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Plant Care

  Pests and diseases

     Examples

 

Guide to the care of Zonal Pelargoniums

     History

     Requirements

     Compost

     Feeding

     Potting On

 

Germination of Seeds

 

 

Pests and diseases

 

The worst enemy is moisture-laden air e.g. Damp, humid or foggy conditions. These conditions leave the plants susceptible to a common problem: Fungal Rot.  It encourages “Blackleg” in Cuttings, which is where the stem rots from the base. Grey mould (Botrytis) may appear where leaf stems are damaged, or petals fall onto the leaf itself.  If a damp petal falls onto a leaf, it will quickly start to rot, and the disease can rapidly spread back along the leaf and into the main stem. It may kill the plant if undetected.  Affected cuttings must be destroyed, but removing the affected tissue can often save mature plants.  Prevention is simple, but time consuming: If it takes you all day to remove the dying flowers, then you have too many plants!   Other preventative measures are, good hygiene (cleaning the greenhouse), and good air circulation and ventilation.  Ventilation is, therefore, still important in the winter, so open the windows slightly whenever the air temperature is above freezing. (It is essential to close them again at night in case of severe frost!)

 

To help prevent rot in cuttings, you can water them with fungicide, or use hormone-rooting powder. Only water cuttings when you think they are almost dry. In adverse conditions I only give enough water to make the soil slightly damp. Except in mid summer, I don’t water cuttings until the day after taking them: Alternatively, I don’t pot them up until the day after taking them.  This gives the damaged stem time to “seal”, and prevent entry of micro-organisms to the cut stem. 

 

Try to avoid over watering geraniums in any circumstance: The golden rule is “If in doubt, Don’t”

Excess moisture adds humidity around leaf area by evaporation from the soil, or from spillages on the bench. It is essential to avoid this when ever possible during the winter. A good tip is to always water in the mornings, so that the air “dries out” a bit before nightfall.  Water lying on a leaf during a cold night will increase the likely hood of frost damage or rot.  During the summer, leaves with water on them will scorch when the sun becomes too hot.  It is also worth remembering that the roots need to breathe air, and if the plant is continuously standing in water it will drown! 

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Examples

Rust (Puccinia Pelagonii Zonalis)  This is a problem if it takes hold. -  However it is easier to treat indoors than outside. It is debilitating and unsightly. It does not usually kill the plants, but if left unchecked, growth is seriously affected and it will be almost impossible to eradicate.  Rust can be treated with chemical sprays purchased from the garden centre. Unfortunately re-infection can be quite a problem.  If your plant has rust, you may first notice a coppery circular discoloration on the leaf: If you look at the underside, you will see a small brownish orange ring (Like tiny brown Polo’s!)  Pick off the leaf very carefully (to prevent the spread of spores) and burn it, or seal it in a plastic bag before disposal.  Spray all your plants, and be extra vigilant for signs of further infection. The “ring” produces microscopic powdery spores, so do not touch it, or you will spread the infection. 

Aphids  Green flies prefer Ivy geraniums, or young Zonal shoots. Whitefly seems to prefer Regal and Scented Geraniums. Blackfly don’t appear to be a problem in my greenhouses. Early sightings and treatment with systemic insecticide is effective.  Whitefly seem to be harder to eradicate than the others.   The Sticky secretions that aphids produce will certainly encourage “Sooty Mould” if the infestation has gone undetected.  The secretions will also attract ants, which are not a problem unless they nest in the pots!   Looking at the plants regularly can prevent aphids from “taking hold”.    A bad infestation of root aphids can kill the plant. They appear as a white “furry” dots around the root ball. So if a plant looks sickly, knock it out from the pot and take a look: If I find any, I spray with systemic insecticide.   

Caterpillars  Pick them off and squash them!    Not much of a problem indoors.  Geraniums outside are usually only affected towards the end of the summer, when unsightly holes appear in the younger leaves and stem tips.  Try spraying with insecticide if the flower buds are being eaten.

