Growing Culinary Herbs Indoors
Growing basil and other herbs through the winter under lights is easy. Here’s how.
By Bill Kohlhaase, Planet Natural
There are plentiful reasons to grow herbs indoors: basil pesto, rosemary chicken, maple and marjoram-roasted turkey, fresh oregano pizza sauce, tarragon salmon, cilantro-flavored salsas and spicy chive dip. The rise of gourmet home cooking as well as the popularity of fresh, home-raised and locally-grown foods has increased demands for fresh herbs. Why not grow your own, year `round? With modern advances in grow lights, growing mediums and self-contained hydroponic systems, raising herbs inside a small corner of your home can add year-round flavors, scents, even profits to your life.
Kitchen gardeners have long grown herbs on windowsills, under kitchen fluorescent bulbs and next to indoor orchid lights (see How to grow herbs indoors during winter). The success of these practices, touted in articles, videos and a few misinformed books, varies greatly. There’s seldom enough light in even the sunniest windowsill to yield more than an infrequent harvest, say a pinch of rosemary in February or a few basil leaves at Christmas. Standard fluorescent lamps could help plants over winter and even produce some harvests depending on how close and intense the lights were. Having herbs under lamps two or more feet away might do little more than keep perennials like oregano, rosemary and sage alive, sometimes barely, until they could be transplanted back in the outdoor garden.
Truth is, growing sustained, harvestable amounts of herbs indoors require long periods of intense light. Abundant light is also required for plants to produce the oils that give herbs their flavor. The rosemary slowly dying on a windowsill in six hours of sunlight will taste nothing like the rosemary that thrives under summer sun. Growing interest in indoor gardening, pun intended, has resulted in products that make year-round culinary herbs growing more efficient and successful. Cool fluorescent grow lights are an improvement over your kitchen fluorescents if properly positioned and reflected. And the new generation of High Intensity Discharge lamps give the expert grower the possibility of large harvests. Combined with advances in hydroponics growing systems, it’s entirely possible for the gardener with the appropriate indoor space to grow her or his favorite herbs year-round, with enough extra to give to friends or even sell at Farmers Markets.
To those ends, I’m turning a corner of my basement into an indoor herb garden, one that will produce sufficient harvests of basil, oregano and rosemary for my kitchen needs as well as supply pinches of thyme, marjoram, mint, chives and sage ahead of their return to the outdoor garden. A love of cooking with fresh ingredients coupled with the so-so quality and price of fresh herbs in grocery markets provided the motivation. Here’s what’s gone into the planning.
Growing Herbs Indoors: Consider This
First thing to consider when planning an indoor garden is the type and quantity of herbs you’d like to grow. Will you be bringing potted rosemary, sage or other perennials in for the winter? Will you be looking to germinate and grow successive crops of cilantro or Italian parsley? What will you need to maintain ideal conditions for your plants? Most culinary herbs do well when the indoor conditions mimic that of the Mediterranean climate, with ample light and somewhat dry, cool conditions. Some, like mint and chives, are less fussy about moisture conditions and light intensity. Planning what herbs you want to grow will influence the type of lighting and planting medium you’ll purchase.
How much of your favorite herbs you use in cooking (or want to sell or give away) should also be considered. If you’re only going to use a scattering of fresh oregano on the occasional homemade pizza or a bit of marjoram in a sauté of mushrooms, then over-wintering a few potted plants under a well-placed fluorescent grow-light on a kitchen shelf should suffice. If, like me, you need enough basil to make pesto on a weekly basis (or for Christmas gifts) or you need enough rosemary sprigs to roast a chicken every Sunday more intense methods are called for.
Where to grow your herbs is another consideration. Basements offer less temperature fluctuations and more easily controlled growing conditions, no matter what the season. Attics can be too hot. Ground floor areas in your home work well but most of us don’t have room for even a small self-contained closet or grow area let alone a clothes or storage closet to convert. Some herb-growing set ups might not compliment a home’s decor. Others, carefully designed, might be its centerpiece.
Those wanting to harvest from the most plants in the smallest space will want to enclose their plants in a reflective grow tent or closet. These small spaces make it easy to control the conditions — light, temperature, humidity, circulation — that will let your plants thrive. Plants can be grown in the open on racks, shelves or hanging baskets, near south-facing windows or under spot lighting, but the less-effective light will result in slow or no growth and little production.
Using reflective materials to contain and mirror light not only increases illumination but can help indoor gardeners to control temperatures as well. There are several sizes of commercial reflective tents available. Or they can easily be constructed by attaching Mylar or space survival blankets to closet walls or simple frameworks. Not all grow closets are closets. They can be made of converted furniture or file cabinets. There are several clever ways of putting together self-contained grow boxes with fluorescent grow lights that utilize plastic storage bins. Creative growers will be limited only by their imaginations and the space they have to work with.
