1 - Repotting Cacti

When you do not strip ALL of the old soil off of the roots, it seems the roots have a difficult time moving from old, compacted, saline, decomposed, ... soil to new soil. Plants that were growing quickly would first sulk and then lose their roots, rot, and die. Inspection would show no root growth from the old to the new soil. So gently shake the old soil off the roots, and then gently wash the remainder off with a garden hose. Check roots and trim off dead or damaged ones. The plants then sit for a few days (depending on the season, plant size...) and are repotted in DRY soil. Water them a week or two later.

 

2 - Rebutias for Everyone

How to Grow Rebutias in the Tropics

Although it is true this genus needs a cold winter rest to keep it healthy, one CAN grow these cacti in the rain forest!

First of all, make the assumption that since the reader has access to a computer, then there exists access to that other piece of technology most westerners could not survive without - a refrigerator.

If refrigerators and computers populate your local ecology then perhaps there also exists "luxury plastic", specifically polythene bags and also Styrofoam cups.

Having enumerated a host of synthetic species, now turn your attention to a few natural ones.  Rebutias make such nice cacti because they are naturally compact, they do tend to offset into mounds after awhile, but individual heads are usually small enough such that even after 10 year's growth, many species fit comfortably into 6" diameter pots. Some Rebutia offset less enthusiastically than others.  My suggestion to tropical growers is they "over winter" one or two Rebutias in the refrigerator. Potted in Styrofoam cups and packed in plastic bags, the plants will be no more obtrusive than a choice wedge of Roquefort an no less sanitary than Friday's fish dinner.

All Rebutias can comfortably tolerate temperatures down to 2 C, most can tolerate frost as well, so simply tuck them far behind everything else and forget about them for 6 months.

The lack of light will not bother them, but it is very important they be absolutely dry before placing in the refrigerator. This is best achieved by letting them dry out inside the house for two weeks before "hibernating" them. Periodically inspect the plants for flower buds, if these appear, continue dormancy another three weeks and then take the plants out, water and very gradually reintroduce them to the sun.

Flowering will occur and after the blooms fade in a week or so, growth will start and continue for another 6 weeks.

After another three months or so, dry them out and refrigerate them for 4 to 6 months.  When actively growing, treat them like regular houseplants - lots of water and some feeding every two weeks.

 

3 - Cacti Care Instructions

Planting bare root cacti

The plants you receive from Nursery are grown in full sun to lightly shaded. During the shipping process, some plants may become de-acclimated. When you receive your bare root cactus be wary of placing them in direct sun especially if over 85 degrees F. It is best to acclimate them to the new conditions with light shade (around 25 per cent shade) for 7 to 14 days to reestablish their ability to endure full sun exposure.

 

Planting un-rooted cuttings

When you receive your un-rooted cutting allow it to dry for at least 7 days before planting (Cereus should be allowed to cure for around 30 days before planting).

Leave cutting in a shady, warm exposure, not direct sun. Then plant it in DRY cactus potting soil and do not water for another 14 days.  Always let the soil dry out completely between watering.  (Soil temps should be 60 to 75 degrees F.)

It is MUCH more likely that a cutting is killed by over watering than under watering. The cutting can't tolerate much moisture until roots have developed.

 

Temperature

An ideal temperature range is from 45 degrees F. to 95 degrees F., but most varieties will tolerate a range of 35 degrees F. to 110 degrees F.

Cacti can endure very high temperatures but they can burn, a full sun exposure on a window ledge can burn your cactus.

Most cacti will freeze if left in freezing temperatures for more than a couple of hours.

 

Soil

Use a sandy, loamy, quick draining cactus soil mix available from most nurseries or stores that sell plants and plant supplies.

 

Light

Southern, western or eastern exposures are best, in that order.

Place your plants in strong, indirect light, in summer.  In winter they may be placed in direct sun, but watch for sunburn, sunlight through a window can be extremely hot and can burn your plants.  Some plants may have to be moved to light shade or protected temporarily with shade cloth.  Turn pots regularly for even growth.

