Monday, July 05, 2010

Strawberry Fields Forever

One of the best parts of this time of year is the abundance of fresh ripe strawberries. Maybe you are getting a big crop of June-bearing strawberries into the freezer or jam jars. Perhaps you have everbearing strawberries and gather a handful here and there, taking a succulent perfect berry as a reward for your gardening that day.

Not sure what kind of strawberries you have? If you get only one or two ripe berries at a time, but plenty of flowers and unripe berries, your plants are likely to be everbearing strawberries, such as Quinalt, rather than June-bearers. The June-bearing ones do a heavy simultaneous crop during the summer, and then go to sleep until next year. In mild-winter zones like the SF Bay Area, sometimes you will get a light fall crop from June-bearers as well.

Solving Berry Problems

Or perhaps your strawberries aren't doing so well. In that case, let's take a look at some common strawberry problems so you have time to fix them and enjoy some luscious summer strawberries! Here's a handy list by symptom, and some fixes to try for each one. If you know what's wrong and are looking for a specific fix, try the AWESOME pest control page at Extremely Green.

Everything eats my berries before I can get them!

  • Mmmm, they must be good! Let's look at common berry-eaters.

  • Birds and squirrels can be defeated with netting.

  • Snails and slugs can be deterred with a safe preparation such as Sluggo, or with crushed eggshells or coffee grounds. If you have containers, you can apply copper tape around the base and snails and slugs will not cross it. Be sure you look around the edges and rims of your container before applying the tape, as you probably have stowaways already aboard.

  • Wormy, grey, eel-like things are nematodes, and they live in the soil. You can remove their access to the berries by mulching with a dry material, such as wood chips or straw, or you can repot your berries (in a container) so that they dangle over the side out of harm's way.

  • There are commercially available mixes of bacteria and spores that combat harmful nematodes that you can order from your local nursery or garden center. I'd suggest planning a repotting of your strawberry planters at the end of the season, with minimal soil retained around the crown roots.

  • Small, stunted berries

  • Strawberries need more water than most people realize. Since the berry is mostly water, lack of water will produce small berries. This is particularly a problem for strawberries in containers, including the traditional multi-pocket terracotta planters. If the soil in your strawberry patch or planter isn't moist and dark about an inch under the top layer, it's too dry!

  • If the berries are 'all seeds' and not really developed, but turn brown, they are not getting pollinated. Strawberries are usually self-fertile, but they need a breeze or friendly bees to transfer the pollen. If your strawberries are completely sheltered from any wind, you might consider moving the planters so they get a light breeze.

  • Berries aren't sweet, or have little flavor

  • Ironically, overwatering may be the culprit here. One summer I went away for almost 2 weeks, and left my strawberry pots in a kiddie pool to self-water thru the base of the pot. I came back to the biggest, reddest, tastiest looking berries I'd ever seen-- supermarket sized and photo perfect. And they had absolutely no flavor whatsoever!! They were literally diluted by overwatering.

  • Sweet but bland or boring berries may lack trace minerals. Be sure to apply greensand or a multimineral mix to your berry patch when you do your winter soil amendments. Also test the PH of the soil-- if it is not even slightly acidic, the flavor of the berries will be 'blunted' and the plants won't do as well. Use an acidic soil amendment such as those available for azaleas and rhododendrons, or mulch with pine needles if you have them available.

  • Only leaves, no flowers/berries

  • If your strawberries aren't flowering and producing berries, you may have been feeding them a high nitrogen fertilizer and not enough other nutrients. Dig in a good all-purpose fertilizer, ideally one for acid-lovers like rhododendrons or azeleas.

  • If the plants seem healthy and you are sure they are well-nourished, have nights been consistently over 55 degrees F for at least 2 weeks? With some of the odd climate patterns we've had, your microclimate may be lagging and your strawberries haven't caught up with the calendar yet.

  • Fungus on berries

  • Almost always a problem with poor drainage in a container, or a waterlogged surface layer on which berries are resting. If it's happening on berries in a strawberry patch on the ground, you may be leaving them to overripen, or have poor soil drainage. If you mulch with straw, make sure you water with soakers under the straw, because wet top straw can harbor mold and mildew that will rot your berries.

  • Correct drainage by adding sand to your container mix or soil patch, making sure that you are using no more than 50 percent compost in the soil mix, and never mulching compost directly onto the strawberry plants-- leave a couple of inches around the crown.

  • White dusty gunk on leaves

  • White dusty gunk on leaves is likely to be powdery mildew, usually only on leaves, with little impact on berries (besides there being fewer of them). Drainage control, plus some varieties are not very resistant to it. Hot weather and damp soil breed the stuff, so if you're expecting a heat wave, water sparingly and only in the cool of the morning or evening. Good mulching of the plants can help reduce the heat buildup in the soil and keep the plant cool, so be sure to mulch well in the summertime. If you have containers, consider moving them into the shade for a few days if the temps go into the high 80F range. Try to make sure your berry plants can take advantage of breezes also, to keep foliage dry.

  • There are few organic treatments for powdery mildew-- preventing it, and pulling leaves that have it, are best. Spraying with neem oil is alleged to stop mildew of various types, as is spraying fat-free milk(!). There are some preparations at your local nursery or garden store that are safe and won't taint the berries-- look for label directions on how and when to apply, and that the produce will be safe to eat.

  • White lumpy gunk around strawberry crowns and stems

  • Ouch, you have cottony scale and getting rid of it will be "fun". Not! "Safer soap" and similar safe preparations will help, as will cleaning off the crowns by hand. You will need to spray daily, sometimes twice daily. You might be over-fertilizing, as scale insects are attracted by fast-growing plants in the same way aphids are. Like aphids, the scale might be being farmed by ants, and stopping the ants with outdoor-safe bait will help you control scale. Never use indoor ant traps outside-- they usually contain arsenic, which will leach into the soil and show up in your veggies!

  • Don't despair, scale can be defeated, but it takes persistence. If your plants are several years old, and you have not been renewing your patch by letting runners root and removing older plants, well, it might be simpler to take out the plants and start fresh next year. It's up to you.

  • Black/brown stems, leaves shriveling

  • If you have leaves and stems going fungal, and rotting or shriveling up, this is probably crown rot. Wet soil and high temperatures encourage crown rot. Besides addressing drainage issues as above, you have several options. Crown rot spores can stay resident in the soil, so if your strawberry plants are in a container, you will want to compost the soil in a hot pile or discard it, and wash the container with a mild bleach solution. If your plants are in the ground, consider either making a new bed, or purchasing replacement plants from known resistant varieties. has an interactive list of strawberry types and is a great source for info on resistant varieties.

  • If you've made it this far, congrats, and I hope your strawberries aren't having any of these problems! Whether your own berries, or ones from a farmstand or farmer's market, enjoy the berry best days of summer!

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