Access to your plants is important. Make sure you can get to the grow space easily and have enough room to water and care for your plants. Moving plants in containers can involve heavy lifting. Make sure there’s room to reach and safely lift plants when they need to be removed. Nearby plug-ins and a water source should be convenient, safe and functional. A drain is helpful but not necessary.
Abundant Light: The Key To Herb-Growing Success
Light is the most important component of your indoor herb growing set-up. If you want frequent harvests, it must be abundant and intense. Not only is the kind of light you use crucial to the survival of your herbs, it will determine how quickly and sturdily your herbs will grow.
Commercial fluorescent lights such as shop lights, have long been used by indoor gardeners and they will keep plants alive if not healthy and productive. But using the latest generation fluorescent grow lights will result in noticeable improvement. Fluorescents are affordable, use less electricity than high-density lights and are cool to operate. With a little care and the right conditions, they will grow herbs in amounts sought by serious kitchen-herb gardeners.
Advances in spectral display and intensity of fluorescents designed specifically for indoor gardening, such as high output T5 lamps, make them a good choice for the casual indoor gardener. A T5 fluorescent light system will put out almost twice the light as a standard T12 fluorescent. Again, positioning fluorescents close to your plants and using reflective materials to corral light in your grow area will greatly improve results. Because they put out little heat, they’re great for warm grow spaces, such as attics, especially if you’re putting your lamps very close to your plants.
Those looking for quick, serious yields should consider High Intensity Discharge (HID) lights. They range in size form 250 watt to 1,000 watt and it’s important to fit them to your space. Using a lamp that is too small for the space will give you uneven results, no matter how much reflective material you use. One that is too large can overheat your grow area and cost you more in electricity and replacement parts. Your indoor gardening supplier can recommend the best wattage size for your grow area. Roughly, a 400-watt light will adequately flood a two square meter (or six square foot) space.
HID lights are of two types: metal halide and high-pressure sodium. Both require ballasts to provide the proper operating voltage. Most growers recommend metal halide lamps for growing leafy herbs. Their blue spectrum light is perfect for encouraging green, bushy growth. High-pressure sodium lights and their red-and-white spectrum lights are best for encouraging blossoms and flowering (use of high pressure sodium may encourage some indoor plants, like basil to prematurely go to seed ). Sodium lights are best for the flowering stage of herbs grown for their blossoms: chamomile, calendula and borage among others. Placement of light and its reflectors is crucial. You should be able to move the lamp as close as necessary to the plants with the ability to raise the light as the plants grow taller. Hanging the light from chains or pulley systems well-anchored in sturdy, overhead supports allows you to move them up and down easily.
Light Emitting Diode or LED grow lights are slowly gaining in popularity. Recent advances in LED systems have made them more convenient for small growers but possibly too expensive for casual culinary herb growers. They have some definite advantages: they use less electricity, produce less heat and can last five or six times longer than HID lamps. And they don’t require a ballast. The jury seems to still be out regarding whether their results, potential savings in electricity and their longevity justify their expense. Again, we have anecdotal evidence of good results, expense be damned. Some LED lights are designed to produce more blue spectrum light than others, a boon to the herb grower.
Use of electricity to power lights and ventilation requires special care. You’ll need to plan your grow-space so that all electrical components — lights, plug-ins, wires, ballasts — are off the ground and away from any water or damp areas. Water and electricity can make for dangerous conditions. Though not needed by most kitchen herb growers, more intricate growing systems that use lots of electricity should be wired with their own fuse box or circuit breakers. If you’re not completely competent at wiring and know all the safety factors, hire an electrician to help you with this. As in all things electric, safety is a primary consideration.
Light sources should be as close to your herbs as possible without burning them. You can test this by carefully putting the back of your hand at the top of your plants. If the heat is uncomfortably warm for your skin, it’s too close.
HID bulbs must be matched to their ballasts, in both type and wattage (some ballasts will accommodate either type of HID lights as long as the wattage is the same). Your indoor growing supplier is your best source of information when pairing lamps ballasts and reflectors.
Soil Or Hydroponics?
Another consideration: will you grow your herbs in soil or use hydroponics (growing without soil)? It’s long been believed that vegetables and herbs grown in soil will naturally taste better. With the advent of advanced hydroponics-nutrient solutions, that belief is changing. Different commercial and/ or homemade hydroponics systems make it easy to introduce nutrients to your plants and a wide array of nutrient solutions will ensure your herbs get everything they would from soil. Again your indoor-gardening supplier is your best source of information regarding which hydroponics nutrient solutions to use.