Air

Desert plants need fresh, circulating air. Leave windows partly open at least part of the day. Desert plants like warm days and cool nights, never place plants on a heater or near a fire place.

 

Water

The soil in the cactus garden needs to be allowed to dry out between watering. Frequency of watering will depend on the heat and humidity in your environment.

This could mean a monthly watering during the growing season for a cool, humid climate or twice weekly watering in a hot, dry exposure.

A general rule is a thorough watering every 3 to 4 weeks during summer and every 6 to 7 weeks during winter.  It is more likely to kill a cactus with excessive watering than under watering, but either extreme can be fatal.

There are no ironclad rules on how much water, light and ventilation a specific plant needs. Provide the range of correct conditions and the cactus will do the rest.

4 - Care Instructions for Desert Plants

Desert plants like to grow by themselves. Don't try to help them; just sit back, and observe and, in time, You will understand their signals to you that they are okay or not okay.

We recommend the following basic rules for plants in pots up to 6" in diameter or in sizes up to 12".

 

Light

Place your plants on a sunny window sill or in strong indirect light. Southern, Western or Eastern exposures are best, in that order.  Watch especially young growth for sun burn during the summer, some plants may have to be moved or protected temporarily. Turn pots regularly for even growth.

 

Air

Desert plants need fresh, circulating air. Leave windows partly open at least part of the day. As desert plants they like warm days and cool nights, never place plants on a heater or near a fire place. They will not thrive in a poorly ventilated, stuffy room!

 

Water

The most popular way to kill a cactus is by over watering.  Use a thin wood stick or pencil and push it deeply into the soil.  If there is moisture left, some sand will stick to the wood which means DO NOT water! But water well when you do water. Probably once a month in the summer, every 6 or more weeks in winter. Don't leave excess water in the saucer, cactus don't like soggy feet.

 

5 - Food for Desert Plants

Desert Plants as a rule don't need much feeding. Fertilize in Spring and Summer with bone meal mixed into the soil or water with Miracle Grow 20-20-20. Slightly increase pot size in the Spring (every 2-3 years).  Use a rope harness and pads of newspaper to lift plant being careful not to replant too deep.  Pack soil tightly. Keep out of direct sun for 10 days.

 

6 - Pests and Diseases

The best method is, of course, prevention. Take the time to inspect each plant regularly.  All desert plants are superbly equipped to adapt to a life in "captivity" but sometimes they become the target of mealy bugs, aphids, scale or fungus disease from incorrect growing conditions.

There are natural and chemical ways to help a plant in such cases.  You may want to consult a cactus culture book at your library.

 

7 - Euphorbia or Columnar Cacti cuttings

How to save your rotting cactus

If your cactus or Euphorbia has turned brown and mushy it probably was over watered.  To save it, you must take a tip cutting of healthy tissue and reroot it. The rotten part cannot be salvaged and could spread if left attached to the healthy tissue.  The rotting may have occurred for several reasons :

1 - The roots died back from disease or lack of water, then it was watered but couldn't take in the water because it had no roots.

2 - The plant was watered too frequently.

3 - Adequate drainage wasn't available.  Taking cuttings: Use a clean, sharp knife or saw and make a smooth cut approximately 2 inches below future soil level and only including healthy tissue.  Dip cut end in solution of 10 parts water and 1 part bleach, or dip freshly cut end in rooting hormone/fungicide powder.

 

Drying cuttings

Place cutting in dry, well ventilated area (not in full sun) for 2 to 6 weeks depending on diameter of cutting.  Good airflow in the area is recommended to speed callousing of cut end and reduce chance of rotting.  Cutting end must be calloused (dried and hardened) before planting or else the cutting may rot in the damp soil. A cutting cannot take in water.  Only roots can "drink" so the cutting can't be watered until roots begin to develop.

 

Planting calloused cuttings

Wrap cactus in many sheets of newspaper to protect your hands and the cactus while repotting.  The container should have good drainage holes.

