librarian2003 (librarian2003) wrote in weagardening, @ 2013-01-25 15:45:00 |
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Current mood: | cold |
Entry tags: | 2012-13, cacti and succulents, wea |
A New Term and a New Start
This journal hasn't been updated in a while. Sorry about that - it's been a case of so much to do, so little time...
But, let's see if we can make a whole new start for 2013.
The snow has put an abrupt ending to any winter jobs we might have been doing, but hopefully warmer weather will move in this weekend, and it will be possible to get back to work rather than just staring moodily out of the window, thinking of all those things-to-do that are piling up.
In the meantime, here's what we have been talking about.
In week 1, we looked at the weird and wonderful beauty of Cacti and Succulents.
Here are the images:
Cacti and Succulents images
And here is the handout:
GARDENING FOR PLEASURE
Cacti and Succulents
What is the difference between a cactus and a succulent? How can you tell them apart? Here is some information to help you tell the difference. ‘Succulent’ is a descriptive term for all the types of plants that store water in their leaves or stems. Cacti are a large family of plants that are all succulents. So, a good rule to remember is that all cacti are succulents, but not all succulents are cacti.
It is thought by many that spines are what differentiates a cactus from other succulents. This is, simply, not true. There are some cacti that are smooth and do not have spines. There are also some succulents that have prickly spines. The way to tell the difference between the spiny cacti and other types of prickly succulents is that cacti have areoles, or spine cushions. The spines, roots and flowers of a cactus will grow only out of these spine cushions. The prickly parts of other succulents do not grow together in this manner.
All cacti come from the New World, ranging from Patagonia in the south to parts of western Canada in the north, except for Rhipsalis baccifera, which also grows in Africa and Sri Lanka, raising something of a mystery. Most occur in very arid semi-deserts. Some are found in the Atacama desert, the driest place on Earth.
The tallest free-standing cactus is Pachycereus pringlei, with a maximum recorded height of 63 ft, and the smallest is Blossfeldia liliputiana, less than half an inch in diameter at maturity. A few species differ significantly in appearance from most of the family. At least superficially, plants of the genus Pereskia resemble other trees and shrubs growing around them. They have persistent leaves and when older, bark-covered stems. Their areoles identify them as cacti, and in spite of their appearance, they, too, have many adaptations for water conservation. Pereskia is considered close to the ancestral species from which all cacti evolved. In tropical regions, other cacti grow as forest climbers and epiphytes (plants that grow on trees). Their stems are typically flattened, almost leaf-like in appearance, with fewer or even no spines, such as the Christmas cactus, Schlumbergera.
Cacti have a variety of uses: many species are used as ornamental plants, others are grown for fodder or forage, and others for food (particularly their fruit). Cochineal is the product of an insect that lives on some cacti.
Succulents grow in almost all parts of the world, apart from the Arctic and the Antarctic. Some of the richest areas for succulents are South Africa and Madagascar, but a fair number grow in North and South America too. In horticultural use, the term "succulent" regularly excludes cacti.
Plants are not either "succulent" or "non-succulent". In many genera and families there is a continuous sequence from plants with thin leaves and normal stems to those with very clearly thickened and fleshy leaves or stems, so that deciding what is a succulent is often arbitrary. Different sources may classify the same plant differently. Occasionally succulents may be aquatic, as with Crassula helmsii, swamp stonecrop or New Zealand pigmyweed.
When buying a cactus or a succulent, check the base of the plants for signs of softness. This indicates a rotting problem and a plant not long for the world. Avoid plants where the new growth is thin and pale in colour. This suggests plants that have been kept in poor light conditions for too long. And always check for insects, especially scale and mealy bug.
All cacti and succulents need bright light areas. If the light is too low, they will often stretch and even round, barrel-shaped cactus will become very thin and elongated.
Cacti and succulents have growth cycles, and it is usually in response to water and temperature. At one time of the year when temperatures are cool and moisture low, succulents will go dormant. When temperatures are warm and moisture more abundant, succulents grow more actively.
Most cacti and succulents have their active growth cycle during the spring and summer, gradually slowing down and going dormant in autumn and winter. Plants with this growth cycle include Echinocactus, Ferocactus, Opuntia, and Notocacus. These plants should be kept warm and well-watered during the natural growth cycle and cool and dry at other times of the year.
