibrous root systems don’t stray, so they tend to grow in clumps.
Don’t prune too hard in autumn, although a tidy up helps protect them from wind rock in the winter.
Cut back in late autumn to early spring to about 15cms above new growth from the soil.
Historical horticulture
Ever since man gave up hunter-gathering, we have grown plants as a source of food. No doubt, our early farming skills were learnt from observing the way plants spread their seeds and the resulting growth of the new seedlings.
These early observations by our forefathers paved the way for our modern horticultural practices.
It was Theophrastus (371-287BC), revered as the father of botany who wrote extensively about cultivated plants, in particular, olives, dates, cabbage, radish, turnip, beet, lettuce, cucumber, leeks, celery and the herbs of coriander, dill, cress, basil, marjoram and purslane.
Theophrastus classified some 500 plants and developed a scientific terminology for describing biological structures. In his work on germination he noted the different ways plants grew from seeds, roots and cuttings.
He observed that seedlings sometimes had dissimilar characteristics from their parents, but that plants grown from cuttings resembled the parent plant and that sometimes, seedlings grown from seed could degenerate, but cuttings didn’t.
The Romans knew about protecting and forcing fruit and vegetables by constructing ‘glasshouses’ from mica, and the Victorian gardeners perfected the bottom heat method used to put roots on cuttings.
The ancient Chinese gardeners understood the budding methods of propagation and the use of rootstocks.
They discovered that it was possible to use herbaceous peony rootstocks to graft tree peonies – this method is still used today.
Diary
October 8: The Australian Plant Society Spring Plant Sale 10am - 4pm Max Fry Hall, Gorge Road Trevallyn.
October 18: The Australian Plant Society meet at the Max Fry Hall on Gorge Rd, Trevallyn, Launceston at 7.30pm. Guest speaker for the evening is Mark Wapstra on “Tasmania’s grassland orchids: in desperate need of help”.
October 19: The Launceston Horticultural Society meet at the Windmill Hill Hall, High Street, Launceston at 8pm. Visitors welcome.