What Is The Best Fertilizer for Christmas Cactus?

There are two big reasons people buy a Christmas cactus plant: how it looks and its holiday bloom.

Here’s the catch. Clemson Extension notes that the Thanksgiving cactus is the one most often found for sale during the winter holidays, so the plant you brought home may be one of its close relatives.

The three holiday cacti share similar care requirements, according to UF/IFAS Extension Flagler County. Bloom time and stem shape are where they differ.

Fertilizing is where the timing gets confusing, so here’s what university extension guidance says about what to feed, when to feed and when to stop.

Which Holiday Cactus Do You Have?

Christmas, Thanksgiving and Easter cactus look alike, and they’re easy to mix up. The feeding advice below is extension guidance for holiday cacti as a group, so it works whichever one you have.

Best Fertilizer for Christmas Cactus

Holiday cacti are epiphytes. Clemson describes them as growing among tree branches in shady rain forests, and says these epiphytic cacti do not grow well in heavy, wet potting mixes.

For feeding, Clemson recommends a half-strength soluble fertilizer, such as a 20-10-20 or 20-20-20 with trace elements. The three numbers are the percentages by weight of nitrogen (N), phosphorus (P) and potassium (K), as Clemson explains.

University of Minnesota Extension keeps it simple: a balanced houseplant fertilizer at half strength. In the fall, when flower buds are forming, it suggests changing to a formula that is low in nitrogen and high in phosphorus and potassium, with 0-15-10 as an example.

Liquid or slow-release? Clemson notes that water-soluble fertilizers are often preferred because dilute solutions reduce the potential for fertilizer burn.

UF/IFAS says soluble fertilizers and slow-release products are both acceptable, and UF/IFAS Flagler County recommends a balanced, slow-release fertilizer during the growing season.

Either way, UF/IFAS suggests reducing the label rate, because excess fertilizer salts can damage the roots.

Products vary a lot, so the label on yours sets its rate. For example, Espoma’s Indoor! Plant Food is a natural and organic liquid concentrate mixed at 1/2 cap (2 teaspoons) per quart, and its page says an 8-ounce bottle makes up to 24 quarts.

Miracle-Gro Indoor Plant Food lists a 1-1-1 analysis, and its page says to apply once a week. Those directions differ from the half-strength monthly routine extension gives for a 20-10-20 or 20-20-20, so read the label before you decide how much and how often.

When or How to Fertilize Christmas Cactus

Feed about once a month, starting when new growth begins in late winter or early spring and continuing through the summer, says Clemson.

UF/IFAS puts the growing season at April to September and says to fertilize every one to two months, and University of Minnesota Extension says monthly from June through August at half strength.

Then stop in late summer. Clemson says to stop fertilizing during the late summer for greater flower bud production in the fall.

Other sources are a little looser: UF/IFAS Flagler County says to reduce or cease fertilizing in fall and winter, when the plant is dormant, and Missouri Botanical Garden also says to reduce fertilization during fall and winter.

The University of Minnesota’s version is to switch to that low-nitrogen, high-phosphorus and potassium formula in the fall while buds form.

One more fall note from Clemson: after the buds set, keep the potting mix evenly moist to prevent bud drop.

To apply, mix the fertilizer at half strength, pour it slowly onto the potting mix so nothing splashes, and work your way around the pot, lifting the stems where you need to.

Epsom Salts: An Optional Magnesium Boost

Clemson’s holiday cactus factsheet says these cacti have a higher requirement for magnesium than many plants. It suggests Epsom salts (magnesium sulfate) monthly during the growing season, mixed at 1 teaspoon per gallon of water, but not in the same week as the regular fertilizer.

Mind the amount: 1 teaspoon per gallon, not a tablespoon. Clemson’s garden guidance on Epsom salt says magnesium is generally already sufficient in most garden spaces and that too much adds unnecessary salt, and University of Minnesota Extension says to use Epsom salts only if a soil test shows a magnesium deficiency.

Those two pages are about garden soil, not potted holiday cacti, so treat Epsom salts as an optional extra rather than a must-have.

Final Tips

Fertilizer is salt-based, and salts can build up. Colorado State University Extension says many fertilizers are salt based and that salts are left behind as moisture evaporates from the soil.

Its signs of buildup are brown leaf tips, yellowing leaves, unaccountable wilting and a whitish crust around the lip of the pot or on top of the soil.

To prevent it, water thoroughly so water drains from the bottom of the pot, discard what drains out and don’t let the plant stand in it. If buildup has already started, Colorado State’s fix is to scrape off the crust and remove half an inch to an inch of potting mix from the surface.

Then rinse the mix by filling the pot to the top with tepid water a couple of times, letting it drain well between rinses, and replace what you removed with new mix. In extreme cases the soil may need to be changed and the plant repotted.

For everyday watering, UF/IFAS says to water only when the upper inch of the potting mix feels dry, and to avoid letting the plants get too dry between waterings.

Clemson says holiday cacti flower best when kept somewhat pot bound and that repotting is necessary only about once every three years, best done in spring.

UF/IFAS agrees that the plant prefers to be a bit root-bound, so don’t choose a pot that’s too large. Clemson’s example mix is 60 to 80% potting soil with 40 to 20% perlite.

Get the timing right and the plant does the rest. University of Minnesota Extension says holiday cacti can live over 100 years and are often passed down from generation to generation, so a little care now can pay off for a very long time.