Sunday, February 19, 2012

The life and times of a Black thumb

“I can’t grow anything I’m a total Black Thumb!”

We’ve heard this line before, If you say this or know someone who utters something like this with regularity then this is the article for you. For those unfamiliar a black thumb is supposed to be the opposite of a green thumb. Generally it is accepted that a ‘black thumb’ is a person whom for whatever reason is convinced they cannot grow any sort of plant.

There are five things any potential black thumb should know; these things also will improve greatly the survival rate of your plants. For those who are planning to give a plant to a potential black thumb

There are five rules to successfully growing house plants.

1.     All Plants need water
2.     All plants have a winter resting period.
3.     All plants will eventually need repotting.
4.     All plants need light to grow.
5.     A stressed or sick plant may get a bug problem.

The first rule is pretty obvious, even the hardiest of cactus and driest of air plants needs some form of water eventually. The key to meeting your plant’s watering needs is to remember what sort of plant it is and what environment it came from. A cactus is used to prolonged periods without great precipitation where as an air plant is used to humidity and foggy mist but no real actual rain. Part of the key to watering is to make sure the soil-media is allowed to dry out completely between watering. If the media is allowed to dry organisms that could cause root rot never get a chance to cause a problem. On the other hand, allowing the soil to dry also guarantees that the plant is able to breathe, as waterlogged soil has reduced airspaces. Lastly, remember to water before the soil contracts away from the pot, at this point you may need to dunk the soil to get it wet again.

Secondly, all plants have a winter resting period that is triggered by the cooling of temperatures and the reduction of light due to the natural reduction of photoperiods caused by the days becoming shorter. Since you cannot do anything about this outside of buying an expensive greenhouse setup to guarantee light year-round, the simple solution is to begin allowing somewhat more time to pass between waterings, and make absolutely sure the soil dries between waterings. During this rest period your average house plant will naturally not be doing much growing, and will need little or no fertilizer as a result, it generally will need just enough water to remain alive but not as much as would be needed to actively grow.

Third on the list is the simple fact that all plants eventually need repotting. It is noteworthy that certain cactus and succulents do respond to being ‘pot-bound’ with the production of flowers and offsets. The aloe, sanseveria, haworthia and, the ox-tongue for example will often produce flowers and offsets in response to being pot bound but will stop this for a while once they are repotted. The act of repotting is that of simple renewal, as the soil like all things eventually goes stale, it loses composition, nutrients and a plant may go into decline if it is no longer able to get what it needs from the soil. Additionally a depleted soil may not hold moisture very well potentially doubling what it takes to keep the soil-media moist. Now without going absolute soil science geek on you readers out there, in short, a soil relies on its organic matter to sustain life, and outside in your yard the organics are being replenished as are the nutrients by the yearly cycles of growth, death and decay. In a potted plant the cycle is not so effective there is only much that can occur in a comparatively sterile environment.  The simplest way to check for repotting is to  simply try to remove the plant from it’s pot, if you see a whole lot of roots circling about the perimeter of the root ball, the plant is likely ‘pot-bound’  or that the roots are holding the current soil so much they make a pot unto themselves.

The fourth point on the list is the fact is that no plant can survive in the absence of natural light. Some can survive, short periods but none will do well under such conditions.  Even the rugged Cast-Iron Plant whose name derives from the fact it was the only plant that could survive the dark saloons of the Wild West cannot survive in an environment with no light at all. Inversely some houseplants cannot tolerate direct sun either, so the simplest way to handle this is to always read the plant tags before you buy and determine where the plant is to go before any money changes hands at the garden center. If a houseplant has brown dry leaf edges it may be getting too much sun.

Lastly, it is an accepted fact that bug problems on your plants are generally of opportunistic nature. The plant became stressed at some point and the bugs moved in somehow to take advantage. The key to avoiding a lot fo this si simply to avoid getting your plants stressed in the first place, by minding how often you water, recognizing the winter rest period, and making sure your plants are not pot-bound and are getting the right amount of light.  Also making sure your plants arrive without pests or diseases by inspecting them will go a long way to preventing problems. Always check under leaves and in the areas where stems or branches meet the main body of the plant. Lastly always have a little spray insecticide handy, as well as rubbing alcohol and cotton swabs.

In closing, it is important to state that knowing what to do is as important as knowing how to do it. For all you black thumbs reading below is my top-ten list of the toughest house plants. For you skilled gardeners yes #1 is a curve ball plant, in the south Cast Iron plant is a garden perennial too, but it must be grown in shade in essence the cast iron plant gives you a two for one deal.

Top 10:  Neglect Proof House Plants
1.     Cast Iron Plant - Aspidistra elatior
2.     Snake Plant – Sanseveria trifasciata
3.     Zanzibar Gem – Zamioculcus zamiifolia
4.     Star Window Plant – Haworthia Cuspidata
5.     Ox-Tongue  - Gasteria liliputana
6.     Heart Leaf Philodendron – Philodendron cordatum
7.     Aloe Vera – Aloe barbadensis
8.     Desert Privet – Peperomia obtusifolia
9.     Peace Lily – Spathiphyllum spp.
10.   Rotary Peperomia – Peperomia verticillata

Please join us next Sunday when part one of the ‘Things to Consider’ series covers early season planting preparation. Thank you for reading, and if any of the above ten plants seems hard for you to find let me know, while it is not published I can tell you where to look for these plants. Lastly, remember to check out the Neighborhood grange web page at:


  1. Thank you for posting and sharing so much information! I can tell I have a lot to learn! I'm from the NGN which posted a link to your blog. I look forward to leaning off your advice and see what I can grow this year! Do you have a link to the extension agency where we would send soil samples? I imagine it might be easy to find online, I guess.... Do you have any position on using a weed barrier? (that black material you lay at the bottom of a box). Sorry, this comment goes better with the post about soil, but- from your post I can see what things I haven't been considering. I have been trying to weigh out what didn't work last year, which I'm not sure I know exactly (there are so many things I'm guessing i did wrong. :) But I know we had a bug problem, I think it was squash bugs? Do you have recommended reading material/websites that would be helpful with that problem?
    Ah, I didn't mean to ask so many questions! :) Thank you so much!!

    1. Welcome to LITFM and thank you for reading, I hope you don't mind if I answer your questions slightly out of order. First off, the site for the Agricultural extension agency at this address:

      On it you can get your soil test results, and they have an estimate for time until test results are available. Also though that site you can find pest and disease information tailored to the North Carolina climate.
      Some good reading, for pest ID can be found in several books but I recommend the pest books from Rodales Organic Press as they often have very high detail photographs which aid field ID greatly. Sunset National's Garden book also has a very detailed pest section along with very inclusive plant information.

      Now about weed block, it's a matter of preference especially if you remove manufacturer's claims from the mix. For note weed barrier is also known as 'weed block' or by it's prettier name 'landscape fabric' which sounds like someones putting draperies or bedsheets out in the yard.

      -Effective when intact.
      -Less weeding!

      -Weeds will appear along edges and through holes.
      -Labor intensive to apply to existing beds.
      -May prevent water infiltration into soil below.

      With the above said, I'm a bigger fan of straight mulch. Normally applied to a depth of at least an inch, up to three inches in problem areas using either pine bark or where erosion is an problem pine straw.