Do not block drainage holes with shards or rock.  A small piece of screen or net works well to hold soil in.  Plant in a commercial "Cactus Mix" soil that provides sharp, fast drainage.  Use barely moist soil at planting time and pack soil down firmly.  Wait 1 to 4 weeks before first watering (depending on cutting diameter and hardness of the calloused cut end).  Do not water in at planting time or it may rot.

Water

Water every 2 to 4 weeks when soil is dry several inches below the surface. Frequency of watering will depend on humidity, heat, lighting, and season of the year.  If soil is completely dry, soak thoroughly.  Large cacti outdoors need to be dry when temperature is cold.  They must have good drainage, no standing water or wet soil in saucer or bottom of pot.  They don't like wet feet (roots).

 

Fertilize

Spring through Summer, every other watering.  Miracle Grow 20-20-20

(1 tsp. per gallon of water).

Indoor Location: Sunny Room.

Outdoor location: Full sun.

There are not ironclad rules on how much water, light and ventilation a specific plant needs.  The coast has several different mini-climate zones and we can only make recommendations based on our knowledge and experience.

 

8 - Cacti Soils

We probably should start a FAQ on this subject since the soil questions come up so regularly.  Any recommendations interact so much with other aspects of culture  that we could make contradictory but equally correct observations.

 

Purposes of soil

The soil mix provides physical support for the plant, acts as a source or reservoir of water and nutrients, allows circulation of air to the roots while protecting them from sun damage and desiccation.  For some species it is also important that the soil serve as thermal storage allowing the plant to survive greater temperature extremes than it could in bare-root form.

 

9 - Natural Soil Components

Most Cact and succulents live in soil with perhaps 3% to 5% organic.

The remainder is mineral and may include particle sizes from clay up to boulders. Finer soils allow less air circulation and tolerate much less water before risking root suffocation and rot.

Conversely, coarser soils require more frequent watering to avoid root death due to desiccation.

Desert soils do not experience the cultivation that worms perform in temperate regions.  Neither do they develop thick layers of humus from which minerals and humic acids leach with each rain.  Rapid surface drying slows the breakdown of plant residues.  In the Sonoran desert, carpenter ants may be the major force for removal of surface residues.

In Africa, it is the termite.  The major source of soil organics does not come from above. It is the roots of prior plant generations.

Except for plants with seeds that must be deposited by flowing water like the river paloverde, plants do not choose their soil.  They try to survive where they are. The soil in which they naturally survive may be optimal and may just be too poor to support any competitors.  Not surprisingly, there are perfect soils in which practically any plant will do well.  Such soils are so rare in nature that no species would evolve to depend on them and no collector would perceive them as the native soil for any particular species.  Nonetheless, such soils artificially can be produced.

 

Available Natural Components

Clay particles array themselves in a fashion that stores water and nutrients and in natural soils prevents both from sinking below the root zone.  They also pack so tightly that root aeration is compromised.  As much as 10% clay in the form of kitty litter may save mixes that would have been too friable to hold plants upright. Clay makes the mix stick together but must be used in moderation.

Fine sand/silt in natural soil holds moisture in narrow inter particle spaces and wicks moisture into the root zone from the subsoil.  This service is not needed for potted plants.  The particles pack too tight for good root aeration and offer little ion exchange capability.  They also do little to support plants structurally.  There is no specific need for sand in a soil mix.

Natural gravels and pebbles improve air circulation but do not hold water or nutrients.  They are often so rounded that plants potted in pure gravel just tip themselves out of the pot.  Sometimes a little clay will hold the mix together but pebbles are best used as a top or bottom dressing or as the starter medium for aero-hydroponic systems.

Those who want to screen their own should discard particles under 1 mm which would pass through the typical kitchen strainer.  The 2 mm to 5 mm particles which pass through 1/4" hardware cloth are useful for soil mixes.  The 5 mm to 10 mm pebbles which pass through 1/2' hardware cloth are best for hydroponics use or as top dressing for large plants.