Growing in soil is recommended for beginners. Those with outdoor gardening experience can easily translate that knowledge to growing indoors. With good drainage, proper soil and nutrients and a minimum of attention, raising herbs in soil is easy. Herbs don’t require a lot of fertilization. In fact, over fertilizing your herb plants will mean more leafing but less flavor. Again, Mediterranean conditions — dry cool conditions with less abundant nutrients and a near neutral or slightly acidic pH level between 6 and 7 — will give the most flavorful results.
Raising plants in soil can be less expensive for those without high-yield expectations. Soil is also more forgiving than hydroponics. Miss a watering or otherwise make a mistake and your plants will probably survive. Mistakes or oversights in hydroponics gardening can have faster and more severe consequences.
Luckily, modern hydroponics systems take away most of the room for error. And when done correctly, growing hydroponically can give quicker and more abundant results. There are a number of ways to make your own hydroponics systems, but even the simplest are quite involved while more sophisticated homemade systems may be beyond the capabilities of the home hobbyist and nearly as expensive as set-ups that can be purchased from gardening supply stores.
Commercial hydroponics systems now come in a wide variety of methods and sizes. Wick systems, which use capillary action, are the simplest. Auto pots use a mechanical float valve that initiates watering when the growing medium goes dry. Ebb and flow systems flood the growing medium and allow it to drain, drawing oxygen down to the root systems. Deep water culture systems use air pumps and air stones to keep water moving through clay stones or pea gravel.
Choosing the right growing medium — coconut coir, soil conditioners, soilless mixes — is a matter of preference and convenience. Coir is favored by many growers because of it ability to wick air as well as moisture to your plants’ roots. It’s also compostable. The indoor gardening experts at Planet Natural can help you match a hydroponics system and growing medium to your needs and skill level.
Ventilation and temperature in your grow space should not be overlooked. Herbs actually thrive in cooler temperatures than you might expect. Keeping your herbs in ideal temperatures — 62 to 72 degrees — can be difficult if using heat-producing grow lights. Using fans or other ventilation to control heat will also refresh the air which your herbs need for growth. Broad-leaf herbs such as basil can consume most of the growth-encouraging CO2 in a small self-contained growing space within hours. Proper air-exchange will prevent this. Extreme conditions, say a damp basement, may require a dehumidifier to keep humidity levels at an ideal 15 – 30 percent.
Know Your Herbs
Experience growing herbs outdoors will go a long way to growing success indoors. Annuals, such as basil, cilantro and lemon balm, can be easily started indoors from seed. Certainly digging up basil from your garden to bring inside ahead of the first frost will keep your plants yielding. But you’ll want new plants to keep your harvests ongoing and to set out in the spring. Don’t start your seed under strong light. Wait until the plants show their first true leaves before moving to a well-lit space. Quick growing herbs such as cilantro won’t regenerate when picked so a constant supply demands fresh seeding. Digging cilantro up from the garden for transplanting indoors produces an inferior product. Both dill and cilantro like cool temperatures. Growing them in a warm closet or tent might keep them from becoming lush or may make them bolt.
Germinating parsley seeds for indoor growing requires cracking the seeds’ hard coat. This can be done by presoaking in warm water or freezing them in ice cubes. When it’s time to plant, put the ice cube with the seed in a potting cup.
Perennial herbs, including marjoram, oregano and rosemary, are mostly difficult to start from seed and should be bought as starts. Sage is a perfect example as it can take two years or more for plants to become established. Grow sage and other perennials in pots large enough to encourage growth. Bringing established outdoor plants in pots to your indoor herb garden will assure survival and fresh harvests.
Choose basil not only for flavor but in sizes to fit your indoor growing space. Globe basils grow more compactly, some lemon-scented basils or specialty basils, including Magi Mountain, will grow to 30 inches or higher.
Thyme, despite its Mediterranean roots, like a good feeding now and then. But make sure it has good drainage. If your plants are growing well, cut them back. They’ll grow even better. Lavender needs less moisture while wintering indoors than it did out in the garden. Make sure its roots are dry to their very ends before watering. Rather than water, flood lavender with light.
Rosemary does better when it develops a deep root system. Plant your outdoor rosemary in deep pots that can be brought inside when colder weather arrives. Long rosemary limbs can be harvested in August and planted in pots indoors where they will root and thrive. Cut the limb to about six inches and anchor in loose soil and place in cool, somewhat shaded conditions. A dip of the stem’s planting end in propagation hormones will help with the rooting process. Tarragon will need to be divided every couple years to assure hardy growth. Just before bringing it indoors for the winter is a good time to divide the plants and repot. Thyme is difficult to grow from seed or cuttings. Buying established plants is the easiest solution.
