Bee swarms, ‘bolting’ lettuce, invasive weeds: July maintenance tips for your Peninsula garden

July gardening tips

What to do if you have a bee swarm

Bees are very active in warm weather. There is simply so much pollen and nectar to collect. Sometimes, a bee colony may swarm. Bee swarms are a natural response to an overcrowded hive, and half or more of the colony departs to look for a new nesting cavity.

If you see a swarm, don’t panic. As in any other time when working around bees, remain calm, move gently, and give them their space. Bees generally swarm when they are looking for a new home. Swarming bees are loaded with food and are not interested in stinging people. 

Contact the Bee Guild to have swarms removed. Their trained Bee Guild members volunteer to capture honey bee swarms on private or public property – in most cases for free.

Don’t ignore bitter zucchini

Zucchinis are part of the cucurbit family, and wild varieties produce the bitter-tasting chemical “cucurbitacin” to deter wildlife from eating them. Cultivated varieties have been bred for low levels of cucurbitacins, though mild bitterness can sometimes develop due to environmental factors like heat or stress.

If you encounter a super bitter zucchini, don’t eat it, and pull out the plant. Extreme bitterness is likely due to seeds from an accidental cross with a wild cucurbit. Plants grown from those seeds may contain high levels of cucurbitacin, which can make people very sick. Read more about bitterness in zucchinis and cucumbers. 

Avoid overwatering succulents 

Succulents store water in their leaves, stems or roots, making them naturally drought-tolerant. The key to healthy succulents? Avoid overwatering. While underwatered succulents can usually recover, overwatering often leads to fatal root rot.

For success, plant in well-draining soil and let it mostly dry out between waterings. Water more frequently during active growing seasons and reduce watering during dormancy. Remember: It’s better to err on the dry side. Learn more about succulent care on our website and join us for our July 12 library talk on these fascinating, water-wise plants.

Watch for ‘bolting’ lettuce

In garden terms, bolting means sending up a flower stalk: This is generally undesirable unless you plan to save seeds. Seed packets say lettuce matures in 60–80 days, but the timing also depends on the weather.

In warm weather, lettuce matures and bolts much faster. In cool temperatures, seedlings grow more slowly but will still mature and bolt eventually. If the center of the lettuce starts to push upwards, that’s a clue that it’s starting to bolt. Another clue is if you tear a leaf and see milky sap instead of clear juices. Harvest as soon as you notice, before the leaves become unpleasantly bitter.  Read more about growing lettuce.

Be persistent in removing bindweed

Have you seen a pretty, morning glory-like flower on a vine that winds through any plant within reach? Field bindweed is one of the most challenging weeds to control because its roots can reach depths of 20 feet or more, and it readily re-grows from root fragments as short as 2 inches.

The only chance of controlling this invasive weed is to stay right on top of it and remove it as soon as you see any of it peeking up out of the ground. Every time it starts growing above ground and photosynthesizing, it stores energy in its roots. This allows it to put out new shoots. It produces many seeds which remain viable for years. Making things even worse, it’s drought-tolerant.

Controlling it isn’t easy, but the UC pest note below discusses options. Chemicals aren’t needed if you’re persistent in removing new growth to prevent seed production and limit the plant’s ability to store new energy in the roots.

Would you like to ask a UC Master Gardener about a plant problem? Submit questions to our Help Desk online. You can also attend our Zoom Plant Clinic Online on July 8 at 7:00 pm.

You can also subscribe to our monthly Tips and Events newsletter. San Mateo residents can also find gardening advice on the UC Master Gardeners of San Mateo and San Francisco website.