Granular diatomaceous earth looks like kitty litter and has particle sizes from 1 mm to 4 mm.  It absorbs water in its pores and supports ion exchange. It is sold as a mechanic's oil absorbent and would be a perfect medium if it were available in coarser form.  It is a great top-dressing because it does not stick together and the surface quickly dries to eggshell color.  Even without much cohesion, its weight and wet-ability provide good plant support. Crushed pumice shares the same characteristics and is available in coarser sizes.  It is not cheaply available in most areas in less than boxcar-sized loads but is the product of choice when available. Crushed basaltic lava rock has larger vesicles and lower silica content. The particles cut into each other providing better physical plant support than any other medium. Lava rock is slightly soluble.  Minerals leach out making the soil more alkaline and it breaks down into smaller particles over time.  A high proportion of lava rock will use the same problems as will sand after enough leaching.

Peat moss is the decomposed remains of temperate bog mosses.  Its fine particle size requires moderation to avoid root suffocation.  It releases humic acids which may combat some root pathogens but in breaking down it competes with the roots for available oxygen.  As a primary component it resists rewetting after drying but in proportions less than 25% and when ground with the other components through 1/4" hardware cloth re-wetting is not a problem.

Peat moss stores water and nutrients well while providing little of its own.  It helps in physical support by holding the soil together but relies on fine roots and fungi to assist in that task.  Peat moss is a thermal insulator and prevents plants from transferring heat to or from the soil. Plants potted in peat moss will have lower heat and cold resistance.

Peat moss lowers the PH of soil and is useful to compensate for lava rock.

Otherwise, one to three tablespoons of lime must be added per cubic foot of peat moss to avoid excess acidity.  Dolomitic lime is preferred to avoid an excess of calcium compared to magnesium.  Peat moss is mined from environmentally sensitive areas with limited regenerative capacity.

Many avoid it for that reason and use the alternatives described below.

 

Artificial Soil Components

Vermiculite is an expanded form of mica.  It holds water and minerals well between its layers.  It tends to shrink when wet and expand when dry and moves a lot when watered. The volume changes can be compensated by about one gram of polyacrylamide crystals per liter.

As with lava rock, the particles break down over time.  Since the surface of vermiculite dries too fast for exposed seedlings while the depths offer too little air circulation for most plants, it should be used sparingly, no more than 25% of the mix.

Rock wool is derived from a mixture of ground stone which is melted, spun and compacted.  It holds water and minerals well but slowly releases alkali like lava rock.  Its fine pore size may suffocate roots except where the smallest cubes of rock-wool are used for seedlings.  In hydroponics use, larger plants are allowed to arrange their roots on the surface of a rock-wool slab while plant support is provided from above.

Bulk rock wool looks like grey cotton and can be used in soil mixes.  The chunks do tend to stick together and aggregate.  Breaking them down through a 1/4" mesh screen embeds a multitude of fine fibers in one's skin.  There are many better alternatives to rock-wool in a mix.

Perlite is an expanded silica.  It is slightly porous, offering some water and mineral storage capacity.  It provides good plant support when wet or dry but tends to suspend itself during watering.  It will let a plant fall over but will stiffen up when the water drains out. It will also float up through a top-dressing.  The main value of perlite is its support for air circulation while also distributing water well through surface wicking.

Many plants grow well in straight perlite with hydroponic feeding.  A pot or tub of perlite can water itself via a fiber wick extending into a vessel of hydroponic solution.  Perlite is an excellent bottom dressing.  To prevent potted plants from wicking up too much moisture from drainage saucers.  Some sources of perlite have high alkali content, mostly potassium and will raise soil PH over time.  There is also a Styrofoam product called styromull with characteristics similar to perlite.  Some European experts recommend it but it does not appear to be available in the Americas.

Baked clay spheres or extrusions which are collectively called grow-rocks in the hydroponic trade provide drainage and air circulation and store significant amounts of moisture and minerals.  They are too coarse to use in other than hydroponic systems and most are too smooth to provide good plant support.  A variant made of expanded shale avoids those limitations and is the equal to pumice.  These products are of little value in low concentrations, becoming expensive pebbles and are too expensive to use in quantity unless one has a local manufacturer.  As with the natural mineral products, shipping costs far exceed the initial cost of the material. As an alternative to peat moss, one can use mixed compost or composted bark chips. Mixed compost may contain manure, fallen leaves, grass clippings, agricultural residue, recycled newspaper and/or sawmill residue.  Most are well composted and can be used like peat moss but without the rewetting problem.

