Portulaca includes nearly 100 species, mostly all native to the tropical regions around the world. Almost all of them are low, spreading succulents, in some places a few species are invasive and others are weedy; some like Portulaca oleracea are edible.
Certainly the most endeared and valuable amongst them from the gardening point of view is the spreading Brazilian native species known botanically as Portulaca grandiflora This little plants is also known as Moss Rose, Sun Rose or Rose Moss or just Garden Portulaca.
This annual branching, dwarf, groundcover has rice-shaped leaves and round, reddish succulent stems. Each stem is covered from its base to the very tip with these narrow leaves that somewhat resemble the configuration of a Pine or Spruce branch but are never prickly but soft and succulent. Stems are very freely branching and soon spread to make dense soft mats which appear from a distance to be almost mossy.
Plants are smothered through Summer with beautifully formed, delicate Rose-like single and double flowers with a central cluster of golden yellow stamens and a pleasing but very subtle scent. They do resemble small Roses or Cactus flowers. Petals are almost diaphanous and silky in solid and multi-tones that appear in a wide range of vivid colours shades except for those blue to purple tones.
Buds develop in a cluster at the end of every stem. Their spreading and often dense succulent appearance covered with these lovely Rose-like (2.5-2.5cm/1-3inches) Rose-like blooms inspired their common name of ‘Rose Moss’.
Portulaca demand dry and hot conditions that remain airy, open, and sunny. New hybrid species have been developed that flower very well in cooler climates during the Summer months. They revel in most open garden beds with soils that drain well and even arid situations such as coastal locations, steep banks, gravel or sandy land, well-drained rockeries, terraces and as edging to borders and pathways. Poorer soils often create bigger, better quality blooms. They are excellent for the dry garden as they resent over watering!
Portulaca seed is very fine and black/silver. It germinates quite quickly and easily in the right situation. The seed can be sown into containers or flats in the sunny and warm glasshouse, with bottom heat, early in the season 4-6 weeks prior to the last frost for later transplanting once the weather warms. Or it can be sown much more easily once the weather has thoroughly warmed in Mid to Late Spring or Early Summer. Once again it can be sown in the sunny warm glasshouse or outdoors in a very bright, sheltered and consistently warm location.
When planted during the warmth of Late Spring and Early to Mid Summer from seed they should be in bloom within six to eight weeks. When planted as advanced seedlings, they can often be in flower within a few days to a couple of weeks.
Often Portulaca is sown direct into a garden bed or rockery where it is meant to grow. In temperate climates it can be sown direct from Early to Mid Summer and in tropical regions it is often sown in Autumn to Spring for flowers during the dry and sunny cooler months. Only problem with sowing direct is that Ants love the seed and often carry it off! Thus sometimes Gardeners with Ant problems sometimes sprinkle Borax over the seed bed or around its edges when the seed is sown.
Seed germinates best and fairly rapidly in a light and fluffy seed raising or potting mix, often with half its volume mixed with propagating sand or pumice. Pre-moisten the mix and then sprinkle the seed lightly over the surface and either lightly scratch it in or very lightly cover it with a tiny skim of additional soil mix. Place the seed container in a very bright or sunny and warm place with no cold drafts. Maintain light but even moisture and do not over=water the seed or emerging seedlings will rot.
Emerging seedlings are as fine as the point of a needle and smaller across than the head of a pin. They are often a reddish or brownish green at first so very difficult to detect without very good eyesight or a magnifying glass. But within a few weeks they will have advanced enough to become recognizable. And then suddenly will advance more rapidly and as the weather becomes summery, their growth will become noticeable almost day-by-day. When sown during cool weather early in the season, seedlings can take 8-12 weeks to flower. But when sown during tropical warmth this time can be reduced to 6-8 weeks!
Portulacas are excellent plants for containers. Because they are so tiny and vulnerable while very young, they are often sown directly into the container in which they are meant to grow and flower. They will grow in quite small pots but often look much more effective in larger decorative bowls and fairly shallow planters. This is because like many other arid zone plants, Portulacas prefer rather constant dry-moist and warm conditions.
But they resent continual changes in the extremes of cold and hot; dry and wet which inevitably occur when smaller containers must be continuously watered, especially with cold water on a hot day. Container-grown Portulaca often does best in near-full sunshine. But frequently looks its best in sites that receive a little bit of late afternoon shade which shelters them from excessive drying and scalding conditions.
Certainly the distinct advantage to container-grown Portulaca is that the pots can be raised for much closer examination of their wonderful flowers. And this is really the only reason to grow these remarkable little treasures.
Each Portulaca flower opens but for one day. And buds often remain closed on cloudy and dull days. Blooms open from early morning as soon as the sunshine hits their semi-open buds. It is easy to tell when a flower bud is about to open as the protective bud sheath begins to open that morning or often the day before; revealing the true colour of the flower still held tightly closed within. Then as the morning sun strikes the emerging bud, each flower springs open rather dramatically in a very short period of time. If one is patient enough to sit and observe or work nearby and look back every minute or so, it is possible to actually see each flower open right before one’s eyes. They make a glorious show when massed together all shimmering and sparkling in the sunlight.
But as soon as the sunlight passes off of the flowers or early evening darkness approaches, the flowers close and that is their end. Every stem contains the buds of multiple flowers; each opening in succession, so more blooms will emerge from the stem over a number of weeks. By then emerging side shoots will produce more stems topped with flower buds. And because these are much-branching plants, blooming will increase and become quite prolific; enough to nearly cover the entire plant with delicate candy-coloured satiny ‘Rose’ blooms for many weeks at their peak of flowering.
From beginning to end the plants flower for nearly the entire Summer season and sometimes well into Autumn. They start with just a few scattered blooms but soon produce more and more before starting to trail off as the weather cools. Pinching-back old spent stems often encourages additional branching and new blooms later in the season.
Portulacas are affected by few diseases or pests. Their greatest vulnerability is often over watering, especially if this coincides with cloudy and cold conditions. Plants quickly rot when confronted with chilling and excessive wet. They are not at all good in shaded sites or wet ground and a period of cloudy and cold conditions especially when combined with heavy rainfall or frost will end their season.
The other thing is that Portulaca, while being an annual succulent plant that is very durable, is surprising sensitive to chemical fertilisers and sprays. While they thrive on small amounts of slow release fertiliser or moderate liquid feeding, they easily burn if ever their sensitive tissues come in direct contact with any caustic chemical fertiliser.
Even a subtle drifting of a systemic insecticide /fungicide chemical spray or herbicide will often defoliate the entire plant and sometimes kills it outright! While there is seldom ever any need to spray Portulaca as it is so seldom attacked, this susceptibility to chemical sprays dictates where it can be successfully planted.
For example, while it could make an attractive groundcover beneath hybrid Roses, the reality that these Roses will almost certainly need some form of toxic spray means that the Portulaca plants would probably be adversely affected by the drifting spray falling upon them. And while they make a superior border plant along a pathway or between paving stones, especially when inter-planted with white or deep purple Alyssum, the Portulaca would be killed if ever herbicidal spray were to be used to eliminate grasses or weeds on the pathway.
In the Language of Flowers, Portulaca means ‘Superior’ and also ‘Confessions of Love’. This plant certainly lives up to its reputation. The flowers are indeed a superior creation of Nature and hold a very special magic. These little treasured blooms are so very special that many a passionate Gardener would have to confess that out of love for the dear Portulaca, they have been reduced to their hands and knees to more closely admire their perfection. Children of all ages will surely find the lovely Rose Moss Portulaca irresistible.
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