The more succulent tree dwellers such as Christmas cactus prefer warm temperatures and moist soils during the late spring and summer and cool temperatures and dry soil for several months before their yearly blooming.
Temperature is an important factor for cacti and succulents. Providing the proper temperature can often result in encouraging the cacti and succulents to bloom. Proper temperature is dependent on whether the plant is growing or dormant. Dormant plants prefer temperatures between 45 and 55 degrees. These cool temperatures combined with occasional light watering ‘hardens’ the plant. Flower buds are more likely to form at the cooler temperatures.
Many cacti, particularly the globe-shaped ones, will bloom readily if given this cool, dry period. Areas right next to windows often provide the perfect growing environment during the winter and can satisfy the cool temperature requirement. Growing at normal room temperatures will by no means harm the plant but if you want to see flowers, cold helps.
During the summer, cacti and succulents like to be outdoors. Locate them where they get light shade and keep them watered.
Even though cacti and succulents can tolerate dry conditions for extended periods, they do like to receive water for best growth. Watering is based first of all on whether they are dormant or growing. During the growing period, water the plants thoroughly when the soil gets dry and don’t let them sit in a saucer of water. Water again only when the soil gets dry. During the dormant period, apply water very sparingly. Let the soil get dry and then apply enough water to slightly dampen the soil. Overwatering during the dormant period can lead to rotting.
These are good starter plants, easy to maintain and often will flower: Mammillaria: Notocactus: Aeoniums
One of the more challenging but truly unique succulents is the Lithops or living stones. In nature, they grow submerged in the soil with only their tops exposed, looking just like pebbles. Allow the soil to dry completely between infrequent light watering during their summer dormant period. In the fall and winter, water the plant more frequently but still maintain the soil on the dry side. The frequent reward for this care is daisy-like flowers in November or December appearing in what looks like a crack in a rock.
Cacti and succulents require a very open and free-draining compost. Use a proprietary compost or make one yourself. A typical recipe is to use John Innes No 2 compost for seedlings and John Innes No 3 for plants two years old and over, mixed with horticultural grit at the rate of 3 parts J.I. compost and 1 part grit. Most prefer a slightly acidic compost (pH6). Some species, such as Echevierias, really hate lime and are probably suited to a peat-based compost.
When potting up use pots that are just the right size for the plant, never too large. Many cacti and succulents have fibrous roots and do not require or use the full depth of a standard pot, and half pots or pans are more suitable. Putting a shallow rooted specimen in a deep pot is counter-productive as the soil below the reach of the roots will stay wet for prolonged periods after watering and may become stagnant. Those species which have tuberous or tap toots may require more depth and will probably grow better in a standard pot.
Bonsai pots can look very effective with caudiciform plants where the caudex (a swollen root or lower stem) is raised up above the compost. Finally, some cacti and succulents are native to limestone areas and often seen growing in cracks in limestone boulders. Such lime-tolerant plants are suitable for planting in a block of tufa and can look very effective as an alternative to alpines.
Handle spiny cacti during repotting without breaking the spines by wrapping a roll of newspaper or paper towel round the sides of the plant. This may be kept in place if required by elastic bands or a wire twist tie. If the spines become entangled, wetting the paper will make it easier to remove, and small bits can be taken off the spines with tweezers. Handling with bare hands is not recommended with Opuntia Sp. as the fine spines (glochids) will break off and become embedded in the skin, or with Mammillaria species with 'fish-hook' spines that tend to catch in the skin.
When repotting, tap the compost around the roots, but never press it in. It will settle when the plant is watered later. Re-potting should not be necessary more than once a year, into the next size pot. When plants are larger, re-potting only becomes necessary when the plant has outgrown the pot, or it does not grow well. It is best to re-pot plants at the beginning of their growing season in early spring. After re-potting, never water until the plant has settled down for week or two in warm weather.
Water freely in spring and summer when the plants are growing well. Water in the early morning once a week if the plants are in the greenhouse, or once a fortnight if in the house on a window sill. Try not to water on cool or wet days, so that plants have a chance to dry off after you have watered.
When you water, water well. Watering little and often will bring the roots to the surface and make them susceptible to drought and they will not grow well. Never leave water standing in the saucer, just give as much as the plant can absorb and water the compost, not onto the plant.