Designing An Indoor Herb Growing Space
My own system is taking shape in a prefabricated shower stall in a basement bathroom that’s no longer used since the kids have grown up and moved out. Though its approximate four-square-feet of floor space is already proving to be smaller than my needs, it has good access to electricity and water and, of course, a floor drain. The room’s exposed joists provide secure anchors for hanging a lamp reflector and the short walls made it easy to build a platform safely above the grow area for a ballast, if needed and power strip.
My goal is to keep the system as simple as possible while making efficient use of the limited space. My lofty ambitions – to grow abundant amounts of basil, enough to sell at our winter Farmers Market, and lesser amounts of rosemary, oregano, marjoram and thyme, small pots each of chives, lemongrass and mint as well as providing a place to start seeds in the spring for outdoor planting and a tray or two of wheatgrass – have made my plans more involved than I hoped. To quote the Rolling Stones, you can’t always get what you want.
I’ve laid a square of 1x1s cut to fit on the floor of the shower on which I’ll lay a metal grate (for drainage) to serve as a floor. It’s here that I’ll start seeds and keep two 6″ x 12″ wheat grass sprouting trays (one of these will have to go when it’s time to start seeds). On this will rest a simple bench stand two-and-a-half feet tall supporting another 30″ x 18″ piece of grating to serve as a table top. Before installing the grow bench, I’ve removed the shower head and attached an eight foot piece of narrow garden hose to the outlet. The shower’s walls were wrapped with one mil, Reflective Mylar to a height of six feet. The white shower curtain at its entrance will have to suffice for now. I haven’t found a good way to attach the Mylar to it without it pulling loose when the curtain is opened. A friend has suggested hanging a space blanket or other reflective survival blanket. And, he points out, it would be less likely to melt or catch fire under hot lamp conditions than the plastic shower curtain.
The back wall of the shower is curved, making it deeper at its center (26 inches) than at its sides. It’s here that I’ll attempt to growing vertically using three modified hanging shower racks of the kind that hang from shower heads and hold soap, shampoo, loofah sponges and the like. Each has three wire shelves with a short containment lip. I’ll use cord to hang them from the top of the shower stall. They will wrap (or nearly) around the back of the shower making a sort of three-tiered terrace from which the basil will grow. Each shelf’s containment lip will allow me to tilt the grow pots, putting the plants closer to the light source.
Most vertical grow systems utilize a grow lamp hung vertically without a reflector. I’ll be using T5 fluorescent bulbs in a reflector, not the most ideal light for a vertical system. The three-tier, vertical growing conditions will make me hang the lamp higher than I would like to start but I’m prepared to discard the idea if I’m not getting good results on the bench top or the vertical terraces. There are vertical lamps systems with reflectors but they’re far too large (45 inch reflectors with 1,000 watt bulbs) for my modest space. Small (3 inch) grow cups will sit at an angle on the hanging shower racks, held up by the lip at the front of each shelf.
My choice of the T5 fluorescent was based on my desire to get maximum growth at the least expense. I’ve heard great anecdotal evidence of the success some indoor gardeners have had with fluorescents, especially in reflective spaces. That fluorescent bulbs use less electricity appealed to my conservationist as well as cheap sides.
I briefly considered a smaller halide lamp for the top section. The basement gets rather cold in the winter and I knew the halide would keep the space toasty. The fluorescents won’t have the same effect and may require that I use a separate space heater to warm the room that contains the shower. I’ll install a small rotational circulation fan from the ceiling. The short walls which leave the space open at the top beneath the floor joists, will allow me to position the fan to either draw warm air away from the plants or direct it back down towards the growing area.
Eventually, I hope to hang a small fluorescent grow light fixture from the table top to light the lower, wheat grass and seed-starting area. I’ll need to be careful to avoid the dangers of mixing dampness, metal and electricity. The plants on the top of the grow bench will be in trays
Using the fluorescent leaves me an option. My friend who recommended the space blanket suggested buying the fluorescent fixture first and using it above the grow bench and gauge the results. Our cold winter basement gives me concern that the fluorescent-only set-up might require an additional heat source, thus canceling any electricity savings. If I need the heat and want better results, I can always move the fluorescent under the table and buy a 250 watt halide lamp, ballast and reflector to hang above the grow table.
I’ve decided to use a passive hydroponics uptake system on the grow bench with plants in both soil and coir as my growing medium. When using soil, all the usual precautions should be taken so as not to introduce insects or disease to the indoor growing area. I’m looking forward to experimenting with different combinations of soil and drainage mediums, including rock wool, and seeing which gives the best results.
I’ll add accessories — thermometer, light timer and more circulation, if necessary — as time goes on. My goal is to have enough basil to make pesto by Christmas and to start bringing basil to our local (indoors) winter Farmers Market as a way to defray a modest amount of my electrical costs. The real reward won’t be cash but a year-round supply of fresh, fragrant culinary herbs. I can taste the pesto now.