From: Hannon <othonna at gmail.com>
on 2011.12.15 at 04:15:24
Hi Christopher,
That is a good point. The "average humidity" for nearby Pomona is 43%, which in reality means daytime humidity mostly <43% and nighttime humidity over 43%, often reaching the dew point. The Los Angeles area is a semi-arid zone with a strong coastal influence. It is not a desert.
The drying of the soil we are concerned with is toward the end of the growing season and during the dormant period. A plant that has just lost its leaves by yellowing and withering should already be in relatively dry soil. It should not be watered until the next growing season in most cases. If the plant has had a good season with vigorous root growth then this root system will help pull water out of the soil just before the leaves die down; the roots are dying back at this point also. Dormant tubers should not be put away wet so to speak but I don't know if humidity alone is enough to prevent soil from drying "enough". This issue will vary between species and genera.
It is worth re-emphasizing that plants are best grown 'snug' in their pots so that the soil dries out regularly and the roots can develop mainly around the perimeter of the rootball, where there is better aeration and more warmth. It is important in avoiding excess moisture whether the plant is dormant or growing, especially with tuberous aroids that experience a pronounced dry season in nature. I like to say that if you can master watering (to your own needs) then you have mastered half of horticultural practice.
There is probably an ideal moisture level for the dormant tubers of any given species but there is also a considerable margin of error for us growers. Sauromatum can grow here outdoors in gardens with winter rainfall when it is dormant (and in St. Louis for that matter); conversely plants like Amorphophallus gigas or A. titanum can suffer if the soil gets so dry that the perennial roots die back. Perennial roots are often a good indication that a plant receives or is adapted to off season rainfall (or watering). Some tuberous aroids have them while others do not.
I hope this helps.
Dylan On 14 December 2011 07:15, D. Christopher Rogers <branchiopod@gmail.com> wrote:
Hiyer, Dylan!
=A0
What are your local humidity levels? It seems that the more humid you are, the harder time one will have keeping the soil in the pots dry.
=A0
Christopher
On Mon, Dec 12, 2011 at 6:38 PM, Hannon <othonna@gmail.com> wrote:
Dear Marek,
The best protection for dormant tubers is the soil that surrounded them in the growing season. It acts like a perfect cocoon. A tuber will have greater exposure to pests and desiccation if taken out of its soil. The idea of unearthing bulbs and tubers after the growth period persists in many hobbyist circles and I believe it is the wrong approach in most cases.=A0
1. Attentive culture should result in no pests in the soil at all. Such pests should be evident in the growing season and treated then, especially root mealy.=A0When withered leaves are removed I push some soil into the hole left by the petiole to prohibit entry by ants, mealies, etc. When=A0the soil dries out as the leaves yellow there should be no moisture at all at the bottom of the pot. "Dry soil" is not as dry as you might think and will retain some beneficial moisture for months while the plant is dormant. (This can be demonstrated by allowing a few small weeds to stay in the pot and observing them 5, 10 or 15 weeks later after zero watering). When they have had a good season (in plastic pots) aroid tubers/corms will often distend the pot so that it is firm and compact; this 'package' is the ideal state for storage over winter (or summer).
2. At the beginning of the season I wait for new shoots to emerge and repot then, when the plant is active. If they are slow to wake up I will water well just ONCE and see what happens. If nothing happens after a few weeks then I unpot and look for signs of trouble. Unless the new roots are well along (with secondary branching) it is easy to transplant a plant starting its growth. In fact, I often wait until a leaf is formed and then shift to the appropriate next size pot. Usually this does not involve disturbing the root ball at all. Note: some geophytes like amorphos and their kin seem to need repotting every 1-2 years while others (including Biarum) can go on for a number of years before new soil is needed. Keep in mind that any soil mix used by a plant that is dormant half the year is only on duty for about six months. Any soil mix that is exhausted in six months is hardly worthy of the name. The addition of coarse sand helps the longevity of a mix substantially.
It can be difficult to gauge the need of a plant for a particular pot size until it is in full growth and it is impossible to know the vigor of a plant until it is growing. Vigor-- not necessarily tuber size-- determines pot size as well as watering needs and the two are closely related. I prefer a smaller pot that needs more frequent watering rather than a relatively large pot that takes too long to dry out. Soil in a container that takes weeks rather than days to dry and justify the next watering is a sign that the pot is too large for the root system. It is important to let the soil surface go very dry between waterings, assuming everything else is in order. I grow over 70 amorpho species and hundreds of other geophytes in 'cramped quarters' and these=A0techniques has been successful to date.
Dylan Hannon
On 12 December 2011 11:02, Marek Argent <abri1973@wp.pl> wrote:
Dear Hannon,
=A0
I keep all tubers dry when they're dormant, even I dont water them until the new bud grows enough large to break.
As for the soil - should the tubers stay in the old soil during the dormancy or should I change it as the roots wither
or when it starts to grow again?
In all the methods there are good and bad things.
=A0
1. Leaving=A0the tuber=A0in the old soil=A0means leaving it with all pests and the soil itself often remains wet too long at the bottom of the pot what may cause rotting. Next season the tuber can start to grow too early and repotting it while producing new roots may be fatal.
=A0
2. Repotting it shortly after the leaves wither - the new soil left dry for a few months loses=A0its moisture and structure, it=A0turns into dust and sand.
=A0
So when is the best time to change soil in pots?
Marek
=A0
=A0
----- Original Message -----
Sent: Saturday, December 10, 2011 3:46 AM
Subject: Re: [Aroid-l] Cultivation of Taccarum
Agreed that keeping it in its pot when dormant is a good idea, as with all geophytes. But Taccarum should be kept DRY when dormant. This is true for probably most but not all tuberous aroids.
On 9 December 2011 05:53, <Zanezirklejr@aol.com> wrote:
Your problem is taking it out of the soil, it needs to be kept in the pot and moist at all times, also needs to be outside not in a window.
=A0
In a message dated 12/7/2011 11:47:28 P.M. Eastern Standard Time, abri1973@wp.pl writes:
Hello,
=A0
I've had Taccarum weddellianum since 2005, every year it produces a leaf and usually a "baby" tuber.
But... it doesn't grow in size almost at all, although the tuber very=A0slowly increases, the leaf is 20-30 cm tall every year.
I use regular pot soil, and the plant is fertilized with natural biohumus.
It grows in a southern window.
When it's dormant I store it without soil in the normal room temperature.
=A0
What do I do wrong? What should I do to make it grow larger?
Here are photos of my plant:
=A0
Please help,
Marek
=A0
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D. Christopher Rogers ((,///////////=3D=3D=3D=3D=3D=3D=3D< 785.864.1714Crustacean Taxonomist and Ecologist
Kansas Biological Survey
Kansas University, Higuchi Hall
2101 Constant Avenue, Lawrence, KS 66047-3759 USA
=A0
Vice President, Southwest Association of Freshwater Invertebrate Taxonomists SAFIT.ORG
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-- "The greatest service which can be rendered any country is to add an useful plant to it's culture"
- Thomas Jefferson Memorandum of Services to My Country, after 2 September 1800
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