Plant Myth: Should You Fertilizer Your Plants with MILK?

June 28, 2023

Fertilize Your Plants and Garden with MILK?

Learn why milk may or may NOT be the answer to your plant and garden woes!

Wondering if all those apps and blogs telling you milk is the next miracle plant and garden fertilizer? Well, let me fill you in on the realities of milk as a "fertilizer" in this week's "What the Halleck" Wednesday!

Grow Tiny Tomatoes Indoors

June 8, 2023

Can I grow tomatoes indoors?

How you CAN harvest tomatoes indoors

Wish you could grow tomatoes indoors?

You can! One of the most successful ways is to go growing miniature tomato cultivars, like Micro Tom (there are lots of others these days!). Micro tomatoes are perfect for indoor gardeners who have limited space don't want to use HID grow lighting (the BIG ones).

Growing a single miniature tomato plant with a 20-30W LED spotlight is totally doable and the perfect beginner project. Tiny tomatoes are usually around 50-60 days to maturity from seedling stage.

If you want to get specific about the light metrics:

  • Tomato seedlings will need a DLI of about 15 Mol/m2/D for the first 2-3 weeks with a PPFD of about 200-300 umol/m2/day.
    • As soon as you see germination occurring turn on your grow light! You don’t want your seedling to stretch due to lack of light. Germination should occur anywhere from 7-10 days, give or take depending on home temperature. Warmer temperatures will speed germination
    • Place your 20W LED grow lamp 12 inches above your seedling pot and run your lamp for 12 hours
    • This will give your seedling a PPFD of approximately 200-300 umol/m2/s
  • Then bump to a DLI of around 20 Mol/m2/day with a PPFD of about 400-600 umol/m2/day for vegetative growth phase, for the next 3-4 weeks.
    • Place your grow light about 8-9 inches above your plants and rune the lamp 13-14 hours
    • This will give your seedling a PPFD of approximately 400-600 umol/m2/s
  • Then shift to a DLI 25-30 Mol/m2/day with a PPFD of around 600-900 umol/m2/day for the flowering and fruiting phase, which is usually around another 3-4 weeks.
    • Place your grow light about 6-8 inches above your plants and run the lamp for 14 hours.
    • This will give your seedling a PPFD of approximately 600-900 umol/m2/s

The duration of each of these lightings stages will depend on the cultivar you're growing, and how many days it takes for that cultivar to reach maturity.

Shifting the intensity of the light (PPFD) can be achieved by raising your lamp (decreases the PPFD) or lowering your lamp (increases the PPFD), and your DLl (Daily Light Integral, how much total light the canopy of your plants receives each day) is influenced by how long you leave your grow lamp on. Running your lamp longer increases DLI, while running your lamp fewer hours decreases your DLI. Note that my recommendations are generalized and your growing conditions and the lamp your using will vary.

Take care to be mindful about the heat generated by your grow lamp. Sometimes the desired PPFD requires a lamp to be placed too close to a plant or seedling that could be sensitive to the amount of heat generated by your grow lamp. So, you'll have to play around a bit with your lamp distance and monitor how your plants respond...favorably, or not!

These are typically determinate tomatoes, so once they fruit and you harvest, you should grow another plant! Consider seeding succession crops a couple of weeks apart so that you always have tiny tomatoes at your fingertips!

Pygmy Sundew Unboxing

March 17, 2023

Itty Bitty Pygmy Sundew Plants

Pygmy Sundews Arrive!

TINY PLANT UNBOXING? You asked for it!

Ok, I’m giving you a behind the scenes on an unboxing of my pygmy sundew order I received yesterday from California Carnivores (this is NOT sponsored in any way, just another in a long series of public admissions of my plant buying addiction). The original vertical video is on my Instagram Channel.

Pygmy sundews (Drosera spp.) are one of my very favorite ITTY BITTIEST plants that are great in a sunny window or lighted grow shelf. And YES they are most happy outdoors so you can also keep them outside on your balcony or patio. I walk you through the 6 species I received in this order plus a few fun care tidbits and how you can nerd out even more on carnivorous plants. You can find more info on these tiny gems in my book “Tiny Plants”. And if you’re interested in the info on morphology or propagules like gemmae, you should join my Botany for Gardeners online course through the UCLA Extension Horticulture & Gardening Program! The first spring section is full, but we’ve got a waiting list started to open a new section. Class starts April 3rd, 2023.


