In keeping with our intuitive desire to share information we've decided to write a monthly blog post about gardening in South Florida. Every month of the year is a little bit different and although some months see more action than others, there's always something new coming or going. If you haven't read the post from July, check it out before reading this one, there is a lot of information in that post that is still very relevant right now. August continues to be considered peak summer, but the main difference this month is that we begin to count down to the beginning of Fall planting. That means there are some "garden chores" to be done.
One of the most valuable pieces of advice we can give you is to test your left over seeds now so that you have a sense for which seeds you'll need to buy fresh. Planning your Fall garden is certainly something you can start doing now, but we recommend waiting until September when you will have access to our resources; for example our workshops and the seeds and veggie starters we will have for sale. Testing left over seeds is a super important step in planning your Fall garden that you can get out of the way now.
First lets talk a bit about seed storage. Seeds should always be stored in a cool dry place, for example your bedroom or even a drawer in your refrigerator. The cold environment in your fridge will preserve your seeds really well, but make sure to store them in an airtight zip lock bag to keep moisture out. Seeds stored in a garage or other place with unstable hot and humid conditions will most likely loose most of their viability. Their germination rate might go from 80% (which is considered average to good) to something like 20% or 30% (which is considered not even worth planting) over the course of one summer.
Now lets talk about testing your seeds. Remember that we are still in peak summer so the temperatures outside are way too hot to get accurate germination results. Besides moisture and sunlight, temperature is one of the major factors in a seeds ability to germinate. Some seed packets include a simplified chart of the optimum germination temperature for that particular variety. On average most seeds require a soil temperature between 60 to 80 degrees Fahrenheit. The temperature of wet soil on a hot August day in South Florida reaches as high as 90 to 100 degrees, especially if it is in direct sun and even more so if it's a small pot or seed starting cell tray. This difference in temperature is enough to inhibit the germination of many plant varieties and sometimes also causes seeds to rot or "cook". To get accurate germination results you'll need to start your seed tests inside of the house. You'll want to plant at least 10 seeds for each variety to get a germination percentage. Once the seeds germinate count the number of sprouts and compare it to the 10 seeds you planted. If 5 grew you have a 50% germination rate, if 8 grew you have an 80% germination rate. Depending on your gardening style, your budget and other factors that may affect your ability to get new seeds, you'll determine what is worth using in the Fall. For example, you may have a favorite variety of lettuce that is now sold out on all seed websites, but you have leftovers and you got a 50% germination rate on your test. It might be better to have some of your favorite lettuce than none at all. If you are direct seeding crops like carrots or radishes with seeds that got a low germination rate you'll want to sow the seeds much closer together than usual to assure maximum yield per square foot.
Another thing to keep on your summer gardening radar are your cover crops, if you planted them. In our July gardening post we talked about the importance of planting cover crops for improving soil quality and breaking pest life cycles. If you planted sunn hemp which is the most highly recommended cover crop for South Florida, it may be getting really tall at this point and will be blooming soon. You'll need to keep a close eye on your sunn hemp when it is 50-60 days old. It typically blooms at about 60 days from when it was sown, but it can start blooming a bit early or late depending on the specific climate. The goal is to cut down sunn hemp right before it blooms and goes to seed. If you recall, one of the ultimate benefits of this legume cover crop is the nitrogen fixing bacteria that live symbiotically on it's roots. The plant will begin to use up that stored nitrogen to produce seed pods. Therefore in order to take full advantage of the benefits of growing sunn hemp you'll want to chop it down before it makes flowers and seeds. If you are interested in planting a sunn hemp cover crop and would like more information, watch us plant sunn hemp in our demonstration garden in this video, and watch farmer Tiff cut it down and process it after 6 weeks of growth in this video.
An old picture from 2013 when we planted a particularly successful field of sunn hemp at our urban farm in North Miami. Notice the height and the beautiful yellow flowers which signaled it was time to chop it all down.
A close up of the nitrogen nodules created on sunn hemp roots by a beneficial bacteria that works symbiotically with the plant to collect nitrogen from the atmosphere. These nodules are basically home made organic fertilizer for your vegetable garden!
Another cover crop we highly recommend using either on it's own or in combination with sunn hemp is buckwheat. Buckwheat is a much smaller and faster growing option which works well in combination with sunn hemp because it helps with weed suppression during the first couple of weeks when sunn hemp tends to be a bit slow and does not provide broad coverage. Buckwheat works beautifully on it's own, especially when you have a short period of time to work with, like right now! It matures within 30 days and provides great weed suppression, a break in pest life cycles, some organic matter and a show stopper bloom of white flowers that attacks bees from far and wide. Buckwheat is pretty easy to manage since it only grows about thigh high and isn't fibrous like many other cover crops. It will naturally collapse after blooming and you can either rake away the small amount of organic matter left behind into your compost bin or you can leave the residue on the surface of your soil and plant right into the soil. It may look a bit messy, but rest assured it is well worth it!
Chris French at French Farms this week, planting a new batch of cover crop seeds in the background with a mature field of blooming buckwheat in the foreground.