Sciariad Flies  (Mushroom Gnats)  The grubs eat roots, which may kill the more vulnerable plants such as seedlings and cuttings.  I trap the adult flies using sticky yellow flypaper, which is hung from the roof, and under the benches. Hopefully they are trapped before laying their eggs in the soil!

Snails and Slugs   I have not found them to be a problem, as they will eat other plants before the geraniums!   (Well they don’t seem to like mine!)   The only problems I have experienced, is if they eat the young seedlings, which will not re-grow.  As I only grow geraniums in my greenhouse, other plants do not attract them in.

Red Spider Mite  This can be very bad if you grow Fuchsias along side your Geraniums, as the mites are initially attracted to the Fuchsias.  The mites are very small, and appear as tiny red dots, usually on the undersides of the leaves. When the plant is infested, you are more likely to see the fine silky webs in which they live. The problem can be quite difficult to treat, although some products are available.

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Guide to the care of Zonal Pelargoniums

 

History

Zonal Pelargoniums are commonly called “Geraniums”. Their botanical name is Pelargonium x Hortorum.    Ancestry includes P. Inquinans and P. Zonale from the Ciconium section of the species. Some others involved are P. Frutetorium and P. Alchemilliodes.  Most of these have a Fibourous root system, and originated in Africa.   “Geraniums” are perennial, given the correct conditions (such as a greenhouse!)

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Requirements

Plenty of good quality light, but not direct scorching sunlight is needed to keep the plants growing vigorously.  Most greenhouses must be shaded in summer to prevent excessive heat. (If it is too hot growth actually slows down)  A temperature of 7’c (45’f) will produce some flowers.  13’c (55’f) is the minimum temperature needed for constant flowering, and light levels need to be high enough to encourage bud formation.  To be free flowering, plants prefer about 16 hrs of good light per day.

 Pelargoniums dislike standing by gas installations or above radiators.  The best form of heating in a greenhouse is by thermostatically controlled Fan Heaters, because they create air movement:  Warm air circulating in winter helps to reduce fungal diseases, and cool air in summer promotes healthier plants. 

When watering the plants, fresh rainwater is best, but personally, I don’t have any problems with tap water. I cheat a bit by taking water out of my pond, and topping up the pond with tap water. If you collect rain water in a water butt, there are several ideas how to keep a water butt fresh:  Some people put charcoal in it, and some keep a couple of fish in it!  My father used the fish method, but I tried that before I had a garden pond, and could never keep them alive!!  Try to ensure that the water is a suitable temperature before using it. Don’t take it straight from water butt that has ice in or very cold tap water!  Leave water to stand in the can for a while, so it warms to “Room Temperature”. 

The air temperature itself must also be considered: - Plants can be stressed by a sudden drop or rise in temperature.  This is most likely to occur in Spring or Autumn when the daytime temperature can be vastly different to that of the Night. The classic symptoms of stress will be a reddening of the lower leaves. (NB: this also happens if plants become too dry!)

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Compost

I do not wish to discuss compost, as most people have their firm favourite.  Some prefer soil-based compost such as John Innes, and some prefer Peat based mixtures.  Peat based (and equivalent substitutes) seem to promote rapid root growth, but dry out very fast. Soil based compost retains moisture longer.  I tend to mix the two together, to get the best of both worlds: -  6 measures of J.Innes to 2 of CocoPeat, with the addition of 1 grit.  (Species prefer more grit)  To this mixture I add a small amount of Charcoal.    I never add moisture-retaining granules, as the soil may retain too much water during the winter months, and the plant may rot!

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Feeding

Some people feed as per the instructions on the packet, which generally advocates once a week.  However, I make up the Feed Solution at ¼ strength and feed at every watering.   Using this method, plants are not missed out or over-watered. 

