Most plants give signs of trouble with their leaves. In general, most plants (and especially berries) should have deep green leaves. Any other variation means trouble. Sometimes it's major. Sometimes it's an easy fix.
If your leaves have a purple tinge: It may mean the weather has been cold, they are just forming, or they are deficient in Potassium. To fix - apply light fertilizer (tomato fertilizer is a good choice, since it is higher in potassium which results in more flowers and more fruit - or buy Organic potassium source.)
If your leaves are yellowing: If they are very bleached it most likely means an iron deficiency. Most home improvement stores sell iron that's easy to use and apply. If they are yellowing in streaks (see photo above) it most likely indicates a manganese deficiency. Plants can become deficient in manganese if the soil is too alkaline, thereby inhibiting uptake by the plant. You can buy manganese sulfate (online only) or if you use an acidifying fertilizer (look for one for azaleas or rhododendrons) they typically contain manganese.
This kind of yellowing can also mean exposure to a neighbor's herbicide use. I get this a lot in the suburbs. Wind carries herbicide drift and can damage the tops of many of my plants. Also, salt from the winter roads and any next door neighbors that let their fertilizers actually spray into your garden cause similar problems.
Unfortunately, yellow streaking - especially with ring patterns or dot formations can also mean viruses. If a plant looks really diseased, rip it out (roots and all!) But if most of your patch is effected, you may have to take them all out. Some viruses like tomato ringspot (also called tobacco ringspot) are caused by microscopic nematodes and will be in your soil for years. hat also means you can't plant tomatoes, peppers, or eggplant where the berries once grew.
Berry plants that get viruses usually produce crumbly, gross berries and you will want to remove them.
If you have light yellow leaves all over (not green in the veins) then you may have a nitrogen deficiency. That's easy enough to fix with any fertilizer (berries respond well to fish emulsions.) Be sure to add a nitrogen rich fertilizer if you have a lot of organic material waiting to decompose (leaves and mulches) because they steal nitrogen from the ground as they break down.
If your leaves are turning orange: It looks powdery on the underside of the leaves and is bright orange. Red raspberries sometimes get a rust virus. It will keep coming back and will not go away. It doesn't really do much to the berries and you can just get used to it or start over. It will kill your purple or black raspberries though.
If your leaves are turning brown: If it's been dry, then it's probably from lack of water. If it's been really wet, the roots may be rotting. If this is the case, you may need to clear out some of your canes to make sure air can circulate and water can drain. If you have clay soil, you will need to amend it before you plant your berries.
Brown, crispy edges usually means fertilizer burn. Too much fertilizer can really hurt plants. Sometimes it will be too late, but the best thing to do is really water the plants liberally to try and wash away the excess fertilizer salts.
Brown edges mean "stress." It can be too much water, too little, too much fertilizer, or attack from an unseen enemy (aphids, blights, viruses) and can lead to death. Usually, though it's one of the above situations and is easy to fix.
If your leaves are turning black: They may have suffered frost damage, though that is unlikely with raspberries except in late fall. They most likely have a virus and will have to be destroyed. Check the canes. If they have black streaks, galls, or other unusual issues, get them out of your garden! If it's limited to one or two canes, remove them or at least remove the diseased sections down to green growth.
If your leaves are grey, white, or moldy: They are most likely molding because of extremely damp weather. This usually make the berries inedible. If this happens, cut off the moldy sections and proceed as normal. You can also use a fungicide to control the mold. If it's widespread, you may need to clean out the whole patch and just wait for new growth in the spring. Rain happens and there's not a lot you can do to stop it except by keeping your berries pruned and preparing the soil so it drains well.
If your leaves have holes: This means someone has been eating them. Look under the leaves and around the stems. Plant marigolds nearby to discourage aphids and other garden pests. Also, get to know which insects are "predators" and leave them alone so they will eat the "pests." Berries bushes are often attacked by slugs, japanese beetles, wasps, and fruit flies. If they are growing in healthy ground (amended well with minerals and organic material) then they should be able to outgrow any insect feeding.
If your leaves are turning red: If they are red on the outside or all the way through, then you have a nitrogen deficiency or you have experienced really cold temperatures. This can happen often in early spring and always happens in the fall. If your leaves are red and splotchy then you have a blight (virus) and will need to watch your plant carefully to determine if you need to remove it.
Fertilize your blueberries with acidifying fertilizer and a sprinkling of bone meal. They are heavy calcium feeders.
If your leaves are turning yellow: This can mean an iron deficiency (especially if the veins are still green) or that your soil ph is not correct. Blueberries need an acidic soil (4.8-6) and you must be sure they have the right soil. They also need good drainage. If you have clay or alkalkine soil, you will need to amend it with peat moss and sulfur. You will have to keep an eye on it every year as your soil will return to it's native state.
Some blueberries naturally have yellow leaves and branches when they are first formed (Northland is a variety that starts off with very light yellow green branches and leaves that green up over the summer.) Most have dark green leaves and shoots (which turn grey and flaky as they age.)
If your leaves are turning brown: Blueberries are very sensitive to fertilizer salts. Be careful not to over fertilize. If you do, then give them extra water to try and wash away the salts. Also - blueberries will die if you use fertilizers containing nitrates. Use ammonium sulfate or a fertilizer made for acid loving plants.
Leaves also turn brown when the plants are low in water. Blueberries have very shallow roots and need water regularly.
If your leaves are small or stunted: This may mean you have root rot, major nutritional deficiencies, ph problems, poor soil (to heavy or too light - clay vs sand), or mealy worms eating the roots. If you see a lot of ants near your plants, then you probably have worms around the roots. The worms eat the roots and the ants "farm" the worms. Gross. You may also have damage from voles, rabbits, muskrats, or ground hogs. All of these animals damage roots and girdle branches. Most of these issues will show up with branch death and slow growth overall.
Branches, buds, and flowers also hold keys to what might be going on with your plants so keep a watchful eye. It's not all gloom and doom with berries, but you need to know what to do when problems arise. Happy gardening!
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