January 10, 2023


My Mantra Word for 2023

I don’t create New Year’s resolutions, but I do usually create a mantra for myself or business each year to keep in mind when making decisions. Recently my good friend and business partner Maria Failla asked me what my word or mantra was for the new year. I’d been noodling on it, but hadn’t nailed down just the right word yet. Then, it hit me…

Totipotency. That’s it, my mantra word for 2023. It’s also one of my very favorite botanical (biological) vocabulary words.

Totipotency (in the context of botany): The ability of a single plant cell to grow, divide, and differentiate into an entire plant

Halleck Fungi Block Print

Halleck Fungi Block Print
My first attempt at wood block printing in 30 years, from a recent fungi illustration I completed. It's not perfect...but it was fun!
PC: Leslie F. Halleck

Most of us get put on a hamster wheel at a young age. We’re all expected and trained to choose one narrow path upon which to earn a living and ultimately define ourselves as adults. The reality is all of us have so much more creative potential and or varied proclivities than that one path allows to manifest. While that one main path can certainly form a strong trunk that anchors and ground us firmly, providing stability and direction, ultimately, we must branch out if we are to grow a large leafy canopy capable of nourishing our whole selves…from roots to shoots.

Just as a seed is totipotent, containing all the genetic information needed to grow and develop into all varied functioning parts of a mature plant, so are we…seed like…totipotent.

While I certainly have an innate passion for plants, nature, and gardening, and have carved out a successful professional path in the horticulture industry, horticulture, singularly, does not define me. As a person, I encompass many seeds of passion, the first being art, that when germinated add necessary flesh to my being.

Totipotency is what guided my decision to take a step back from all my hard-earned work in the horticulture industry, and start a well-earned sabbatical. A sabbatical that will allow me to also take a step back from myself, observe and see what is missing, and begin to germinate all the other seeds of passion from which manifest my whole self.

The last few tough years of the pandemic have “helped” to break down those hard seed coats. After all, you can’t manifest your totipotency before first breaking whatever dormancy has been holding you back. That’s the theme and plan for the next year, the year I spend being 50. My days are and will be filled with new learning, creativity, and manifesting in tangible form a massive backup of art that’s been building up, patiently dormant, for far too long. And of course, I’m sure I won’t be able to resist a few interesting planty projects or opportunities if they manifest as well along the long as they help me branch out.

I hope you’ve found your word, or mantra, for the new year that helps illuminate any and all new paths and branches you hope to add to your very big and very whole tree of life.

What's the Difference Between Thanksgiving Cactus, Christmas Cactus, and Easter Cactus?

January 11, 2022

Learn About the Different Types of Holiday Cactus

I was contacted a few months ago by a reporter looking for accurate information on holiday cactus. I wrote up detailed answers to all their questions...only to get ghosted! SO, their loss is your gain. I decided to put up my detailed response as a blog post for paywall required!

Christmas Cactus

Q: Could you provide some background information on what a Christmas Cactus is, and the different types?

A:Christmas cactus are an unusual type of cactus that grows as an epiphyte or lithophyte (grows on trees or rocks), in habitats that are a bit shady and humid. Not exactly the type of environment you think of when you think cactus! Plants sport bright showing flowers in an array of vivid colors.

There is quite a bit of confusion when it comes to Christmas cactus, and the related Thanksgiving cactus and Easter cactus (in the Northern hemisphere). The name Christmas cactus refers to species and hybrids of cacti that bloom around Christmas time and belong to the genus Schlumbergera, which includes nine distinct species. Plants are Native to the coastal mountains of south-eastern Brazil.

There are also hybrids between the species. When you buy Christmas cactus, you’re usually buying a hybrid cultivar we call Schlumbergera x buckleyi, a cross between S. russelliana × S. truncata.