The Feed Packet will have an NPK ratio. This is the amount of these elements present in the food.  N=Nitrogen, which is responsible for healthy leaf growth. (Valuable for a spring “Boost”).  P=Phosphourus which is responsible for healthy roots.  K=Potassium, which is necessary for flower and fruit (i.e. seed) formation: a valuable asset in late spring and summer. Some people change the type of feed according to the season.  The best formula for Zonal Pelargomniums is reported to be N:15.1  P:2.1  K23.5   The brand which is nearest to this ratio is Phostrogen Tomato Food which is N:12.5  P:5  K: 24.5   (There are several types so do check the  Packet)  Feeding during the winter is not usually recommended, as the Light and heat is not usually sufficient to produce vigorous growth, and so it is better to let the plant “rest”.  Lush growth produced in winter is more likely to attract pests and diseases. 

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Potting On

If you have any doubts about potting on, don’t do it!  When a plant needs to be potted on it will look disproportionately large in comparison to its existing pot.  You will find that it is one of the first plants to require additional watering on a hot day.  If it is “Pot Bound” (Too long in the same pot) it may increase flowering, but cease growth. The leaves will be smaller than usual, and start to look unhealthy.  Surprisingly, plants that are “Over potted” will also not grow well.  Growth will be slow, and the plant will look “lost” in its pot.  As a guide, for example, a plant in a 3”  pot will require 4 or 4 ½”  pot when it is ready to pot on.

Once you have chosen your next (clean!) pot, invert the plant and tap the rim of the pot gently on the bench. Support the plant by placing the fingers of your other hand over the soil and around the stem. The plant should come out of the pot with the soil and root ball intact. Always ensure that the plant was watered about 2 days before potting on. This ensures that the root ball will be neither too wet nor too dry.  Position the plant in its new pot, so the lower leaves are almost touching the rim. You may need to put some soil in the bottom first to adjust the height. 

Now, surround the plant with fresh compost. Fill it almost to the top, and tap it gently to settle the soil. (Restrain the plant at the correct level whilst doing so.)  Do not firm the soil by sticking your thumbs in it! You will almost certainly shear off some of the roots. If necessary gently push the soil down round the edges using the blunt end of a pencil. Try to avoid pushing it into the existing root ball.

Air pockets can be created around the root ball if the soil does not settle properly.  To avoid this happening, (and without risking damage to the roots by pressing on them), you can try the following: - Fill your new pot half way with soil. Using an empty pot of the same size as the one currently holding the plant, push it firmly into the larger pot. Assuming the soil is of the correct consistency, a hole of exactly the right size will be created when the smaller pot is removed. The plant can simply be placed into it, and additional soil added on top if necessary.

 

 

For further reading I suggest: Miniature and Dwarf Geraniums.  By H. Baghurst (ISBN 0747002185)  or one of the books by Jan Taylor.

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Germination of Seeds

(Zonal Pelargoniums – referred to in the text as Geraniums)

 

This is aimed at someone who has never grown a seed before, so please forgive me if you feel I’m stating the obvious….

 

The usual recommended method of seed germination is by sowing “shelled” seeds in pots or trays of moist seed compost, then covering them with a sprinkling of fine sand.

In the natural state, geranium seeds have an outer husk which protects it and provides it with the feathery transport system. example to follow shortly  Whilst you can sow the seed in this natural state, it is much better to “shell” (de-husk) it. The germination rate is much better, and there is less likelihood of the seed rotting. The disadvantage of shelling the seed yourself is that it can be tricky to get the outer layer off without damaging the enclosed seed, and it is quite time consuming if you have lots of seeds !

 

Propagators are recommended for seed germination as they maintain a constant temperature via a heating element at the bottom of the container.  However the purchase of such equipment for just a few seeds may not be economical.  I sow my seeds in sealable containers, half filled with moist vermiculite.  Tupperware containers are a very useful for this, but the containers you get when you order a take-away meal are just as good ! example to follow shortly

I prefer vermiculite to normal seed compost because, once the seeds have germinated, they can be lifted straight out of it with very little likelihood of damage to the roots.  Vermiculite is very light.  Even U.C. Compost is heavy by comparison, and can cling to the stem or roots and break them as the seedling is lifted.

