Growing organic basil (pronounced bay-zul) is both easy and rewarding. We use it as a fresh herb all summer in various dishes, especially Asian and Italian cuisine. Sweet basil is typically the most common variety you’ll find if you’re planning on growing organic basil. Tropical areas in India and Asia have been growing basil for at least 5000 years. The name basil comes from the Greek, βασιλεύς (basileus), and means “king,” and it’s a member of the mint family.
When to Plant Basil
Because we reside (through no choice of my own) in a Northern climate area, we always plant basil indoors about 6 to 8 weeks ahead of the last frost. Basil needs around 70 to 80 days to reach maturity, although if you’re careful not to overdo it you can remove a very small amount of lower leaves ahead of that time. As there are many varieties of basil you can grow, check with your local seed distributor or a reputable national seed supplier. You can either plant or transplant basil after the last frost of the spring. Basil is a warm weather plant and while it doesn’t like temperatures below 50°F, we’ve been able to grow some varieties in our area.
Best Location to Plant Basil
Basil is a sun lover; in Southern climates it requires around 6 hours a day, and as you move North to our area, it needs about 8 hours daily. Make sure not to crowd your basil plants; air circulation around the plants is required for plant health. Fungal diseases almost always begin in damp conditions where your plants can’t dry out by noon. Basil is a semi-fragile plant, so it should be protected as much as possible from the wind.
Preparing The Soil to Plant Basil
Basil, like many herbs, likes soil that drains well and is nutrient rich. Organic basil should grow well with organic compost and/or composted manure. The pH range for growing basil is between 6.0 and 7.5. Basil is a heavy Nitrogen (N) feeder, and compost, composted manure, or bloodmeal are good sources of Nitrogen Basil does very well in raised beds if your soil doesn’t drain well. Our soil is pretty rocky, and although it’s a bit clayish, the rocks help it to drain well. Adding composted materials to clayish soils also helps it to drain well, and helps retain water in sandy soils. Prepare your soil to a depth of 6 to 8 inches by mixing in 2 to 3 inches of compost or composted manure into about a 6 inch cubic foot area where the seed or plant will be planted. That’s about the size and depth of an average garden shovel.
Choosing The Right Seed Varieties for Your Area
Basil typically grows between 12 and 24 inches tall. The varieties we grow up North average about 12 to 14 inches tall, but tropical basil will usually grow up to 24 inches. Choose your seeds based on the climate zone you live in (your seed supplier will know what varieties grow best in your zone). Also, check with your county extension for diseases that may afflict basil in your area and choose seed varieties that are resistant to those diseases (such as fusarium wilt) if there are any.
Germinating Basil Seeds
Basil seed germinate best at around 65° to 85°F; at 65°F your seeds will germinate in 10 to 14 days and at 85°F they’ll take 5 to 7 days. Basil seeds, like most seeds that you plant in shallow soil, need a modicum of light, either artificial or sunlight, to germinate. If you’re planting outdoors (not recommended in the Northern climate zones), wait until night time temperatures are above 50°F.
If you’ve planted “heirloom” basil seeds, you will have the ability to save your seeds for next year’s crop. If you plant disease resistant varieties, they’re typically hybrid seeds and you won’t be able to harvest the seeds to plant next season. Personally, and I may get into trouble with seed purists, am not opposed to using hybrid seeds, although GMO seeds may be an entirely different animal (literally). We’ll be posting an article on GMO soon. We’ll look at all sides of the argument over GMO, and explain the difference between sysgenic and transgenic GMO (Europe outlawed GMO’s, or so we’ve been told, but they outlawed transgenic, not sysgenic GMO). OK, now that I’m back from that rabbit trail…let’s save some seeds. First, make sure your basil doesn’t seed until fall. Let the flower and dry, then pick the dried flowers and lay them on a jellyroll pan or similar. Let them sit for a few days, then bounce the tray on your table or counter-top lightly, or tap the bottom of the pan and let the seeds roll out and collect them.
Starting Basil Indoors
It’s always the best practice to use a sterile potting soil to start your plants indoors. For starting basil seeds, it’s a good idea to add a bit of lime (dolomite) and sand to your mix (also sterile). There are lots of containers to start your seeds in…if you have the budget to do it, soil blocks are the most environmentally sound way to start seeds, followed by peat pots or “jiffy pellets,” then any re-usable plastic tapered seed tray or container you may have laying around. Just make sure if you’re using cottage cheese or yogurt cartons that you poke some holes in the bottoms to allow for proper drainage. Plant 2 or 3 seeds about 1/4 inch deep in the potting mix. You’ll want to plant extra in case one or two fail to germinate which is common with many herb varieties. Once your basil seedlings have 4 true leaves, thin the plants to the strongest surviving plant per cell or carton.