Bark chips have a much lower surface to volume ratio.  They offer good drainage and can be used in high concentrations without suffocating roots.  They do not offer good support and slide over each other easily but are much less likely to float up than perlite.  Eastern sources of bark have predominantly 1 cm and larger particle sizes while western sources are below 1 cm.  One can screen it and use the same particle sizes as were recommended for gravel.  Bark is not fully composted. It releases humic acids slowly so that little lime is needed to regulate PH but it can absorb significant amounts of nitrogen from the soil mix during its initial breakdown.  One can add a tablespoon of dolomite per cubic foot and 2% to 3% by dry weight of nitrogen in some soluble form to a dampened mix and let it re-compost a few weeks before use.

 

Favorite Mixes

My favorite mix for aero-hydropomc use is equal parts of pea gravel and bark chips which will pass through 1/2" hardware cloth but not 1/4" hardware cloth.

My current favorite mix for daily watering with hydroponic solution is equal parts of granular diatomaceous earth, perlite and screened bark chips.  All pass through 1/4" hardware cloth but not through a 1 mm screen.

My favorite mix for gift plants which will be watered irregularly with our local alkaline water contains equal parts of peat moss, vermiculite, perlite and granular diatomaceous earth with 1/2 tsp of polyacrylamide crystals, one tablespoon of Osmocote pellets and two tablespoons of bone meal per gallon of mix.  The mix goes through 1/4" hardware cloth just to break up the lumps. Most cacti and succulents live in soil with perhaps 3% to 5% organics.

 

Sand

A lot of people over here use sand in their mixes. It is the simplest way to improve drainage.  We have choices available : from the yellow type builders sand over gravel like sands on to pure quartzite sands (used to polish cement floors over here).  Although I agree that the material can be totally inert it is a good weight compensation for those that want to grow in pure peat-like soils & enhance drainage.

 

Vermiculite

Experiences here show that it collapses after drying with NO regain or regeneration of form, forming a layer of mica pellets shutting off the soil in a most dreadful way.

 

Perlite

We used to have intensive algae growth on perlite when exposed to direct sunlight

Occasionally I add a bit of charcoal if I can get it and I have experimented with Diatomaceous Earth (DE). If pumice is not available then pearlite or even vermiculite can be used. Pumice is great because it does not float as easy as pearlite. It also has a cation exchange capacity that releases water and fertilizer over a period of time rather that all at once. I also add Osmacote when I actually use the soil. The one quality that these soil less mixtures have over a soil based mixture it that they drain fast. The water poured into the pot drains through in a mater of seconds. The mix is wet in the pot but the water does not stand there.

Have any of you ever experimented with using the water retaining gel material. It is sold under a variety of names but one commercial version is "Agrosoke". It is a crystalline looking powder but when put into water, it absorbs about 20X its weight in water and swells up. It is used extensively by the growers of tropical plants. It seems like it might have some benefit to us in providing an extended source of water without making things soggy. It might work in ways similar to Zeolite.

During a long time, I grew the plants in a peal-based potting-soil mix (two-thirds coarse sand, one-third Metromedia 360 potting-soil which is great for geraniums and such) and discovered that after about 2 years in a pot the plants started to lose their roots and die from what I affectionately term the "orange rot". I tried everything? I tried all sorts of recipes for my potting soil. I carefully monitored the soil moisture. I used dangerous chemicals as soil drenches (bad side-affects!). I repotted often trying all sort of things with the unhealthy roots (dip in chinosol, cut,...), but then many of the plants died immediately after repotting. Watching a 6 year-old, blooming-size Sclero mesae-verde dissolve into orange-mush is not a happy sight!

For test the hypothesis that peat was the problem I ran a number of tests growing the same or similar plants in a peat-based mix and a native-soil mix. The results were uniformly and stikingty similar, after a few years, plants grown in peat-based mixes became sickly while those grown in the native-soil mix remained healthy.