No water should be given at all from about mid September until the end of March, except for winter-growing species.
Some of the South African succulents, usually plants from winter rainfall areas (e.g. Lithops, Conophytums and some other Mesembryanthemums, Testudinaria elephantipes, Tylocodons, and a few Aloes) grow during the autumn and winter months. Their watering should reflect this.
Lithops should be watered from the early summer to the early autumn. Flowers usually appear from late August into the autumn, depending on the species. Water is then withdrawn as the weather becomes colder, and the outer skin allowed to shrivel to a papery epidermis, before watering commences again in the summer. Dried outer skins can be carefully removed to improve the appearance of plants and improve availability of light to the plant bodies.
Conophytums tend to have an even later autumn / winter growing period, and generally flower at the beginning of their growing season. Watering should be during the late summer - early autumn and spring, with a break during the coldest winter months. However, keep an eye on the condition of your plants and start watering before they dry out too much, or they may not recover from their resting period.
When the plants are growing, add some fertilizer when watering. Phostrogen or Chempak No 8 is best, but any fertiliser low in nitrogen but high in potash is very suitable for all cacti and succulents.
Cacti have very few pests and diseases. The most common is mealy bug which may attack the plant and its roots, but watering with systemic insecticide will usually eradicate them. Vine weevil can also be a problem.
The majority of cacti can be propagated by cuttings. Sometimes it may be necessary to treat an established plant as a cutting, if for example the root system rots. For all cuttings ensure a clean cut with no residual damaged material remaining. The cutting must be aired for a few days to allow the cut flesh to callus over sufficiently to form a waterproof seal. Cuttings are set in a rooting mixture of two parts sand to one part peat, which should be barely moist. The cuttings themselves should not be buried but simply rested on the compost. Bottom heat helps and extra moisture in the form of occasional mist spraying can be given. June is normally the best month for taking cuttings but care should be taken to avoid excessive heat and direct sunlight until evidence of new growth appears. The rate of rooting is extremely variable with vigorous forms rooting in a matter of days, and others taking much longer. Mixing a little hormone rooting powder into the compost may speed up the rooting process. If rooting occurs quickly pot the plants on only if a month or so of good growing weather can be expected. In other cases it is best to delay repotting until there are signs of activity in the following growing season.
Many species of succulent plants and cacti produce small plants at the base of the parent plant. These offsets can usually be easily pulled or cut off the main plant, allowed to dry for a few days and potted up individually. The main plant often benefits from removal of offsets which can divert energy from the main stem, and removal of offsets may be essential to the production of a large solitary specimen.
Other species produce miniature plants on the edges of leaves, flower stems or flower heads, and these can also be removed and potted up.
These plants can also be grown from seed, some more easily than others. Seed generally needs a temperature above 25 degrees C for germination, so without a heated propagator, an airing cupboard, or shelf over a radiator is best, but move into a good light as soon as the first germination occurs. Use a gritty compost low in fertilizer. Keep barely moist, but make sure the surface does not dry out.
Quiz
Try a quiz on differentiating between cacti and succulents:
http://cactiguide.com/cactus_quiz/
Jo Hanslip
March 2010
Revised January 2013
Our sites of the week are here:
GARDENING FOR PLEASURE
Spring Term 2012/13
Sites of the week : Week 1
1 For information on cacti and succulents
The British Cacti and Succulent Society
http://www.bcss.org.uk
2 For an interesting and informative succulent site, including good cultivation advice and lots of images
The Succulent Plant Page
http://www.succulent-plant.com
3 An article on the Rhipsalis site discussing the mystery of the geographical distribution of Rhipsalis. Follow the links for all three pages of this article.
Rhipsalis
http://www.rhipsalis.com/maxwell.ht
4 Cacti for sale from Ralph, a professor at Cardiff University. Very reasonable prices.
Ralph’s Cacti for Sale
http://ralph.cs.cf.ac.uk/cacti/fors
5 A good range of plants for sale, and good cultivation advice.
Surreal Succulents
http://www.surrealsucculents.co.uk
6 An excellent information and image site.
Cacti Guide
http://cactiguide.com
Jo Hanslip
January 2013
Does anyone have anything to share about these topics? If so, just comment below.
Jo