Halleck Holiday Cactus

Halleck Holiday Cactus
Visual differences between different species of holiday cactus
PC: Illustration & copyright Leslie F. Halleck

Thanksgiving Cactus

Thanksgiving cactus (or the false Christmas cactus) is S. truncata or hybrids thereof, with plants that bloom a little earlier than Christmas cactus. You can distinguish this species and its cultivars by the more pointed “teeth” on the leaves, versus the more rounded symmetrical teeth on Christmas cactus leaves.

Easter Cactus

Easter cactus, which are related and look like Christmas cactus with a series of rounded teeth on the leaves, has been reclassified as Rhipsalidopsis gaertneri -and hybrids thereof - but you’ll find them under a number of other pseudonyms in the Schlumbergera and Hatiora genera. They, as their common name would indicate, bloom around Easter time.

Top Tips for Caring for your Holiday Cactus

Providing enough light indoors is always your number one priority for the success of any houseplant. While Christmas cactus can tolerate lower light levels, if you are very careful not to overwater, the whole point of growing them is to get them to flower.

Plants will need medium to high light to bloom their best, so choose a southern or eastern window exposure if you have it or add a small grow light to your area as we head not the darker days of winter.

Water plants so that the growing media stays moist to the touch (but not soggy) and does not dry out completely between waterings. Plants are resilient, so if you forget to water and plants shrivel a bit, you can usually revive them with a good soaking.

Plants are very happy in a bright sunroom and grouped with other plants, which helps raise humidity.

Propagate Your Holiday Cactus

Vegetatively propagating holiday cactus is simple, as you can take stem tip cuttings or propagate new plants with just one whole leaf (roots and bud shoots will develop from the base of the leaf, just like many other types of succulents).

  • Carefully remove a section of stem or entire leaf pad by either twisting it off or using sharp clips.
  • Allow your cutting to rest on a dry surface for 2-3 days before you place into a small pot with moist potting soil or plug trays.
  • Let the growing media approach dry between light waterings, and before you know it cuttings will begin developing roots and buds.
  • Tips: Don’t take cuttings when plants are budding or in flower, and only take cuttings from healthy disease and pest free plants.

Note: be sure your particular plant is not a patented cultivar (it will say on the plant label or have PPAF on the label), as it is not legal for you to propagate or distribute patented plants.

IF/THEN COLLECTION at the Dallas Zoo

September 30, 2021

MUST SEE: The IF/THEN Collection Display of Women Scientists

Sponsored by The Texas Women's Foundation


Little known fact, I volunteer weekly at the Dallas Zoo as a keeper aide in the Zoo North Birds Department. Yes, it's true, every Wednesday morning you're likely to find me cleaning and tending the flamingo habitat at the zoo. The enclosure, a huge sunken garden, is populated with a flock of about 80 or so flamingos, plus several species of ducks, southern screamers, cranes, and a goose. My volunteer time at the zoo is something I look forward to every week and I love being able to give back to their animal conservation efforts.

I also happen to be a member of the Texas Women's Foundation and an avid women's empowerment advocate. So when I was taking a walk around the zoo grounds after my volunteer shift last week, I was beyond thrilled to discover this brand new IF/THEN Collection exhibit at the zoo! It's expertly deployed along the underground tunnel that connects Zoo North with the Wilds of Africa section of the zoo.

The striking, 333-foot-long mural, complemented by kiosks, features 12 amazing women who are making a difference in the fields of science, technology, engineering, and mathematics (STEM) whose work promotes conservation, advances research, educates the public, and inspires those around them. This temporary installation is generously funded by a grant from the Lyda Hill Philanthropies’ IF/THEN® Fund at Texas Women’s Foundation.

Be sure to walk yourself, and your kids, through this inspiring and informative display when you are at the zoo. You can find more details HERE. And be sure to show your daughter's what a scientist looks like!

Can I Grow Carrots Indoors with Grow Lights?

September 26, 2021

Indoor Gardening: Growing Carrots Indoors

It's al little trickier than you might think...

So, I received a question over on my youtube channel about growing carrots indoors...specifically, would 4 HO T5 retrofit LED bars in an 8-lamp Fluorescent fixture be enough to grow carrots indoors? I thought I'd share my answer with you here, as managing environmental conditions for many root crops can get a little tricky indoors:


It depends! My UCLA Extension Horticulture students LOVE getting this answer from me, but hear me out. It depends on the environment in which your growing - is there any other natural light, or does all the light come from the 4 (42-wattish LED bars?), the PPF output of each of the LEDs, and how long you leave them on. If you had a PAR meter, you could measure the PPFD of the 4 LEDs in combination, and adjust the height and duration for the desired crop...but you may find you can't produce an adequate DLI for fruiting/rooting crops, which really need the equivalent of full sun conditions.