For example, I planted about 40 pots of seed of Pedios, Scleros, and Toumeyas in both the peat-based mix and the native-soil mix. The seeds germinated equally well in both mixes (after winter stratification) resulting in more than 300 seedlings. During their first year of life I could see little difference between plants in the two mixes.  During the second year, plants in the peat-based mix grew more slowly and their death rate was higher.

I repotted all of them in the spring of the third year and discovered that the roots of plants grown in the peat-mix were sickly and that in many pots more than half the plants had orange-rot in their roots. Repotting these plants was a mess with a significant time taken in plant surgery. The plants grown in the native-soil mix were uniformly healthy and no cases of orange-rot were observed. Easy plants nourish in this mix also.

63% Coarse sand (.1 -1 mm diameter).

25% Soil, a fine Aeolian soil from a location that has knee-high native grass during the summer.

12% White agricultural pumice.

 

Soils some tips

Regular potting soil (humus, not peat based).

Vermiculite (holds moisture long enough for the roots to use it).

Perlite (speeds up drainage).

Pumice (speeds drainage even more).

Oak leaf mold (excellent for root development, which many succulents need).

Coarse sand (not fine "play sand" but closer to gravel if possible)

Then I mix them up in approximately these proportions:

Three or four scoops each of soil and sand two or three scoops each of perlite, vermiculite and pumice one scoop of oak leaf mold.

Realize that the whole idea is to hold the plant upright and provide the roots with avenues to water and nourishment. Most succulents don't like a lot of fertilizing. And never never never let them sit in water. Wet them well when you do water, but make sure it drains out completely.

Succulent roots sip that water up FAST and may just keep sipping until they drown if you let them sit in a puddle (that sounds uncomfortable, doesn't it?) The vermiculite gives them a little more time to sip while allowing the roots to have air as well. Generally I water about once a week in the summer when they are all outside in varying degrees of sun, a bit more for the ones that are visibly growing. In the winter I don't water much, maybe once a month for some, not at all for some from December to March - for this you have to get to know your own plants' needs. Some plants need some regular light watering to keep the roots from drying out completely. Others need complete rest from water.

 

Honestly, I think the most important thing is to pay attention - know when a plant is growing, know when it is in trouble. That's why people who "talk" to their plants have good luck: They are paying attention!

The key to using additive such as perlite and pumice, and even coarse sand, is to make sure you use a high enough percentage so that they exert a positive influence on the amount of macro pore space.

 

I then figured out that the root system developed more rapidly then the rest of the plant at first, especially if you make some efforts to let dry in between the watering (in order to develop a good root system).

 

Please allow me to clarify my understanding of the role of pumice and prelate. Certainly they do retain some moisture, but they mainly serve to keep the soil from compacting, thus allowing the bulk of the water to drain through. This is what I mean when I say they "speed up drainage." As a result, the roots have access to air as well as nutrients and moisture, which is what they need during growth periods.

I use 60% sand, 27% soil, and 13% white pumice.

 

My own soil mixture that is working fine (here in tropical country - hot 24C. to 37C. and heavy rain during rainy season) is :

1 Liter of normal land (yellow not heavy land !).

3 Liters of river sand (I use sea or construction sand that I clean clean and clean again and again without any problems).

1 Liter of charcoal that I scratch in very small parts.

I mix all.

I use 20 cm pots and put into the first 6-8 cm of the soil ONE spoon tea of this material that is a water retaining gel (the residue of contact eyes lens in fact). I use that because in hot season the soil look like dry after two days. I also put a nail at the bottom (just because my mother use it with all her plants - giving some iron is great vitamin for the plants she said -)

I water and fertilize (pokon and 15-15-15 alternated) once a week both in hot season and rainy season (all my Cacti are under verandah on the East side, that mean strong sun until twelve).

A good way to check the soil is to put in the evening a thin piece of wood till the bottom of the pots (not too close of the roots !) and early morning keep it out, if some particles of sand are still glued on the wood than there is enough water left.

Hope you enjoy the reading and please send me your comments.