 

Fill your chosen container to a third of its depth with dry vermiculite. Gradually add cooled previously boiled water until the vermiculite sticks together when squeezed, but does not drip out water. At this stage the vermiculite will have swollen to occupy about half the container space. example to follow shortly

Please note that moist means “damp to the touch” - With any stage of the plants life this must never be confused with “wet” which suggests that water would drip out of the compost or vermiculite if you were to squeeze it. Geraniums hate prolonged wet and rot easily. After germination, they aren’t over keen on high humidity either…..

 

Sow the seeds carefully on the surface of the moist vermiculite, leaving about a centimetre between them, and then put the lid on. To encourage the majority of your seeds to germinate at the same time, a constant temperature of around 22*c /72*f must be evenly maintained.  Any sudden drop in temperature (such as at night) can hinder germination.  – Even a slightly cooler temperature is preferable to a fluctuating temperature.

 

Containers with a snug fitting lid don’t leak water, and so they can be put in warm places such as the airing cupboard. Alternatively, some domestic appliances generate a constant heat source. For example, on the top of the fridge can actually be quite warm, but I wouldn’t recommend on top of the TV!      I have no preference for excluding light, but, wherever you put them, they must be checked every day.  The seeds should start to germinate within a week of sowing. However, if none of the seeds have germinated within 3 weeks, add a tiny drop more water to the container. - Don’t worry if you can’t supply the ideal: So long as the seeds are swelled and Coppery-Brown in colour they are alive and will germinate sooner or later.  (I never cover the seeds, so that I can see them)   Always retain compost with “Un-germinated” seeds in it, and use it for something else because geranium seeds can remain viable for long periods of time, and It is not unusual to have a Geranium seedling coming up with my tomatoes……

Once the seeds begin to germinate, make sure the container is brought near a good source of natural light. Remaining in the dark in a humid atmosphere for even a day too long may at best cause over-lengthening of the stem leading to weakness, or worse they will rot and die.

Wait until the two seed leaves have appeared and are uncurled,  example to follow shortly  then pot them up. This is the optimum time to transfer your seedlings with minimum damage. At this stage they are vulnerable to rotting if the stem is even mildly bruised.

 

Prepare your chosen seed compost in a small pot. The compost should be mildly damp, so that if you poke in a dibber (or pencil) a hole remains when the dibber is removed. Very gently take your seedling by the seed leaves (cotyledons). Avoid touching the delicate stem. If the root is already extended down into the vermiculite you may want to gently loosen around it with a thin dibber. I use the handle end of a teaspoon. Carefully lift your seedling out of the container and hold it in the hole made in the pot of seed compost. The seed leaves should be a 3-5 millimetres above the level of the compost. Trickle some very fine dry sand into the hole around the seedling until the hole is filled. Do not press the soil with your fingers. Water the seedling with cool previously boiled water.  Adding a fungicide is optional.

 

Stand the seedling in the lightest possible place you have. A greenhouse maintained at room temperature is best. If you only have a windowsill, make it a South facing one, and turn the pot slightly everyday. (To prevent the developing plant becoming lop-sided).

Seedlings can actually survive temperatures right down to 1*c, but the lower the temperature, the slower the growth will be, which increases the chance of rotting off. Although the seedlings cope much better with dry heat as opposed to damp cold, it must also be remembered that baking the poor little things in a very sunny place which is hotter than 28*c is not a good start in life either !

 

I have been talking about various differences in temperature, because you may wish to sow your seeds at any time of the year. Keeping a constant temperature is more important for bedding geraniums, as it more desirable that they germinate and grow uniformly. Ideally, these should be sown in a heated greenhouse around the beginning of February, so that they will be flowering in June. However, my seeds are more suitable for enthusiasts, rather than for people who want summer bedding displays, so it doesn’t really matter what time of year they are sown, as long as you can provide the correct requirements.

 

The most important after care for your seedling is adequate light, and not getting the leaves or the soil too wet. – Touch the soil; if it feels slightly moist, or if couple soil grains stick to your finger, don’t water it again yet ! – You can also tell if there is sufficient moisture in the soil by its weight. Get used to how that size of pot feels when it has dry soil in it, and when the soil’s wet. If sufficient water is already present in the pot, the pot will weigh between the two extremes of dry and wet.

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