DLI for Carrots

Let's assume a VERY general assumption that each of your new 42-watt Leds in the 5000-6400 K can each generate a PPFD of around 25 umol/m2/s at 12" above the plants (this is fiction, as I can't measure you lamps). So, 4 of them gets you a potential PPFD of 100 umol/m2/s. If you ran them for 1 hours that gets you a DLI (daily light integral) of around 4.3 Mol/m2/'s is only sufficient for low to very low light plants (definitely not fruiting/rooting crops). Carrots need a DLI in the range of 20-30 Mol/m2/day.

Now, if you put the lights closer to the plants it would increase your PPFD and thus your DLI...but you probably don't want to get any closer than that for maturing plants because it may burn the foliage or make conditions too hot for carrots – germination and root formation is best at cooler temps between 55-75F (13-24C) (of course in seedling/germination stage those lights need to be 3-4" from the seeds/seedlings, then raised as they grow). So you’re probably going to need to make sure the lamps are at least 18” above the plants, which will significantly reduce the PPFD.

Now, the PPF and thus potential PPFD of each of your LEDs might be more, but I can't know that unless I know more about the lamps and I can measure the PPFD with a PAR meter. So, I just got up on a chair and measured the light from TWO 6400k LEDs in a fixture in my office (I don’t know the age of these lamps but I’d suspect they are a couple of years old). The PPFD at 12" below the lamps (with additional light in my space) was 55.5 umol/m2/ the fictional example I just used above is probably pretty close to being accurate (4 of them would give me a little over 100 umol/m2/s at 12” and a low . So, if you use 8 lamps instead, you can ballpark doubling that PPFD, and get a DLI when run for 12 hours of around 10 Mol/m2/day which is sufficient for a lot of plants…but probably not beefy carrots!

Carrots are Long-day Plants

You can also increase the DLI by leaving the lamps on can grow many crops under grow lights running them anywhere from 14-24 hours. BUT here is the tricky part - carrots are long-day plants (photoperiodic) and they are triggered to bolt and flower by longer days/shorter nights (light period longer than 12 hours). SO, if you ran the lamps longer than around 12 hours a day to get a higher DLI you’ll trigger flowering, which stops taproot formation and makes it woody and unpalpable. Therefore, for indoor carrots (and other long day root crops), you really need to increase your light intensity as much as you can during a shorter, 12-hour photoperiod. So, MORE light intensity = MORE lamps during a shorter time period. With new, HO T5 quality LEDs, (such as Agro LEDs) You should potentially be able to hit a 20 Mol/m2/day DLI with 6-8 of the lamps run for 12 hours per day.

You can learn more about all of these metrics in my book Gardening Under Lights.

Tiny Plants: Codonanthe devosiana

September 23, 2021

A cute little African violet relative that likes to live on the dry side.

Looking for a miniature yet mighty houseplant that's easy to grow and flowers?

My cute little Codonanthe devosiana is blooming away under lights in my dining room...

Codonanthe devosiana is one of my favorite tough and tiny houseplants that gifts me with blooms indoors year-round. This succulent-like trailing gesneriad, related to African violets, sports dark, soft, pubescent leaves accented with the cutest white to pinkish trumpet-shaped flowers. OH, and in the wild species of Codonanthe have beneficial relationships with tree ants! Very cool.

These trailers are cute in small pots or hanging baskets. Mine has resided happily in this 2.5” porous terra cotta pot for a good while.

Just like African violets, Codonanthe spp. will do best and bloom with supplemental light indoors, unless you have more intense natural light. They can dry between waterings, but in small pots that will happen frequently, so you’ll probably water this plant more often than you would other succulent-like plants.

Happy #NationalIndoorPlantWeek

Back to top

Tips in your inbox


Sign up for the E-Newsletter for my latest green industry news updates for pros + plant and gardening hobbyists.