Transplanting to Outdoors
As you approach the final frost date for your climate zone, you’ll want to prepare your basil for being transplanted to your garden. This process is called “hardening off” and is kind of like weight-training for plants (very loosely speaking). Move your plant trays out of doors for a couple hours a day to start with (not too much sun initially), and increase the out-of-doors sunlight hours for one or two weeks. The reason you do this is that you may kill or stunt your plants if you don’t prepare them for transplanting, just like you wouldn’t run a 10K race without physically preparing (unless you’re completely bonkers!). You’ll want your basil plants to have 4 to 6 mature leaves when you transplant them, and if possible, don’t transplant them if the night temps are falling lower than 50°F. The optimal daytime temperature for most basil varieties is about 85°F Your soil should be prepared per our instructions above. When planting your basil plants, slide the soil and root mass out of the pot (unless you’ve used soil blocks or peat pots).
Using a small garden trowel, create a hole large enough to accommodate the soil/root mass, and lifting the plant very carefully (I grasp the whole plant in the palm of my hand), slide it into the hole and gently pack the dirt in around the roots.
We plant our plants about 12 inches apart. This allows them plenty of air circulation which helps them avoid moisture-related fungal diseases. You can make double or triple rows, spacing the rows 6 to 12 inches apart, and then 30 to 36 inches between the doubled/tripled rows.
You may also trim the tops back to 6 inches or so in height to encourage lateral branching (and more leaves).
One thing I should also mention is that you can also root basil from cuttings from mature plants.
Planting Basil Seeds in Your Garden
As previously mentioned, unless you live in a warmer, Southern climate zone, we suggest you start your plants indoors. If you live in a more Southern region, you can seed your plants directly in your garden. Again, make sure your nighttime temps are 50°F or higher; this will typically mean your daytime temps are also at least 70°F. In the same way as outlined above, make your rows in doubles or triples, but plant 8 to 10 seeds per inch. Same as above, plant the seeds approx. 1/4 inch deep. Why so many seeds? They germinate more sporadically most of the time if started outdoors, so you’ll want to be able to make sure you’ve got plenty to choose from when you thin them out. Basil is a delicate seedling, and the soil should not crust over after planting. You can either lightly mist the soil a couple times a day or add a light layer of vermiculite over the seeds to keep the soil from developing a crust.
Successfully Growing Basil Until You Can Eat It
As previously discussed, you should thin your plants to about 6 to 12 inches apart for the best results. You can eat the plants you thin, or they also transplant relatively easily. Pinch back your plant tops to encourage the plants to become bushier. This also will help the flavor of basil and keeps it from going to seed, at which point it becomes flavorless and woody. Basil doesn’t like to dry out or get too hot. It will go to seed or stop growing, so it’s a good idea in hot climates to plant in an area where they can get afternoon shade. We don’t have to worry much about it here in the great white North. If you do see your basil starting to flower and go to seed, just pinch off the tops of the plants (not the flowers). Pinching off the flowers as they form does not stimulate new foliage; in fact it encourages flowers to form in the axils of the leaves thus reducing the yield of the plant. Mulching will help keep your basil plants cooler in the summer heat. We’ll cover that in the next section.
If perchance, you get a late cold snap, use row covers to protect your basil from a frost.
If you’ve prepped your soil per the instructions in the above section on preparing your soil, you shouldn’t really need to fertilize your plants during the growing season.
Mulching and Weeding
Mulching with grass clippings, chopped leaves, or barley straw helps both to retain soil moisture and control weeds. If you don’t mulch, make sure you don’t let the weeds take over your basil patch. Basil doesn’t compete very well with weeds. Weed carefully close to your plants and cut the weeds off at ground level if they’re too close to the plants.
If you use organic mulches like grass clippings, it will help keep you from needing to use as much water on your basil. Basil needs about 1 to 2 inches of water every week to 10 days to make sure the roots have enough moisture. If you dig down a couple inches near your basil plants, and the soil is moist, you probably don’t need to irrigate. As with most plants, drip irrigation is better than overhead watering with sprinklers, but if you don’t have that option, water in the early morning so your basil plants have a chance to dry out by noon. If your plants stay wet, you’ll likely have problems with mildew or fungus. Finally, if you overwater basil, it can make the leaves lose flavor.
Companion Planting and Rotation Considerations
Starting with plants that basil plays well with…
Basil planted next to tomatoes is supposed to help their flavor. We did it last year, but honestly, I didn’t have anything to compare it to, and as we used OGM last year, the flavor was outstanding on all our tomatoes, both near and away from the basil.
Basil is said to repel thrips, flies, and mosquitoes; funny thing, I didn’t know mosquitoes bothered veggies, but I’m thinking I’ll put a few plants in my bedroom!
Basil grows well around petunias, oregano, peppers, and asparagus as well.
Petunias apparently fend off leaf-hoppers, some aphids, Mexican bean beetles, and asparagus beetles. Hot peppers also are supposed to prevent root rot and fusarium in basil. Plants that don’t play well with basil? Rue, which doesn’t play well with sage either, and rosemary, which basil will eradicate. Although I’ve read that basil should be rotated on a 2-year rotation, we’ve had no problem with planting it in the same area 2 years in a row, but maybe I just like to tempt fate!
You can pluck leaves from your basil once it has about 8 leaves. Snip the top of the plant off, leaving 4 leaves; this will encourage the plant to expand laterally (it’ll get bushier). You should be able to harvest leaves up until the first frost in the autumn. Alternate the plants you harvest so that you’ll have a steady fresh supply of basil herbs. You can harvest one or two times weekly.
Basil is good mainly for fresh eating, but can also be dried, although it loses much of it’s flavor when dried.
To dry basil, tie the basil stems together upside down in a warm, preferable dark area for a week or so.
You can also use a food dryer and lay the stems in the trays.
Remove the dried leaves and seal in an airtight container (I use mason jars) and store the dried basil in a cool, dark area or root cellar. It should keep for a year. Another method I consider now to be superior is to quickly blanch the leaves (a quick dip in boiling water suffices), then freeze them in airtight zip lock-style bags or another airtight container. Basil will keep in your fridge for a week or more, but it loses flavor over time, so it’s best if you keep your crop rotating until the first fall frost. One of the main ingredients for pesto is basil, so one way we preserve basil is to make pesto, put it into airtight containers, and freeze it (omit the cheese and add it upon thawing if your pesto recipe includes it).
Preventative and Natural Solutions to Common Pests
Japanese beetles and grasshoppers like to eat basil leaves (can’t blame them for that, can you?!).
Row covers are probably the most effective way to deal with these pests. You can also spray them off for temporary relief.
Slugs also like basil leaves. Diatomaceous earth is effective in ridding your basil patch of slugs, but it has to remain dry or you need to reapply it after a rain or irrigating.
Root rot disease is a group of fungal diseases that cause the roots of many plants, including basil, to rot and die prematurely, taking the entire plant with it. Planting basil in sunny areas with well-draining soil and moderate watering will usually prevent this fungus from destroying your basil plants. If your basil plants happen to contract root rot, dig up the dying plants and dispose of them to an area where they can’t affect other plants (such as your garbage can). Downy Mildew usually develops on the lower leaves only as that’s where moisture often stays.
Again, don’t over water, choose resistant varieties, and don’t crowd your plants.
You can treat your plants with a homemade fungicide spray if you do spot some downy mildew.
You can also make this organic fungicide spray using bicarbonate of soda (baking soda). In a gallon of water add a couple drops of organic olive oil, a couple drops of environmentally-friendly liquid soap, and 3 tablespoons of baking soda. Spray it on your basil leaves to effectively control all of the above fungi.
You should rotate your basil to a new area if your plants are affected by downy mildew.
Fusarium wilt is a soil-borne fungus that causes various plants to suddenly wilt and usually strikes when the plants are mature. Early signs of fusarium wilt include brownish streaking in the stems and leaves suddenly dropping. Once again, over watering is key in bringing this disease on, so if your soil drains well and you don’t over water, you’ll likely not see much of this disease.
Of course, you can plant resistant varieties as well, but if you do have an outbreak of this disease, the pathogens can last in the soil up to 12 years; don’t plant any mint family members in the area for that long. Bacterial leaf spots or basil shoot blight is another damp condition disease. It shows up with spots on the leaves (hence the name) and premature leaf loss. You can plant resistant varieties, but also follow the no-crowding rule, don’t over-water, and plant in soil that drains well, or add enough organic matter so that it does drain well. And, of course, if you do have an outbreak of leaf spots, rotate your basil away from that area next year. Lastly, gray mold; as basil is an herb and herbs are susceptible to gray mold, it is important to remove affected leaves or the entire plant may die. Don’t harvest the plants during rainy spells or when wet as the pathogens may spread from plant to plant.
Of course, don’t over water. Plant in well-drained soil. Rotate your basil out of the area next season. And if you aren’t morally opposed to hybrid seeds, find resistant varieties if gray mold is a problem in your area.
Barry Brown is a 3rd generation organic gardeners who is passionate about a sustainable and natural lifestyle.